Selective adsorption of palladium(II) from aqueous solution using epichlorohydrin crosslinked polyethylenimine-chitin adsorbent: Batch and column studies

Selective adsorption of platinum group metals (PGMs) from mixed metals solution is still a challenging issue. Here, we reported the effective palladium (Pd(II)) separation from a multi-metal solution by epichlorohydrin crosslinked polyethylenimine-chitin composite (PEI-chitin), a pH-dependent selective adsorbent. The possible adsorption mechanism of PEI-chitin for Pd(II) was revealed by FE-SEM-EDS, FTIR, and XPS characterization. The adsorption performance of PEI-chitin towards Pd(II) was evaluated by batch and column experiments. In batch adsorption experiments, the theoretical Pd(II) uptake on PEI-chitin calculated using the Langmuir model was 872.1 mg/g, which was 4.4 and 8.5 times higher than that of the Amberjet 4200 and SYL-0830, respectively. The Pseudo-first-order model described the adsorption of PEI-chitin for Pd(II), and the adsorption equilibrium was reached within 10 min, which was faster than that of Amberjet 4200 and SYL-0830. The effect of pH experiment proved that the optimal pH for selective adsorption was 1.0. The column adsorption properties were measured at different flow rates, bed heights, and initial concentrations, and the breakthrough curves were well represented by the Thomas and Yoon-Nelson models. Moreover, the PEI-chitin demonstrated good selective performance for Pd(II) in the column system. The exhausted adsorbent was easily regenerated under acidified thiourea solutions and was reusable repeatedly.

Automated summary

Selective adsorption of palladium (Pd(II)) from a multi-metal solution was achieved using pH-dependent selective adsorbent PEI-chitin. The adsorption capacity of PEI-chitin for Pd(II) was higher than other commercial adsorbents, with faster adsorption kinetics observed. In column experiments, PEI-chitin demonstrated good selectivity and regenerability for Pd(II).