Purification Of Trace Iodine In The Production Of Ionic Membrane Caustic Soda By Resin Adsorption

In order to solve the problem of iodine exceed standard seriously affecting the working life of ionic membrane in the production of ionic membrane caustic soda,the purification of iodine in brine by resin adsorption was carried out in this thesis.The parameters for the elimination of iodine from raw brine and refined brine were obtained in our laboratory,and subsequently the pilot-scale experiment for the purification of iodine in refined brine was further carried out,by which relative parameters for iodine purification needed in the industrialized process were acquired,and it provided important basic data for the effective solution of iodine problem in chlor-alkali industry.Main conclusions presented in this thesis are summarized as following.(1)For the determination of trace iodine in brine:the analysis method of iodine in brine by As(III)-Ce4+ catalytic spectrophotometry was improved.The linear range was extended to 1.5 mg/L under the condition of decreasing the usage of arsenite and without sampie digestion.Meanwhile,the reliability for the analysis of trace iodine in brine was confirmed by these indexes such as precision,recovery,detection limit.(2)For the purification of iodine in raw brine:the iodine in raw brine can be effectively adsorbed by macroporous anion exchange resin at pH=2.0 and Eh=520 mV.The concentration of iodine can be decreased to no more than 0.2 mg/L.This result shows that the purification of iodine in brine by adsorption is feasible.(3)For the purification of iodine in refined brine:the optimum reduction conditions of iodine for iodine conversionin refined brine were acquired.A 5 L brine adsorbed by 20 g resin can decrease the concentration of iodine to less than 0.2 mg/L at the conditions pH=2.0 and Eh=500 mV through adjusting voltage with Na2SO3 solution.(4)For the elution and regeneration of resin:the optimum composition of the eluent 10%NaCl + 5%NaOH + 10%Na2SO3 was selected through a series of investigations.The results of cyclic use of resin showed that cyclic operation had little influence on the adsorptive property of resin.(5)For the pilot-scale experiment:the optimum pH and Eh were 1.9 and 520 mV respectively for the purification of iodine in refined brine when they were adjusted with HCl and Na2SO3 through automatic control devices.When refined brine containing 1 mg/L iodine was adsorbed by 200 cm×?30 cm ion exchange column filled with through a series of anion exchange resin at the selected conditions,the concentration of iodine in processed brine was no more than 0.2 mg/L after stable operation 19 days.