An ESIX Process With Self-electrical-energy Recuperation For Desalination And Extraction Of Lithium

As an environmentally benign ion separation and recovery technique,electrochemically switched ion exchange?ESIX?technology has attracted great attention.In the ESIX process,the ion uptake and release can be controlled directly by modulating the redox states of electroactive materials deposited on the conductive substrate,thereby separating ions in the treatment liquid and achieving film regeneration.The ESIX process is mainly driven by the potential,thus,no secondary waste can be produced.However,ESIX technology also has some technological inadequacies,such as the electrical energy is needed for the ion-capturing and ion-releasing in this ESIX process,and the relative energy consumption is high.In order to realize the energy recycling and improve ion recovery efficiency of ESIX technology,the ESIX system with self-electrical-energy recuperation was developed in this study.Energy can be generated in the system during extracting ions,which can provide part of the required energy for the ion release process.Seawater desalination is one important source of fresh water resources,and its effective utilization is becoming a significant source of fresh water.In this study,aiming at seawater desalination,iron ferricyanide?FeHCF?and polypyrrole?PPy?materials were prepared by chemical precipitation method firstly.Then two materials were made into film electrodes and used as Na-storage and Cl-storage electrodes,respectively.The ESIX process with self-electrical-energy recuperation was successfully used to remove NaCl from the simulated seawater solution,and the ion exchange capacity and energy consumption under different operating conditions were investigated.Under the optimal operating condition,the ion exchange capacity is 79.6 mg·g^-1 with a low energy consumption of 0.14 kWh·m^-3.Futhermore,86%of its initial desalination capacity was maintained even after 100 cycles.Compared to the traditional ESIX process without self-electrical-energy recuperation for desalination,this process also decreased 65%of energy consumption.On the other hand,with the rapid development of new energy,electronic information products,and the widespread application of lithium-ion batteries,the demand and price of lithium have increased significantly.Aiming at the lithium recovery,?-MnO₂ and bismuth oxychloride?BiOCl?materials were synthesized by hydrothermal method firstly.Then two materials were fabricated into film electrodes and used for selective extraction of Li⁺and Cl^-ions.The ESIX process with self-electrical-energy recuperation was successfully applied to extraction of lithium from brine,and the ion exchange capacities of the?-MnO₂ and BiOCl coated electrodes at different current densities were investigated.The extration of LiCl was measured by the ESIX system at the optimum current density.Ion exchange capacities of ESIX system in LiCl solutions with different concentrations were also investigated.The ion exchange capacity of the ESIX system can reach 42.02 mg·g^-1 in a 10 mM LiCl solution.The energy required of the ESIX process with self-electrical-energy recuperation during one cycle is about 13.5 Wh·mol^-1.Even after 200 cycles,the novel ESIX process can maintain 96.2%of the initial capacity.In addition,compared to the conventional ESIX process without the self-electric regeneration energy subsystem for the extraction of lithium,this process can decrease 66%of energy consumption.