Treatment of Wastewater from Dye Industries using Electrochemical Technology

Abstract

Electrochemical oxidation is an emerging advanced wastewater treatment technology for refractory organic wastewaters from industrial sources including dyes, tannery, pharmaceuticals, landfill leachates, etc. The present study attempts to treat a synthetic wastewater containing Reactive Black-5 dye by indirect electro-oxidation. The removal of dyes from textile wastewater prior to its discharge or reuse is a challenging task. Indirect electrochemical oxidation has been an alternative method for the decontamination of dye wastewater. Electrochemical-oxidation of Reactive Black-5 (RB-5) was conducted for degradation using DSA type electrode. In the study, for electro-oxidation, electrode was indigenously fabricated in laboratory using titanium as substrate. This substrate was coated using different metal oxides RuO2, Sb2O5 and SnO2 by thermal decomposition method. Effects of fabricated electrodes Ti/NiO-CoO-Sb2O5-SnO2, Ti/NiO-AgO-Sb2O5-SnO2, Ti/ZrO-RuO2-Sb2O5-SnO2, Ti/CeO-RuO2-Sb2O5-SnO2, Ti/CoORuO2- Sb2O5-SnO2and Ti/AgO-RuO2-Sb2O5-SnO2were studied on synthetic organic dyes Reactive Black-5for degradation and decolourization. Laboratory scale batch reactor was used for degradation and decolorization studies for 500 and 1000 ppm of dye solution with constant ionic strength at nutral pH, current density at 50 mA/cm2 and distance between electrodes at 8mm were kept constant for all experiments. Colour, COD and TOC reduction were observed using UV spectrophotometer, COD and TOC reactor. Surface morphology and composition of the fabricated electrode coatings were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) respectively. Coating microstructure was analyzed by X-ray diffraction (XRD). Maximum colour, COD and TOC reduction was respectively 99%, 90% and 52% in Reactive Black-5 employing Ti/ZrO-RuO2-Sb2O5-SnO2 electrode. It has been experimentally proved that Titanium based DSA’s are one of the best electrode for Electrochemical oxidation process. However, the future scope for the existing work would typically involve preparation of elelectrodes using different combination of metal oxide with different coating techniques, testing can be made at different electrodes gap, at varying current density, at varying type of electrolyte and its concentration, increase the number of plates, changing the orientation of arrangement of electrodes and finally arriving upon the optimal dimensions and input parameters that can lead to treat the actual wastewater coming out from dye industries.