Competitive removal of PGMs from aqueous solutions via dendrimer modified magnetic nanoparticles

Abstract

Competitive adsorption of Au(III)- Pd(II)-, and Pt(IV)-chlorido species were carried out using generation 3 diaminobutane poly(propylene) imine dendrimer micelle (G3-DM15) and palmitic acid (C15-acid) modified superparamagnetic iron oxide nanoparticles (SPIONs). The efficacy of the adsorbents in the recovery of the three metal chlorido species were tested by varying the solution pH and the contact time. SPIONs modified with both the G3-DM15 and C15-acid were not only stable in very acidic conditions (compared to the unmodified SPIONs) but also selective to Au(III)-Cl species with percentage efficiencies of more than 98%. The adsorption of the three metal chlorido species onto the four adsorbents obeyed the Langmuir isotherm. The unmodified SPIONs (ADS 1) and dendrimer modified SPIONs (ADS 2 and ADS 4) gave the highest maximum adsorption capacities for Au(III)-Cl species [17.07 mg g−1 (ADS 1), 6.48 mg g−1 (ADS 2) and 8.31 mg g−1 (ADS 4)] compared to SPIONs modified with only C15-acid (ADS 3) (1.17 mg g−1). The adsorption kinetics were evaluated using three kinetic models; pseudo-first-order, pseudo-second-order and intraparticle diffusion. The adsorption kinetics for all the three metal chlorido species best fitted the pseudo-second-order kinetics model. Desorption studies showed that all three metal chlorido species can be recovered from the adsorbents.