Asymmetric Capacitive Deionization With Resin-activated Carbon Electrodes For Separating And Enriching Vanadium

Vanadium is an important rare metal that has been widely used in emerging industries because of its unique properties.At present,extracting vanadium from vanadium-bearing shales,while the acid leaching solution contains various impurity ions.Therefore,it is imperative to achieve environment-friendly and high-efficiency separation and enrichment of vanadium from the acid leaching solution.In this study,three kinds of anion exchange resins were used with activated carbon?AC?to fabricated the resin/AC composite electrodes in capacitive deionization to investigate the effect of adding resin on composite electrode properties as wettability,pore distribution and electrochemical properties.Moreover,the adsorbing and separating vanadium were investigated by asymmetric capacitive deionization,and exploring the cyclic stability performance.The main conclusions this study as listed below:1.The resin/AC composite has excellent specific surface area,pore volume,wetting property and electrochemical performance,indicating resin/carbon composite has great potential as electrode materials for the electro-adsorption in capacitive deionization.The increasing of the pH of solution is beneficial to the adsorption of vanadium by composite electrode,and can reduce the reduction rate of vanadium by capacitive deionization process because of the various vanadium species in the solution with different pH.The adsorption of vanadium is slightly effected by the operational voltage may be due to that the adsorption of vanadium is mainly dependent on ion exchange with resins and only a minority of vanadium is adsorbed by electrostatic adsorption.But as operational voltage going up,the reduced vanadium in solution increased.2.The performance of adsorbing and separating vanadium from solution by asymmetric is effected by the pH of solution and operational voltage.The adsorption capacity of vanadium and separation factor increases with pH going up.The reduction rate and energy consumption decrease because VO₂⁺declines with pH increase.The higher operational voltage can enhance the selective of asymmetric capacitive deionization,but show poor effect on adsorption V,this is because faradic reaction has negative impact on adsorption in asymmetric capacitive deionization process.The reduction of V and energy consumption also enhance for enough VO₂⁺to be reduced.Combined with the adsorption and separation behavior of vanadium in the solution,the redox reaction in adsorption process can be reasonably utilized in the asymmetric capacitive deionization to improve the separation effect of the composite electrode on the ions in the solution.3.Separation and enrichment of vanadium in solution can be achieved by asymmetric capacitive deionization process.Short-circuiting is beneficial to wash impurity ions from electrodes adsorbing vanadium because impurity ions mainly are adsorbed on electric double layers,short-circuiting can make electric double layers dismissing thus impurity ions are released into wash water.3M H2SO4 can desorb vanadium from electrodes and it can be repeatedly used to enrich V.Compared with the desorbed solution obtained by different capacitance adsorption,the asymmetric capacitive deionization process has better separation and enrichment performance.