Treatment of simulated brominated butyl rubber wastewater by bipolar membrane electrodialysis

A large amount of wastewaters containing sodium bromide (NaBr) is usually generated during the production of brominated butyl rubber; it can cause contamination of the environment. In this study, a method was reported to regenerate hydrobromic acid (HBr) and sodium hydroxide (NaOH) from a simulated NaBr wastewater by bipolar membrane electrodialysis (BMED). Sodium hydroxide may be recycled in the neutralization washing process of preparing the brominated butyl rubber. The effects of operation parameters, such as sodium bromide concentration, current density, and initial acid and base concentrations, on regeneration were analyzed, on the basis of proper energy consumption and current efficiency. The results indicated that a low energy consumption and a high current efficiency were achieved when the concentration of sodium bromide was in the range of 11,000–16,000 mg/L with both the initial concentration of the acid and base at about 0.10 mol/L. Additionally, it was also demonstrated that a high current density applied to the BMED stack usually resulted in both higher energy consumption and current efficiency. Finally, a discharged NaBr concentration of 133.9 mg/L, which was far below the discharge standard of water pollutants for industry, could be obtained from the initial concentration of 16,000 mg/L after the operation of BMED process for 3.5 h. Therefore, this process cannot only achieve the elimination of environmental pollution, but also the recycling of resources.

Graphical abstractSchematic of BMED system operating principle: the principle of BMED lies in the use of a bipolar membrane where water is splitted into H+ and OH− under a reverse bias current. Because of the technical advancements, economical competence, and environmental benignity, it is firstly used to treat the simulated brominated butyl rubber wastewater. The process was optimized. The NaBr concentration drops to 133.9 mg/L after 3.5 h operation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Treatment of wastewater of brominated butyl rubber using bipolar membrane electrodialysis (BMED) was firstly reported. ► The regenerated NaOH may be recycled in the neutralization washing process of preparing brominated butyl rubber. ► The performance results confirm the feasibility of treating the industrial wastewater of brominated butyl rubber by BMED.