Complexation during Sorption of Palladium(II) Ions by Chemically Modified Silica

Abstract

Complexation during the sorption of palladium(II) ions from chloride media by chemically modified silicas has been studied. Due to the use of mesoporous silicas with an average pore diameter of >10 nm for their synthesis, these sorbents do not change their volume in aqueous and organic media and have high mass transfer characteristics. The dependences of the sorption of Pd(II) ions from chloride solutions under static conditions as a function of time, HCl concentration, and Cl– ion have been obtained; sorption isotherms are constructed. Based on the experimental data, a conclusion has been made about the coordination mechanism of sorption, which has been proved by a combination of spectral methods (IR, UV-VIS, and X-ray photoelectron spectroscopy). The structure of sulfur-containing sorbents and their complexes with palladium has been modeled using the DFT M06 quantum-chemical method in the def2tzvp basis in the gas phase and taking into account the H2O solvent. The performed calculations make it possible to substantiate the nature of the dependence of sorption on the acid concentration and to confirm the formation of palladium(II) complexes with bidentate coordination of ligands in the silica phase modified with thiosalicylic and mercaptoacetic acids.

Chelating polymers with valuable sorption potential for development of precious metal recycling technologies

A special attention is currently focused on the recovery of Au, Ag, Pt, Pd and Rh from both primary and secondary sources. From the wide range of sorbents that have been used in this respect, the required selectivity is proved only by the chelating polymers containing donor N, O and S atoms in their functional groups. This work presents the recent published researches on this topic, pointing out the capabilities of chelating sorbents based on organic synthetic polymers for a sustainable development. The chelating sorbents are differentiated and reviewed according to their synthesis strategy and compatibility with synthetic and real matrices. First, an overview on the novel functionalized polymers and impregnated resins with good selectivity for the recovery of most valuable precious metals from synthetic leach solutions is given. Subsequently, the performances of these materials in the selective and preconcentrative recovery of Au, Ag, Pt, Pd and Rh from simulated and real leachates are discussed. The viability of an integrated approach for the determination of precious metals from simulated solutions by solid phase spectrometry is highlighted. The transposition of chelating polymers’ potential in challenging technologies for precious metal recovery-reuse-recycling needs further research on directions that are proposed.