Electrochemical Coagulation for Textile Effluent Decolorization

1. Electrochemical Coagulation for Textile Effluent Decolorization University of Massachusetts Dartmouth Chapter Sigma Xi Scientific Research Society 12th UMass Dartmouth Research Exhibition April 25-26, 2006 Jared McGarrahan Department of Textile Sciences University of Massachusetts - Dartmouth Chen-Lu Yang Advanced Technology & Manufacturing Center University of Massachusetts - Dartmouth Introduction Fig. 2 Current efficiency The three most commonly used dyestuffs in textile industry are reactive, acid, and dispersed dyes. One dye from each group, C.I. Reactive Blue-19, C.I. Acid Red-266, and C.I. Disperse Yellow-218 was chosen to study the feasibility of electrochemical coagulation for color removal. The Fe-coagulation process is effective for color removal from textile effluents. The associated sludge must be dealt with. The by-product of the process, NaClO, is a strong oxidizing agent that can be used to further decompose the dye structure. Sodium chloride is essential in this process because the existence of NaCl reduces power consumption, depassivates the electrochemical system, and forms NaClO for dye decomposition. The decomposition of adsorbed dye molecules might be caused by the existence of ferrous ions or NaClO. Fig. 3 Dye type versus color removal Anode: Fe - 3e- Fe+3 Fe - 2e- Fe+2 2Cl- - e-  Cl2 Cathode: 2H2O + 2e-  H2 + 2OH- Producing: Fe+2 (aq)Fe(OH)2(s) Cl2(g) Fe+3 (aq)Fe(OH)3(s) H2(g) OH- (aq) HClO(aq) ClO-(aq) Fig. 1 Color removal and pH change Conclusions Reactive Blue-19 • Fe-coagulant is effective for color removal • Significant sludge generated • NaCl depassivates the electrochemical system • NaCl reduces power consumption • Long-term stability test is needed Acid Red-266