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St. Paul’s Convent School
Iron “sucks”! 鐵之吸收術師
By
Zoe Chu (朱曦瑜)
Karen Lau (劉愷寧)
Cherry Liu (廖卓齡)
Cherie Wong (黃意喬)
Stephanie Yeung (楊穎琪)
Teacher Advisor: Mrs. T. Tam (林少欣)
Submitted for participation in the Fifteen Hong Kong Chemistry Olympiad for Secondary Schools
From St. Paul’s Convent School
聖保祿學校 March 2010
Presentation materials: 1 CD-R disc (1 video clip and several digital photographs incorporated in a PowerPoint Presentation)
Abstract
Our research paper involves using a common household waste - used hand warmer powder to treat water pollutants. As the chemical composition of used hand warmer powder might resemble another frequently used industrial adsorbent - hydrous ferric oxide, we hypothesised that used hand warmer powder might exhibit similar effects on heavy metal ions, phosphate and dichromate. We synthesized hydrous ferric oxide to test our hypothesis. We have also investigated the adsorption abilities of materials isolated in the hand warmer powder, treated hand warmer powder and powder of different brands in order to derive a method which optimizes adsorption effects. After experimentation, we found that for adsorbing PO4
3− and Ni2+ ions, the used hand warmer powder should be treated with dilute hydrochloric acid; for adsorbing Cr2O7
2−, Zn2+, Cu2+ and Pb2+ ions, no treatment is needed; and the longer the adsorbents are allowed to stand in the solutions, the more pollutants will be adsorbed. We also packed burettes and a compartmentalized filtration device with the most effective adsorbent among untreated hand warmer powders and passed solutions of heavy metal ions, phosphate and dichromate into it to simulate real life situation, it was found that the burette is a much more effective device.
Contents
Page
Introduction
1 - 2
Part I - Preparation of various adsorbents
IA - Preparation of hydrous ferric oxide (HFO)
IB - Preparation of Processed Hand Warmer Powder (HWP)
3 - 15
Part II - Investigating the effectiveness of anion adsorption on
various adsorbents
IIA - Determination of PO43-
adsorption
IIB - Determination of Cr2O72-
adsorption
16 - 37
Part III - Investigating the effectiveness of cation adsorption on
various adsorbents
IIIA - Determination of Zn2+
adsorption by EDTA titration
IIIB - Determination of Cu2+
and Ni 2+
adsorption by colorimetric
measurement
IIIC - Determination of Pb2+
adsorption by gravimetric analysis
through precipitation
IIID Determination of hardness adsorption by EDTA titration
38 - 77
Part IV Investigating the effectiveness of filtration device and the
regeneration of HFO in the device
78 - 89
Sources of Error and Suggestions for Improvements
90 - 93
Conclusion
94 - 97
References
98
P. 1
Introduction
Water pollution has been a serious problem worldwide. The clean water sources round the
globe have become very limited and waste water such as factory effluents contains many
pollutants like heavy metals ions, harming the wildlife and human environment when
discharged. Many people have been making an effort in finding new and better ways of
water treatment in order to reuse water. But so far most water treatment programs involve
a huge amount of resources and are very expensive even for both commercial and
domestic use.
After reading a number of academic papers as reference, we found that iron compounds
were claimed to be effective in adsorbing anions like phosphate as well as various heavy
metal ions such as copper(II) and nickel(II) ions, the major pollutants found in waste
water. Thus in this project, our group will try to explore a cheaper and more recyclable
way to treat water, using iron compounds. We will also make an attempt in using used
hand warmer powder with iron oxides as its main ingredient to treat waste water. Hand
warmer powder can be commonly found in households and so it would be a good
domestic adsorbent source.
In part I, we will first prepare hydrous ferric oxide (HFO) of different structures by
mixing iron(III) chloride solution and aqueous sodium hydroxide or ammonia and
varying the pH of the supernatant liquid. Since the chemical composition of used hand
warmer powder might be similar to that of HFO, we will identify substances present in
the powder, possibly unused iron, hydrous iron(III) oxide, activated carbon and
vermiculite, and try to isolate them. HFO prepared under different pH, hand warmer
powder of different brands, hand warmer powder treated with hydrochloric acid under
different conditions, iron filings, iron(III) oxide and activated carbon will later be tested
as adsorbents.
Vermiculite + Activated carbon
P. 2
In part II, we will focus on the effectiveness of anion adsorption. For part IIA, we will
investigate the effectiveness of the adsorbents mentioned above on phosphate adsorption
by colorimetric measurement with the addition of ammonium molybdate followed by
tin(II) chloride to the treated water samples. The phosphate content of each treated water
sample can be obtained by comparing the absorbance with a calibration curve.
For part IIB, we will investigate the effectiveness of dichromate adsorption on the
adsorbents mentioned above by colorimetric measurement as the colour intensity of
dichromate solution changes with its concentration. We will also investigate the effect
of time on dichromate solution adsorption of a particular adsorbent by varying the
duration of the adsorbent in contact with dichromate solution.
In part III, we will investigate the effectiveness of the adsorbents on heavy metal ions (e.g.
Cu2+
, Zn2+
, Pb2+
, Ni2+
) and hardness (i.e. Ca2+
, Mg2+
) adsorption. For part IIIA, the effect
of Zn2+
adsorption will be determined by carrying out titration against EDTA. For part
IIIB, the effect of Cu2+
, Ni2+
adsorption will be investigated by colorimetric measurement,
with the addition of ethane-1,2-diamine to the water samples containing Cu2+
and Ni2+
.
For part IIIC, the effect of Pb2+
adsorption will be investigated. Yellow precipitate will be
formed by adding excess KI solution to the treated water samples with Pb2+
. The
precipitate will then be allowed to dry and the Pb2+
content can then be determined
indirectly by measuring the dry mass of the precipitate of each sample. For part IIID,
the effect of Ca2+
, Mg2+
and hardness of mineral water adsorption will be determined by
carrying out titration against EDTA. We will also investigate the effect of time on Cu2+
solution adsorption of a particular adsorbent by varying the duration of the adsorbent in
contact with dichromate solution.
Our ultimate aim is to find out a way of treating hand warmer powder so that its
effectiveness in removing harmful substances in water is at its highest.
In part VI, we will determine the effectiveness of toxic ions removal by hand warmer
powder-packed columns. Known volumes of phosphate, dichromate, copper(II), zinc,
lead(II) and nickel(II) ion solutions will be allowed to pass through the
Warmergotchi-packed columns. The amount of the remaining anions / metal cations in
the resulting solutions will be determined by gravimetric measurement. Moreover, we
will also investigate the effectiveness of the regeneration of hydrous ferric oxide, by
adding dilute sulphuric acid to the adsorbents to reverse the reaction.
P. 3
Part IA Preparation of hydrous ferrous oxide (HFO)
Objective:
To prepare samples of hydrous ferrous oxide under different pH conditions
Principle:
Hydrous ferric oxide are obtained from reacting FeCl3(aq) with NaOH(aq) until the pH of
the supernatant liquid reached pH 5, pH 7 and pH 9. This is to investigate under which
pH would produce a hydrous ferric oxide of a high level of activity. To attain the desired
pH, the pH of the supernatant liquid is determined by using a pH paper, if the pH is too
low, dilute aqueous sodium hydroxide is added and when the pH is too high, dilute
hydrochloric acid is added as needed. HFO can also be produced by reacting FeCl3(aq)
with alkaline NH3(aq).
Fe3+
(aq) + 3OH(aq) Fe(OH)3(s)
The brown Fe(OH)3 precipitate is aged with the mother liquor for 5 days. Then, the
supernatant liquid is filtered under suction and the while being washed with water until
acid free. The aging of the reactant mixture and the washing steps as described are
important to develop the physical properties such as high surface area and abrasion
resistance of the final product. After filtering the precipitate under suction until shrinkage
of the precipitate is complete, it is dried at 60℃ in an air oven for sufficient duration to
reduce the water content of the product. If the drying step is initiated before sufficient
water has been removed by filtering under suction, the product will be too soft. The
product is then prepared for use by grinding.
Fe(OH)3(s) FeO(OH)(s) + H2O(l)
hydrous ferric oxide (HFO)
Chemicals used:
Anhydrous iron(III) chloride
1M sodium hydroxide solution
P. 4
1M ammonia solution
1M hydrochloric acid
Apparatus used:
Electronic balance
Glassware
Suction filter
Oven
Procedures:
1. 7.60g of anhydrous iron(III) chloride was
weighed accurately and was transferred to a large
beaker.
2. 1M sodium hydroxide solution was added to the anhydrous iron(III) chloride until
the pH value of the supernatant liquid has reached pH 5.
3. The above procedures were repeated and the pH values of the supernatants were
adjusted to pH 7, 9 and 11 respectively, in which suitable volumes of 1M
hydrochloric acid were added in order to adjust the pH.
4. 1M ammonia solution was used instead of 1M sodium hydroxide solution in one
condition under pH 7.
The mixtures were allowed to stand for 5 days.
pH 5
(NaOH)
pH 5
(NaOH) pH 7
(NaOH)
pH 9
(NaOH)
pH 11
(NaOH)
pH 7
(NH3)
P. 5
5. The mixtures were filtered under
suction and the residues were washed
and collected.
6. The residues were dried in the oven at 60˚C for about 12 hours, which were then
ground and weighed.
Results:
Mass of HFO obtained under different experimental conditions:
Batch Mass of
anhydrous FeCl3
(g)
1M NaOH
(cm3)
1M HCl
(cm3)
pH
value
Mass of HFO
made (g)
1 7.60 118 (NaOH) - 5 3.30
2 6.08 89.5 (NaOH) - 5 2.75
3 7.60 140.5 (NaOH) 1.25 7 5.18
4 7.60 285 (NH3) - 7 4.40
5 7.60 130 (NaOH) - 9 3.80
6 3.04 123.5 (NaOH) 65 11 1.31
P. 6
Discussion:
Results show that the yield of HFOs was the highest under the pH condition of pH 7. The
thickness and fineness of the solids were after the five-day period was observed to be
different for different pH conditions. The mass of solid after filtration and drying was
found to be the greatest for the condition under pH7. Thus, we found that pH 7 is a
favourable condition for the formation of HFO.
P. 7
The filtration procedure for the
condition of pH 5 was most
time-consuming and repetitive. Not
only did the mixture filter slowly, but
the residues of the condition pH 5
often passed through the filter paper
and entered the filtrate. It can be
deduced that the particle size of the
HFO formed under pH 5 was the
smallest, leading to easier blocking
and passing through of filter paper
pores. This may have an effect on the
adsorption ability of HFO due to an increased surface area.
As seen from the above photo, the supernatant liquid of the second
left beaker (Batch 2) appears to be quite reddish-brown. We
deduced that it may be due to experimental errors during the
adjustment of pH value. The actual pH of the supernatant liquid
may be below pH 5, or that the mixture was stirred excessively,
which results in a lot of iron(III) ions (reddish-brown in colour)
still in aqueous form without being precipitated out, thus giving
the supernatant liquid a reddish-brown colour. It can be deduced
that minimizing the mixing of the precipitate and supernatant
liquid was important to obtaining a higher yield of HFO.
By comparing the yields of batches 3 and 4, the HFO yield of batch 3 which used sodium
hydroxide was higher than that of batch 4 which used ammonia solution. Although 1.25
cm3 of 1M hydrochloric acid was added to the mixture in batch 3, this volume was
considered insignificant compared to the 140.5 cm3 of 1M sodium hydroxide present.
Therefore, we found that sodium hydroxide solution was a better alkali to be used in the
preparation of HFO than ammonia solution.
Batch 3
pH 7 (NaOH)
Batch 4
pH 7 (NH3)
P. 8
Part IB Preparation of Processed Hand Warmer Powder (HWP)
Objective:
To identify and isolate materials remained in used hand warmer powder by different
treatments.
Principle:
The materials remained in used hand warmers were isolated and investigated individually
for their adsorption effects. Used hand warmers usually consist of unused iron, hydrous
iron(III) oxide, NaCl, activated carbon, and vermiculite. Different treatments would be
used to find out which one would produce hand warmer packs with the best adsorption
effect.
Treatments: Changes in the amount of the following substances: Implications:
Fe Hydrous
ferric
oxide
Fe2O3 Vermiculite Activated
carbon
Dilute HCl
(2 hrs, 4 hrs, 6
hrs)
Reduced
*
Reduced
*
Unchanged Unchanged Unchanged Fe2O3 takes up a
much larger
proportion than Fe in
the known mass of
the treated hand
warmer
Dilute HCl +
Heat
(2 hrs, 4 hrs, 6
hrs)
Reduced
*
Reduced
*
Reduced
*
Unchanged Unchanged Fe2O3 takes up a
similar proportion as
Fe in the known mass
of the treated hand
warmer
Conc HCl
(2 hrs, 4 hrs, 6
hrs)
Almost
completely
removed
*
Almost
completely
removed
*
Almost
completely
removed
*
Unchanged Unchanged The treated hand
warmer contains
mostly vermiculite
and carbon, with very
little Fe and Fe2O3. Conc HCl
(48 hrs)
Completely
removed
Completely
removed
Completely
removed
Unchanged Unchanged The treated hand
warmer contains pure
vermiculite and carbon.
* The amount removed increases with time.
P. 9
The adsorption effects of iron powder, iron(III) oxide, and activated carbon available in
the laboratory would also be investigated to see which component in the hand warmer
powder with the best adsorption effect is mainly responsible for adsorbing the ions, and
to see with what treatment can the adsorption effect of used hand warmer powder be
optimized.
Chemical used:
2M hydrochloric acid
11M hydrochloric acid
Hand warmer powder (白元)
Apparatus used:
Hotplate magnetic stirrer
Suction filter
Oven
Electronic balance
Glassware
Procedures:
Treatment A
1. 300 cm3 of 2M hydrochloric acid
was added to 20.0g of used hand
warmer powder.
2. The mixture was allowed to stand for
2 hours.
3. The mixture was filtered under
suction and the residue was washed
and dried in an oven.
4. The above procedures were repeated
twice, where the mixtures stood for 4
hours and 6 hours respectively.
P. 10
Treatment B
1. 300 cm3 of 2M hydrochloric acid was added to 20.0g of used hand warmer
powder.
2. The mixture was heated at 60 ˚C for 2 hours.
3. The mixture was filtered under suction and the residue
was washed and dried in an oven.
4. The above procedures were repeated twice, where the
mixtures were heated for 4 hours and 6 hours respectively.
Treatment C
1. 300 cm3 of 2M hydrochloric acid was added to 20.0g of
used hand warmer powder.
2. The mixture was allowed to stand for 2 hours.
3. The mixture was filtered under suction and the residue was washed and dried in
an oven.
4. The above procedures were repeated twice, where the mixtures stood for 4 hours
and 6 hours respectively.
Treatment D
1. 200 cm3 of 11M hydrochloric acid was
added to 20.0 g of used hand warmer powder.
2. The mixture was allowed to stand for 2 days
in a fume cupboard till the remaining powder was no
longer magnetic.
3. The mixture was filtered under suction and
the residue was washed and dried in an oven.
P. 11
Results:
Mass of hand warmer powder (HWP) obtained after treatments
Batch of
HWP
(20.0g
each)
HCl added Time
(hours)
Heated?
(Y/N)
Mass of Processed
HWP made (g)
%
yield
(%)
Volume
(cm3)
Molarity
A1 300 2M 2 N 13.04 Average
12.70
63.52
A2 300 2M 4 N 13.48
A3 300 2M 6 N 11.59
B1 300 2M 2 Y(60 ˚C) 6.46 Average
6.803
34.02
B2 300 2M 4 Y(60 ˚C) 6.26
B3 300 2M 6 Y(60 ˚C) 7.69
C1 100 11M 2 N 6.06 Average
5.33
26.63
C2 100 11M 4 N 5.59
C3 100 11M 6 N 4.33
D 200 11M 48 N 3.22 Average
3.04
15.20
200 2M 48 N 2.86
A1 B1 C1 D
A2
A3
B2
B3
C2
C3
P. 12
Observations and inferences made on the HWP remained
Batch of HWP Treatment Observation Magnetic
Used hand
warmer
powder
-- a mixture of black powder, brown powder
and shiny solids
Yes
A add dil HCl solution turned green, colourless gas
bubbles evolved
Yes
B heat with dil
HCl
solution turned greenish yellow, colourless
gas bubbles evolved
Yes
C add conc HCl solution turned brown, colourless gas
bubbles evolved
slightly
D add conc HCl
(48 hrs)
solution turned brown, colourless gas
bubbles evolved
No
Used Hand Warmer Powder
P. 13
Discussion:
The hand warmer powder manufacturer claimed
that the hand warmer powder contained iron,
activated carbon, vermiculite, and sodium
chloride (assuming negligible mass). Thus we
deduced that the used hand warmer powder
contained unreacted iron, iron(III) oxide,
vermiculite, activated carbon and sodium
chloride. The series of treatments we conducted
allowed us to prepare samples of used hand
warmer powder which underwent different
treatments and enabled us to confirm the constituents present in each of them.
Based on the above results and observations, we made some deductions. If the resulting
powder is magnetic, it can be deduced that iron and iron(III) oxide may be present. The
presence of black powder may be due to the activated carbon. The appearances of shiny
solids may be due to the mineral vermiculite. Any
sodium chloride would have dissolved in the mixture
and thus would not be present in the processed HWP.
As for the original HWP, sodium chloride would also
dissolve in the aqueous solution in which the powder is
to be placed into for adsorption. Therefore, the
presence of sodium chloride can be negligible.
Deduced composition in processed HWP under different treatments
Batch of HWP Treatment Composition in remaining powder
original -- Fe + Fe2O3 +
vermiculite + activated C
A add dil. HCl traces of iron + mainly Fe2O3 +
vermiculite + activated C
B heat with dil. HCl traces of Fe + traces of Fe2O3 +
vermiculite + activated C
C add conc. HCl traces of Fe2O3
vermiculite + activated C
D add conc. HCl for 2
days
vermiculite + activated C
P. 14
Processed HWP
Together with the investigation of adsorption effects of
independent materials from the HWP, the adsorption effect of used
HWP under different treatments can be compared. By taking these
results into account when we are going to investigate the
adsorption effects on different ions, we can adjust our treatment for
the HWP to produce HWP with the most adsorption effects.
From the results of treatment A, it was observed that the solution
turned green and colourless gas bubbles evolved. We deduced that most iron has
dissolved in the acid to form Fe(II) ions, producing colourless gas bubbles giving the
solution a green colour. Since treatment A mainly removed iron, what remained in the
residue were traces of iron, mainly iron(III) oxide, vermiculite and activated carbon. In
our further investigations to be followed, if the adsorption effect of untreated used HWP
is higher than that of treatment A, then it can be deduced that iron has the ability to
adsorb. This could be confirmed by comparing the adsorption effect of iron powder
alone.
A1
A2
A3
B1
B2
B3
C1
C2
C3
D
P. 15
From the results of treatment B, the solution was observed
to be greenish-yellow. This shows that the amount of
iron(III) oxide that dissolved in acid to give yellowish Fe(III)
ions was greater than that in treatment A. Thus in the
processed HWP in treatment B, the proportion of iron and
iron(III) oxide would be similarly low. In our following
investigations, if the adsorption effect of processed HWP in
treatment A was much better than that in treatment B, it can
be deduced that iron(III) oxide was effective in adsorption.
For the processed HWP in treatments C and D, the composition in the remaining powder
should be similar, in which there only remains mainly vermiculite and activated carbon.
Since the treatment time for treatment C is shorter than that of D, there would probably
be more iron(III) oxide traces in C than in D. If our hypothesis, iron(III) oxide possesses
adsorption ability, is correct, then the adsorption effect of processed HWP from treatment
C would be better than that of D.
C1 D
P. 16
Part IIA PO43-
adsorption
Objective:
To investigate the effectiveness of PO43-
adsorption on various adsorbents by colorimetric
measurement
Principle:
Phosphate binds to hydrous ferric oxide through a direct ionic interaction between one or
two negatively charged oxygen ions on the phosphate with the ferric ions (Fe3+
) in the
solid. The figure below shows phosphate in solution bound via two ionic bonds, with the
displacement of hydroxide.
Since phosphate binging takes place at the surface of the HFO instead of deep below the
surface, the larger the surface area, the more phosphate the adsorbent can bind.
To investigate the effectiveness of adsorbing phosphates by adsorbents, the Molybdenum
Method is used. Phosphate in water combines with heptamolybdate to form a yellow
complex. When SnCl2(aq) is added, the yellow complex turns blue as the oxidation state
of molybdenum changes +6 to +5.
7H3PO4 + 12(NH4)6Mo7O24 + 51H+
→ 7(NH4)3PO4∙12MoO3 + 51NH4+ + 36H2O
Mo(VI)-yellow complex + Sn2+
→ Mo(V)-blue complex + Sn4+
The intensity of the blue colour produced is proportional to the amount of phosphate ions
present, and the absorbance can be measure using a colorimeter. A calibration curve
O
Fe
Fe
OH
OH
+ P
OH
O-
O
O- Fe
Fe
O
O
+ 2H2O + H+
O
P
OH
O
P. 17
would be first made with the colorimeter readings of PO43-
solutions with various
concentrations. By comparing the absorbance of the water samples treated with various
adsorbents with the calibration curve, the phosphate concentration in the solutions can be
obtained. The types of adsorbents used include the different forms of HFO prepared
previously so as to compare which method would create the best adsorbent for PO43-
.
Chemicals used:
Ammonium Molybdate ( (NH4)6Mo7O24.H2O)
Tin(II) chloride (SnCl2.2H2O)
Sodium phosphate (Na3PO4)
2M Hydrochloric acid (HCl)
11M Hydrochloric acid (HCl)
HFO 1 (prepared with NaOH at pH 5)
HFO 2 (prepared with NaOH at pH 5)
HFO 3 (prepared with NaOH at pH 7)
HFO 4 (prepared with NH3 at pH 7)
HFO 5 (prepared with NaOH at pH 9)
HFO 6 (prepared with NaOH at pH 11)
Iron filings (Fe)
Iron(III) oxide powder (Fe2O3)
Activated carbon
Vermiculite + activated carbon
A1 – Processed Hand warmer powder (treated with dilute HCl for 2 hours)
A2 – Processed Hand warmer powder (treated with dilute HCl for 4 hours)
A3 – Processed Hand warmer powder (treated with dilute HCl for 6 hours)
B1 – Processed Hand warmer powder (treated with dilute HCl with heat for 2 hours)
B2 – Processed Hand warmer powder (treated with dilute HCl with heat for 4 hours)
B3 – Processed Hand warmer powder (treated with dilute HCl with heat for 6 hours)
C1 – Processed Hand warmer powder (treated with concentrated HCl for 2 hours)
C2 – Processed Hand warmer powder (treated with concentrated HCl for 2 hours)
Ammonium Molybdate
Tin(II) chloride
Sodium phosphate
P. 18
C3 – Processed Hand warmer powder (treated with concentrated HCl for 2 hours)
Hand warmer powder (白元)
Hand warmer powder (ドうくん)
Hand warmer powder ( Warmergotchi)
Hand warmer powder ( Pocket Sun)
Hand warmer powder (ホカロン)
Various adsorbents
Apparatus used:
Electronic balance
Colorimeter
Glassware
P. 19
Procedures:
Preparation of ammonium molybdate solution
2.4g of (NH4)6Mo7O24.H2O (molar mass: 1235.86 g)was added to 100 cm3 1M
H2SO4(aq). The result solution has a concentration of 0.0194 M.
Preparation of Tin(II) chloride solution
1.0g of SnCl2(molar mass:325.63 g) was added to 100 cm3 1M HCl(aq). The result
solution has a concentration of 0.0307 M.
Colorimetric measurements of phosphate solutions
1. 0.5g of Na3PO4.12H2O was added to 250.0 cm3 of deionised water. Then the
standard solution of PO43-
(aq) was diluted in different ways listed as follows:
A. 5.0 cm3
of standard solution in 250.0 cm
3 of deionised water
B. 10.0 cm3
of standard solution in 250.0 cm3
of deionised water
C. 15.0 cm3
of standard. solution in 250.0 cm3
of deionised water
D. 20.0 cm3
of standard solution in 250.0 cm3
of deionised water
E. 25.0 cm3
of standard solution in 250.0 cm3
of deionised water
F. 35.0 cm3
of standard solution in 250.0 cm3
of deionised water
G. 45.0 cm3 of standard solution in 250.0 cm3 of deionised water
2. 25.0 cm3
of each solution was pipetted into a 100 cm3
beaker.
A B C D E F G
P. 20
3. 2.0 cm3 of 0.0194 M ammonium molybdate solution was added to each beaker.
4. 12.0 cm3 of 0.0307 M tin(II) chloride solution and 25.0 cm
3 of deionised water
were pipetted to each beaker.
5. The solutions were then transferred to the test tubes.
6. The colour intensities of the solutions were compared with a colorimeter.
Colorimetric measurements of phosphate solutions with various adsorbents
1. 20.0 cm3
of solution G was pipetted into each beaker containing
0.5 g of an adsorbent.
A B C D E F G
A B C D E F G
P. 21
2. The mixtures were allowed to stand for 9 hours.
3. The mixtures were filtered and the collected filtrate was made up to 30 cm3 with
deionised water.
5. 5.0 cm3 of filtrate was pipetted into a 100 cm
3 beaker.
6. 2.0 cm3 of 0.0194 M ammonium
molybdate, 12.0 cm3 of 0.0307
M SnCl2 and 25.0 cm3 of
deionised water were added into
each beaker.
7. The mixtures were transferred
into test tubes.
8. The colour intensities of the
mixtures were tested with a
colorimeter.
P. 22
Results:
Absorbance values of phosphate solutions A to G
Solutions A B C D E F G
Absorbance 0.18 0.34 0.50 0.65 0.85 0.95 1.40
Calibration Graph for Standard Phosphate Solution
A B C D E F G
P. 23
Absorbance of Various Phosphate Solutions after Adsorption
Adsorbent (20.0 cm3 diluted to 30.0
cm3)
Absorbance of
phosphate
solution
(Absorbance x
1.5)
% change in
absorbance
(#)
Concentration
of phosphate
solution
(× 10-4
mol dm-3
)
1. HFO 1 (NaOH, pH 5) 0.05 (0.075) -99.58% 0.37
2. HFO 2 (NaOH, pH 5) 0.02 (0.03) -98.33% 0.2888
3. HFO 3 (NaOH, pH 7) 0.06 (0.09) -95.00% 0.8664
4. HFO 4 (NH3, pH 7) 0.015 (0.0225) -98.75% 0.2166
5. HFO 5 (NaOH, pH 9) 0.33 (0.495) -72.50% 3.1962
6. HFO 6 (NaOH, pH 11) 0.31 (0.465) -74.17% 2.99
7. Hand warmer powder (白元) 0.54 (0.81) -55.00% 5.4236
8. Iron filings 0.98 (1.47) -18.33% 10.44
9. Iron(III) oxide powder 0.90 (1.35) -25.00% 9.50
10. Activated carbon 0.30 (0.450) -28.57% 9.40
11. Vermiculite + activated carbon 0.30 (0.45) -75.00% 2.888
12. A1 – Processed HWP (dil. HCl + 2 hr) 0.045 (0.0675) -96.25% 0.321
13. A2 – Processed HWP (dil. HCl + 4 hr) 0.15 (0.225) -87.50% 1.363
14. A3 – Processed HWP (dil. HCl + 6 hr) 0.03 (0.045) -97.50% 0.173
15. B1 – Processed HWP (dil. HCl + 2 hr + heat) 0.20 (0.30) -83.33% 1.87
16. B2 – Processed HWP (dil. HCl + 4 hr + heat) 0.75 (1.125) -37.50% 7.749
17. B3 – Processed HWP (dil. HCl + 6 hr + heat) 0.55 (0.825) -54.17% 5.532
18. C1 – Processed HWP (conc. HCl + 2 hr) 0.295 (0.4425) -75.42% 2.836
19. C2 – Processed HWP (conc. HCl + 4 hr) 0.26 (0.39) -78.33% 2.48
20. C3 – Processed HWP (conc. HCl + 6 hr) 0.30 (0.45) -75.00% 2.888
21. HWP (ドうくん) 0.22 (0.33) -81.67% 2.07
22. HWP ( Warmergotchi) 0.20 (0.3) -83.33% 1.866
23. HWP ( Pocket Sun) 0.70 (1.05) -41.67% 7.187
24. HWP (ホカロン) 0.34 (0.51) -71.67% 3.302
25. Control / (1.8) / 13.165
# = absorbance of phosphate solution after treatment – absorbance of control
absorbance of control × 100%
P. 24
Concentration of Phosphate Solutions after Adsorption by Different Adsorbents
(From left to right)
HFO pH5 (x2), pH7 (x2),pH 9, pH 11,
(From left to right)
Iron(III)oxide, iron filings, A1-3, B1-3, control
P. 25
Discussion:
From the graphs above, we can see that HFO 4 is most effective in the removal of
phosphate while activated carbon is least effective. The absorbance values of HFO were
the lowest in average, while those of processed hand warmer powder varied.
Among the HFO samples, we found that the absorbance of HFO treated in acidic or
neutral mediums (samples 1 to 4) were higher than that of HFO treated in an alkaline
medium (samples 5 to 6). But the general adsorption performance of HFO samples was
very satisfactory.
(From left to right)
HFO pH5
HFO pH5
HFO pH7
HFO pH7
HFO pH9
HFO pH11
Control
P. 26
The adsorption power of the original hand warmer powder sample (sample 7) was found
to be higher than those of iron filings, iron(III) oxide and activated carbon alone. But
since suspension was observed in the samples of iron filing and iron(III) oxide powder,
the absorbance values above could not accurately reflect their effectiveness in the
removal of phosphate alone. The effectiveness in the removal of phosphate is higher
when a mixture of the above ingredients is used.
(From left to right)
HWP (白元)
Iron fillings
Iron(III) oxide powder
Activated carbon
Vermiculite + activated carbon
Control
P. 27
Most of the treated hand warmer powder samples were found to be more effective
phosphate adsorbents than the original hand warmer powder. Among the processed hand
warmer powder samples (A1 to C3), the absorbance values of samples with the addition
of dilute HCl(A samples) were lower than those of samples with addition of concentrated
HCl or heating with dilute HCI. Referring to part I about the preparation of processed
hand warmer powder, samples C1 to C3 are mainly composed of vermiculite and
activated carbon. The experimental absorbance values of C samples matched with that of
the mixture of vermiculite and activated carbon. It is likely that C samples have similar
compositions.
As for samples A1 to B3, A samples mainly comprises iron(III) oxide, while B samples
contains more iron atoms and less iron(III) oxide in composition. As the absorbance
values of A samples were significantly lower than those of B samples, it can be deduced
that iron(III) oxide is more effective than iron in the removal of phosphate ions.
(From left to right)
A1, A2, A3
B1, B2, B3
control
P. 28
Among all hand warmer powder brands, Warmergotchi hand warmer powder was found
to be the most effective phosphate adsorbent while the lowest effectiveness was observe
for Pocket Sun hand warmer powder.
From the above data, we can see that some used hand warmer powder samples, like
sample 21 (ドうくん) and sample 22 (Warmergotchi), can also serve as effective
phosphate adsorbents, as compared to the percentage change in absorbance of HFO
samples.
To maximise the effectiveness of the hand warmer powder, the powder can be first treated
with dilute hydrochloric acid and allowed to stand for above 2 to 6 hours, since the
adsorption power of such treated samples have similar or even higher phosphate removal
power than HFO samples.
(From left to right)
HWP (白元)
HWP ( Pocket Sun)
HWP ( Warmergotchi)
HWP (ドうくん)
HWP (ホカロン)
Control
P. 29
Part IIB Cr2O72-
adsorption
Objective:
To investigate the effectiveness of Cr2O72-
adsorption on various adsorbents by
colorimetric measurement and the time effect on adsorption abilities.
Principle:
Dichromate ions are stable only in acidic medium and will be converted to chromate ions
at high pH:
Cr2O72-
+ H2O 2CrO42-
+ 2H+
When dichromate ions in the solution are in contact with the basic surface of HFO, the
chromate ions formed would then be absorbed by HFO according to the following
equation due to the high surface positive charge density of HFO. The an electrostatic
attractive force between the solid adsorbent and adsorbate causes the chromate ions to
bind to HFO.
To investigate the effectiveness of chromium(VI) adsorption of various adsorbents, the
colorimeter is used to measure the absorbance of the water samples, the lower the
absorbance, the more effective is the adsorbent used.
To investigate the effect of time on chromium(VI) adsorption of a particular adsorbent,
the time period for the adsorbent being in contact with dichromate solution is varied and
the absorbance values are compared.
O
Fe
Fe
OH
OH
+ Cr
OH
O-
O
O Fe
Fe
O
O
Cr + 2H2O + H+
O
O
O
P. 30
Chemicals used:
0.01M Potassium dichromate (K2Cr2O7)
Various adsorbents
Apparatus used:
Electronic balance
Colorimeter
Glassware
Procedures:
1. 25.0 cm3
of 0.01M K2Cr2O7 was added to 0.5g of different adsorbents in a
beaker.
2. The mixtures were allowed to stand for 9 hours. Solution samples containing
HFO at pH 7 and ホカロン hand warmer powder were allowed to stand for 1, 3,
5 and 7 hours respectively.
3. The mixtures were filtered and the filtrate collected was transferred into its
respective test tube.
4. The colour intensities of the mixtures were determined with a colorimeter.
P. 31
Results:
Dichromate adsorption:
Adsorbent absorbance % change in absorbance
1. HFO (NaOH, pH 5) 1.0 -50.00%
2. HFO (NaOH, pH 7) 0.85 -57.50%
3. HFO (NaOH, pH 9) 0.925 -53.75%
4. Hand warmer powder (白元) 1.50 -25.00%
5. Iron filings 2.0 0.00%
6. Iron(III) oxide powder 1.80 -10.00%
7. Activated carbon 1.30 -35.00%
8. Vermiculite + activated carbon 1.70 -15.00%
9. A2 - Processed HWP (dil. HCl + 4 hr) 1.75 -12.50%
10. B2 - Processed HWP (dil. HCl + 4 hr + heat) 1.80 -10.00%
11. C2 - Processed HWP (conc. HCl + 4 hr) 1.70 -15.00%
12. HWP (original, Pocket Sun) 1.50 -25.00%
13. HWP (original, Warmergotchi) 1.45 -27.50%
14. HWP (original, ドうくん) 1.30 -35.00%
15. HWP (original, ホカロン) 1.20 -40.00%
16. Control 2.0 /
# = absorbance of dichromate solution after treatment – absorbance of control
absorbance of control × 100%
P. 32
Time effect on dichromate adsorption:
Duration Cr2O7
2-
+ HFO (pH 7)
% change in
absorbance
Cr2O72-
+ HWP (ホカロン)
% change in
absorbance
Control 1.7 / 1. /
1 hr 1.4 -17.6% 1.7 0%
3 hr 1.2 -29.4% 1.6 -5.9%
5 hr 1.1 -35.3% 1.5 -11.8%
7 hr 0.9 -47.1% 1.5 -11.8%
Control HFO pH7 (1 hr→3hrs→5hrs→7hrs) HWP ホカロン(1 hr→3hrs→5hrs→7hrs)
P. 33
Discussion:
Dichromate absorption:
From the data above, HFO treated in a neutral medium (sample 2) was found to be most
effective in the removal of dichromate while iron filings (sample 5) were shown to be the
least effective adsorbents.
The average adsorption power of HFO was the highest among all absorbents. HFO
treated in neutral and alkaline mediums (samples 2 and 3) were found to have better
adsorption effects than that treated in an acidic medium (sample 1). It is likely that
neutral and alkaline mediums favour dichromate adsorption of HFO. Moreover,
dichromate ions are likely to be converted to chromate ions at high pH and therefore
absorbed by HFO.
(From left to right)
HFO (NaOH, pH 5)
HFO (NaOH, pH 7)
HFO (NaOH, pH 9)
Control
P. 34
According to the data above, the adsorption power to adsorb dichromate was found to be
higher for hand warmer powder than that of each ingredient. However, as suspension was
observed in the samples of iron filings and iron(III) oxide powder, the absorbance values
above could not accurately reflect their effectiveness in the removal of dichromate alone.
Compared with the sample with activated carbon alone, the effectiveness in the removal
of dichromate was found to be lower for the mixture of activated carbon and vermiculite.
It can be deduced that vermiculite is not effective or even hinders the removal of
dichromate.
(From left to right)
HWP (白元)
Iron filings
Iron(III) oxide powder
Activated carbon
Vermiculite + activated carbon
Control
P. 35
Among the treated hand warmer powder samples, the one treated with concentrated
hydrochloric acid (sample 11) had a slight higher dichromate adsorption power than the
other treated samples. However, the original hand warmer powder was found to be more
effective than all treated samples.
(From left to right)
HWP (白元)
A2
B2
C2
HWP (Pocket Sun)
HWP (Warmergotchi)
HWP (ドうくん)
HWP (ホカロン)
Control
P. 36
Among all the brands, hand warmer powder of brand ホカロン was shown to be the
most effective dichromate adsorbent.
Although the average dichromate adsorption power of HFO is the highest, some used
hand warmer powder samples, like sample 14 (ドうくん) and sample 15 (ホカロン)are
also very effective in the removal of dichromate. Thus they are also desirable dichromate
adsorbents because they are easily available for domestic use. They also save much time
and cost spent on the preparation of HFO.
For both and PO43-
and Cr2O72-
adsorption, HFO samples were found to be the most
effective adsorbents. Moreover, the hand warmer powder mixture works better than the
separate pure components do.
However, different treatments of hand warmer powder did not show a big discrepancy in
the effectiveness of dichromate removal, unlike the case in phosphate adsorption. In
dichromate adsorption case, the original hand warmer powder was found to be even more
effective than the treated samples. Thus we recommend used hand warmer powder of the
mentioned brands for phosphate and dichromate removal. As for phosphate removal, an
even more effective way will be treating the powder with dilute acid for 2 to 6 hours
before use.
P. 37
Time effect on dichromate absorption:
Regarding the optimum amount of time for the immersion of adsorbents in dichromate
ion solution, with HFO at pH7 as the adsorbent, the absorbance of the solution was found
to decrease with time. As for ホカロン being the adsorbent, adsorption was generally
more effective when the mixture was allowed to stand for a longer period of time.
However, the percentage decrease in absorbance remained unchanged after 5 hours.
P. 38
Part III Investigating the effectiveness of metal ions adsorption
on various adsorbents
The adsorption abilities of HFO on different metal ions is investigated. At an oxide
surface such as HFO, a surface functional group is typically represented as an amphoteric
hydroxyl group (e.g. =FeOH, =FeO-, =FeOH2
+). An electrostatic attraction arises from
the development of surface charge.
Zinc ions can be removed by HFO adsorption according to this equation.
>FeOH + Zn2+
(aq) → FeOZn+ + H
+(aq)
Copper(II) ions, nickel(II) ions and lead(II) ions are removed by HFO adsorption
according to this equation, similar to zinc ions reaction with HFO.
>FeOH + Cu2+
(aq) → FeOCu+ + H
+(aq)
>FeOH + Ni2+
(aq) → FeONi+ + H
+(aq)
>FeOH +Pb2+
(aq) → FeOPb+ + H
+(aq)
These ions can also be removed by displacement reaction when reacting with iron:
Fe + Cu2+
→ Fe2+
+ Cu
Fe+ Ni2+
→ Fe2+
+ Ni
Fe+ Pb2+
→ Fe2+
+ Pb
Activated carbon can also adsorb some of the metal ions since activated carbon has high
surface area. Individual particles are convoluted and display various kinds of porosity.
These micropores allow adsorption to occur, since adsorbing material can interact with
many surfaces simultaneously.
P. 39
Part IIIA Determination of Zn2+
adsorption by complexometric
titration
Objective:
To determine the effectiveness of Zn2+
adsorption on various adsorbents by
complexometric titration.
Principle:
Complexometric titration can be carried out to determine any change in the concentration
of Zn2+
in a given solution. Any decrease in the volume of burette solution
(ethylenediaminetetraacetic acid, also known as EDTA solution) used to reach the end
point would indicate that some Zn2+
has been adsorbed by the adsorbents.
To find out the adsorption effect of various adsorbents on Zn2+
, equal mass of each
adsorbent is allowed to stand for several hours in standard zinc sulphate solution. The
mixtures are then filtered to remove the adsorbents. Eriochrome Black T, which acts as an
indicator for the end point of the reaction, and buffer solution (pH 10), which regulates
the pH of the solution in the conical flask during the titration, is added to the diluted
filtrate in the conical flask. The standard ZnSO4 is treated similarly and is titrated against
EDTA along with the filtrate solutions, such that the volume of EDTA required for
complete reaction with the other solutions can be compared with it to determine whether
adsorption of zinc ions by the adsorbents have taken place. The reaction taking place was:
Zn2+
+ EDTA4-
→ ZnEDTA2-
wine red blue
Colour changes from wine red to light blue at the end point.
Chemicals used:
Various Adsorbents
0.01M ZnSO4 (aq)
0.01M EDTA solution
P. 40
pH10 NH3/ NH4Cl buffer solution
Eriochrome Black T
Deionized water
Apparatus used:
Glassware
Electronic balance
Procedures:
1. 25.0 cm3 of 0.01M ZnSO4 (aq) was added to a
250 cm3 volumetric flask with a pipette.
Deionized water was added up to the graduation
mark. 250.0 cm3 of 0.001M ZnSO4 (aq) was
obtained.
2. 50.0 cm3 of 0.01M EDTA solution was added to
a 250 cm3 volumetric flask with a pipette.
Deionized water was added up to the graduation
mark. 250.0 cm3 of 0.002M EDTA solution was
obtained.
3. 25.0 cm3 of 0.01M ZnSO4 (aq) was added to 0.5
g of each adsorbent and the mixture was allowed
to stand for 9 hours.
4. The mixture was filtered. The obtained filtrate
was made up to 250.0 cm3 in a 250 cm
3 volumetric
flask.
5. 25.0 cm3 of the diluted filtrate was added to a
clean conical flask with a pipette.
6. 4.0 cm3 of pH10 NH3/NH4Cl buffer solution was
added to the conical flask, followed by the addition of
0.1g Eriochrome Black T.
P. 41
7. The diluted filtrate was titrated against 0.002M EDTA solution. The end point was
reached when the colour of the filtrate changed from wine red to light blue.
8. 0.001M ZnSO4 (control) was also titrated against 0.002M EDTA solution.
Results:
1. HFO (NaOH, pH5)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 31.80 31.40 27.70
Initial reading (cm3) 4.90 4.30 0.90
Titre (cm3) 26.90 27.10 26.80
Mean titre (cm3) 26.93
2. HFO (NaOH, pH7)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 21.20 22.80 20.70
Initial reading (cm3) 2.80 4.30 2.20
Titre (cm3) 18.40 18.50 18.50
Mean titre (cm3) 18.47
3. HFO (NaOH, pH9)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 19.90 21.70 18.70
Initial reading (cm3) 3.70 5.50 2.60
Titre (cm3) 16.20 16.20 16.10
Mean titre (cm3) 16.17
P. 42
4. HWP (白元)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 25.10 25.10 47.90
Initial reading (cm3) 3.10 3.00 25.80
Titre (cm3) 22.00 22.10 22.10
Mean titre (cm3) 22.07
5. Iron fillings
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 22.50 21.40 25.70
Initial reading (cm3) 1.80 0.75 5.00
Titre (cm3) 20.70 20.65 20.70
Mean titre (cm3) 20.68
6. Iron(III) oxide
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 33.00 29.60 32.70
Initial reading (cm3) 6.40 3.00 6.20
Titre (cm3) 26.60 26.60 26.50
Mean titre (cm3) 26.56
7. Activated carbon
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 28.00 28.90 27.80
Initial reading (cm3) 1.40 2.40 1.30
Titre (cm3) 26.60 26.50 26.50
Mean titre (cm3) 26.53
8. Vermiculite + activated carbon
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 30.50 35.00 29.00
Initial reading (cm3) 5.10 9.50 3.40
Titre (cm3) 25.40 25.50 25.60
Mean titre (cm3) 25.53
9. A2 – Processed HWP (dil. HCl + 4hr)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 28.80 27.10 39.70
Initial reading (cm3) 3.80 2.00 14.50
Titre (cm3) 25.00 25.10 25.20
Mean titre (cm3) 25.10
P. 43
10. B2 – Processed HWP (dil. HCl + 4hr + heat)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 28.60 26.80 31.05
Initial reading (cm3) 2.40 0.60 4.75
Titre (cm3) 26.20 26.20 26.30
Mean titre (cm3) 26.23
11. C2 – Processed HWP (conc. HCl + 4hr)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 27.10 32.90 37.30
Initial reading (cm3) 1.10 6.90 11.40
Titre (cm3) 26.00 26.00 25.90
Mean titre (cm3) 25.96
12. HWP (ドうくん)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 20.25 38.00 20.70
Initial reading (cm3) 2.65 20.30 2.90
Titre (cm3) 17.60 17.70 17.80
Mean titre (cm3) 17.70
13. HWP (Warmergotchi)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 38.25 19.15 36.75
Initial reading (cm3) 20.75 1.50 19.15
Titre (cm3) 17.50 17.65 17.60
Mean titre (cm3) 17.58
14. HWP (Pocket Sun)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 17.10 32.85 18.55
Initial reading (cm3) 1.40 17.10 2.80
Titre (cm3) 15.70 15.75 15.75
Mean titre (cm3) 15.73
15. HWP (ホカロン)
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 41.00 24.20 23.95
Initial reading (cm3) 18.60 1.80 1.50
Titre (cm3) 22.4 22.4 22.45
Mean titre (cm3) 22.42
P. 44
12. Control
Titration 1 Titration 2 Titration 3
Final Reading (cm3) 29.20 28.00 30.60
Initial reading (cm3) 2.10 1.00 3.55
Titre (cm3) 27.10 27.00 27.05
Mean titre (cm3) 27.05
Discussion:
Combining the experimental results, we made the following ranking on the effectiveness
of Zn2+
adsorption on various adsorbents.
Rank No. Adsorbent Mean
Titre
(cm3)
% Change in
Mean Titre (#)
1. 14. HWP ( Pocket Sun) 15.74 -41.8%
2. 1. HFO (NaOH, pH 9) 16.167 -40.2%
3. 13. HWP ( Warmergotchi) 17.58 -35.0%
4. 12. HWP (ドうくん) 17.69 -34.6%
5. 2. HFO (NaOH, pH 7) 18.467 -31.7%
6. 3. Iron filings 20.68 -23.5%
7. 4. Hand warmer powder (白元) 22.07 -18.4%
8. 15. HWP (ホカロフ) 22.42 -17.1%
9. 5. A2 - Processed HWP (dil. HCl + 4 hr) 25.10 -7.21%
10. 6. Vermiculite + activated carbon 25.53 -5.62%
11. 7. C2 - Processed HWP (conc. HCl + 4 hr) 25.96 -4.03%
12. 8. B2 - Processed HWP (dil. HCl + 4 hr +
heat)
26.23 -3.03%
13. 9. Activated carbon 26.53 -1.92%
14. 10. Iron(III) oxide powder 26.56 -1.81%
15. 11. HFO (NaOH, pH 5) 26.93 -0.44%
16. 16. Control 27.05 /
(#) =
x 100% mean titre of zinc solution after treatment – mean titre of control
mean titre of control
P. 45
From the above table and graph, we can see that the untreated hand warmer powder
(Pocket Sun) gave the best result in adsorbing Zn2+
ions among all adsorbents, which was
even better than the results of the HFOs. Two other hand warmer powders were also
relatively effective in adsorbing Zn2+
ions as they reduced the amount of ions by around
35%, while HFO at pH9 reduced it by around 40%. Among the HFOs produced, HFO
(NaOH, pH 9) and HFO (NaOH, pH 7) had the best two effects in adsorbing Zn2+
ions.
Conversely, the HFO produced in acidic medium had extremely poor adsorption effects.
It was also found that the untreated hand warmer powder had better adsorption effects
than the treated ones. As for the components of the hand warmer powders, they had worse
adsorption effects than most of the original hand warmer powders, showing that the
original hand warmer powders which contain different components were more suitable
for adsorbing Zn2+
ions.
The best adsorbent for Zn2+
P. 46
Part IIIB Determination of Cu2+
and Ni2+
adsorption by
colorimetric measurement
Objective:
To determine the effectiveness of Cu2+
and Ni2+
adsorption on various adsorbents by
colorimetric measurement and the time effect on the adsorption abilities.
Principle:
To find out the reduction on copper(II) ions or nickel(II) ions by the various adsorbents, a
known volume of standard copper(II) sulphate solution or nickel(II) chloride solution is
added to the adsorbents and filtered. The filtrate is then treated with an excess of ethane-1,
2-diamine so that all the Cu2+
(aq) or Ni2+
(aq) can be converted to their corresponding
purple complex ions.
Cu2+
(aq) + 2H2NCH2CH2NH2 [Cu(H2NCH2CH2NH2)2]2+
(aq)
pale blue purple
Ni2+
(aq) + 3H2NCH2CH2NH2 [Ni(H2NCH2CH2NH2)3]2+
(aq)
green violet
The intensity of the purple colour produced is proportional to the amount of
copper(II) ions or nickel(II) ions present, and the absorbance can be
measured using a colorimeter. The colorimeter readings are compared with
that of the original solutions treated with ethane-1, 2-diamine, which act as
the control, to see if any copper(II) ions or nickel(II) ions have been
adsorbed.
To investigate the effect of time on Cu2+
adsorption of a particular adsorbent,
the time period for the adsorbent being in contact with dichromate solution is
varied and the absorbance values are compared.
Chemicals used:
0.1M ethane-1,2-diamine
0.01M CuSO4 (aq)
P. 47
0.01M NiSO4
Various adsorbents
Apparatus used:
Glassware
Electronic balance
Colorimeter
Procedures:
1. 25.0 cm3 of 0.01M CuSO4 (aq) was added to 0.5 g of
each adsorbent and the mixtures were allowed to stand
for 9 hours. In addition to this, solution samples
containing HFO at pH 9 and ホカロフ hand warmer
powder were allowed to stand for 1, 3, 5 and 7 hours
respectively.
2. The mixtures were filtered. 5.0 cm3 of each obtained
filtrate was mixed with 5.0 cm3 of 0.1M
ethane-1,2-diamine.
The mixtures were poured into test tubes respectively to obtain their absorbance in a
colorimeter.
3. Steps 1-3 were repeated with 0.01M NiSO4 and all mixtures were allowed to stand for
9 hours only.
P. 48
Results:
Copper adsorption:
Colorimetric measurement
0.01M Cu2+
0.01M Ni2+
Adsorbent absorbance absorbance
1. HFO (NaOH, pH 5) 0.37 0.05
2. HFO (NaOH, pH 7) 0.15 0.005
3. HFO (NaOH, pH 9) 0.07 0.035
4. Hand warmer powder (白元) 0.32 0.045
5. Iron filings 0.28 0.05
6. Iron(III) oxide powder 0.38 0.037
7. Activated carbon 0.22 0.04
8. Vermiculite + activated carbon 0.35 0.035
9. A2 - Processed HWP (dil HCl + 4 hr) 0.38 0.04
10. B2 - Processed HWP (dil HCl + 4 hr + heat) 0.37 0.044
11. C2 - Processed HWP (conc HCl + 4 hr) 0.36 0.05
12. Hand warmer powder (ドうくん) 0.39 0.055
13. Hand warmer powder (Warmergotchi) 0.34 0.048
14. Hand warmer powder (Pocket Sun) 0.20 0.044
15. Hand warmer powder (ホカロン) 0.23 0.023
16. Control 0.425 0.06
(From left to right)
Nickel solutions after adsorption
HFO (NaOH, pH 5), HFO (NaOH, pH 7), HFO (NaOH, pH 9), HWP (白
元), Iron filings, Iron(III) oxide powder, Activated carbon, Vermiculite +
activated carbon, A2, B2, C2, Control
P. 49
Time effect on copper adsorption:
Duration Cu
2+
+ HFO (pH 9)
% Change in
Absorbance
Cu2+
+ HWP (ホカロン)
% Change in
Absorbance
Control 0.38 / 0.38 /
1 hr 0.24 -36.8 0.34 -10.5
3 hr 0.19 -50.0 0.20 -47.4
5 hr 0.16 -57.9 0.17 -55.3
7 hr 0.14 -63.2 0.14 -63.2
Control HFO pH7 (1 hr→3hrs→5hrs→7hrs) HWP ホカロン(1 hr→3hrs→5hrs→7hrs)
P. 50
Discussion:
Copper adsorption:
Based on the experimental results, we made the following ranking on the effectiveness of
Cu2+
adsorption on various adsorbents.
Colorimetric Measurement
0.01M Cu2+
Rank No. Adsorbent Absorbance % Change in
Absorbance
(#)
1. 2. HFO (NaOH, pH 9) 0.07 -83.5
2. 3. HFO (NaOH, pH 7) 0.15 -64.7
3. 14. Hand warmer powder (Pocket Sun) 0.2 -52.9
4. 7. Activated carbon 0.22 -48.2
5. 15. Hand warmer powder (ホカロン) 0.23 -45.9
6. 5. Iron filings 0.28 -34.1
7. 4. Hand warmer powder (白元) 0.32 -24.7
8. 13. Hand warmer powder (Warmergotchi) 0.34 -20
9. 8. Vermiculite + activated carbon 0.35 -17.6
10. 11. C2 - Processed HWP
(conc HCl + 4 hr)
0.36 -15.3
11. 10. B2 - Processed HWP
(dil HCl + 4 hr + heat)
0.37 -12.9
1. HFO (NaOH, pH 5) 0.37 -12.9
12. 6. Iron(III) oxide powder 0.38 -10.6
9. A2 - Processed HWP
(dil HCl + 4 hr)
0.38 -10.6
13. 12. Hand warmer powder (ドうくん) 0.39 -8.2
16. 16. Control 0.425 /
(#) = absorbance of copper solution after treatment – absorbance of control
absorbance of control (From left to right)
HFO (NaOH, pH 5), HFO
(NaOH, pH 7), HFO (NaOH,
pH 9), Hand warmer powder
(白元), Iron filings, Iron(III)
oxide powder, Activated
carbon, Vermiculite +
activated carbon, A2, B2, C2,
Control
x 100%
P. 51
HFO at pH9 and HFO at pH7 were the best two adsorbents of Cu2+
ions among all
adsorbents while the effectiveness of HFO at pH5 was still far lower than that of HFO at
pH9 and HFO at pH7. As for the untreated hand warmer powders, although they were not
as effective as HFO at pH9 and HFO at pH7, two of them led to reduction in absorbance
by over 45%, showing that they can also be used to adsorb Cu2+
ions.
Most of the untreated hand warmer powder had better adsorption effects than the treated
ones. Also, the hand warmer powder named Pocket Sun had better adsorption effects than
the separate components of hand warmer powder.
(From left to right)
HFO (NaOH, pH 5), HFO (NaOH, pH 7), HFO (NaOH, pH 9), Hand warmer powder (白
元), Iron filings, Iron(III) oxide powder, Activated carbon, Vermiculite + activated carbon,
A2, B2, C2, Control
HWP ドうくん,
HWP Pocket Sun,
HWP Warmergotchi,
HWP ホカロン
HWP ドうくん,
HWP Pocket Sun,
HWP Warmergotchi,
HWP ホカロン
P. 52
Time effect on copper adsorption:
Concerning the optimum length of time for the immersion of absorbents in Cu2+
solution,
with HFO at pH9 as the adsorbent, the percentage decrease in absorbance was found to
increase with time. As for ホカロン being the adsorbent, adsorption was more effective
when the mixture was allowed to stand for a longer period of time. In short, the
percentage decrease in absorbance was found to increase with time for both adsorbents,
HFO at pH9 and ホカロン.
P. 53
For the effectiveness of Ni2+
adsorption on various adsorbents, the ranking is as follows:
Colorimetric Measurement
0.01M Ni2+
Rank No. Adsorbent Absorbance % Change in
Absorbance (#)
1. 2. HFO (NaOH, pH 7) 0.005 -91.7
2. 15. Hand warmer powder (ホカロン) 0.023 -61.7
3. 3. HFO (NaOH, pH 9) 0.035 -41.7
8. Vermiculite + activated carbon 0.035 -41.7
4. 6. Iron(III) oxide powder 0.037 -38.3
5. 7. Activated carbon 0.04 -33.3
9. A2 - Processed HWP
(dil HCl + 4 hr)
0.04 -33.3
6. 10. B2 - Processed HWP
(dil HCl + 4 hr + heat)
0.044 -26.7
7. 14. Hand warmer powder (Pocket Sun) 0.045 -25.0
4. Hand warmer powder (白元) 0.045 -25.0
8. 13. Hand warmer powder
(Warmergotchi)
0.048 -20
9. 1. HFO (NaOH, pH 5) 0.05 -16.7
5. Iron filings 0.05 -16.7
11. C2 - Processed HWP
(conc HCl + 4 hr)
0.05 -16.7
10. 12. Hand warmer powder (ドうくん) 0.055 -8.33
11. 16. Control 0.13 /
(#) = absorbance of nickel solution after treatment – absorbance of control
absorbance of control
(From left to right)
HFO (NaOH, pH 5), HFO
(NaOH, pH 7), HFO
(NaOH, pH 9), Hand
warmer powder ( 白 元 ),
Iron filings, Iron(III) oxide
powder, Activated carbon,
Vermiculite + activated
carbon, A2, B2, C2,
Control
x 100%
P. 54
The experimental results showed HFO at pH7 was the best adsorbent in adsorbing Ni2+
ions, followed by the untreated hand warmer powder ホカロン being the second best
adsorbent. The untreated hand warmer powder ホカロン led to a reduction of 61.7% in
absorbance, showing that it had better adsorption effects than HFO at pH9, components
of hand warmer powders and the treated hand warmer powders.
In adsorbing Ni2+
ions, two of the treated hand warmer powders (treated with dilute
hydrochloric acid for 4 hours, with and without heat) and three of the separate
components of hand warmer powders (vermiculite, activated carbon and iron(III) oxide
powder) performed better than some of the untreated hand warmer powder. Nevertheless,
it is important to note that the untreated hand warmer ホカロン is still quite effective in
adsorbing Ni2+
ions and can therefore be used to adsorb Ni2+
ions.
(From left to right)
HFO (NaOH, pH 5), HFO (NaOH, pH 7), HFO (NaOH, pH 9), Hand warmer powder (白元), Iron filings, Iron(III) oxide powder, Activated
carbon, Vermiculite + activated carbon, A2, B2, C2, Control, HWP ドうくん, HWP Pocket Sun, HWP Warmergotchi, HWP ホカロン
P. 55
Part IIIC Determination of Pb2+
adsorption by gravimetric
analysis through precipitation
Objective:
To determine the effectiveness of Pb2+
adsorption on various adsorbents by gravimetric
analysis through precipitation.
Principle:
To find out the reduction of Pb2+
by the various adsorbents, a known volume of Pb2+
solution is added to the adsorbents and filtered, same volume of an excess of potassium
iodide is added to the filtrate and yellow precipitates is formed.
Pb2+
(aq) + 2I(aq) PbI2(s)
colourless bright yellow ppt
The mixture is then filtered again to obtain the precipitates. The precipitates are washed,
dried and weighed. The mass of the precipitates is proportional to the number of moles of
Pb2+
present, lead(II) ions have been successfully adsorbed by the adsorbents if the mass
of the lead(II) iodide of a particular sample is lower than that of the control.
P. 56
Chemicals used:
Various adsorbents
0.01M Pb(NO3)2
0.2M KI
Apparatus used:
Glassware
Electronic balance
Stopwatches
Procedures:
1. 0.5 g of various adsorbents were added to 25.0 cm3 of
0.01 M Pb(NO3)2 and were allowed to stand for 9 hours.
2. 10 cm3 of 0.2M KI (in excess) was added to the filtrate
to precipitate out all the PbI2(s).
3. The mass of each dry filter paper was measured.
The mixture was filtered and the total mass of the filter
paper and the precipitate was measured after the filter
paper was dried.
4. The mass of precipitate was calculated.
Mass of precipitate (g) =
Total mass of filter paper and precipitate – Mass of each
dry filter paper
P. 57
Results:
Gravimetric analysis
0.01M Pb2+
Adsorbent Mass of precipitate (g)
1. HFO (NaOH, pH 5) 0.10
2. HFO (NaOH, pH 7) 0.12(*)
3. HFO (NaOH, pH 9) 0.10
4. Hand warmer powder (白元) 0.09
5. Iron filings 0.03
6. Iron(III) oxide powder 0.11
7. Activated carbon 0.10
8. Vermiculite + activated carbon 0.10
9. A2 - Processed HWP (dil HCl + 4 hr) 0.10
10. B2 - Processed HWP (dil HCl + 4 hr + heat) 0.11
11. C2 - Processed HWP (conc HCl + 4 hr) 0.10
12. Hand warmer powder (ドうくん) 0.12 (*)
13. Hand warmer powder (Warmergotchi) 0.10
14. Hand warmer powder (Pocket Sun) 0.11
15. Hand warmer powder (ホカロン) 0.10
16. Control 0.12
(*) The colour of the precipitate was not bright yellow, implying that the precipitate
may contain other compounds and so the mass of precipitate was greater than the
control.
(From left to right)
Control, HFO (NaOH, pH 5), HFO (NaOH, pH 7),
HFO (NaOH, pH 9)
Hand warmer powder (白元),A2, B2, C2
Activated carbon, Vermiculite + activated carbon,
Iron filings, Iron(III) oxide powder
HWP ドうくん, HWP Pocket Sun, HWP ホカ
ロフ, HWP Warmergotchi
P. 58
Discussion:
The effectiveness of Pb2+
adsorption on various adsorbents were compared and the
ranking is as follows:
Gravimetric Analysis
0.01M Pb2+
Rank No. Adsorbent Mass of
Precipitate (g)
% Change in Mass
of Precipitate (#)
1. 5. Iron filings 0.03 -75
2. 4. Hand warmer powder (白元) 0.09 -25
3. 1. HFO (NaOH, pH 5) 0.10 - 16.7
3. HFO (NaOH, pH 9) 0.10 - 16.7
7. Vermiculite + activated carbon 0.10 - 16.7
8. Activated carbon 0.10 - 16.7
9. A2 - Processed HWP (dil HCl + 4 hr) 0.10 - 16.7
11. C2 - Processed HWP (conc HCl + 4 hr) 0.10 - 16.7
13. Hand warmer powder (Warmergotchi) 0.10 - 16.7
15. Hand warmer powder (ホカロン) 0.10 - 16.7
4. 14. Hand warmer powder (Pocket Sun) 0.109 -9.2
5. 6. Iron(III) oxide powder 0.11 -8.3
10. B2 - Processed HWP (dil HCl + 4 hr +
heat)
0.11 -8.3
6. 12. Hand warmer powder (ドうくん) 0.12 0
2. HFO (NaOH, pH 7) 0.12(*) 0
7. 16. Control 0.12 /
(*) The colour of the precipitate was not bright yellow, implying that the precipitate may
contain other compounds and so the mass of precipitate was greater than the control.
(#) = mass of precipitate from lead(II) solution after treatment – mass of precipitate from control
mass of precipitate from control
adsorbance of control
(From left to right)
HFO (NaOH, pH 5), HFO (NaOH, pH 7), HFO (NaOH, pH 9), Hand warmer powder (白元), Iron filings,
Iron(III) oxide powder, Activated carbon, Vermiculite + activated carbon, A2, B2, C2, Control
x 100%
P. 59
In the case of adsorption of Pb2+
ions, iron filings was the best adsorbent since iron metal
effectively precipitates Pb2+
ions from its aqueous solution. The second best adsorbent,
untreated hand warmer powder (白元) had better adsorption effects than the HFOs and
the treated hand warmer powders. Some other used hand warmer powders like
Warmergotchi and ホカロン had similar adsorption effects as HFO at pH 5 and 9 and
components of used hand warmer powders like vermiculite and activated carbon. In short,
to adsorb Pb2+
ions, iron filings and the hand warmer powder (白元) are preferred to be
used.
P. 60
Combining results from part IIIA, IIIB and IIIC, we can see that among the HFOs
prepared, HFO(NaOH, pH 7) and HFO(NaOH, pH 9) were the two adsorbents with the
best effects in adsorbing Zn2+
, Cu2+
and Ni2+
ions. However, we noticed that another type
of HFO – HFO(NaOH, pH 5) had relatively
poor effectiveness in adsorbing Zn2+
and Cu2+
ions as compared to the other two HFOs. It was
especially poor in adsorbing Zn2+
ions and
could only reduce the amount of Zn2+
ions by
0.444%. This implies that the pH value of HFO
affects its effectiveness in adsorbing metal ions.
For instance, HFO produced in a neutral or
alkaline medium better adsorbs Zn2+
, Cu2+
and
Ni2+
ions.
Nevertheless, the effectiveness of Pb2+
adsorption on different HFOs was quite different
from that of Zn2+
, Cu2+
and Ni2+
adsorption. The
effectiveness of Pb2+
adsorption on HFO(NaOH,
pH 7) and HFO(NaOH, pH 9) was significantly
lower than that of Zn2+
, Cu2+
and Ni2+
ions
adsorption on them while the effectiveness of
Pb2+
adsorption on HFO(NaOH, pH 5) was still
quite low.
In short, among the three types of HFOs, HFO(NaOH, pH 9) was found to be the most
suitable in adsorbing Zn2+
and Cu2+
ions while HFO(NaOH, pH 7) was found to be the
most suitable in adsorbing Ni2+
ions. As for the adsorption of Pb2+
ions, considering the
fact that the amount of yield of HFO(NaOH, pH 9) during production was greater than
that of HFO(NaOH, pH 5), it was found to be the most appropriate in adsorbing Pb2+
ions.
The effectiveness of metal ions
adsorption on hand warmer powders was
another main focus of this part. It was
found that some used hand warmer
powder had similar or even better
adsorption effects than the HFOs in
P. 61
adsorbing metal ions. For example, in adsorbing Zn2+
ions, the hand warmer powder
(Pocket Sun) reduced the amount of ions by 41.8%, which was greater then the
percentage reduced by the HFOs. Therefore, the hand warmer powders are also effective
in adsorbing metal ions and may even have better adsorption effects than the HFOs.
Having known that hand warmer powders are effective in adsorbing metal ions, we
looked into whether treated or untreated hand warmer powders had better adsorption
effects. It was found that untreated hand warmer powders were generally more effective
in adsorbing Zn2+
and Cu2+
ions. For the adsorption of Ni2+
ions, the hand warmer
powder ホカロン reduced the amount of ions by 61.7% while the treated hand warmer
powders reduced the amount of ions by 25% on average only. While for the adsorption of
Pb2+
ions, the hand warmer powder (白元) performed better than the treated ones while
other hand warmer powders had similar adsorption effects as the treated ones. Therefore,
as most untreated hand warmer powders were more effective than the treated ones or had
similar adsorption effects as the treated ones, the untreated hand warmer powders are
more suitable for adsorbing metal ions so as to save resources for treating them.
P. 62
As the hand warmer powder is composed of
different substances, the adsorption effects of
these substances were investigated too to see
whether these separate pure components of hand
warmer powder adsorb better than the original
hand warmer powder. From the experimental
results, we noticed that for the five brands of hand
warmer powders investigated, most of them had
better or similar adsorption effects than their
components. For instance, 3 brands of hand
warmer powders investigated performed better
than their components in adsorbing Zn2+
ions.
This showed that the adsorption of metal ions
with the original hand warmer powders is
preferred to with the components of hand warmer
powders. Hence, costs and resources of separating
the components of used hand warmer powders
can be saved when preparing adsorbents for metal
ions adsorption.
P. 63
From all the results above, it was shown that
some of the used untreated hand warmer
powders were even more effective in
adsorbing metal ions than the HFOs. Thus, it
is a good idea to make use of used hand
warmer powders to remove pollutants from
industrial wastewater in order to conserve our
environment. This is because there is no cost
in using the used hand warmer powders
which are considered as waste and the used
hand warmer powders are not difficult to
obtain. Also, by using used hand warmer powders to remove pollutants in wastewater, the
volume of solid waste can be reduced which in turn reduce the pressure on the already
over-burdened landfills.
In order to put this environmentally-friendly idea into
practice, collection bins of used hand warmer powders
can be set up in various places, for instance, MTR
stations and lobbies of residential buildings so the
collected powders can be transported to different
sewage treatment station to remove pollutants from
wastewater.
P. 64
Part IIID Determination of hardness adsorption by EDTA
titration
Objective:
To investigate the adsorption ability of used hand warmer powder to remove hardness of
water.
Principle:
Natural mineral water contains calcium and magnesium ions, resulting in hardness of
water which brings about inconvenience in domestic water usage as well as
environmental problems. In this part, we investigated the ability of used hand warmer
powder to adsorb calcium and magnesium ions in both laboratory solutions and in
commercial mineral water. In order to determine the amount of calcium and magnesium
ions present, titration of the solution against a standard solution of
ethylenediaminetetraacetic acid (EDTA) can be carried out in alkaline medium based on
complexation reactions. Calcium and magnesium ions can be removed by adsorption
according to these equations.
>FeOH + Ca2+
(aq) → FeOCa+ + H
+(aq)
>FeOH + Mg2+
(aq) → FeOMg+ + H
+(aq)
In experiment A, the Ca2+
and Mg2+
adsorption ability of various adsorbents will be
investigated using laboratory reagents. Various adsorbents will be stood for several hours
in standard calcium and magnesium solutions respectively. Titration against EDTA
solution will be carried out to determine the concentration of calcium and magnesium
ions after treatment. Control experiments will be carried out for comparison of results. As
calcium ions, magnesium ions, calcium-EDTA complex and magnesium-EDTA complex
are colourless, a suitable indicator that will change colour at the equivalence point has to
be used. Eriochrome Black T. is chosen as the indicator, in which end point is reached
when the wine red colour changes into a blue colour in high pH. A buffer of
ammonium-ammonia at pH 10 will be added to maintain a steady pH value.
Ca2+
+ EDTA4-
→ CaEDTA2-
wine red blue
Mg2+
+ EDTA4-
→ MgEDTA2-
wine red blue
P. 65
In experiment B, the Ca2+
and Mg2+
adsorption ability of different brands of used hand
warmer powder will be investigated using a commercial brand of mineral water. Same
masses of used hand warmer powder will be stood in a fixed volume of mineral water for
several hours. Titration against EDTA solution will then be carried out as in experiment
A to determine the metal concentrations after the treatment.
Mineral water contains other metal ions apart from
calcium and magnesium. Since EDTA solution reacts
directly with many metal ions, the presence of other
metal ions in mineral water may interfere with the
result. The metal cations present in the commercial
brands of mineral water which are in relatively
significant amounts are Ca2+
, Mg2+
, Na+ and K
+. The
alkali metals, sodium and potassium, do not react with
EDTA solution thus their presence can be ignored.
Other metal ions would be precipitated out under high
pH and are not complexed by EDTA, thus their
presence can also be ignored. A control of unadsorbed
mineral water will be titrated as well for comparison. A
smaller volume of EDTA solution used for titration of
filtrates than the control would mean that there is a
reduction in calcium and magnesium ions after adsorption, thereby indicating that used
hand warmer powder is effective in removing hardness of water.
Chemicals used:
Various Adsorbents
0.01M CaCl2 (aq)
0.01M Mg(NO3)2 (aq)
0.01M EDTA solution
“No Frills” bottled mineral water
pH10 NH3/ NH4Cl buffer solution
Eriochrome Black T
Deionized water
P. 66
Apparatus used:
Glassware
Electronic balance
Procedures:
Experiment A
1. 25.0 cm3 of 0.01M CaCl2 (aq) was added to a 250 cm
3 volumetric flask with a pipette.
Deionized water was added up to the graduation mark. 250.0 cm3 of 0.001M CaCl2
(aq) was obtained.
2. 50.0 cm3 of 0.01M EDTA solution was added to a 250 cm
3 volumetric flask with a
pipette. Deionized water was added up to the graduation mark. 250.0 cm3 of 0.002M
EDTA solution was obtained.
3. 25.0 cm3 of 0.01M CaCl2 (aq) was added to 0.5 g of
each adsorbent and the mixture was allowed to stand for 9
hours.
4. The mixture was filtered. The obtained filtrate was made
up to 250.0 cm3 in a 250 cm
3 volumetric flask.
5. 25.0 cm3 of the diluted filtrate was added to a clean conical
flask with a pipette.
6. 4.0 cm3 of pH10 NH3/NH4Cl buffer solution was added to
the conical flask, followed by the addition of 0.1g
Eriochrome Black T.
P. 67
7. The diluted filtrate was titrated against 0.002M EDTA solution. The end point was
reached when the colour of the filtrate changed from wine red to blue.
8. 0.001M CaCl2 (aq) (control) was also titrated against 0.002M EDTA solution.
9. The above procedures were repeated using Mg(NO3)2 (aq) instead of CaCl2 (aq)
Experiment B
1. 1.0 g of each brand of used hand warmer powder was weighed
separately.
2. 50.0cm3
of “No Frills” mineral water was pipetted into each
sample of used hand warmer powder.
3. The mixture was left to stand for three and a half hours.
4. The mixture was filtered. The obtained filtrate was made up to
250.00 cm3 in a 250 cm
3 volumetric flask.
5. 25.0 cm3 of the diluted filtrate was added to a clean conical
flask with a pipette.
6. 4.0 cm3 of pH10 NH3/NH4Cl buffer solution was added to the
conical flask, followed by the addition of 0.1g Eriochrome
Black T.
7. The diluted filtrate was titrated against 0.002M EDTA solution. The end point was
reached when the colour of the filtrate changed from wine red to blue.
8. 50.0 cm3
of “No Frills” mineral water was pipetted into a 250cm3
volumetric flask and
made up to 250.0cm3 as the control.
9. 25.0 cm3
of the control solution was also titrated against 0.002M EDTA solution.
P. 68
Results:
Calcium ion adsorption titrations:
1. HFO pH 5
Titration 1 Titration 2 Titration 3
Final reading (cm3) 24.10 44.20 26.50
Initial reading (cm3) 3.80 24.10 6.30
Titre (cm3) 20.30 20.10 20.20
Mean titre (cm3) 20.20
2. HFO pH 7
Titration 1 Titration 2 Titration 3
Final reading (cm3) 27.10 24.60 28.20
Initial reading (cm3) 6.50 4.10 7.50
Titre (cm3) 20.60 20.50 20.70
Mean titre (cm3) 20.60
3. HFO pH9
Titration 1 Titration 2 Titration 3
Final reading (cm3) 33.10 17.00 31.20
Initial reading (cm3) 19.00 2.70 17.00
Titre (cm3) 14.10 14.30 14.20
Mean titre (cm3) 14.20
4. HWP (白元)
Titration 1 Titration 2 Titration 3
Final reading (cm3) 25.40 23.15 23.60
Initial reading (cm3) 7.10 4.70 5.30
Titre (cm3) 18.30 18.45 18.30
Mean titre (cm3) 18.35
5. Iron filings
Titration 1 Titration 2 Titration 3
Final reading (cm3) 21.60 25.65 35.10
Initial reading (cm3) 2.40 6.60 16.00
Titre (cm3) 19.20 19.05 19.10
Mean titre (cm3) 19.12
P. 69
6. Iron(III) oxide
Titration 1 Titration 2 Titration 3
Final reading (cm3) 25.50 23.90 21.75
Initial reading (cm3) 5.70 3.90 1.75
Titre (cm3) 19.80 20.00 20.00
Mean titre (cm3) 19.93
7. Activated carbon
Titration 1 Titration 2 Titration 3
Final reading (cm3) 24.40 25.60 21.10
Initial reading (cm3) 4.50 5.60 1.10
Titre (cm3) 19.90 20.00 20.00
Mean titre (cm3) 19.97
8. Vermiculite + Activated carbon
Titration 1 Titration 2 Titration 3
Final reading (cm3) 20.20 20.80 39.70
Initial reading (cm3) 1.20 1.70 20.80
Titre (cm3) 19.00 19.10 18.90
Mean titre (cm3) 19.00
9. A2
Titration 1 Titration 2 Titration 3
Final reading (cm3) 25.40 44.50 19.40
Initial reading (cm3) 6.35 25.40 0.70
Titre (cm3) 19.05 19.10 18.90
Mean titre (cm3) 19.02
10. B2
Titration 1 Titration 2 Titration 3
Final reading (cm3) 44.30 26.00 27.70
Initial reading (cm3) 25.90 7.50 9.10
Titre (cm3) 18.40 18.50 18.60
Mean titre (cm3) 18.50
11. C2
Titration 1 Titration 2 Titration 3
Final reading (cm3) 25.40 44.90 25.40
Initial reading (cm3) 6.10 25.40 6.10
Titre (cm3) 19.30 19.50 19.30
Mean titre (cm3) 19.37
P. 70
12. HWP (ドうくん)
Titration 1 Titration 2 Titration 3
Final reading (cm3) 22.40 23.00 23.80
Initial reading (cm3) 2.60 3.40 4.20
Titre (cm3) 19.80 19.60 19.60
Mean titre (cm3) 19.67
13. HWP (WarmerGotchi)
Titration 1 Titration 2 Titration 3
Final reading (cm3) 21.40 19.70 37.60
Initial reading (cm3) 3.30 1.70 19.70
Titre (cm3) 18.10 18.00 17.90
Mean titre (cm3) 18.00
14. HWP (Pocket Sun)
Titration 1 Titration 2 Titration 3
Final reading (cm3) 18.60 35.40 20.80
Initial reading (cm3) 1.70 18.60 3.80
Titre (cm3) 16.90 16.80 17.00
Mean titre (cm3) 16.90
15. HWP (ホカロフ)
Titration 1 Titration 2 Titration 3
Final reading (cm3) 25.90 28.70 39.40
Initial reading (cm3) 7.30 10.00 20.70
Titre (cm3) 18.60 18.70 18.70
Mean titre (cm3) 18.67
16. Control
Titration 1 Titration 3 Titration 3
Final reading (cm3) 23.00 22.30 41.90
Initial reading (cm3) 3.20 2.60 22.30
Titre (cm3) 19.80 19.70 19.60
Mean titre (cm3) 19.70
P. 71
Magnesium adsorption titrations:
1. HFO pH5
Titration 1 Titration 2 Titration 3
Final reading (cm3) 28.50 25.20 36.30
Initial reading (cm3) 5.10 2.00 12.90
Titre (cm3) 23.40 23.20 23.40
Mean titre (cm3) 23.33
2. HFO pH7
Titration 1 Titration 2 Titration 3
Final reading (cm3) 26.50 24.70 24.70
Initial reading (cm3) 2.30 0.65 0.50
Titre (cm3) 24.20 24.05 24.20
Mean titre (cm3) 24.15
3. HFO pH9
Titration 1 Titration 2 Titration 3
Final reading (cm3) 26.00 49.60 26.40
Initial reading (cm3) 1.00 24.70 1.60
Titre (cm3) 25.00 24.90 24.80
Mean titre (cm3) 24.90
4. Iron(III) oxide
Titration 1 Titration 2 Titration 3
Final reading (cm3) 24.40 25.60 47.00
Initial reading (cm3) 0.20 1.50 22.70
Titre (cm3) 24.20 24.10 24.30
Mean titre (cm3) 24.20
5. Activated carbon
Titration 1 Titration 2 Titration 3
Final reading (cm3) 39.30 35.50 35.90
Initial reading (cm3) 4.30 0.60 1.10
Titre (cm3) 35.00 34.90 34.80
Mean titre (cm3) 34.90
P. 72
6. Vermiculite + activated carbon
Titration 1 Titration 2 Titration 3
Final reading (cm3) 24.30 26.40 25.40
Initial reading (cm3) 0.60 2.90 1.80
Titre (cm3) 23.70 23.50 23.60
Mean titre (cm3) 23.60
7. A2
Titration 1 Titration 2 Titration 3
Final reading (cm3) 23.30 25.10 23.90
Initial reading (cm3) 1.20 3.05 1.80
Titre (cm3) 22.10 22.05 22.10
Mean titre (cm3) 22.08
8. B2
Titration 1 Titration 2 Titration 3
Final reading (cm3) 23.00 26.10 40.20
Initial reading (cm3) 0.85 3.90 18.30
Titre (cm3) 22.15 22.20 21.90
Mean titre (cm3) 22.08
9. C2
Titration 1 Titration 2 Titration 3
Final reading (cm3) 25.20 25.45 25.70
Initial reading (cm3) 1.35 1.40 1.80
Titre (cm3) 23.85 24.05 23.90
Mean titre (cm3) 23.93
10. Control
Titration 1 Titration 2 Titration 3
Final reading (cm3) 26.00 25.80 49.20
Initial reading (cm3) 0.70 0.70 24.20
Titre (cm3) 25.30 25.10 25.00
Mean titre (cm3) 25.13
P. 73
Mineral water hardness adsorption titrations:
1. HWP (白元)
2. HWP (ドうくん)
1 2 3 4
Final burette reading (cm3) 12.15 19.60 26.90 24.40
Initial burette reading (cm3) 4.55 12.25 19.60 27.00
Titre (cm3) 7.60 7.35 7.30 7.40
Mean titre (cm3) 7.35
3. HWP (Warmergotchi)
1 2 3
Final burette reading (cm3) 14.50 21.05 27.50
Initial burette reading (cm3) 7.85 14.50 21.05
Titre (cm3) 6.65 6.55 6.45
Mean titre (cm3) 6.55
4. HWP (Pocket Sun)
1 2 3 4
Final burette reading (cm3) 7.45 11.90 16.50 20.90
Initial burette reading (cm3) 2.20 7.40 12.20 16.55
Titre (cm3) 5.25 4.50 4.30 4.35
Mean titre (cm3) 4.38
5. HWP (ホカロン)
1 2 3
Final burette reading (cm3) 10.80 19.30 27.80
Initial burette reading (cm3) 2.20 10.80 19.30
Titre (cm3) 8.60 8.50 8.50
Mean titre (cm3) 8.53
6. HWP (Control)
1 2 3
Final burette reading (cm3) 14.60 25.40 35.80
Initial burette reading (cm3) 4.10 14.90 25.40
Titre (cm3) 10.50 10.50 10.40
Mean titre (cm3) 10.47
1 2 3
Final burette reading (cm3) 13.70 22.90 31.70
Initial burette reading (cm3) 5.10 14.40 23.10
Titre (cm3) 8.60 8.50 8.60
Mean titre (cm3) 8.57
P. 74
Discussion:
Effectiveness of Ca2+
adsorption:
From the above graph, it can be seen that most the mean titre for most adsorbents were
lower than that of control, indicating that there was a decrease in calcium content. Among
the different brands of used hand warmer powder, Pocket Sun has the best adsorption
effect while ドうくん has the poorest adsorption effect.
0
5
10
15
20
25
Mea
n t
itre
(c
m3)
Adsorbents
Mean Titre of Calcium Solutions after Treatment
Rank No. Adsorbent Mean Titre
(cm3)
% Change in
Mean Titre (#)
1. 3 HFO (NaOH, pH 9) 14.20 -27.9%
2. 14 HWP ( Pocket Sun) 16.90 -14.2%
3. 13 HWP ( Warmergotchi) 18.00 -8.6%
4. 4 Hand warmer powder (白元) 18.35 -6.9%
5. 10 B2 – Processed HWP (dil. HCl + 4 hr + heat) 18.50 -6.1%
6. 15 HWP (ホカロフ) 18.67 -5.2%
7. 8 Vermiculite + activated carbon 19.00 -3.6%
8. 9 A2 – Processed HWP (dil. HCl + 4 hr) 19.02 -3.5%
9. 5 Iron filings 19.12 -2.9%
10. 11 C2 – Processed HWP (conc. HCl + 4 hr) 19.37 -1.7%
11. 12 HWP (ドうくん) 19.67 -0.15%
12. 6 Iron(III) oxide powder (*suspension observed) 19.93 +1.2%
13. 7 Activated carbon 19.97 +1.4%
14. 1 HFO (NaOH, pH 5) 20.20 +2.5%
15. 2 HFO (NaOH, pH 7) 20.60 +4.6%
16. 16. Control 19.70 /
(#) =
x 100% mean titre of calcium solution after treatment – mean titre of control
mean titre of control
P. 75
Certain data obtained were found to be unusual, i.e. the mean titre obtained was even
higher than that of the control, which should not be the case because the concentration of
calcium ions should not be higher than that of the original solution it started with. To
explain this result, we hypothesized that some of the iron present in HFO may have
somehow dissolved into the calcium solution to form iron ions. Since EDTA reacts with
iron ions, the volume of EDTA solution used would be greater than that of calcium ions
alone.
Another possible explanation is due to experimental errors.
Effectiveness of Mg2+
adsorption:
0
5
10
15
20
25
HFO (NaOH,
pH 5)
HFO (NaOH,
pH 7)
HFO (NaOH,
pH9)
Control
Mea
n T
itre
(cm
3)
Adsorbents
Mean Titre of Calcium Solutions after
Treatment of HFOs
Rank No. Adsorbent Mean Titre
(cm3)
% Change in
Mean Titre (#)
1. 9 A2 – Processed HWP (dil. HCl + 4 hr) 22.08 -12.13%
2. 10 B2 – Processed HWP (dil. HCl + 4 hr + heat) 22.08 -12.13%
3. 1 HFO (NaOH, pH 5) 23.33 -7.16%
4. 8 Vermiculite + activated carbon 23.60 -6.09%
5. 11 C2 – Processed HWP (conc. HCl + 4 hr) 23.93 -4.78%
6. 2 HFO (NaOH, pH 7) 24.15 -3.90%
7. 6 Iron(III) oxide powder 24.20 -3.70%
8. 3 HFO (NaOH, pH 9) 24.90 -0.92%
9. 7 Activated carbon 34.90 +38.88%
10. 12. Control 25.13 /
(#) =
x 100% mean titre of magnesium solution after treatment – mean titre of control
mean titre of control
P. 76
From the above graph, we can see that processed hand warmer powder (dil. HCl + 4 hr)
and processed hand warmer powder (dil. HCl + 4 hr + heat) had the best two effects in
adsorbing Mg2+
ions among all adsorbents. However, a complete comparison among all
adsorbents was not possible since upon adding buffer solution of pH 10 to magnesium
solution treated by untreated used hand warmer powder, brown precipitate was observed.
Upon adding indicator, colour of solution turns brownish red instead of the usual wine
red, and upon adding EDTA solution, the solution turned light brown, the end point
cannot be easily detected. Thus, the Mg2+
adsorption ability of used hand warmer powder
was unable to be investigated.
Although experimental results were not able to be obtained, we are still able to deduce
the Mg2+
adsorption ability based on available data. With the exception of activated
carbon (in which the results were unusual for both calcium and magnesium), all other
data attained in the magnesium experiment showed positive adsorption results. After
comparison with the adsorption results of the same adsorbents in the calcium experiment,
it can be deduced that used hand warmer powder can adsorb magnesium ions as well,
because all the hand warmer powder were effective in adsorbing calcium ions.
0
5
10
15
20
25
30
35
40
HFO
(NaOH, pH 5)
HFO
(NaOH, pH 7)
HFO
(NaOH, pH9)
Iron(III)
oxide powder
Activated
carbon
Vermiculite
+ activated carbon
A2 -
Processed HWP (dil.
HCl + 4 hr)
B2 -
Processed HWP (dil.
HCl + 4 hr +
heat)
C2 -
Processed HWP (conc.
HCl + 4 hr)
Control
Mea
n T
itre
(cm
3)
Adsorbents
Mean Titre of Magnesium Solutions after Treatment
P. 77
Effectiveness of hardness adsorption from mineral water:
To confirm our conclusion drawn from experiment A which used laboratory reagents,
mineral water was also adsorbed. Results show that all brands of used hand warmer
powder investigated have positive adsorption results. Pocket Sun has the best adsorption
effect, which is consistent with experiment A.
Since EDTA solution reacts with both calcium and magnesium ions, the mean titre
obtained is a reflection of the overall sum of calcium and magnesium ions that have been
adsorbed. Thus, it is not possible to determine the actual decrease in concentration of the
respective two metal ions. Nonetheless, it can be concluded that there is a reduction in the
amount of calcium and magnesium ions after adsorption by used hand warmer powder.
Thus, used hand warmer powder is effective in removing hardness of water.
P. 78
Part IVA Investigating the effectiveness of filtration device
and the regeneration of HFO in the device
Objective:
To determine the effectiveness of toxic ions removal by hand warmer powder-packed
column.
Principles:
To find out the effectiveness of toxic ions removal by hand warmer powder-packed
column, a known volume of phosphate, dichromate, copper(II), zinc, lead(II) and
nickel(II) ion solutions are allowed to pass through the Warmergotchi-packed columns.
After washing the columns several times by deionized water, the amount of the remaining
anions / metal cations in the resulting solutions can be determined by gravimetric
measurement. For phosphate and dichromate, an excess of aqueous lead(II) nitrate is
added to the solutions in order to precipitate out any remained phosphate and chromate
ions as insoluble lead(II) phosphate and lead(II) chromate.
Pb2+
(aq) + PO43-
(aq)→ Pb3(PO4)2 (s)
Pb2+
(aq) + CrO42-
(aq) →PbCrO4 (s)
For metal cations, an excess of aqueous sodium carbonate is added to precipitate out any
remained metal ions as insoluble metal carbonates.
M2+
(aq) + CO32-
(aq) →MCO3 (s)
The precipitates are washed, dried and weighed. The mass of the precipitates is
proportional to the number of moles of phosphate or dichromate or metal ions unadsorbed,
if the ions have been successfully adsorbed by the Warmergotchi-packed column, the
mass of the precipitates would be lower than that of the control.
The reaction for the adsorption of cations by hydrous ferric oxide is as follows:
>FeOH + M2+
(aq) → FeOM+ + H
+(aq)
In order to regenerate hydrous ferric oxide, dilute sulphuric acid should be added to the
adsorbents to reverse the reaction.
P. 79
Chemicals used:
0.01M PbNO3 (aq), NiSO4 (aq), ZnSO4 (aq), K2Cr2O7 (aq), CuSO4 (aq), Na3PO4 (aq)
Hand warmer powder (Warmergotchi)
1M Na2CO3 (aq)
0.5M Pb(NO3)2 (aq)
Apparatus used:
Electronic balance
Glass wear
Procedures:
1. 15g of untreated used “Warmergotchi” hand warmer powder
was packed in each of six burettes as shown.
2. 25 cm3
of each ion solution was pipetted and allowed to run
through the packed hand warmer powder column for adsorption.
P. 80
3. The columns were washed for three times with 25 cm3 of deionised water each time.
4. The filtrate collected was treated with 0.5M Pb(NO3)2(aq) and 1M Na2CO3(aq)
respectively. The precipitates obtained were filtered under suction, washed and dried
in an oven.
5. The mass of the precipitate was weighed and compared with that generated from the
control solution.
Precipitates
formed by
lead(II) control
Precipitates
formed by treated
lead(II) solution
Precipitates
formed by zinc
control
Precipitates
formed by treated
zinc solution
Phosphate solution Dichromate solution
Metal ions solution
Precipitates
formed by
copper(II) control
Precipitates
formed by
nickel(II) control
Precipitates formed by
treated nickel(II) solution
Precipitates
formed by treated
nickel(II) solution
Precipitates formed
by treated
copper(II) solution
Precipitates formed
by dichromate
control
Precipitates formed
by treated
dichromate solution
Precipitates
formed by
phosphate control
Precipitates formed
by treated
phosphate solution
P. 81
Results:
Mass of precipitates formed by
control solution
Mass of precipitates formed by
solution treated by Warmergotchi
Lead(II) phosphate 1.89g 1.44g
Copper(II) carbonate 0.34g 0g
Zinc carbonate 0.30g 0.22g
Lead(II) carbonate 0.70g 0g
Nickel(II) carbonate 0.29g 0.02g
Lead(II) chromate 2.09g 1.20g
Discussion:
From the above table and graph, it can be shown that the Warmergotchi-packed column is
extremely effective in adsorbing different ions. Despite the success of adsorbing different
ions from solutions, it took a long time for some solutions, phosphate solution in
particular, to pass through the Warmergotchi-packed column, resulting in the formation of
iron ions precipitates which came from iron ions washed down from the Warmergotchi
column for treated phosphate, zinc and lead(II) ions solution.
P. 82
However, some solutions, such as copper(II) solution and nickel(II) solution took a
relatively shorter time to pass through the Warmergotchi-packed column. Nickel (II) and
copper(II) solution were therefore used for the second part of the experiment.
Separate nickel(II) solution was treated by the same Warmergotchi-packed column for
three times, the resulting mass of nickel(II) carbonate formed by reacting the filtrate with
sodium carbonate solution is as follows.
1st round 2
nd round 3
rd round Control
Mass 0.02g 0.18g 0.21g 0.29g
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
1st round 2nd round 3rd round Control
Mas
s
Mass of nickel(II) carbonate after different rounds of treatment
P. 83
Separate copper(II) solution was treated by another Warmergotchi-packed column for
three times, the resulting mass of copper(II) carbonate formed by reacting the filtrate with
sodium carbonate solution is as follows.
1st round 2
nd round 3
rd round Control
Mass 0g 0.2g 0.23g 0.34g
The results for both copper(II) and nickel(II) solutions show an increasing mass of
precipitates formed with increasing number of treatment using the same
Warmergotchi-packed column. This shows that the Warmergotchi-packed column
becomes less effective with increasing number of treatments.
1st round 2
nd round
3rd
round
Ni2
+
1st round 2
nd round
3rd
round Cu2+
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
1st round 2nd round 3rd round Control
Mas
s
Mass of copper(II) carbonate after different rounds of treatment
P. 84
Our group tried to regenerate the Warmergotchi-packed
column by adding dilute sulphuric acid to it. Copper(II)
solution was then added to the column. The resulting
solution showed a lighter blue colour than that of the
control solution, indicating that the regeneration was
successful.
Lighter
Cu2+
solution
treated by
regenerated
column
Control
Control
P. 85
Part IVB Comparing the effectiveness of burette columns and
compartmentalized container as filtration device
Objectives:
To compare the effectiveness of toxic ions removal by hand warmer powder-packed
column with that of a compartmentalized filtration device.
Principles:
To compare the effectiveness of ions adsorption by hand warmer powder packed in a
column or a compartmentalized filtration device, a known volume of a mixture of cations
solutions are allowed to pass through the Warmergotchi placed in the two devices. After
washing the columns several times by deionized water, the amount of the remaining
metal cations in the resulting solutions can be determined by gravimetric measurement.
An excess of aqueous sodium carbonate is added to precipitate out any remained metal
ions as insoluble metal carbonates.
M2+
(aq) + CO32-
(aq) →MCO3 (s)
The precipitates are washed, dried and weighed. The mass of the precipitates formed after
passing through the burette and the device are compared to see which is more effective.
Chemicals used:
0.05M NiNO3(aq), ZnNO3(aq), CuNO3(aq)
Hand warmer powder (Warmergotchi)
1M Na2CO3(aq)
Apparatus used:
Electronic balance
Glasswear
NiNO3 ZnNO3 CuNO3
P. 86
Procedures:
1. 50g of untreated used „Warmergotchi‟ hand warmer powder was packed into a burette
and filtration device.
2. 50cm3 of the cations mixture was allowed to run through the packed hand warmer
powder, another 100cm3
of it was allowed to run through the filtration device.
3. The column and the device was washed for three times with 25cm3 of deionized water
each time.
4. The filtrate collected was treated with 1M Na2CO3 (aq), the precipitates obtained
were filtered under suction, washed and dried in an oven.
5. The mass of the precipitate was weighed and compared with that generated from the
control solution.
6. The percentage change in mass for the burette and the filtration device was compared.
Results:
Device used Mass of precipitates
formed by control
solution
Mass of precipitates
formed by treated
solution
Percentage
change in mass
Burette column 0.86 0.04 -95.3%
Filtration device 2.76 2.58 -6%
Precipitates formed by cations
mixture treated by burette
column
Precipitates formed by
cations mixture control
Precipitates formed by
cations mixture control
Precipitates formed by cations
mixture treated by burette
column
Precipitates formed by
cations mixture control
Precipitates formed by cations
mixture treated by
compartmentalized filtration
device
P. 87
Discussion: In view of the long time taken for most
solutions to run through the entire burette,
another device was used for adsorbing
pollutants. Warmergotchi hand warmer powder
was placed in the device, and a mixture of
cations solution was poured into the device.
The cations solution contains nickel(II) nitrate
solution, copper(II) nitrate solution and zinc
nitrate solution. This is to test the
Warmergotchi-packed device‟s ability to
remove heavy metal ions. However, lead(II)
ions is not included in the solution because
upon adding lead(II) nitrate solution to the mixture, white precipitates are formed.
This may be due to impurities like SO42
or Cl present in nickel(II) nitrate, copper(II)
nitrate or zinc nitrate which form precipitate with the lead(II) ion.
The same cation solution
was added to another
burette packed with the
same mass of Warmergotchi
as the one in the device
mentioned above. Separate
cations solution was treated by
the same Warmergotchi-packed
column to see the whether the
column is still effective after
being used once.
The results show that the burette column is much more effective than the filtration device.
Despite the long time required for solution to pass through the burette column, the
increased contact time of pollutants with the adsorbents prove to be very effective in
removing the pollutants. Hence the burette column is a much better device for treating
water.
Control
Cations mixture
solution treated by
Warmergotchi
column for the 1st
round
Cations mixture
solution treated by the
same Warmergotchi
column for the 2nd
round
P. 88
Comparisons between different adsorbents
Adsorbents PO43
Cr2O72
Zn2+
Cu2+
Ni2+
Pb2+
Ca2+
Mg2+
Overall
score
HFO (NaOH,
pH 5)
☆☆☆☆☆ ☆☆☆☆☆ ☆ ☆☆ ☆ ☆☆ / ☆☆☆☆ 2.5
HFO (NaOH,
pH 7)
☆☆☆☆☆ ☆☆☆☆☆ ☆☆☆☆☆ ☆☆☆☆ ☆☆☆☆☆ / / ☆☆☆ 3.38
HFO (NaOH,
pH 9)
☆☆☆ ☆☆☆☆☆ ☆☆☆☆☆ ☆☆☆☆☆ ☆☆☆ ☆☆ ☆☆☆☆☆ ☆ 3.63
白元 (original) ☆☆ ☆☆☆ ☆☆☆☆ ☆☆☆ ☆☆ ☆☆ ☆☆☆ / 2.38
Iron filings ☆ / ☆☆☆☆ ☆☆☆ ☆ ☆☆☆☆☆ ☆☆ / 2
Iron(III) oxide
powder
☆ ☆☆ ☆ ☆☆ ☆☆☆ ☆ / ☆☆☆ 1.63
Activated
carbon
☆ ☆☆☆☆ ☆ ☆☆☆☆ ☆☆ ☆☆ / / 1.75
Vermiculite +
Activated
carbon
☆☆☆ ☆☆☆ ☆☆ ☆☆ ☆☆☆ ☆☆ ☆☆ ☆☆☆☆ 2.63
Processed hand
warmer powder
(dil. HCl + 4
hr)
☆☆☆☆ ☆☆ ☆☆ ☆☆ ☆☆ / ☆☆ ☆☆☆☆☆ 2.38
Processed hand
warmer powder
(dil. HCl + 4 hr
+ heat)
☆ ☆☆ ☆☆ ☆☆ ☆☆ ☆ ☆☆☆ ☆☆☆☆☆ 2.25
Processed hand
warmer powder
(conc. HCl + 4
hr)
☆☆☆ ☆☆ ☆☆ ☆☆ ☆ ☆☆ ☆☆ ☆☆☆ 2.13
HWP (original,
ドうくん)
☆☆☆☆ ☆☆☆☆ ☆☆☆☆☆ ☆ ☆☆☆☆ / ☆ / 2.38
HWP (original,
Warmergotchi)
☆☆☆☆ ☆☆☆ ☆☆☆☆☆ ☆☆ ☆☆☆☆☆ ☆☆ ☆☆☆☆ / 3.13
HWP (original,
Pocket Sun)
☆☆ ☆☆☆ ☆☆☆☆☆ ☆☆☆☆ ☆☆ ☆ ☆☆☆☆ / 2.63
HWP (original,
ホカロフ)
☆☆☆ ☆☆☆☆ ☆☆☆☆ ☆☆☆☆ ☆☆☆☆ ☆☆ ☆ / 2.75
Key:
☆☆☆☆☆: Lowest absorbance/ smallest mass of precipitates formed/ smallest titre
(Lowest concentration of an adsorbate)
☆: Highest absorbance/ smallest mass of precipitates formed/ smallest titre (Highest
concentration of an adsorbate)
/: Poor results (i.e. absorbance close to or higher than that of control; titre close to or greater
than that of control; mass of precipitates close to or greater than that of control)
P. 89
From the table above, it can be seen that HFO (NaOH, pH 9) is the most effective
adsorbent, while HFO (NaOH, pH 7) is the second most effective adsorbent. ホカロン,
Pocket Sun and mixture of vermiculite and activated carbon are also effective adsorbents.
The worst adsorbent is iron(III) oxide powder, followed by activated carbon. Iron filings,
processed hand warmer powder (conc. HCl + 4 hr) and processed hand warmer powder
(dil. HCl + 4 hr + heat) also perform poorly.
Although hand warmer powders do not perform as well as HFO, considering the fact that
used hand warmer powder shows good adsorption ability for phosphate ions, and also
ranks quite high among all the adsorbents used, with ホカロン at 3rd
place and Pocket
Sun at 4th
place, it is still useful to use used hand warmer powder to adsorb pollutants
from wastewater. This is particularly true because HFO, the most effective adsorbent, is
very time consuming to produce, whereas hand warmer powder is a domestic waste that
can be obtained easily. Moreover, hand warmer powder can be used to adsorb pollutants
directly since generally speaking, treated hand warmer powders do not perform better
than untreated ones.
P. 90
Sources of Error
Part IA: Preparation of hydrous ferric oxide (HFO)
1. The adjustment of pH value during the preparation of HFO may not be accurate
due to discrepancies in determining the colour of pH paper.
2. The addition of hydrochloric acid to adjust the pH of the supernatant liquid may
interfere with the formation of hydrous ferrous oxide.
3. There is mass loss during the transfer of hydrous ferrous oxide from filter papers
onto watch glasses for drying in the oven.
4. There is mass loss during the transfer of dried, grinded ferrous oxide from mortar
to watch glass for weighing.
Part IB: Preparation of Processed Hand Warmer Powder (HWP)
1. Although the hand warmer powder used in all four treatments is of the same brand,
the composition in different packets may be different, resulting in an unfair test.
2. There is mass loss during the transfer of processed hand warmer powder from
filter papers onto watch glasses for drying in the oven.
3. It is difficult to judge the proportion of iron and iron(III) ions present in the
mixture by just looking at the colour of the solution, so our deductions about the
composition in the various processed hand warmer powder may not be true.
4. There may be other substances present in the used hand warmer powder, apart
from those that we deduced, which may or may not affect the overall adsorption
ability of processed hand warmer powder.
Parts II: Investigating the effectiveness of anion adsorption on various adsorbents
1. The markings of the colorimeter were not fine enough that discrepancies among
the readings could not be observed or determined accurately.
2. Suspension was observed in some adsorbent samples and thus some colorimeter
readings were affected and could not reflect the actual situation.
3. The samples with phosphate or dichromate solution were allowed to stand for 9
hours without intermittent or continuous stirring. This may affect the adsorption
performance.
P. 91
Part III: Investigating the effectiveness of cation adsorption on various adsorbents
1. The end point of titration in Part IIIA was difficult
to detect and different people might have different
sensitivity to the end point.
2. In part IIIB, suspension was formed so the reading
from the colorimeter might not be accurate.
3. In Part IIIC, ions other than Pb2+
might be
precipitated out which contribute to the mass of
precipitate.
4. In Part IIID, the treated mineral water and the
EDTA solution were both diluted 5 times before
titration, any small amount of addition or loss of
mineral water or solution during handling of
chemicals would lead to a relatively high percentage of experimental error.
5. There may be impurities present in the solution which maybe react with EDTA
solution, resulting in an inaccurate determination of results in Part IIID.
Part IV: Investigating the effectiveness of filtration device and the regeneration of HFO
in the device
1. PO43-
, Cr2O72-
and metal ions solution took a long time to pass through the burette
columns, allowing iron compounds from the burette column to be dissolved in the
ions solution, resulting in the formation of brown precipitates after treatment of
the solution by the Warmergotchi column.
2. PO43-
, Cr2O72-
and metal ions cannot be completely washed out of the
Warmergotchi powder by 3 rounds of deionized water, particularly for the
compartmentalized device since deionized water used to wash the powder would
pass through the Warmergotchi powder much quicker than in the burette columns,
this result in an increase of the mass of the precipitates formed at the end of the
experiments.
P. 92
Suggestions for Improvements
Part IA: Preparation of hydrous ferric oxide (HFO)
1. Measure the pH of the supernatant using a pH meter.
2. Add sodium hydroxide solution slowly and gradually to prevent overshooting of
pH value of the supernatant liquid.
3. Instead of transferring the hydrous ferrous oxide from filter papers to watch
glasses, place the filter papers which hold wet hydrous ferrous oxide after
filtration into the oven for drying directly. The mass of dried hydrous ferric oxide
can be determined by the subtraction of the mass of the piece of filter paper which
has been initially weighed from the total mass of the filter paper and its contents
after drying.
4. After drying in the oven, obtain the mass of the dried hydrous ferrous oxide
before grinding by subtracting the mass of the watch glass from the total mass of
watch glass and its contents.
Part IB: Preparation of Processed Hand Warmer Powder (HWP)
1. Mix all the packets of the used hand warmer powder of the same brand together
and take out samples for treatments from this large batch, so as to ensure more
similar compositions for each sample.
2. Instead of transferring the processed hand warmer powder from filter papers to
watch glasses, place the filter papers which hold powder after filtration into the
oven for drying directly. The mass of dried powder can be determined by the
subtraction of the mass of the piece of filter paper which has been initially
weighed from the total mass of the filter paper and its contents after drying.
3. More conditions for treatments can be conducted on the used hand warmer
powder, such as using acid concentrations in between 2M and 11M or adopting
time lengths in between 2, 4 and 6 hours. Comparisons can be made easier and
more reliable to obtain more accurate deductions about the compositions of the
processed hand warmer powder.
Parts II: Investigating the effectiveness of anion adsorption on various adsorbents
1. Use a colorimeter with finer markings.
2. Use filter paper with finer pores when filtering the adsorbents.
3. Stir the mixtures at intervals evenly throughout the standing process.
P. 93
Part III: Investigating the effectiveness of cation adsorption on various adsorbents
1. Assign one person to carry out all titrations in order to reduce the errors caused by
human factors.
2. Instead of doing gravimetric analysis through precipitation in Part IIIC, use
another determination method to cross check the results.
3. A higher concentration of EDTA could be used to reduce the percentage error.
Another improvement is to perform the titrations for a larger number of times
such that a more reliable result can be obtained.
Part IV: Investigating the effectiveness of filtration device and the regeneration of HFO
in the device
1. Insert cotton wool intermittently between Warmergotchi powder in a burette
column to relieve the pressure from the lower part of the burette column,
resulting in a quicker flow of the ions solution, reducing the formation of brown
precipitates due to presence of iron ions.
2. Increase the number of washings to be carried out after each round.
P. 94
Conclusion
Part I: Preparation of various adsorbents
To create the adsorbents necessary to remove pollutants from water, our group has
chosen to synthesize hydrous ferric oxide from chemicals available in the laboratory
since according to other research, HFO is a successful adsorbent for many pollutants and
may also resemble the composition of hand warmer powder. Our group has also chosen a
second approach towards creating an adsorbent: To use used hand warmer powder to
adsorb pollutants, such that these materials can be recycled and used for water treatment.
In synthesizing HFO, it was noted that a supernatant liquid of pH 7 creates the most
amount of precipitates. A supernatant liquid of pH 5 creates precipitates that are too small,
though the surface area of the precipitates must be significantly greater, it is difficult to
collect. It was also noted that sodium hydroxide is a better solution to use than ammonia
solution since using sodium hydroxide solution would produce more precipitates.
Hand warmer powder was also used to adsorb pollutants. By using different treatments,
we were able to deduce roughly the composition of the hand warmer powder, and we
could use the treated hand warmer powder to carry out further experiments to test which
treatment produces the best adsorbents. Although the hand warmer powder may exhibit
weaker adsorption abilities, hand warmer powder is a domestic waste, and by putting the
used powder into good use, the powder will not be wasted and this is environmentally
friendly.
Part II: Investigating the effectiveness of PO43
and Cr2O72
adsorption on various
adsorbents
For PO43
adsorption, HFO (NH3, pH 7) is the most effective while iron filings is the least
effective. Generally speaking, HFO formed are most effective in adsorbing PO43
ions,
and while the adsorption ability of processed hand warmer powder and unprocessed hand
warmer powder varied, they are still comparable to that of HFO.
Among the HFO samples, HFO produced in an alkaline medium shows better adsorption
effects of phosphate ions than that in acidic or neutral medium. However, the general
adsorption performance of HFO samples is still very satisfactory.
pH 5
(NaOH)
pH 5
(NaOH) pH 7
(NaOH)
pH 9
(NaOH)
pH 11
(NaOH)
pH 7
(NH3)
P. 95
Among the processed hand warmer powder samples, those treated with dilute HCl was
found to be very effective in adsorbing PO43
ions, with the PO43
concentration reduced
by more that 90%. It was also found that iron(III) oxide is more effective than iron in the
removal of phosphate ions.
Among all hand warmer powder brands, WarmerGotChi
hand warmer powder was found to be the most effective
phosphate adsorbent while the lowest effectiveness was
observed for Pocket Sun hand warmer powder.
For Cr2O72
ions, HFO produced in a neutral medium
was found to be the most effective in the removal of
dichromate while iron filings were shown to be the least
effective adsorbents. It was also found that vermiculite is
not effective or even hinders the removal of dichromate.
For HFO, the average adsorption power was the highest among all absorbents. Moreover,
HFO produced in neutral and alkaline mediums were found to have better adsorption
effects than that produced in an acidic medium.
For hand warmer powder, it was found out that the original hand warmer powder is more
effective than all treated samples. For optimized adsorption effects, untreated hand
warmer powder should be used.
Among all the brands, hand warmer powder of brand ホカロン was
shown to be the most effective dichromate adsorbent while the lowest
effectiveness was observed for Pocket Sun hand warmer powder.
Although the average dichromate adsorption power of HFO is the
highest, some used hand warmer powder samples are also very
effective in the removal of dichromate.
P. 96
Part III: Investigating the effectiveness of metal ions adsorption on various adsorbents
HFO produced in a neutral or alkaline medium adsorbs Zn2+
, Cu2+
and Ni2+
ions better
than that of HFO produced in an acidic medium. For Pb2+
ions, HFO produced in acidic
and alkaline medium perform better than that in neutral medium.
It was found that among the three types of HFOs, HFO(NaOH, pH 9) is the most suitable
in adsorbing Zn2+
and Cu2+
ions while HFO(NaOH, pH 7) is found to be the most suitable
in adsorbing Ni2+
ions. As for the adsorption of Pb2+
ions, taking into consideration of the
fact that the amount of yield of HFO(NaOH, pH 9) during production was greater than
that of HFO(NaOH, pH 5), and the production of HFO (NaOH, pH 9) was much was
easier than that of HFO (NaOH, pH 5), HFO (NaOH, pH 9) was taken to be the most
effective HFO in adsorbing Pb2+
ions.
As for used hand warmer powder, they are shown to be just as effective in adsorbing
metal ions as HFOs. It was also found that with the exception of Ni2+
, untreated hand
warmer powders were more effective in adsorbing metal ions than untreated ones,
For Zn2+
ions, the most effective adsorbent is Pocket Sun. For Cu2+
, it is HFO synthesized
at pH 9, followed by Pocket Sun. For Ni2+
, it is Warmergotchi. For Pb2+
ions, iron filings
were the best adsorbent, followed by the hand warmer powder 白元. The adsorption
effect of the hand warmer powder, with the exception of Pocket Sun and ドうくん, were
even better than that of the HFOs and it was found that untreated hand warmer powders
adsorbed Pb2+
ions better than the treated ones.
Considering the adsorption effects of all the ions tested, HFO (NaOH, pH 9) is the best
adsorbent, followed closely by HFO (NaOH, pH 7). The weakest adsorbent is iron(III)
oxide, followed by activated carbon and iron filings.
Although the used hand warmer powders are not among the best adsorbents, they were
proved to be quite effective, in particular Warmergotchi and ホカロン, of negligible cost
and are easily available. They could be potential adsorbents to treat industrial wastewater.
HFO (NaOH, pH9) HFO (NaOH, pH7)
P. 97
Experiments on Ca2+
and Mg2+
were also carried out to test the effectiveness of hardness
removal of different adsorbents. For Ca2+
, HFO synthesized at pH 9 was most effective,
followed by untreated Pocket Sun. For Mg2+
, hand warmer powders processed by dilute
HCl performed the best, followed by HFO synthesized at pH 5.
Part IV: Investigating the effectiveness of filtration devices and the regeneration of HFO
in the device
A filtration device was made by packing Warmergotchi powder into a burette column. It
was found that such device is extremely effective in removing pollutants since it allows a
large contact area and long contact time for the adsorption of different ions, PO43
solution, Cr2O72
solution and all the other metal ions solution passed through the column
all showed a significant decrease in the mass of precipitates formed upon adding lead(II)
nitrate solution and sodium carbonate solution compared with that of the control.
Though the effectiveness of the Warmergotchi-packed column decreases with the number
of times a solution has run through it, regeneration of its adsorption ability was found to
be possible by passing the used column with dilute sulphuric acid.
In view of the solutions taking a long time to pass through the burette columns, a
compartmentalized device was used to see if this could replace the very effective burette
columns. It was found that the reduction in heavy metal ions after being treated in the
new device is significantly lower than that of the burette columns, indicating that such
device is not as effective as the burette column.
Despite the long time it takes for the solution to pass through the burette column, it is still
better to use the burette column to ensure a greater removal of pollutants from effluents.
Cu2+
1st round
Cu2+
2nd round
Cu2+
3rd
round Cu2+
2nd
round
Cu2+
1st round
P. 98
References
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Hydrous Ferric Oxide: An Adsorbent for Chromium(VI)-Contaminated Industrial
Wastewater Treatment. Water Environment Research. Department of Chemistry,
Presidency College, West Bengal, Kolkata, India.
De Jager, Pieter Christiaan. (2002) A phosphate sorption and desorption study on an acid
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Kersten, Michael; Kulik, Dmitrii A. (2005) Competitive Scavenging of Trace Metals by
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Ltd.
http://chemlab.truman.edu/CHEM222manual/pdf/edta.pdf
http://en.wikipedia.org/wiki/Complexometric_titration
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