Miscible Polymer Blend Membranes Bearing Pyrrolidone for Fractioning Sulfuric Acid and Sulfates

ABSTRACT Ion exchange membranes of new chemistry based on polymer blends are proposed through a convenient solution‐blending process using the hydrophobic commodity polymer polyvinyl chloride (PVC) and the hydrophilic polyvinylpyrrolidone (PVP), which are completely miscible. The pyrrolidone groups can be protonated to form oxonium ions, functioning as transient fixed positive charges for fractioning sulfuric acid and sulfates via diffusion. The influence of PVC molecular weight and the membrane composition on the physical, chemical properties, and mass transfer performance of PVC‐PVP blend membranes was systematically investigated. After equilibrium in 2.68 mol/L sulfuric acid, the sulfuric acid, and water contents in the blend membranes increase with the increase of the membrane PVP contents (20–75 wt%). The permeability coefficients of sulfuric acid and ferrous sulfate for the blend membranes also exhibit a gradual increase. Membranes of mass transfer properties comparable to commercial ones can be easily obtained by tuning the membrane PVP contents. It is proved that the larger sulfuric acid permeability over sulfates (FeSO 4 as an example) is due to both larger solubility and diffusion coefficient of sulfuric acid in the membrane phase. The optimal PVC‐PVP blend membranes have shown nice performance in fractioning sulfuric acid from sulfates, when treating titania waste acid. This study provides valuable guidance for the design of high‐performance yet low‐cost ion exchange membranes with pyrrolidone chemistry from commodity polymers for resource recovery.