Towards sustainable chlorine dioxide production via HClO3 generation using bipolar membrane electrodialysis

Chlorine dioxide (ClO 2 ) is a key green oxidant in the increasing demand for sustainable industrial and environmental applications. Its inherent instability requires in - situ generation, but conventional methods rely on highly concentrated commercial acids and produce significant chemical waste, limiting their environmental viability. To address this challenge, this study explores an alternative route for converting sodium chlorate (NaClO 3 ) into its acidic form, chloric acid (HClO 3 ), with the goal of replacing conventional acidic media and reducing the environmental footprint of ClO 2 production. For this purpose, the technical feasibility of generating HClO 3 via bipolar membrane electrodialysis (BMED) was evaluated using three representative configurations: 1) BM-CEM-BM (BM: bipolar membrane; CEM: cation exchange membrane), 2) BM-AEM-BM (AEM: anion exchange membrane), and 3) BM-AEM-CEM-BM, implemented in a custom 3D-printed filter-press cell. The results revealed that both the ClO 3 - and Na + transfer rates were strongly influenced by the selected configuration. Notably, a current density of 750 A m −2 was found sufficient to obtain concentrations of 0.87 mol L −1 HClO 3 and 0.96 mol L −1 NaOH, with purities exceeding 93 % and 95 %, respectively, when the BM-AEM-CEM-BM configuration was used. Additionally, the process proved viable under both batch and continuous operation, confirming its scalability. Finally, the in - situ generation of ClO 2 was evaluated by reducing NaClO 3 and HClO 3 with H 2 O 2 . The findings indicate no evidence of ClO 2 generation from NaClO 3 under the tested conditions, whereas its acidic form (HClO 3 ) obtained via BMED efficiently produces ClO 2 , confirming that BMED is a promising route for in situ ClO 2 generation.