Thermo‐responsive ReO₄⁻ composite membranes with SiO₂ modified: Preparation, performances and application in secondary resources

Abstract

With the continuous depletion of global rhenium resources, the separation and purification of rhenium (Re) from secondary resources became very important. Herein, an imprinted composite membrane with “flexible chain” thermo‐responsive imprinted separation layer structure (Re‐TIICM) was prepared to achieve selective separation and recovery of Re from secondary resources with complex composition. Re‐TIICM's thermo‐responsive imprinted separation layer occurred sol/gel phase transition by adjusting the temperature, which effectively mitigated the trade‐off between selectivity and desorption. The structure and performance of Re‐TIICM under optimum process conditions were tested and evaluated. The results showed that Re‐TIICM exhibited a maximum adsorption capacity of 0.1036 mmol/g at 35°C, a separation degree of 4.37 (MnO4− as disturbing ions), and remained good adsorption capacity and selectivity after 9 adsorption/desorption cycles. When Re‐TIICM was applied in secondary resources, the purity of Re increased from 35.412% to 70.208% after one adsorption/desorption cycle, showing a great potential for industrial applications.

Study on the Preparation and Performances of Thermoresponsive Imprinted Polymers for Selective Separation and Purification of Ru(III)

“…The size of the imprinted cavities decreased, which made the template more difficult to enter, and the number of effective adsorption sites became fewer. Therefore, the adsorption capacity was the lowest …”

“…46 The characteristic peak at 1536 cm −1 was the deformation vibration of N−H in N-MAM. 47 The characteristic peaks at 1457 and 1396 cm −1 were the deformation vibration of −CH− in AA, N-MAM PDEA, and chitin. The characteristic peaks at 1251 cm −1 could be assigned to the stretching vibrations of C−N and O�C−O in N-MAM, PDEA, chitin, and AA.…”

“…In addition, the rate of desorption decreased due to the increasing concentration of Ru(III) in the desorption solution and the increasing diffusion resistance. 47 Finally, with the desorption taking place, the adsorption would coexist, and the adsorption rate would increase with the desorption ratio; as the desorption and adsorption rates became equal, the desorption would reached equilibrium.…”

“…Therefore, the adsorption capacity was the lowest. 47 In order to investigate the adsorption process of Ru(III)-TIIP on Ru(III), the adsorption kinetic data were fitted by the pseudo-first-order and pseudo-second-order models. The results of the fitting are shown in Figure 4b,c and Table S5, from which it could be seen by comparison (R 2 ) that the pseudo-second-order model better describes the adsorption process, indicating that the adsorption of Ru(III)-TIIP on Ru(III) was mainly controlled by diffusion.…”

“…As the concentration increased, the adsorption was gradually transferred to ICD and FAL, the affinity was weakened, the equilibrium constant decreased, and the increasing degree of Q e gradually decreased. 47 Considerably, Q e (33 °C) > Q e (25 °C) > Q e (40 °C), which was due to the introduction of the temperature-sensitive block PDEA-b-P(DEA-co-AM). The temperature-sensitive block could regulate the shape of the imprinted cavities by changing the external temperature.…”