Design of smart ion-selective membranes based on ion-imprinted polymers (IIPs) using photopolymerization method for cadmium ion (Cd ²⁺ ) adsorption

Abstract Ion imprinted polymers (IIPs) are polymeric materials that possess specific recognition cavities capable of selectively binding target ions. This study aims to synthesize Cd 2+ -based IIPs as selective adsorbents for cadmium ions. The synthesis was carried out using Cd(NO 3 ) 2 ·4H 2 O as the template ion, MAA as the functional monomer, EGDMA as the crosslinker, and DMPP as the initiator. The synthesized IIPs were characterized using FTIR. The FTIR spectrum shows a difference in the C–O absorption band, namely 1,144.75 cm −1 on NIP and 1,145.41 cm −1 on IIPs-Cd. Then, the C–O absorption band shifted to 1,144.05 cm −1 when Cd was extracted from IIPs-Cd, but the absorption band reappeared at 1,144.72 cm −1 after Cd 2+ rebinding, which indicated the presence of Cd–O coordination interaction and confirmed that the printing process was successful. The highest adsorption capacity was achieved at an MAA: EGDMA ratio of 1 mmol:4 mmol, pH 4, an extraction time of 60 min, a contact time of 30 min, and an initial Cd 2+ concentration of 25 mg/L, yielding a maximum adsorption capacity of 0.6528 mg/g. The adsorption process followed the Langmuir isotherm model with an R 2 value of 0.9551 and exhibited high selectivity toward Cd 2+ compared to competing ions Zn 2+ , Cu 2+ , and Pb 2+ .