Modified Poly(vinylidene fluoride) by Diethylenetriamine as a Supported Anion Exchange Membrane for Lithium Salt Concentration by Hybrid Capacitive Deionization

Abstract

This paper shows the investigation for the optimal anion exchange membranes (AEM) supporting the desorption step of the HCDI process. The chemical modification of PVDF by diethylene triamine created the AEM. To confirm the ion-exchange character of materials, the chemical analysis with FTIR, SEM, surface energetics, and transportation analysis were applied. Next, the investigated membranes were applied for the sorption and desorption of lithium chloride. The specific sorptive parameters were higher according to the incorporation of the nitrogen groups into polymeric chains. Considering the desorption efficiency, membranes modified by four days were selected for further evaluation. The application in the HCDI process allowed reaching the desorption efficiency at 90%. The system composed of PVDF-DETA4 membrane was suitable for sorption 30 mg/g of salt. By applying the PVDF-DETA4 membrane, it is possible to concentrate LiCl with four factors. The anion exchange character of the developed membrane was confirmed by adsorption kinetics and isotherms of chlorides, nitrates, sodium, and lithium. The prepared membrane could be considered a perspective material suitable for concentration salt with electro-driven technologies for the above reasons.