Silica-supported thiourea resin for efficient recovery of Pd(II): Batch, column and mechanism study

Palladium is versatile in many industrial applications due to its distinct physicochemical properties . Due to the scarcity of natural resources and the growing market demand, palladium recovery from wastes such as spent catalysts is receiving increasing attention. Here, a silica-supported thiourea resin (SiPS-TU) was prepared and applied to separate Pd(II) from spent catalysts. The SiPS-TU was fabricated through in situ polymerization and post modification method using amorphous macroporous silica as the matrix. Experimental results suggested that the optimal acidity for the adsorption process was 0.1 M under selected range, and the uptake of SiPS-TU was affected by H + and Cl − . The adsorbent showed rapid sorption kinetics with an equilibrium attained in 30 min, while more than 3 h was required for the commercial D840 resin. Column tests showed that SiPS-TU had excellent dynamic separation property for Pd(II) in continuous process. Around 215 bed volumes (430 mL) of Pd(II) solution could be effective treated by the SiPS-TU bed before breakthrough at 4 mL/min, while D840 resin bed was less effective under equivalent conditions (20 mL). In view of its satisfactory adsorption performances, palladium was successfully separated from the catalyst leaching solution by SiPS-TU. XPS spectra and DFT calculations indicated that the adsorption mechanism of SiPS-TU for Pd(II) mainly involved anion exchange and coordination. In conclusion, this study provides a feasible material for palladium recovery from practical leachate.