Towards the production of chlorine dioxide from electrochemically in-situ produced solutions of chlorate

Abstract

BACKGROUND: This work focuses on the electrochemical production of chlorate solutions for direct use and integration in the manufacture of chlorine dioxide (ClO2), from the perspective of manufacturing portable ClO2 electrochemical generators. RESULTS: Chlorate production was evaluated from the oxidation of sodium chloride (NaCl) contained in brackish solutions (20 g L−1) and brines (200 g L−1) in single chamber flow electrochemical cells. Efficiency in chlorate ion (ClO3−) production increased with temperature and NaCl concentration, but the use of brackish solutions led to a higher quality product, as compared to the brines, with lower concentration of chlorine and hypochlorous acid. To evaluate the production of ClO2, samples corresponding to two different qualities of the electrogenerated solutions underwent stripping to exhaust chlorine, before being mixed with hydrogen peroxide (H2O2) and sulfuric acid. Results showed that using a chlorate solution obtained from the electrolysis of 20 g L−1 NaCl solution at 50 mA cm−2 and passing 57.35 Ah L−1, a maximum concentration of 33.3 mmol L−1 ClO2 could be attained, which corresponds to a maximum conversion of 48.75%. CONCLUSIONS: Efficiency of the synthesis depends on both the purity of chlorate and the H2O2/ClO3− ratio. This confirms that in-situ electrogenerated chlorate can be used to manufacture ClO2, but there are still many gaps to be overcome and further work must be carried out to optimize the production of the desired oxidant in a portable ClO2 device. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).