Amino- and sulfur-containing POSS for highly efficient and selective extraction of platinum group elements from acidic solution

Abstract

As the platinum group elements (PGEs) are very important, expensive, and scarce in the earth's crust, the selective extraction and recovery of these elements from electronic wastes is an efficacious strategy to address the increasing demands for these elements' resources. This study reports the design and execution of a novel amino- and sulfur-containing polyhedral oligomeric silsesquioxane (POSS–S-DETA) for highly efficient and selective extraction of precious PGEs such as Pd(II) (PdCl42−) and Pt (IV) (PtCl62−) from acidic aqueous medium. The developed material shows not only very high adsorption efficacies of 505.4 ± 18.1 mg g for Pd(II) and 433.9 ± 13.9 mg/g for Pt (IV), but also proficient selectivity for these PGEs in presence of various interfering metal ions such as Mg(II), Zn(II), Cu(II), Pb(II), Cd(II), and Fe(III). The sorptions of these PGEs accord with the Langmuir isotherm, pseudo-second-order, aswellas intraparticle diffusion kinetic models. The thermodynamic data demonstrates that the sorptions of these PGEs are endothermic and spontaneous. Density functional theory (DFT) calculation shows that strong binding energies are involved among POSS-S-DETA and these PGEs during adsorption. The adsorption mechanism is found to be the electrostatic interaction, hydrogen bonding, and chelate bond formation among the active functional sites of POSS-S-DETA and the used PGEs. The developed material not only demonstrates proficient acid-resistance at pH 1, but also shows excellent repeatability for these PGEs up to eight consecutive cycles. So, these results suggest that the developed POSS-S-DETA has high potential for practical application in the selective adsorptive elimination of PGEs from acidic solution.