Ion injection bipolar membrane electrodialysis realizes over 8 mol/L NaOH conversion from a brine stream

Abstract The chlor‐alkali process is currently the predominant technology for caustic soda production but has several major challenges, such as enormous energy demand and supply–demand imbalance between NaOH and Cl 2 in downstream industries. Herein, we propose a novel ion‐injection bipolar membrane electrodialysis (IJBMED) system that is capable of boosting water splitting in a bipolar membrane with an ultrahigh current density while omittance concentration polarization in anion‐ and cation‐exchange membranes. The results indicate that the IJBMED approach enables one‐step conversion of the NaCl‐containing brine stream into 8.12 mol/L NaOH with specific energy consumption of 0.79 kWh/kg NaOH (23 wt.% → 25 wt.%), compared to 2.15 kWh/kg NaOH (28 wt.% → 30 wt.%) for the chlor‐alkali process. The advantages of low energy consumption and omittance of chlorine emissions suggest that IJBMED might be a promising alternative to the chlor‐alkali process, revealing a new route to reshape the chemical industry for caustic soda production.