IJRIT International Journal of Research in Information Technology, Volume 1, Issue 5, May 2013, Pg. 19-23

International Journal of Research in Information Technology (IJRIT)

www.ijrit.com

ISSN 2001-5569

Electro-coagulation for Acid dye effluent Ankit V. Patel 1, Prof. N. M. Patel 2, Prof. N. R. Vaghela 3 1

M.E. student, Dept. of Chemical Engineering, Gujarat Technological University, Ahmedabad, Gujarat, India 2 Associate Professor, Dept. of Chemical Engineering, Vishwakarma Government Engineering Collage, Ahmedabad, Gujarat, India 3 Associate Professor, Dept. of Chemical Engineering, Vishwakarma Government Engineering Collage, Ahmedabad, Gujarat, India

Abstract This work was carried out for acid dye effluent from dye industry by the electrocoagulation process in batch experiments at a laboratory scale and ambient temperature (30 °C). In the batch experiment, the effect of various parameters including the current density, initial wastewater pH and electrolysis time, color removal and COD reduction was examined. Optimal metal ion depletion was attained with a current density of 7.868 mA/cm2; an initial wastewater pH is 7.4 and a 30 min electrolysis time. Under these conditions, COD removals from acid dye effluent employing electro-coagulation with different electrode series like Al-Al, Fe-Fe and Fe-Al (Anode and Cathode) electrodes. Our results indicated that partial COD removal for Al-Al, 55%; for FeFe, 65% and Fe-Al, 72% and color was also change at a current density 7.868 mA/cm2 .The efficiency of the electro-coagulation is 70%.

Keywords: Electro-coagulation, Acid dye effluent, current density, COD reduction.

1. Introduction Water, a major natural resources essential for human life, is continuously contaminated with different hazardous chemicals released from various industries. River, canal, estuaries and other water-bodies are being polluted by indiscriminate discharge of industrial effluents as well as other anthropogenic activities and natural processes. The continuous depletion of ground water, shortage in rainfall and huge consumption of water by industries has made clean water as a scarce commodity. Dye industries are considered to be most polluting sector in term of effluent composition and discharge volume [3]. These effluents are not aesthetic by their color but also interfere in the penetration of light. Furthermore, it contains organic and inorganic chemicals that are toxic, carcinogenic, and mutagenic/teratogenic for microbes and fish species. The large quantity of organic colored wastewater generated by textile, leather, plastic or mineral processing industries became a big environmental problem. It was essential that approximately 1-15% of dye is lost during dying and fishing processes and released, generating large amount of waste waters. The characteristics of those wastewaters are either high or low Ankit V. Patel, IJRIT

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pH(alkaline or acidic medium, depending on the process used), high temperature, high oxygen demand(COD), high concentration of coloring material. As a consequence, it is a great need to treat dye effluents before discharging to the receiving water stream to comply with the stringent environmental legislation [5]. There are many procedures to remove dyes from colored effluents such as: adsorption, precipitation, chemical degradation, photo-degradation, biodegradation, chemical coagulation and electro-coagulation. Adsorption and precipitation are very time consuming and costly processes, with low efficiency [7]. More recently, studies have focused on color and chemical oxygen demand (COD) remove from dye effluent using electro-coagulation (EC). Electro-coagulation (EC) is a process that consists in creating metallically hydroxide flocs in the wastewater by electro-coagulation of soluble anodes. Electro-coagulation has successfully been employed for the treatment of strong effluent such as electroplating, laundry, slaughterhouse and chemical industry wastewater [5]. By taking into account the necessity of pH adjustment for the usually extremely alkaline dye effluent, it seems to make more sense to apply the EC process to high-strength, low volume and slightly acidic effluent from the dying operations. In this study, the efficiency of electro-coagulation for wastewaters containing acid dye using aluminum (Al) and iron (Fe) electrode series like Al-Al, Fe-Fe and Fe-Al electrode was investigated.

2. Material and methods 2.1 Electro-coagulation Experiments Wastewater was obtained from a tank containing a mixture of exhausted dyeing solution at a dye manufacturing factory. The Experimental setup is shown in Fig. 1. Experiments were carried out at laboratory scale in an electrocoagulation reactor made of borosile glass equipped with two electrodes one anodes and one cathode with identical dimensions. Both aluminum (99.50%) anodes and iron (99.52%) cathode were made from plates with dimensions 100mm*50mm*6mm and the distance between two electrodes was 1 cm. The electrodes were connected to a digital DC power supply. All the runs were performed at constant temperature of 27 °C. The current density was adjusted to a desired value and the coagulation was started. At the end of the electro-coagulation experiments, the solution was filtered and their color and COD were analyzed. At the end of the run, the electrodes were washed thoroughly with water to remove any solid residues on the surfaces, dried and re-weighted.

Ankit V. Patel, IJRIT

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Fig.1 Schematic diagram of experimental setup Chemical oxygen demand (COD) and Total dissolve and suspended solids (TDS) were carried out according to the Standard Methods for Experimentation of Water and Wastewater. The pH was measured by a pH meter. Conductivity was determined by a conductivity meter. The pH and Conductivity were adjusted to a desired value using NaOH or H2SO4 and NaCl respectively.

3. Result and discussion 3.1 Effect of electrode on COD removal and other parameter The pretreated sample has the initial COD equal to 1958 mg/l. After EC run of 30 minutes and a settling time of 5 minutes the treated water samples were analyzed for the residual COD. The results has been discussed at 7.868 mA/cm2, 8 volt and an inter electrode distance was kept 1 cm. Table 2 give the effect of electrode on COD removal and other parameter. The COD measurement of the different sample was made. At low pH (pH=5) and high pH (pH=8) the sufficient sludge formation did not take place. Therefore, the adsorption of dye could not perform effectively at low or high pH. The residual COD was found to be minimum for an initial pH equal to 7.At low pH, the solution protons are reduced at cathode to H2 and the same proportion of hydroxide ions cannot be produced.

Al-Al Electrode

Conductivity (µS)

COD (mg/liter)

Color change

Initial

88

1958

Dark Bluish

Final

82

892

Dark Brown

Fe-Fe Electrode

Ankit V. Patel, IJRIT

Conductivity (µS)

COD (mg/liter)

Color change

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Initial

88

1958

Dark Bluish

Final

78

681

Orange

Fe-Al Electrode Initial

Conductivity (µS)

Color change

88

COD (mg/liter) 1958

Final

65

546

Light Orange

Dark Bluish

Table 2: Effect of electrode on COD removal and other parameter

3.2 Effect of current density on COD removal The COD removal by electro-coagulation process is affected by applied current density. Current density is 7.868 mA/cm2. Different set of experiments were performed for varying density, inter-electrode distance was kept at 1 cm. It was found that the COD removal increases with increasing current density. This is ascribed to the fact at high current density, the extent of anodic dissolution increases, resulting in a greater amount of precipitate for the removal of pollutants.

4. Conclusion Electro-coagulation (EC) is the one the most promising, emerging alternative treatment methods that have more recently been applied for the treatment of industrial waste waters. In the present study acid dye effluent was treated via electro-coagulation using different electrode series like Al-Al, Fe-Fe and Fe-Al (Anode and Cathode) electrodes under different operating conditions. Result have shown that COD and color removal efficiencies as well as sludge production rates were affected by applied electric current and initial pH. COD can be reducing as per the electrode change. For Al-Al electrode, the COD can reduce 55%, for Fe-Fe electrode, the COD can reduce 65% and for Fe-Al electrode, the COD can reduce 72%.

5. Acknowledgement On successful completion of my thesis “Electro-coagulation: for liquid effluent from dye waste” I would like to thanks Prof. N.M. Patel, Head of the Department for his valuable advice, co-operation and encouragement. My sincere thanks to Prof. N.M. Patel & Prof. N.R. Vaghela, Associate Professor of Chemical Engineering Department, who helped me in my thesis not only with her valuable advice & guidance but also with her great motivation and encouragement. Ankit V. Patel, IJRIT

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