A Reversible Or Irreversible Absorption-based Hollow Fiber Supported Gas Membrane Process For Enriching Bromine From Brine

Hollow fiber supported-gas-membrane?SGM?process for enrichment of bromine from brine has advantages of large specific surface area,high mass transfer rate,low energy consumption,less occupied area and flexible operation and so on.However,the membrane itself is one of the key factors restricting the industrial application of SGM process for enriching bromine.The membrane for enriching bromine must have strong resistance to oxidation of chlorine and bromine and corrosion of acid and base.PTFE membrane has strong hydrophobicity,anti-oxidation and anti-corrosion ability,which is the ideal membrane material for enriching bromine from brine.In this study,the experiments of SGM process for enriching bromine based on irreversible absorption?NaOH as absorbent?and reversible absorption?NaBr as absorbent?were respectively carried out by using PTFE hollow fiber membrane module.The experimental results of NaOH as absorbent showed that existence of chloride ions in brine was one of the key factors affecting the enrichment of bromine by SGM process.A higher chloride concentration could decrease the mass transfer rate in SGM process because of the association between chloride ions and molecular bromine.The temperature had a great effect on the overall mass transfer coefficient and the recovery rate of bromine,and the increase of temperature could improve the mass transfer rate significantly.The feed-in concentration of bromine,feed-in flow rate and the concentration and flow rate of stripping solution had little effect on mass transfer process.During the continuous operation for 3 months,PTFE hollow fiber membrane module showed good stable operation performance.Based on a stronger association between Br₂ and Br?than that between Br₂ and Cl?,NaBr instead of NaOH was selected as the absorbent for enrichment of bromine from brine.The results showed that NaBr as absorbent for enriching bromine by SGM process was feasible and bromine could be enriched for>14 times.Among the influencing factors of SGM process,the operating temperature and the concentration of NaBr in the stripping solution had a great influence on mass transfer rate;the initial concentration of bromine in stripping solution,the flow rate of feed and stripping solution had a slight influence,and the feed-in concentration of bromine had almost no effect on mass transfer process.Conventional distillation could be further used to regenerate the used absorption solution,and a stream containing 80wt%was obtained as a raw product from top of the column,and the regenerated NaBr solution could be obtained from the bottom.Mathematical model was established to characterize the mass transfer when NaBr and NaOH respectively served as absorbent,in which the association between Br₂ and Br?or Cl?was considered.This study provides the technical foundation and the new idea for the industrial application of SGM process for enrichment of bromine from brine.