Flocculation of Reactive Blue 19 (RB19) using Alum and the Effects of Catalysts Addition
Removal efficiency both of Color and COD will be
increased when amount Alum is increased however
efficiency will increase to a point that the increase is
insignificant, even if addition of Alum dosage is done. With
the use of Alum alone as the flocculent, the speed of
removed color is faster than COD. For example with 500mg
Alum, color removal efficiency is 84% and COD is
68%.With the support of catalyst Ca(OH)2, the
treatmentability of Alum can be improved up to around 22
% for concentration and 25% for COD.Ca(OH)2 produced
high sludge volume, so only use Ca(OH)2-like catalyst for
Alum, it is not recommended to use Ca(OH)2 alone in
treatment by flocculation. In using large amount Ca(OH)2 ,
pH will increase and probably above 7.5, adjustment of pH
should be done to promote flocculation process. With the
use of PACl as catalyst, the treatment ability of Alum can
be improved up to around 35 % for concentration and 37%
for COD. When using PACl, use only a small amount to
make the removal efficiency increase significantly for both
Color and COD.PACl is able to create the larger flocks, the
polluting matter can branch this flocks and aids for settling.
It is advantageous to use PACl to shorten the treating time
and consequently save construction costs (tank, barrel
smaller).PACl is not a chemically corrosive, so it is good
for equipments in the treatment process. In conclusion,
using PACl instead of other chemical in flocculation is
recommended.
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International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-2, Mar-Apr- 2018
ISSN: 2456-1878
www.ijeab.com Page | 358
Flocculation of Reactive Blue 19 (RB19) using
Alum and the Effects of Catalysts Addition
Le Phu Tuan1, Vu Thi Kim Oanh1, Le Duy Khuong2, Nguyen Hai Hoa1, Alfienido S. Burce3
1Vietnam National University of Forestry
2Ha Long University
3University of the Philippines, Diliman
Abstract— There are a variety of primary coagulants which
can be used in a water treatment plant. One of the earliest,
and still the most extensively used, is aluminum sulfate, also
known as alum. Aluminum Sulfate (Alum) is one of the most
commonly used flocculent in waste water treatment
processes. Effectiveness of Alum in flocculation process is
determined by many factors such as the effluents pH,
flocculent dose as well as the use of catalyst to improve
efficiency rate of flocculation. Hence special attention to
these factors especially the use of catalyst has been brought
about by this study. Experiments were carried out using
Reactive Blue 19 Dye as the contaminant of waste water
and two catalysts namely Calcium Hydroxide (CaOH2) and
Poly Aluminum Chloride (PACl) were evaluated. The
results obtained proved that indeed after addition of
catalysts, removal efficiency rates of Alum can be increased
up to 25% using Calcium Hydroxide and up to 35% using
Poly Aluminum Chloride compared to Alum alone. The
optimum conditions for this study were at pH 5.5 ~7.5, 300
mg/L of Alum 30seconds of rapid mixing time with 300 rpm
, 30rpm of mixing rate for 5 minutes and 30 minutes of
settling time. Moreover, Alum showed the highest
performance under these conditions and using 50 mg/L
PACl as catalyst with 98.52% of COD reduction and
90.60% of color reduction. In conclusion, Alum with the
support of PACl as catalyst is an effective coagulant, which
can reduce the level of COD and Dye Color in Reactive
Blue 19 contaminated wastewater.
Keywords— Alum, Reactive Blue 19, Calcium Hydroxide,
Poly Aluminum Chloride and Flocculation.
I. INTRODUCTION
Flocculation is the process of forming larger agglomerates
of particles in suspension orof small agglomerates already
formed as a result of coagulation through high molecular
weight polymeric materials.[1] Flocculation is used in
applications such as water purification, sewage treatment,
cheese production, and brewing. It is also used in surface
and physical chemistry, biology, and civil engineering.
Flocculent describes a chemical or substance that promotes
flocculation and usually has a positive
charge.[2]Flocculation occurs when small particles in a
solution lose their repelling forces and begin to attract one
another. The small particles then bond together to form
“flocks” or “flakes.” Under most circumstances, a
flocculent is necessary to begin the flocculation process.
The most common flocculents are iron, aluminum,
magnesium, and calcium. When flocks are fully formed,
they can be removed from the solution they are in through
traditional filtration methods.[3]
Example:
Aluminum:
Simple : Al2(SO4)3. 18H2O (using for experiment)
Double: AlK3(SO4)3.18H2O and Al(NH4)3(SO4)3.18H2O
Iron: FeCl3. 6H2O and FeSO4. 7H2O
Hydrolysis process of Al2(SO4)3. 18H2O
After put alum into waste water, hydrolysis reaction
occurs as follows
Step 1 Al3+ + H2O = Al(OH)2+ + H+
Step 2 Al(OH)2+ + H2O = Al(OH)2+ + H+
Step 3 Al(OH)2+ + H2O = Al(OH)3 + H+
Total Al3+ + 3H2O = Al(OH)3 + 3 H+
General reaction: Al2(SO4)3 + 6H2O =
2Al(OH)3* + 3H2SO4
The attractive forces between the flocculation substance and
the pollutants in wastewater are the force Vander Walls,
creation of solid particles with larger size and easily settled
down by the gravity.With flocculation process, no chemical
reaction occurs which absorbs only physical.
Influence pH to the flocculation process in using Al2(SO4)3.
- pH < 4.5: Flocculating process will not occur
- 5.5 < pH < 7.5: good for flocculating process
- 7.5 < pH: decreased efficiency
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-2, Mar-Apr- 2018
ISSN: 2456-1878
www.ijeab.com Page | 359
Reactive Blue 19 (RB19) was chosen for this study because
it is most commonly used material for dying cotton, wood,
and silk with molecular weight 626.54 corresponds to 2-(3-
(4-Amino-9,10-dihydro-3-sulpho-9,10-dioxoanthracen-4-
yl)aminobenzenesulphonyl)vinyl)disodium sulphate. The
structure of the Reactive Blue 19 is given as below.[4]
Fig.1: Molecular Structure of Reactive Blue 19 (RB19)
II. MATERIALS AND METHODS
2.1 Sample preparation and materials
A 1000ppm stock solution of RB19 was used to prepare 20
liters of 10ppm concentration waste water. After about 10
mins of homogenous mixing,1-liter sample was
immediately transferred to each of the Jars of the Jar Test
Equipment.
2.2 Flocculent and catalysts preparation
Stock solution of Aluminum Sulfate (Alum) should be
prepared before starting the experiment. 100 g of Alum was
pulverized and dissolved to 1 liter in a volumetric Flask and
is well shaken to ensure that the Alum is well dissolved.
Calcium Hydroxide and PolyAluminum Chloride were
prepared from reagent bottles and weighted with an
Analytical Balance starting from 25mg for Ca(OH)2 with
25mg increments and 50mg for PACl with 10mg
increments respectively.
2.3 Jar Test
A conventional jar test apparatus was used in the
experiments to coagulate sample of RB19 solution by using
Alum, Alum with Ca(OH)2 and Alum with PACl. It was
carried out as a batch test, accommodating a series of six
beakers together with six-spindle steel paddles. Besides, the
sample of wastewater was adjusted from the initial pH 3.6
to pH about 7.5 in the experiments due to flocculation will
not occurin an acidic aqueous phases. The pH was
controlled by adding either strong acid (HCl) or strong base
(NaOH). Before fractionated into the beakers containing 1L
of solution each, the samples of wastewater were mixed
homogeneously. Then, the samples ought to be measured
for Absorbance and COD for representing an initial
concentration. After the desired amount of Alum was added
each of the solutions, the beakers were agitated at constant
mixing time and speed, which consist of rapid mixing (300
rpm) for 30 seconds and slow mixing (30 rpm) for 5
minutes. After the agitation being stopped, the suspension
was allowed to settle for 30 minutes. Finally, a sample was
withdrawn using a pipette from the top inch of supernatant
for Absorbance and COD measurements which representing
the final concentration. All tests were performed at an
ambient temperature in the range of 26-30°C. In the
experiment, the study was conducted by varying a few
experimental parameters, which were Alum dosage (100-
500 mg/L) and Catalyst, for Ca(OH)2 dosage(25-150 mg/L)
and PACl dosage(10-50mg/L) in order to study their effect
in flocculation and obtain the optimum condition for each
parameter as well as the best catalyst to be used.
2.4 Data Analysis
The COD test was performed by colorimetric method using
HACH Model DR/890 Colorimeter and HACH COD Vials
High Range (HR). It is used to measure the oxygen demand
for the oxidation of organic matters by a strong chemical
oxidant which is equivalent to the amount of organic
matters in sample. Moreover, Absorbance was measured by
using UV-VIS Spectrophotometer SP-300 Plus which the
sample was filled into a sample cell and put into the cell
holder for measurement. While the pH of wastewater was
measured by using a digital Horiba pH meter F-21. The pH
meter was calibrated by using buffer solutions of pH 4.0
and pH 7.0 before starting the experiments.
III. RESULTS AND DISCUSSIONS
Studies on the effects of Alum dosage and the use of
Catalysts are the experiments which were conducted in
order to investigate the optimum capacity of Alum in
flocculation process. Since the Chemical Oxygen Demand
(COD) level inRB19 contaminated wastewater is
considered as the most important parameter, so it has been
used as the indicator on the flocculation capacity of Alum in
these experiments by supporting with other important
parameter which is RB19 concentration in terms of
absorbance.
3.1 Effect of Alum dosage
Dosage was one of the most important parameters that has
been considered to determine the optimum condition for the
performance of Alum in flocculation. Basically, insufficient
dosage or overdosing would result in the poor performance
in flocculation. Therefore, it was crucial to determine the
optimum dosage in order to minimize the dosing cost and
obtain the optimum performance in treatment.The effect of
dosage was analyzed at pH 7.5, 300 rpm of mixing rate for
30 seconds and 30 rpm of mixing rate for 5 minutes and 30
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-2, Mar-Apr- 2018
ISSN: 2456-1878
www.ijeab.com Page | 360
minutes of settling time for a range of Alum dosage which
varied from 100 mg/l to 500 mg/l. Besides, the sample of
wastewater was adjusted from the initial pH of 3.6 to pH 7.5
due to flocculation will not occur in acidic aqueous
phases.[5]
(a) (b)
(c) (d)
Fig.2: Effects of Alum dosage on (a) Color and Concentration (b) Color removal efficiency(c)COD Concentration (d)COD
Removal Efficiency.
The results were presented in Figure 2(a) which showed the
effects of Alum dosage on Color in terms of Absorbance
and Concentration of RB19. While Figure 2(b) showed the
effects of Alum dosage on RB19 color removal efficiency
in percentage reduction. Figure 2(c) showed the effects of
Alum dosage on COD concentration in mg/L. While Figure
2(d) showed the effects of Alum dosage on RB19 COD
removal efficiency in percentage reduction.
From the jar test experiment, Removal efficiency for both
Color and COD will be increased when amount of Alum is
increased, however efficiency will increase to a point that
the increase is insignificant, even if addition of Alum
dosage is done.For the Alum dosage of 300 mg/L, Alum
recorded the optimum reduction of parameters, which were
the reduction of 84.57% and 68.45 % for Color and COD
respectively. Therefore, the optimum Alum dosage in this
research was 300 mg/L.
3.2 Effect of Catalysts
Addition of catalysts Calcium Hydroxide (Ca(OH)2) and
PolyAluminum (PACl) was evaluated using a controlled
dosage of Alum which is 300mg/L. The same conditions
apply for the rotational stirring speed, agitation and settling
time from previous experiment. The range of dosage used
for Ca(OH)2 is from 25mg/L to 150 mg/L with 25mg/L
increments while for PACL is from 10mg/L to 50mg/L with
10mg/L increments. pH level is also controlled by adding
either strong acid (HCl) or strong base (NaOH).
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-2, Mar-Apr- 2018
ISSN: 2456-1878
www.ijeab.com Page | 361
(a) (b)
(c) (d)
(e) (f)
Figure 2. Effects of Catalysts on Color and Concentration for(a)Ca(OH)2,(b)PACl, COD removal for (c)Ca(OH)2, (d)PACl and
Comparison of Ca(OH)2 and PACl on (e)Color removal efficiency and (f)COD removal efficiency.
The results were presented in Figure 3(a) which showed the
effects of addition of Ca(OH)2 on Color in terms of
Absorbance and RB19 concentration. While Figure 3(b)
showed the effects of addition of PACl dosage on Color in
terms of absorbance and RB19 concentration. The effects
on COD removal for addition of Ca(OH)2 and PACl is
shown in Figure 3(c) and 3(d) respectively. Figure 3(e) and
3(f) showed a comparison between Ca(OH)2 versus PACl in
terms of Color and COD Removal efficiencies.
From the jar test experiment, the curves for the both Color
and COD graphs were decreasing as catalyst dosage is
increased. Removal efficiency for both Color and COD will
be increased when amount of catalysts is increased,
however efficiency will increase to a point that the increase
is insignificant, even if addition of catalyst dose is done. For
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-2, Mar-Apr- 2018
ISSN: 2456-1878
www.ijeab.com Page | 362
the Ca(OH)2 dosage of 100 mg/L, Ca(OH)2 recorded the
optimum reduction of parameters, which were the reduction
of 95.03% and 78.96% for Color and COD respectively. For
the PACl dosage of 50mg/L, PACl recorded the highest
reduction of parameters, which were the reduction of
98.52% and 90.60% for Color and COD respectively.
Therefore, the best catalyst to support Alum in flocculation
process is PACl with a dosage of 50mg/L.
IV. CONCLUSION
Removal efficiency both of Color and COD will be
increased when amount Alum is increased however
efficiency will increase to a point that the increase is
insignificant, even if addition of Alum dosage is done. With
the use of Alum alone as the flocculent, the speed of
removed color is faster than COD. For example with 500mg
Alum, color removal efficiency is 84% and COD is
68%.With the support of catalyst Ca(OH)2, the
treatmentability of Alum can be improved up to around 22
% for concentration and 25% for COD.Ca(OH)2 produced
high sludge volume, so only use Ca(OH)2-like catalyst for
Alum, it is not recommended to use Ca(OH)2 alone in
treatment by flocculation. In using large amount Ca(OH)2 ,
pH will increase and probably above 7.5, adjustment of pH
should be done to promote flocculation process. With the
use of PACl as catalyst, the treatment ability of Alum can
be improved up to around 35 % for concentration and 37%
for COD. When using PACl, use only a small amount to
make the removal efficiency increase significantly for both
Color and COD.PACl is able to create the larger flocks, the
polluting matter can branch this flocks and aids for settling.
It is advantageous to use PACl to shorten the treating time
and consequently save construction costs (tank, barrel
smaller).PACl is not a chemically corrosive, so it is good
for equipments in the treatment process. In conclusion,
using PACl instead of other chemical in flocculation is
recommended.
REFERENCES
[1] M.A. Hughes., Coagulation and Flocculation, Part 1,
in Solid-Liquid Separation, 3rd ed., L.Svarosky, (ed),
Butterworth & Co (Publishers) Ltd,1990, 74.
[2] Samuel D. Faust, Osman M. Aly (1999). Chemistry of
water treatment (2nd ed. ed.). Chelsea, MI: Ann Arbor
Press. ISBN 9781575040110.
[3] Victor K. Lamer., Theory of Flocculation, Subsidence
and Refiltration of Colloidal Dispersions Flocculated
by Polyelectrolyte. Columbia University, New York,
N.Y.
[4] Droste, R. L., Theory and Practice of Water and
Wastewater Treatment, John Wiley & Sons, New
York,1997, pp. 384-415.
[5] Corbitt, R. A. 1990, The Standard Handbook of
Environmental Engineering, McGraw-Hill, New York,
pp. 6.92; 9.25.
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