Removal of sulfide, sulfate and sulfite ions by electro coagulation

Abstract

The removal of various species of sulfur from beamhouse of tannery wastewater and also from synthetic samples was studied by electro-flotation technique. Consumable anodes of iron and aluminum and insoluble anode of titanium were tested as anodes. It was found that iron and aluminum anodes were effective for the removal of suspended solids, sulfide, sulfite and sulfate. Progress of simultaneous coagulation of suspended solids during electro-flotation was measured using particle size analysis. Coagulation was found to be essential for effective flotation of suspended solids. Metal ions generated in situ by electrolytic oxidation of anode were found to react with dissolved sulfide ions. Metal sulfides thus formed as colloidal suspension were coagulated and floated simultaneously by hydrogen bubbles generated from cathode. Simultaneous occurrence of precipitation, coagulation and flotation was observed during electro-flotation. X-ray diffraction studies were conducted to identify the nature of sulfide phase formed during electrolytic precipitation. The effect of pH, current density and initial concentration of pollutants was studied and the results are discussed. The removal of sulfite and sulfate ions is explained by zeta-potential measurements. (C) 2004 Elsevier B.V. All rights reserved.