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(Mohammad et al., 2013). The dye under
investigation, Tartrazine (otherwise known asE102
or FD&C Yellow 5) is a coal-tar derivative that is
used to colour foods, cosmetics, and other
products, it is a lemon yellow azo dye used as a
food colouring. It is found in certain brands of
fruit squashes, fruit cordial, coloured fizzy drinks,
instant puddings, cake mixes, custard powder,
soups, sauces, ice cream, ice lollies, sweets,
chewing gum, marzipan, jam, jelly, marmalade,
mustard, yoghurt and many convenience foods
together with glycerin, lemon and honey products.
It is cheaper than beta carotene and therefore used
as an alternative to beta carotene to achieve similar
colour. The water-soluble Tartrazine is used in
drugs especially shells of medicinal capsules,
syrups and cosmetics. It has a yellow menace,
whose wide use in industry and its water-soluble
nature maximizes its chances to be as contaminant
in industrial effluents. It catalyzes the
hyperactivity and other behavioral problems like
asthma, migranes, thyroid cancer, etc .Because of
its hazardous health effects, foods and drinks
containing Tartrazine are avoided. The present
study is aimed at to its removal from a wastewater
using Electrocoagulation technique. The study has
been carried out under different variables, like
electrolyte concentration, pH, different potential
and dye concentration and a convenient and
economically viable process has been developed
by involving an iron and steel electrodes (Alok et
al., 2007).
However, various physical–chemical
techniques, such as chemical coagulation,
adsorption, reverse osmosis and ultrafiltration,
were available for the treatment of aqueous
streams to eliminate dyes. But those later are
limited by the low concentration ranges that can be
treated coupled with the high concentrations in
reject streams. Further, the main drawback of
chemical coagulation process is the addition of
excess chemicals. In recent years, ozonation and
photo oxidation have been proposed as alternative
methods to the high cost of these methods which
leads to further consideration. Indeed,
electrochemical method has been successfully
tested to deal with dyeing wastewater. But as for
some dyes, which have good water solubility and
small molecule weight, traditional electrochemical
ways do not work effectively. Electrocoagulation
is a process consisting of creating metallic
hydroxide flocs within the wastewater by electro
dissolution of soluble anodes, usually constituted
by iron or aluminium. This method has been
practiced for most of the 20th century. Recently,
there has been renewed interest in the use of
electrocoagulation owing to the increase in
environmental restrictions on effluent wastewater.
Indeed, electro coagulation has been tested
successfully to treat urban wastewater, restaurant
wastewater and oil–water emulsion. It has also
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been used to remove clay suspension and heavy
metal (Zaroual et al., 2006) .
Electrocoagulation (EC) is regarded as a
potentially effective method for treating textile
wastewater with high decolourization efficiency
and relatively little sludge formation. Several
researchers reported treatments of dye wastewater
based on the EC method. EC with metallic
electrodes is a technique using a current to
dissolve metal such as Fe, steel or Al sacrificial
anodes immersed in polluted water, giving rise
corresponding metal ions to form Fe (II) and/or Fe
(III) or Al(III) species with hydroxide ions.
Depending on pH, these species act as coagulants,
leading the contaminates to coagulate. In general,
the following processes take place during the EC
treatment :
1. Electrode reactions to produces metal ions from
Fe electrode and H2 gas atthe cathode
At the anode
M → Mn+
+ ne-
At the cathode
2 H+
+ 2e- _______
H2
where M is the metal and n is the number of
electrons transferred for the formation of
coagulants in the wastewater.
The removal of dyes with coagulants by
sedimentation or by electro flotation with evolved
H2(g). While other electrochemical reactions
involving reduction of organic impurities and
metal ions at the cathode and coagulation of
colloidal particles (Mohammad et al., (2013).
Electrocoagulation is a technology that has been
being developed in recent years and represents an
alternative method for these industries waste water
treatment. It have several comparative advantages
if compared to traditional technologies to study the
removal of azoic tartrazine dye from aqueous
solutions .Simulated waste water with different
concentrations of tartrazine was treated with
electrocoagulation process. For this purpose: pH,
potential and treatment time was monitored. This
study results establish the technical feasibility of
electrocoagulation process and used to remove
color from aqueous solutions under optimized
dosing and pH control.
MATERIALS AND METHODS
In the present investigation, samples of simulated
wastewater were treated in the presence of NaCl
which act as electrolyte. Experiments were
proceeded, at a laboratory scale, in cell equipped
with iron and steel electrodes acting as (anode and
cathode respectively with 9x3cm2
area each).
Nearly 500cm3
(30 mg/L-70mg/L) wastewater was
placed in the electrolytic cell. At the end of the
experiment, the solution was filtered and analyzed
by T80 UV/VIS spectrometer. Apparent colour of
samples was determined by measuring the average
absorbance at 425 nm by using T80 UV/VIS
spectrometer. pH of the solution was determined
with the passage of electrolysis time.
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Electrolytic assembly
RESULTS AND DISCUSSION
Effect of Electrocoagulation Time and
Concentration for the Removal of Dye
The Table no 1-5 represents the variation in the
absorbance and pH of Tartazine dye solution with
respect to time and change in dye concentration.
The absorbance was decreased with the increase in
electrolysis time which is in good agreement with
literature. After 70min, about 50% decolourization
efficiency of effluent was achieved by electrolysis
process. The concentration of dye was varied from
30-68 mg/L. Graphical study from figures no.1-5
it was observed that at low concentration the
system was in basic medium and at high
concentration it was in acidic medium. At 52 mg/L
change in pH was very small and at 30 mg/L large
changes in pH was observed. K-factor corresponds
to the concentration of dye after the electrolysis
process.
This is a simple quantitation method (K-factor
method) used when the absorbance and
concentration are directly proportional
(Concentration = K × Absorbance), and a
conversion factor K is given.
Effect of Electrolysis Potential on pH and
Absorbance of Dye Solutions
The evolution of absorbance at 425 nm with the
variation of electrolysis potential from 1-15 volts
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is represented in Table 6. It shows that the
decolourization of effluent is not changing rapidly
with the increase in electrolysis potential. The
change in absorbance was not significantly
changed due to variation in potential. The
evolution of absorbance at 425 nm with
electrolysis potential from 1-15 volts is
represented in Fig. 6. It shows that the
decolourization of effluent is not rapidly changed
with the increased in electrolysis potential. The
Figure.7 represents that the pH of the system was
nearly neutral during potential scan.
Effect of Electrolysis Time on pH
The variations of pH of the solution during
electrolysis are shown in Figure. 1-5. From Figure
1, it can be observed that the pH of the effluent
changed with the electrolysis time.
Table 1: Effect of pH by the variation in time and concentration of Tartrazine Dye(68mg/L)
s.no Time(min) pH Absorbance K -Factor color
1 0 6.73 1.752 17.515 Pale Yellow
2 10 7.13 1.378 13.778 PaleYellow
3 20 7.69 0.853 8.527 PaleYellow
4 30 7.54 0.764 7.640 LightYellow
5 40 7.12 0.805 8.0521 LightYellow
6 50 7.04 0.871 8.7102 LightYellow
7 60 7.00 0.842 8.4201 LightYellow
8 70 6.84 0.789 7.8901 LightYellow
Table 2: Effect of pH by the variation in time and concentration of Tartrazine Dye(60mg/L)
s.no Time(min) pH Absorbance K -Factor color
1 0 7.48 2.150 21.500 Pale Yellow
2 10 8.26 1.347 13.472 PaleYellow
3 20 8.60 1.262 12.621 PaleYellow
4 30 9.09 1.246 12.460 LightYellow
5 40 9.25 1.251 12.510 LightYellow
6 50 9.16 1.175 11.752 LightYellow
7 60 9.17 1.159 11.590 LightYellow
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Table 3: Effect of pH by the variation in time and concentration of Tartrazine Dye(52mg/L)
s.no Time(min) pH Absorbance K -Factor color
1 0 6.75 1.863 18.636 Pale Yellow
2 10 6.71 1.266 12.664 PaleYellow
3 20 6.56 1.035 10.350 PaleYellow
4 30 6.64 1.033 10.330 LightYellow
5 40 6.85 1.160 11.600 LightYellow
6 50 6.68 1.005 10.050 LightYellow
7 60 6.55 0.981 9.815 LightYellow
Table 4: Effect of pH by the variation in time and concentration of Tartrazine Dye(40mg/L)
s.no Time(min) pH Absorbance K Factor color
1 0 7.97 1.990 19.900 Pale Yellow
2 10 8.40 0.924 09.245 PaleYellow
3 20 8.80 0.860 08.600 PaleYellow
4 30 9.37 0.880 08.800 LightYellow
5 40 9.39 0.861 08.612 LightYellow
6 50 9.38 0.837 08.370 LightYellow
Table.5: Effect of pH by the variation in time and concentration of Tartrazine Dye(30mg/L)
s.no Time(min) pH Absorbance K Factor color
1 0 7.320 2.042 20.422 Pale Yellow
2 10 10.81 1.194 11.94 PaleYellow
3 20 11.26 1.087 10.87 PaleYellow
4 30 10.69 1.002 10.02 LightYellow
5 40 10.50 1.011 10.11 LightYellow
6 50 10.59 1.029 10.29 LightYellow
7 60 11.14 0.978 9.780 LightYellow
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Table 6: Effect of potential scan on pH and absorbance of Tartrazine Dye solution(40mg/L)
Voltage(volt) pH Absorbance
0 7.05 2.422
1 7.05 2.352
2 7.05 2.250
3 7.06 2.225
4 7.07 2.204
5 7.07 2.164
6 7.08 2.143
7 7.08 2.131
8 7.07 2.150
9 7.06 2.124
10 7.05 2.111
11 7.04 2.054
12 7.03 2.090
13 7.02 2.029
14 7.01 2.103
15 7.00 2.100
Fig[1]:Effect of pH by the variation in time and concentration of Tartrazine Dye (68mg/L)
Fig[2]: Effect of pH by the variation in time and concentration of Tartrazine Dye(60mg/L)
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Fig [3]: Effect of pH by the variation in time and concentration of Tartrazine Dye(52mg/L)
Fig[4]: Effect of pH by the variation in time and concentration of Tartrazine Dye(40mg/L)
Fig[5]: Effect of pH by the variation in time and concentration of Tartrazine Dye(30mg/L)
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Fig[6]:Effect of electrolytic potential on pH of electrolytic dye solution(40mg/L)
Fig [7]: Effect of electrolytic potential on pH of electrolytic dye solution(40mg/L)
Current Efficiency
The current efficiency is the ratio of the actual
electrode consumption to the theoretical values. It
is an important parameter for the
electrocoagulation process because it affects the
life time of the electrode. So, the both theoretical
and experimental values of consumed electrode
were determined. The first one is calculated by
using Faraday’s law of electrolysis:
m = ItM/ZF
where Z = 2 is the number of electrons
corresponding to iron oxidation, M is the
molecular weight (g/mol) and F is Faraday’s
constant(96500 C) and the second value is
determined by weighing the electrode before and
after experiment. Results show that the both
values are similar and increases with the
electrolysis time and potential.
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Mechanism of the Reaction
In the case of electrocoagulation process using
iron anode, proposed mechanism for the
production of metal hydroxide have been
developed.
• Mechanism I:
Anode : 2Fe → 2Fe+2
+4e−
2Fe2+
+5H2O + 1/2O2→ 2Fe(OH)3(s) + 4H+
Cathode : 4H2O + 2e−→ 4OH− +2H2(g)
Overall reaction : 2Fe + 5H2O + 1/2O2
→ 2Fe(OH)3(s) + 4H2(g)
• Mechanism II:
Anode : Fe → Fe2+
+2e -
Fe2+
+2OH−
→ Fe(OH)2(s)
Cathode : 2H2O + 2e−
→ H2+2OH−
Overall reaction : Fe + 2H2O → Fe(OH)2(s) +
H2(g)
In the present experimental system during
electrolysis process, it was observed that the dye
solution change its color during electrolysis
process and bubbles of gas were also observed at
the cathode. After the passage of time, the effluent
becomes clear and a green and yellow sludge was
formed. The green and yellow colours can
probably be attributed due to the oxidation of iron
into Fe(II) and Fe(III) hydroxide. Metal
hydroxides formation occurs following the
mechanisms I and II as cited above. These
hydroxide flocs have a large specific surface area
that can remove pollutants by adsorption, surface
complexation or electrostatic attraction. The
removal efficiency depends on the quantity of iron
generated, which was bounded with the passage of
the reaction time and potential for the electrolysis.
By the variation of time and potential, the
distribution of the coagulation density is more
effective. This can produce the related coagulation
and maximum removal of pollutants.
Consequently, high removal efficiency of colour is
observed at high time and high potential in a basic
environment, simultaneous formations of ferric
hydroxide/oxides are also expected. Precipitates of
Fe (III) hydroxides thus formed have a coagulating
character better than Fe(II) hydroxide, because
Fe(OH)3 is more stable than Fe(OH)2. Then, the
removal efficiency is good.
Generally, the mechanism of
electrocoagulation for wastewater treatment is
very complex. . However, the colour removal may
involve, besides adsorption, complexion with the
iron hydroxide forming ionic bonds. Colour
removal can also take place if some of the
substituent, which determines the colour, is
altered. Another more probable mechanism can be
consider for electrocoagulation, consist in ferrous
hydroxide formation. It’s about sweep
flocculation. The precipitate can physically sweep
the pollutants from the suspension. This
mechanism does not involve any change in charge.
Furthermore, the lower removal efficiency at low
time and potential can be explained by the fact that
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the amount of precipitate formed is not enough.
But, when we enhance the electrolysis time or
when the electrolysis potential increases, the
solution practically becomes exempt of the iron
because the middle grow more rich by hydroxyl
ions(OH−). Generally, the quantity of dissolved
iron found in all tests is very weak, which can be
attributed to alkaline pH of wastewater, because
the iron precipitates totally in this range of pH.
CONCLUSION
Electrocoagulation is an efficient process to treat
simulated wastewater having elevated levels of
dyes and metals exceeding WHO standard. The
purification of waste was carried out by adopting
electrocoagulation method. The time and potential
are the most important operation variables for
treatment efficiency. The results showed that
about (70 min and 5V) are optimum time and
potential conditions. The removal efficiency was
found to be 50% at 70 min.
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