Selective adsorption of Pd (II) by ion-imprinted porous alginate beads: Experimental and density functional theory study

In this study, a novel thiourea grafted porous sodium alginate-based adsorbent was synthesized by combining ion-imprinting and direct templating method. Due to ion-imprinting, the prepared adsorbent has demonstrated outstanding selectivity towards Pd (II) from bi-metallic solution at different pH values. Langmuir and both pseudo-first and pseudo-second kinetic equations were used to describe the adsorption isotherm and kinetics, respectively. FT-IR, XPS, and SEM-EDX analyses suggested that selective adsorption of Pd (II) was dominated by electrostatic interactions at pH 1.0 and chelation on imprinted sorption sites at pH 3.0. Density functional theory (DFT) calculation further explained the effect of ion-imprinting and provided two binding configurations, which is consistent with characterization analyses. The pregnant adsorbent can be regenerated and reused by thiourea solution in dilute hydrochloric acid. Therefore, the synthesized adsorbent would be useful as a selective adsorbent for the enrichment of Pd (II) from effluents. (C) 2020 Elsevier B.V. All rights reserved.