Electrochemical Oxidation of Wastewaters from the Instant Coffee Industry Using a Dimensionally Stable RuIrCoOx Anode

Abstract

The electrochemical oxidation of wastewater from an industrial plant producing instant coffee was studied using a dimensionally stable anode comprised of titanium with a film of ruthenium, iridium and cobalt oxides, Ti/Ru(40%)Ir(40%)Co(20%)Ox. Prior to the electrochemical treatment, the wastewater was subjected to a flocculation process. The anodic oxidation was performed at a controlled potential and monitored as a function of electrolysis time. HCl or NaCl was used as a support electrolyte. The efficiency of the wastewater purification process was evaluated through measurements of the chemical oxygen demand (COD), color, turbidity and UV-vis spectra. The flocculation process reduced the COD by 32% with respect to the initial value. The reductions in COD, color and turbidity induced by anodic oxidation depended on the electrolysis time and the support electrolyte used. NaCl was a more effective than HCl for reducing the COD. It is hypothesized that the oxidation of organic compounds proceeds indirectly via active chlorine species.