Integration Of Electrodialysis Technology For The Development Of Lithium From Primary And Secondary Resources

With the rapid development of modern electronics industry,lithium,as the lightest metal in nature,has gradually occupied the market with its wide application.Nowadays,the global resources of lithium are mainly classified as the primary resources and secondary resources.For primary resources,lithium mostly exists in the salt lake brines,clays,ores and seawater.Especially,about 62%of global lithium resources are deposited in the salt lake brines.For secondary resources,about 5-7%of lithium resources are deposited in the spent LIBs and the wastewater generated during LIBs production.Due to the fact that the traditional lithium extraction technology is high in pollution and energy consumption,electrodialysis technology has been emerged as the advantages of high efficiency,low energy consumption and environmentally-friendly.Therefore,this paper proposed an integrated electrodialysis technology for the recovery of lithium from primary and secondary resources.The first work of this paper mainly integrated selectrodialysis?SED?and bipolar membrane selectrodialysis?BMSED?to treat salt lake brine for the production of lithium hydroxide.The first step of SED process was preliminarily extracting lithium from high Mg²⁺/Li⁺ratio brine,and the second step of BMSED process was applied to prepare high purity Li OH.The current density and SED stack?CIMS/ACS,CSO/ASV?were used to investigate the membrane fouling and separation performance during SED process.Results indicated that when the current density is less than 12 m A/cm² and monitoring the p H of electrode solution below 7,the SED stack can effectively avoid membrane fouling.In addition,the separation performance for divalent ions by using CIMS/ACS stack was superior to CSO/ASV stack.In BMSED process,the purpose was to combine the monovalent selective ion-exchange membrane with bipolar membrane?FBM?inside the membrane stack to remove divalent ions and simultaneously produce Li OH.The results showed that the current density was optimized at 6 m A/cm².Compared with FBM/ASV/CSO stack and FBM/AMX/CMX stack,FBM/ACS/CIMS stack exhibited superior current efficiency approach 99%by using FBM/ACS/CIMS stack.Another work proposed an industrial lithium-containing wastewater depth concentrating system integrating reverse osmosis?RO?and electrodialysis?ED?.Specifically,the lithium-containing wastewater was primary purified with Ca²⁺and Mg²⁺by cation-exchange resins,and the effluent was pre-concentrated by RO process.Subsequently,a multi-stage ED process was used for deep concentrating of RO retentate,and Li₂CO₃ was extracted from the ED concentrated solution by adding of Na₂CO₃.The tested parameters were:RO operating pressure,ED voltage drop,conductivity of ED feed solution,ED volume ratio and ED operating mode.Compared with ED process,RO as the pre-concentrating process can reduce the energy consumption from 26.67 k W·h/m³ to 7.81 k W·h/m³.As the increase of RO retentate conductivity,the process capacity of ED process can be improved,and the cost of ED process can be decreased to 0.47$/kg.Furthermore,the final Li Cl concentration can approach as high as 87.09 g/L with the second-stage ED process?V_d:V_c=3:1?,while the total system concentration factor of 12.32 can be achieved.During the second-stage ED process,the experiment was stopped in region 1 could reduce the energy consumption of 7.71 k Wh/m³ and simultaneously,the dilute solution can be treated by RO again.