Tannery wastewater: Organic load and sulfide removal dynamics by electrochemical oxidation at different anode materials

Abstract The electrochemical oxidation of a real tannery effluent with very high organic load and sulfide content was assessed by galvanostatic electrolysis, utilizing different electrode materials, Ti/Pt/PbO 2 , Ti/Pt/SnO 2 – Sb 2 O 4 and BDD. Assays were run for 8 h, under a current density of 30 mA cm −2 , in a batch with stirring electrochemical cell. The efficiencies of the electrodes were tested by evaluating variations in chemical oxygen demand (COD), total carbon (TC), dissolved organic carbon (DOC), N-containing compounds, sulfide and sulfate. Although all the tested materials have proved to be very effective in organic load and sulfide abatement, BDD electrode showed the best performance in the removal of COD and TC, with similar behavior to the other two electrodes in DOC removal. Ti/Pt/SnO 2 – Sb 2 O 4 was the least efficient in the oxidation of N-containing compounds to NO 3 − , despite providing considerable production of gaseous nitrogen compounds, which reduces the total nitrogen load present in the treated effluent. Sulfide removal was more intense at BDD, being Ti/Pt/SnO 2 – Sb 2 O 4 the most effective in the oxidation of S 2 − to SO 4 2 − . Regarding specific charge and energy consumptions, BDD showed the best results, even when compared to other studies from the literature. These results show that electrochemical oxidation can be an effective treatment to tannery wastewater, regarding COD, N-containing compounds and sulfide removals.