Au(III), Pd(II) and Pt(IV) adsorption on amino-functionalized magnetic sorbents: Behaviors and cycling separation routines

In this paper, superparamagnetic Fe3O4@SiO2-NH2 nanoparticles were applied to adsorb Au(III)/Pd(II)/Pt(IV) in HCl medium. The successful synthesis of Fe3O4@SiO2-NH2 was characterized through TEM, SEM and FT-IR. Electrostatic interaction between magnetic NPs and metal anions was proposed as the main adsorption mechanism by zeta potential analysis. Maximum adsorption capacities and adsorption behaviors under metal anions concentrations, acidity, NaCl, kinetic and isotherm models were investigated. Notably, the Fe3O4@SiO2NH2 shows the excellent acidity and salinity resistance on Au(III), Pd(II) adsorption. The separation routine among Au(III), Pd(II) and Pt(IV) was proposed. As investigated, Pt(IV) could be isolated due to the less adsorption amount onto Fe3O4@SiO2-NH2 (<= 1%). Then, the adsorbed Au(III) was eluted selectively by HCl+ N-hexanol alcohol + ethanol + H2O2 mixing solution. Then, the adsorbed Pd(II) was completely eluted by thiourea solution. The recovery efficiencies of Au(III), Pd(II) and Pt(IV) were kept over 92%, 97% and 94% respectively, during 5 turns of cycling separation experiments. Total loss amount of Fe is around 7%. Hence that, the particle demonstrates the good stability and high adsorption capacity, which possess great potential for practical Au(III), Pd(II) and Pt(IV) separation.