Water Composition and Electrocatalytic Aspects for Efficient Chlorine Generation

摘要

This work evaluates the water disinfection performance of the Activ'H2O system based on in situ production of oxidizing agents. The system is composed of two identical dimensionally stable anodes (DSA) made of iridium-ruthenium oxide layer deposited on a titanium plate (Ti/IrO2-RuO2). Herein, we have characterized and assessed the oxidizing power of in situ produced species and their inhibitor agents. The disinfectant power was evaluated according to the hypochlorous acid (HClO) production, ensuring the best microbiological water quality, which increases proportionally with the increase in applied electric current. High chloride concentration with low current density leads to higher current efficiency and low chlorate production without producing any H2O2 or perchlorate. A high flow rate of chloride solution slightly improves mass transfer, and active chlorine production follows, helping to keep the produced neutral HClO away from the electrical double layer (EDL). However, in conventional tap water, non-electroactive anions like sulfates, nitrate, chlorates, and bicarbonate had a negative effect on active chlorine production rate due to the transfer of competing chloride ions inside the EDL. Polyvalent anions like SO42- migrate faster, and the hydrated size of electrostatically adsorbed polyvalent and monovalent anions leads to steric clutter. Inhibition rate followed the order SO42- > ClO3- > NO3- > HCO3-; this trend is correlated with the molar concentration ratio, migration rate, and hydration radius of the non-electroactive anions. Switching polarity proved effective in weakening competition with monovalent anions, despite current losses accompanied by each switch. However, it was ineffective with polyvalent ions.