Electrolytic membrane recovery of bromine from waste hydrogen bromide streams

A novel electrochemical process was developed for the recovery of bromine from waste gas‐phase hydrogen bromide streams. It uses a molten‐salt‐saturated membrane to electrolytically decompose hydrogen bromide into its molecular constituents, which are separated into a hydrogen‐enriched waste stream and a pure bromine product stream. Single‐cell studies were carried out in a configuration consisting of two cell housings (vitreous carbon), two gas‐diffusion electrodes (reticulated vitreous carbon or graphite felt), and a molten salt [(Li 0.575 K 0.133 Cs 0.292 )Br] saturated membrane (zirconia). Single‐cell results at 300°C, based on process stream concentrations ranging from 25 to 75% hydrogen bromide at 50 to 300 mL/min, demonstrated current densities exceeding 1 A/cm 2 and removals as high as 95%. Water and acetone (as a light organic contaminant) addition to the process feed, as well as exposure to thermal cycling, showed no deleterious effects on cell performance. Preliminary economics indicate this to be a viable process.