Chitosan-Comodified Surface-Grafted Thermosensitive Ion-Imprinted Composite Membrane for the Selective Recognition and Separation of ReO₄^–

With decreasing global rhenium resources, it has become important to separate and purify rhenium in secondary resources, so a preparation strategy for a chitosan-comodified surface-grafted thermosensitive ion-imprinted composite membrane (CS-Re-TIICM) was developed in this work. The key of this design was that the two ends of a poly(N,N-diethylacrylamide) (PDEA) chain were grafted onto the imprinted polymer separating the layer matrix and the surface of the membrane, respectively, which aimed to improve the selectivity and desorption ratio of this material simultaneously. The structure and morphology of this material were characterized by FTIR and SEM, respectively. In addition, CS-Re-TIICM was applied to the secondary leaching solution of the high-temperature alloy to test the actual separation effect, and results showed that CS-Re-TIICM, possessing thermoresponsive recognition sites, and the structure of the imprinting cavity could be adjusted by temperature, which helped this material achieve good selective separation and purification performance for ReO₄^–. The maximum adsorption capacity was 0.1071 mmol/g at 35 °C. CS-Re-TIICM not only showed an excellent selectivity (separation ReO₄^–/MnO₄^– of 3.90 in the presence of interfering ion MnO₄^–) but also presented an excellent desorption performance (desorption ratio of 68.94%) and good reusability (adsorption capacity of 0.0425 mmol/g, desorption ratio of 59.13%, and separation degree of 1.24). When CS-Re-TIICM was applied to the secondary leaching solution of high-temperature alloys, the purity of Re was increased from 35.41% to 65.10% after one adsorption/desorption cycle, which depicted a prospective application in the industrialized separation of ReO₄^– from a complex environment.