Electrosynthesis of hypochlorous acid in a filter-press electrolyzer and its modeling in dilute chloride solutions

Abstract This paper shows computational fluid dynamic (CFD) simulations during the accumulation of hypochlorous acid (HClO), through the anodic oxidation of chloride ion (Cl−), in acidic condition at pH 3, in a filter-press cell equipped with a Ti|Ir-Sn-Ru oxides plate and a 316 stainless-steel plate as the anode and cathode, respectively. The flow plant considers the filter-press cell coupled with a recirculation tank. The chloride oxidation modeling consisted of solving a tertiary current distribution problem by coupling the average diffusion-convection equation for turbulent flow. The model considered the side oxygen evolution reaction (OER). The experimental validation of Cl− depletion and HClO accumulation was made by electrolysis trials using 0.002 m3 of two solutions containing 15 and 35 mol m-3 NaCl at pH 3, at current densities of 50, 100, 150 and 200 A m-2, and flow rate of 0.003 m3 min-1. The best electrolysis was reached at 200 A m-2, achieving 12.2 mol m-3 HClO after four hours, with current efficiency and electrolytic energy consumption of 25 % and 0.023 kWh (g HClO)-1, respectively. Experimental electrolysis data agree well with CFD simulations, highlighting that only 25 % of the applied current produced HClO and the OER consumed the rest.