Preparation, characterization and adsorption characteristics of diatom-based Cd(II) surface ion-imprinted polymer

In order to effectively treat wastewater containing heavy metal ions and form comprehensive utilization of resources, we prepared a novel diatom-based Cd(II) ion-imprinted polymer (Dt-IIP) based on surface imprinting technique by using the diatomite as a matrix material and 3-mercaptopropyltrimethoxysilane (MPS) as a functional monomer. Through SEM, XRD, XPS, TGA, FTIR and Elemental analysis to confirm the structural transformation and composition changes of the materials during the preparation process. The optimal pH, kinetics, adsorption isotherms and thermodynamics of ion-imprinted polymer for Cd(II) adsorption process were investigated. The experimental results showed that the optimal pH value of the adsorption process was 6.0 and the theoretical maximum adsorption capacity was 5.5025 mg g(-1). The adsorption reaction conformed to the Langmuir isotherm model and kinetic data was more suitable to be explained by pseudo-second-order model. Furthermore, the thermodynamic adsorption process was spontaneous and endothermic. The analysis of XPS and FTIR revealed that the adsorption of Cd(II) ions was achieved mainly through the interaction of Cd(II) ions with thiol groups. Compared with non-imprinted polymer (Dt-NIP), Dt-IIP possessed a higher adsorption capacity and superior selectivity for target ions. In addition, test of regeneration showed that the Dt-IIP was reusable and stable.