The design and adsorption behaviors study of Pd(II) removal materials deriving from quantitative electron transfer ratio evaluation

Abstract

Currently searching for effective noble metal separation material is generally blind and time-consuming. Although theoretical calculation has been widely applied to explain the adsorption mechanism, the quantitative coordination effect between ligand and metal remains to be explored especially in the material screening stage. In this study, Pearson’s theory and Koopmans' theory were used to calculate the electron transfer ratio (ΔN) from different ligands containing N, S, and O to PdCl2. The quantitative evaluation contributed to the design of efficient ligands including EA (ΔN =0.5929), DB (ΔN =0.5483), and AT (ΔN =0.4885). And the corresponding polystyrene materials CMPS-EA, CMPS-AT, CMPS-DB were successfully synthesized via chemical modification. According to the adsorption experiment, the per mmol of ligand adsorption capacity from CMPS-EA, CMPS-DB and CMPS-AT for Pd(II) were 0.67 mmol/mmol, 0.17 mmol/mmol and 0.11 mmol/mmol, respectively, exhibiting a positive correlation with the results of ΔN. Moreover, CMPS-EA could efficiently remove 98.01% Pd(II) in the presence of multiple competing metal ions with five times concentration higher than Pd(II). In column study, the breakthrough point (Ct/C0 =0.05) for CMPS-EA was 666–676 BV in 1 mmol/L Pd(II) solution and up to 95% desorption efficiency within 50 BV. The adsorption differences and mechanism of CMPS-EA, CMPS-AT and CMPS-DB were further investigated by FTIR, XPS, ESP, and NBO.