Regulation of Polyvinyl Alcohol/Sulfonated Nano-TiO₂ Hybrid Membranes Interface Promotes Diffusion Dialysis

It is important to emphasize that the adjustment of an organic-inorganic interfacial chemical environment plays an important role during the separation performance of composite materials. In this paper, a series of hybrid membranes were prepared by blending polyvinyl alcohol (PVA) solution and sulfonated nano-TiO₂ (SNT) suspension. The effects of different interfacial chemical surroundings on ions transfer were explored by regulating the dosage content of SNT. The as-prepared membranes exhibited high thermal and mechanical stability, with initial decomposition temperatures of 220-253 °C, tensile strengths of 31.5-53.4 MPa, and elongations at break of 74.5-146.0%. The membranes possessed moderate water uptake (WR) values of 90.9-101.7% and acceptable alkali resistances (swelling degrees were 187.2-206.5% and weight losses were 10.0-20.8%). The as-prepared membranes were used for the alkali recovery of a NaOH/Na₂WO₄ system via the diffusion dialysis process successfully. The results showed that the dialysis coefficients of OH^- (U_OH) were in a range of 0.013-0.022 m/h, and separate factors (S) were in an acceptable range of 22-33. Sulfonic groups in the interfacial regions and -OH in the PVA main chains were both deemed to play corporate roles during the transport of Na⁺ and OH^-.