Preparation and Adsorption Performance of Polyvinyl Chloride/Polyacrylonitrile Blended Lithium Ion-Sieve Membrane

To address the limitations of ion-sieve powder in industrial applications and to facilitate the industrial application of lithium extraction through ion sieves, this study utilized the solvent exchange method to prepare a PVC/PAN-H_1.6Mn_1.6O₄ lithium ion-sieve membrane, which exhibited both stable mechanical properties and excellent hydrophilicity. The membrane structure was characterized by XPS, FT-IR, BET, SEM, and other analytical techniques. The results revealed the presence of hydrophilic cyano groups (–C≡N) in the blend ion-sieve membrane, accompanied by micropores with dimensions ranging from 20 nm to 40 nm. Under the conditions of PVC:PAN = 7:3, the binder concentration of 13%, and H_1.6Mn_1.6O₄ content of 25%, the adsorption capacity of the ion-sieve membrane reached 1261.5 mg/m². The Langmuir adsorption isothermal model and the pseudo-second-order kinetic model indicated that the adsorption process of Li⁺ followed a multi-step controlled monolayer chemisorption process. Simultaneously, the ion-sieve membrane demonstrated exceptional selectivity and remarkable cycle stability for Li⁺ in the multi-ion coexistence system. This study provides guidance for the excellent application of lithium ion-sieve membranes in efficiently recovering Li⁺ from Salt Lake brine.