Recycling Vanadium and Proton-Exchange Membranes from Waste Vanadium Flow Batteries through Ion Exchange and Recast...

This study aims to provide a system to recycle vanadium resources and recover membranes from waste proton-exchange membranes. This research is divided into two parts. To begin, ion exchange batch and column experiments were applied to adsorb vanadium in a membrane. In this process, the waste membrane was initially dissolved in a 50% ethanol solution, and the suspension obtained by dispersing the membrane had 74 mg/L of vanadium. Then, Dowex G26 resin was used to adsorb vanadium from the membrane dispersion in the ion-exchange process. The adsorptive behavior and optimal parameters were explored in this study. The vanadium ions were then eluted by HCl to obtain an enrichment solution, and the V₂O₅ was received through precipitation and calcination methods. After obtaining the vanadium-free dispersion, the recycled membrane was prepared by recasting it in the second part. The characteristics of the recycled membrane, such as the moisture, FTIR spectra, ion-exchange capacity, and ion conductivity, are discussed. The results revealed that the adsorption capacity of vanadium through Dowex G26 was 81.86 mg/g. The eluting efficiency of HCl was 97.5%, and the optimal parameters of the precipitation and calcination processes were set as pH 5, NH₄Cl:V = 2:1, and 350 °C. The moisture of the recycled membrane was 25.98%, and the IEC was 0.565 meq/g. The consequences of FTIR and ion conductivity demonstrated that the vanadium in the recycled membrane was eliminated by the ion-exchange method; however, the microstructure of the recycled membrane was influenced during ion exchange and recasting.