Electrochemical oxidation process for the treatment of coke‐plant wastewater

Abstract

Wastewater from a coke plant was treated by using an electrochemical oxidation process. After electrolysis for two hours with a lead dioxide coated titanium anode (PbO₂/Ti), COD in the coke plant wastewater was reduced from 2143 mg/L to 226 mg/L and a COD removal efficiency of 89.5% was obtained. In addition, about 760 mg/L ammonium in the wastewater was completely removed simultaneously. These results indicate that electrochemical oxidation process demonstrates an excellent efficacy for the treatment of coke plant wastewater. In this study, anode material, chloride concentration, current density, and pH value were found to have significant influences on both COD removal efficiency and current efficiency in electrochemical oxidation process. Among four anode materials investigated, PbO₂/Ti which is inert to the adsorption of phenolic oligomer served the best COD removal efficiency. And, better COD removal efficiencies were obtained as electrolysis experiments were operated under higher current density and chloride concentration. In this study, an indirect oxidation effect of chlorine/hypochlonte generated during electrolysis plays an important role in the removal of pollutants from coke plant wastewater. Consequently, lots of chlorinated byproducts (as TOX) were formed in the beginning of electrolysis, but the derivative TOX can also be removed after electrolysis.

Key words:

• Electrochemical oxidation process
• Coke‐plant wastewater
• COD
• TOX
• Ammonium