Electrochemical oxidation of phenolic wastewaters using a batch-stirred reactor with NaCl electrolyte and Ti/RuO2 anodes

Abstract

An electrochemical oxidation (EO) process with Ti/RuO2 anodes was applied to treat phenolic wastewaters. In order to optimise the system, different operating conditions were tested. The nature of the electrolyte and the applied current density greatly affected the process, while the concentration of the electrolyte as well as the initial pH had a sparingly impact. The optimum operating conditions attained, 10gL−1 of NaCl, 119mAcm−2 and initial pH3.4, allowed the complete removal of the total phenolic content (TPh) and chemical oxygen demand (COD) when applied to a simulated phenolic mixture. SEM analysis revealed no morphological differences on the surface of the anode before and after it being used in EO. Neuronal studies were performed to verify the impact of the synthetic phenolic effluent, before and after the EO treatment, in the formation of neuronal reactive oxygen species (ROS). The treated effluent had a milder effect, compared to the raw one, but neuronal activity became enhanced after its removal. Regarding the depuration of an undiluted real olive mill wastewater (OMW) under the optimised parameters, the treatment achieved 100% of TPh removal and 17.2% of COD removal. Thus, the EO can be considered a satisfactory pre-treatment process to real wastewaters, since all phenolic content can be removed in 180min.