Ion-imprinted chitosan fiber for recovery of Pd(II): Obtaining high selectivity through selective adsorption and two-step desorption

Selective separation of platinum group metals from acidic solutions is of great importance due to their cumulative supply risk and environmental concern. In this study, a Pd(II) ion-imprinted chitosan fiber (ICF) was prepared as the novel adsorbent, and a well-designed two-step desorption process was implemented for selectively recovering Pd(II) from acidic solution containing Pd(II) and interfering metals of Co(II), Ni(II), Cu(II) and Pt (IV). The ICF showed higher selectivity for Pd(II) adsorption, comparing the non-imprinted chitosan fiber (NICF) towards other metals adsorption. The first selective desorption was achieved by NaOH solution, since only Pt (IV) adsorbed on the ICF in a small amount could be eluted, without any acting on Pd(II) ions. The second desorption process was carried out using acidified thiourea solution for the exclusive Pd(II) ions desorption. Therefore, much higher selective recovery of Pd(II) was achieved through ICF with a good selective adsorption performance and a well-designed desorption process. Furthermore, the mechanisms of selective adsorption and desorption were investigated by X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD) analyses. Finally, ICF-packed column system was conducted using synthetic multiple metals solution and a practical hydrometallurgy wastewater as influent, respectively, with a good adsorption capacity of 87.2 mg g⁻¹ and 94.2 mg g⁻¹, resulting quite high concentrated effluent consisted of 97.4% of Pd(II) and 99.5% of Pd(II), respectively. It was opened up a promising designed material and technique for selectively recovering Pd(II) in the further practical large-scale application.