Comparative study of electrode material (iron, aluminium ... · textile industry wastewater. Hence,...

INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 4, No 4, 2013

© Copyright by the authors - Licensee IPA- Under Creative Commons license 3.0

Research article ISSN 0976 – 4402

Received on November 2013 Published on January 2014 519

Comparative study of electrode material (iron, aluminium and stainless

steel) for treatment of textile industry wastewater Akanksha 1, Roopashree G. B2, Lokesh K. S.3

1- Department of Environmental Studies and Resource Management, TERI University,

New Delhi, India

2- Department of Environmental Engineering, S J College of Engineering, Mysore, India

[email protected]

doi: 10.6088/ijes.2014040400008

ABSTRACT

Electrocoagulation method with iron, aluminium and stainless steel electrodes is used, to treat

the textile industry wastewater in batch reactor. The performance of electrocoagulation (EC)

process was investigated for colour and chemical oxygen demand (COD) reduction, energy

consumption and instantaneous current efficiency was also observed using these electrodes.

The effects of the relevant key operating conditions such as voltage and electrolysis time

were studied in order to evaluate the performance of electrodes. The result indicates that

electrocoagulation is very efficient and was able to achieve colour removal (99.46%) at 14V

in 80 min and COD removal (90.12%) in 80 min at a potential of 8V in the presence of iron

electrode. The COD and Colour removal by aluminium and stainless steel electrodes were

achieved at high voltages. The energy consumption was low in case of iron electrode when

compared to aluminium and stainless steel electrode for the maximum COD removal. The

effluent wastewater was clear but requires post treatment to meet direct discharge standards.

Keywords: Electrocoagulation; Iron, Aluminium, Stainless Steel, Electrode, Textile

wastewater.

1. Introduction

World has entered into a new era where sustainability is the main factor to encounter the

challenges of depletion of our reserves and environmental upsets. Wastewater is the main

cause for irreversible damages to the environment and also contributes to the reduction of

fresh water reserves, creating threats to the next generation. Many industries consume fresh

water and exhaust as a wastewater. It should be treated properly to reduce or eradicate the

pollutants and achieve the permissible limit for its reutilization in the industrial/agriculture

process to promote sustainability. Effluent with high colour and high COD are common in

industries like textile, paper, leather and mineral processing. Electrocoagulation is an

alternative technology for wastewater treatment and recovery of valuable chemicals from its

sludge. Successful electrocoagulation treatment of various industrial effluents has been

reported by various researchers as it is considered to be potentially an effective tool for

treatment of wastewater with high removal efficiency of COD and colour.

Electrocoagulation treatment of textile dye have been analysed on a lab scale and found good

results with regard to removal of COD, colour, turbidity and dissolved solids at varying

operating conditions. Iron electrode is found superior than aluminium as sacrificial electrode

material in terms of COD removal efficiency and energy consumption (Kobya et al.

2003).The effectiveness of aluminium and iron electrode in reduction of pollutants from Palm

Comparative study of electrode material (iron, aluminium and stainless steel) for treatment of textile industry

wastewater

Akanksha et al International Journal of Environmental Sciences Volume 4 No.4, 2014

520

oil mill effluent (POME) reported by Nasution et al., 2013 and concluded that

electrocoagulation is faster than other existing process.

The effects of operating parameters such as electrolyte concentration, applied electrical

current, pH and time play an important role on the decolourization and COD removal

efficiency. The electrocoagulation was found very efficient with iron electrode and able to

achieve 100% colour and 84% COD removal within 3 min at potential 600mV (Zaroual et al.,

2006). The acid dye bath (ADB) effluent was simulated and treated by electrocoagulation

method using aluminium and stainless steel electrode. The results showed that 91% colour

and 36% COD was removed within 30 min from 1.5 litres ADB using aluminium electrode,

whereas almost the same treatment efficiencies could be reached with stainless steel electrode

within 15 min (Arslan-Alaton et al., 2008).The stainless steel electrode is found more

effective for colour and COD removal under optimum conditions in case of red 120 dyes

(Senthil et al., 2010).

Since electrical energy requirements are a direct function of treatment time,

electrocoagulation with aluminium resulted in two-fold electrical energy consumption (17

kWh per m3 wastewater) as compared with energy consumption using stainless steel

electrodes (8 kWh per m3 wastewater) (Arslan-Alaton et al. 2008).Electrocoagulation was

also found effective in removal of elements like arsenic, phosphate, nitrate & fluoride

(Kumar et al., 2010: Choi et al., 2010) when present in aqueous solution. Since iron,

aluminium and stainless steel electrodes have not been compared in detail for the treatment of

textile industry wastewater. Hence, the purpose of this study is to compare the treatment of

textile wastewater by electrocoagulation using aluminium, stainless steel and iron electrodes.

In addition, the effect of relevant operational variables, voltages and electrolysis time on the

process performance is explored. The three technical criteria which are of primordial

importance are BOD5/COD ratio, colour removal and electrode efficiencies. The two criteria

which may directly influence the process economy, especially operational costs, are energy

and electrode consumptions.

2. Materials and methods

2.1. Sampling procedure for electrocoagulation treatment

The textile wastewater contains dyes which impart colour and large amount of chemicals and

acids are used, which are responsible for the high value of COD. The sample used in this

study was collected from textile manufacturing industry in 20 litre polyethylene containers

just before the equalization tank of the existing effluent treatment plant and stored with

preservatives prior to its use in the experiments. The composite samples were collected.

2.2. Characterization of raw textile wastewater

The parameters assessed for textile industry wastewater are pH, COD, BOD5 (at 20°C),

Nitrates, Phosphates, Chlorides, Conductivity and Sulphates using standard methods (APHA,

2005). The characteristics of textile wastewater are shown in Table 1. The twelve samples

were analysed.


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Table 1: Initial characterization of textile industry wastewater

Parameters Value

Chemical oxygen demand (COD) (mg/L) 12960 and 17800

Biochemical oxygen demand (BOD5) (mg/L) 2674

pH 4.68

Conductivity (µS) 1775

Nitrates (mg/L) 5.28

Chlorides (mg/L) 199.93

Sulphates (mg/L) 8.98

Phosphates (mg/L) 39.40

Colour (Absorbance method) 0.2783

The parameters analysed for raw wastewater such as nitrates, sulphates and chlorides

were found to be within the discharge limits (Table 2)

Table 2: Textile wastewater discharge Standards as per CPCB India

Parameters CPCB (India)

Temperature Shall not exceed 5°C above the

ambient temperature of the receiving

body

pH 6.0-9.0

BOD5 (mg/L) 30

COD (mg/L) 250

Nitrate mg/L 20

Phosphate (mg/L) 5

Sulphates (mg/L) 1000

Chlorides (mg/L) 1000

Colour 400 Hz unit

Source: India Specific Standards, CPCB

2.3. Reactor setup

The materials used in this study are iron electrode, aluminium electrode and stainless steel

electrode. There are six monopolar electrodes, three anodes and three cathodes of the same

dimension (5cm×5cm×1mm). Materials are procured from metal shops. The batch reactor

setup was done at lab scale as shown in Figure 1. Electrodes were connected to the positive

and negative terminals of the DC power supply. In each run, 1 litre solution of wastewater

was placed in electrolytic cell. The different voltages (8V, 10V, 12V, 14V) were set for each

electrode material and the coagulation was started. The gap between the electrodes was

maintained at 1 cm and maintained throughout the experiment. Electrolytic cell is kept on the

digital magnetic stirrer by adjusting speed to around 500 rpm to maintain homogeneous

mixing of solution in the reactor. Before each run, electrodes were washed with water and


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522

dipped in 15% hydrochloric acid in order to remove dust from the electrode plates and thus

weigh the electrodes after drying. At the end of each run, the electrode plates are washed with

water, dried and finally weighed. The reactor was run for 80 min and supernatant was

retrieved from the reactor at an interval of 20 min. The subsequent treated sample was filtered

using whattman filter paper and filtrate was used for the characterization. In this study,

individual effects of electrolysis time and applied voltage were quantified on colour and COD

reduction.

Figure 1: Experimental setup of electrocoagulation treatment (Murthy et al., 2011)

2.4. Analysis of sample

All the reagents were prepared as per the standard methods. The pH, COD and colour were

determined at all intervals and BOD5 was observed at 80 min for different voltages. Table 3

shows the method used for the analysis of various parameters. The colour was determined by

absorbance method and the instrument used recorded the spectra over 200nm to 800nm range.

Colour was monitored till the disappearance of absorbance peaks. It was evaluated by using

the formula,

Abs (%) = [(Absi-Absf)/Absi]*100 (1)

Where, Abs (%) = Absorbance in percentage, Absi = Initial absorbance of the raw sample,

Absf = Absorbance of the treated samples at regular intervals (Murthy et al., 2011)

Table 3: Analysis of Various Parameters

Sl

No

Parameters Instrument used Method

1 COD (mg/L) Closed Reflux (DRB

200)

Closed Reflux Titrimetric

Method

2 pH pH meter (LI127) Instrumental Method

3 Conductivity (S/cm) Conductivity meter Instrumental Method

4 Phosphates (mg/L) Spectrophotometer

(DR5000)

Vanodomolybdophosphoric

Acid Method


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5 Chlorides (mg/L) Titrimetric method Argentometric Method

6 Sulphates (mg/L) Spectrophotometer Turbidimetric method

7 Nitrates (mg/L) Spectrophotometer Phenol Disulphonic Acid

method

8 Colour Scanning Mini

Spectrophotometer

(200-800nm)

Absorbance method

2.5. Kinetics for electrocoagulation

2.5.1. Energy consumption

The energy consumption was calculated by using the formula given below (Bhaskar et al.,

2008)

E= (Vit*1000)/(60(C0-Ct)Sv) (2)

Where,

E=Energy consumption in kWh/kg of COD

Sv=Sample volume in litres

C0 & Ct=initial and final concentration in mg/L

V=voltage

I=current in A

t=electrolysis time

2.5.2. Instantaneous Current Efficiency

It was calculated by using the equation given below

ICE= {((COD)t-(COD)t+dt)/(8*I*dt)}*F*V*100 (3)

Where,

ICE= Instantaneous Current Efficiency

(COD)t& (COD)t+dt=Chemical Oxygen Demand at time t and t+dt in g/L

V=volume of effluent in litres

I= current in A

dt=change in time in seconds

F=Faraday’s constant=96,487 C/mol

Table 4, shows the reaction at the anode and cathode. The flocks are formed as metal

hydroxides in the electrocoagulation process.

Table 4: Electro-oxidation of Iron and Aluminium Electrode

Aluminum electrode Iron electrode

At anode:

Al → Al3+

+ 3e

2Al + 6H2O + 2OH

−

→ 2Al (OH)4−

+

3H2

At anode:

4Fe(s)→ 4Fe

+

2(aq) + 8e-

4Fe2(aq)

+ 10H2O

(l) + O

2(g)→4Fe(OH)

3(s) +8H

+

(aq)


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524

At cathode:

3H2O + 3e → 3/2H

2+ 3OH

−

At cathode:

8H+

(aq) + 8e

-

→4H2(g)

Overall reaction :

2Al(s) + 6H2O

(l)→2Al(OH)

3(s) +

3H2(g)

Overall reaction:

4Fe(s)

+ 10H2O

(l) + O

2(g) →4Fe(OH)

3(s)+4H

2(g)

Source: (Kobya et al., 2003: Zaroual et al., 2006)

3. Results and discussion

3.1. Efficiency of Electrodes with Regard to Colour and COD Reduction

Electrocoagulation test was carried at different voltages (8V, 10V, 12V, 14V) and at different

electrolysis time using electrodes of Iron, Aluminium and Stainless Steel material for the

treatment of textile industry wastewater. The volume taken was 1 litre. The variation of COD

removal efficiency and colour removal efficiency with electrolysis time is shown in Figure 2

& 3 of iron electrode. It was observed that maximum COD removal was 90.12% at 8V at 80

min and colour removal was 99.46% at 14V at 80 min., similar results were reported by

Zaroual et al., 2006 at 600mV in 3 min with respect to colour reduction. But, COD removal

was low.

Figure 2: COD Removal Efficiency Using Iron Electrode

The maximum COD removal efficiency was experienced for both aluminium and stainless

steel electrode at 14V at 80 min and was 92.97% and 87.23%, respectively (Figure 4 & 6).

However, the maximum colour removal efficiency was 96.22% at 10V in 20 min for

aluminium and 89.29% at 12V at 80 min for stainless steel electrode (Figure 5 & 7). The

simulated acid dye bath (ADB) effluent was prepared and treated by electrocoagulation

method using aluminium and stainless steel electrode. The results obtained by this

experiment showed 91% colour and 36% COD removal within 30 min using aluminium

electrode, whereas almost the same treatment efficiencies was reached with stainless steel

electrode within 15 min (Arslan-Alton et al., 2008). Similarly, Senthil kumar et al., 2010

found stainless steel more effective against reduction of colour in case of red 120 dyes.


wastewater


525

Figure 3: Colour Removal Efficiency Using Iron Electrode

Figure 4: COD Removal Efficiency of Aluminium Electrode

Figure 5: Colour Removal Efficiency of Aluminium Electrode


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526

Figure 6: COD Removal Efficiency of Stainless Steel Electrode

Figure 7: Colour Removal Efficiency of Stainless Steel Electrode

3.2. Energy consumption

As seen from the figure 8, 9 and 10, the energy consumption for iron, aluminium, stainless

steel electrode was 0.0866 kWh/kg of COD, 0.3974 kWh/kg of COD and 1.2318 kWh/kg of

COD, respectively for maximum COD removal efficiency. It is observed that the less energy

was consumed by iron electrode as compared to energy consumed by other two electrodes for

maximum COD removal efficiency. The energy consumption is lower with iron, while the

electrode consumption is lower generally with aluminium (Bayramoglu et al., 2004). As

stated in literature study, electrical energy requirements are a direct function of treatment

time. Electrocoagulation with aluminium, resulted in two-fold electrical energy consumption


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527

(17 kWh per m3 wastewater) as compared with electrocoagulation using stainless steel

electrode (8 kWh per m3 wastewater) as reported by Arslan-Alaton et al., 2008.

Figure 8: Energy Consumption for the Removal of COD (Iron Electrode)

Figure 9: Energy Consumption for the Removal of COD (Aluminium Electrode)

Figure 10: Energy Consumption for the Removal of COD (Stainless Steel Electrode)


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528

3.3. Instantaneous Current Efficiency (ICE)

In Figure 11, 12 & 13, the change of instantaneous current efficiency (ICE) with electrolysis

time during electrocoagulation treatment is exposed here. ICE values are high during initial

hour with low energy consumption and as time proceeds ICE decreases with high energy

consumption. Comparable trends were observed for other two electrodes. It indicates that

high ICE value show less energy consumption for maximum COD removal efficiency of iron

electrode. Similar changes of ICE value with electrolysis time during electrochemical

treatment are explained by Wang et al., 2006.

Figure 11: Instantaneous Current Efficiency for the Removal of COD by Iron Electrode

Figure 12: Instantaneous Current Efficiency for the Removal of COD by Aluminium

Electrode


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529

Figure 13: Instantaneous Current Efficiency for the Removal of COD by Stainless Steel

Electrode

3.4. Anode dissolution

Figure 14, represents the value of anode dissolution of iron, aluminium and stainless steel

electrode. The values are found different at different voltages for all the three electrodes. The

low anode dissolution is observed for iron electrode at 8V and shows maximum COD

removal efficiency at this voltage. The high value of anode dissolution at 12V by stainless

steel electrode represents maximum reduction of colour and COD. It may be due to high

ionization rate (Dikusar et al., 2007). Kobya et al., 2003 treated textile wastewater by

electrocoagulation technique using iron and aluminium electrode and reported that iron is

superior to aluminium as sacrificial electrode material in terms of COD removal efficiency

and energy consumption.

Figure 14: Anode Dissolution of Iron, Aluminium and Stainless Steel Electrodes


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530

3.5. BOD5/COD ratio

Table 5, indicates increasing trend of BOD5/COD ratio as compared to initial wastewater

sample for all the electrodes. The value of BOD5/COD ratio after electrocoagulation

treatment is above 0.3. Hence, it can be concluded that the non-biodegradable wastewater is

changed to biodegradable effluent. BOD5/COD ratio is an indicator (Murthy et al., 2011) for

biodegradability.

Table 5: Values of BOD5/COD Ratio for Different Electrodes

Voltage Iron Aluminium Stainless steel

0 0.20 0.15 0.20

8V 0.95 0.24 0.63

10V 0.97 0.92 0.75

12V 1.05 1.057 0.78

14V 1.09 1.082 0.70

4. Conclusion

Electrocoagulation is an efficient process to treat textile industry wastewater characterized by

presence of high COD concentration and colour content. In this connection, the study was

conducted for the treatment of textile industry wastewater by applying the electrocoagulation

method. Iron, aluminium and stainless steel electrodes were tested for their efficiencies with

regard to colour and COD reduction. This efficiency varies with electrode material. Iron

electrode was found to be more efficient than other electrodes in colour and COD removal.

On the other hand, the high efficiency of COD removal was found at 8V in the presence of

iron electrode and 14V in the other two electrodes. Energy consumption was less with iron

when compared to aluminium and stainless steel electrode for the maximum COD removal.

The results conclude that the electrode material play an important role in electrocoagulation

method for treatment of textile industry wastewater. An economic aspect has to be taken care

before selection of electrode material characteristics with regard to current efficiency.

5. References

1. APHA (2005), Standard methods for the examination of water and wastewater, 21st

edition, American Public Health Association, Washington, D. C.

2. Arslan-Alaton I., Kabdasl I., and Sahin Y, (2008), Effect of Operating Parameters on

the Electrocoagulation of Simulated Acid Dye Bath Effluent, The Open

Environmental & Biological Monitoring Journal, 1, pp 1-7.

3. Bayramoglu M., Kobya M., Can O. T. and Sozbir M., (2004), Operating cost analysis

of electrocoagulation of textile dye wastewater, Separation and Purification

Technology, 37, pp 117–125.

4. Bhaskar Raju G., Thalamadai Karuppiah M., Latha S. S., Parvathy S. and Prabhakar

S, (2008), Treatment of Wastewater from Synthetic textile industry by

electrocoagulation – electrooxidation, Chemical Engineering Journal, 144, pp 51-58.


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5. Choi J. H., Maruthamuthu S., Lee Tae-Hyun Ha H. G., Bae J. H. and Alshawabkeh A.

N. (2010), Removal of phosphate from agricultural soil by electro kinetic remediation

with iron electrode, Journal of Applied Electrochemistry, 40, pp 1101–1111.

6. Dikusar A.I., Ivanenkov I. A., Saushkin B. P., SilkinS. A. and Yushchenko S. P.,

(2007), High Speed Anode Dissolution of Heat Resistance Chrome-Nickel Alloys

Containing Tungsten and Rhenium: I. Chloride Solutioh, Surface Engineering and

Applied Electrochemistry, 43(1), pp 1-10.

7. Industry Specific Standards, Central Pollution Control Board (CPCB), India,

Available at http://cpcb.nic.in/Industry_Specific_Standards.php, accessed during

November 2013.

8. Kobya M., Can O. T. and Bayramoglu M., (2003), Treatment of textile wastewaters

by electrocoagulation using iron and aluminium electrodes, Journal of Hazardous

Materials, B100, pp 163–178.

9. Kumar N. and Sanjeev Goel S. 2010, Factors influencing arsenic and nitrate removal

from drinking water in a continuous flow electrocoagulation (EC) process, Journal of

Hazardous Materials,173, pp 528–533.

10. Murthy U. N, Rekha, H. B., and Bhavya J. C., (2011), Electrochemical Treatment of

Textile Dye Wastewater Using Stainless Steel Electrode, International Conference on

Environmental and Computer Science,19, pp 64-68.

11. Nasution M. A., Yaakob Z., Ali E., LanNg B. and Abdullah S. R. S, (2013), A

Comparative Study Using Aluminium and Iron Electrodes for the Electrocoagulation

of Palm Oil Mill Effluent to Reduce its Polluting Nature and Hydrogen Production

Simultaneously, Pakistan Journal of Zoology, 45(2), pp 331-337.

12. Senthil Kumar P., Umaiyambika N. and Gayathri R (2010), Dye removal from

aqueous solution by Electrocoagulation process using stainless steel electrode,

Environmental Engineering and Management Journal, pp 1031-1037.

13. Wang B., Kong W. and Ma H, (2006), Electrochemical Treatment of Paper Mill

Wastewater using Three Dimensional Electrodes with Ti/Co/SnO2-Sb2O5 Anode,

Journal of Hazardous Material, 146(1-2), pp 295-301.

14. Zaroual Z., Azzi M., Saib N. and Chainet E. (2006), Contribution to the study of

electrocoagulation Mechanism in basic textile effluent, Journal of Hazardous

Materials, 131, pp 73–78.

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