Treatment of dyeing wastewater by combined sulfate radical based electrochemical advanced oxidation and electrocoagulation processes

Electrochemical advanced oxidation process (EAOP) and electrocoagulation (EC) are two promising techniques that have been used for the abatement of wide variety of organic contaminants. However, a few researchers have reported the combined use of these techniques for real wastewater, which is important for field implementation of the techniques. This article presents the comparative performance of combined sulfate radical based EAOP + EC and EC + EAOP processes for the treatment of real field dyeing wastewater. Pt/Ti plate was used as anode and iron plate was used as cathode. It was found that sulfate radical was generated by both cathodic reduction of persulfate and activation of persulfate by ferrous ions. Anodic oxidation by Pt/Ti anode and indirect electrochemical oxidation processes are also contributed in pollutant removal. Instantaneous current efficiency was found to increase with increase in persulfate concentration and with reduction in COD. EAOP followed by EC was found to be better approach than EC followed by EAOP as the former combination yielded higher COD reduction of 93.5% with lesser specific energy consumption and lesser sludge generation. Sludge generated after the treatment process was characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray powder diffraction (XRD) techniques.