A reversible absorption-based supported gas membrane process for enriching bromine from brine by using thin PTFE hollow fibers

Enrichment of bromine from brine using a PTFE hollow fiber-based supported gas membrane (SGM) process was studied. The experimental data demonstrated that the overall mass transfer coefficient obtained for feed containing Cl− such as real brine was much smaller than that for a simple aqueous bromine solution, which was mainly due to the association of Br2 with Cl− in the brine. Based on the stronger association between Br2 and Br− than that of Br2 and Cl−, NaBr instead of NaOH was selected as an absorbent for enrichment of bromine from brine. The results showed that NaBr as absorbent for enriching bromine using the SGM process was feasible and bromine could be enriched for > 14 times. Conventional distillation could be further applied to regenerate the stripping solution used, and a bromine-enriched stream was obtained as a raw product. A mathematical model was established to characterize the mass transfer of bromine when brine containing chloride ions was used as feed and NaBr or NaOH served as absorbents and the association between Br2 and Br− or Cl− was considered. The lab and pilot-scale study demonstrated that the PTFE membrane contactor was stable for a long-term operation of > 12 months.