Understanding the Adsorption Behavior and Mechanism of Pt(IV) and Pd(II) on Super Amino-Modified Monodispersed PGMA Microspheres

The present investigation described the application of high-capacity amino-group-functionalized polyglycidyl methacrylate monodispersed microspheres (PGMA-N) in the adsorption of Pt(IV) and Pd(II) ions from simulated wastewaters. The adsorption capacities of Pt(IV) and Pd(II) on PGMA-N were determined to be 3.93 and 4.99 mmol<middle dot>g(-1), respectively, at 298 K and pH similar to 4. These capacities are greater than those reported for other adsorbents in the literature. Rapid adsorption kinetics were observed for Pt(IV) and Pd(II) on PGMA-N; equilibrium was reached within 15 min. Co2+, Cu2+, Ni2+, Fe3+, Al3+, and Cr3+ were utilized as representatives for competitive adsorption of metal ions, and the good separation selectivity of PGMA-N was observed for Pt(IV) and Pd(II) at pH 1-3. The pH range in which the adsorbent demonstrated optimal selectivity was extended to 1-6 with the addition of EDTA. The -NH2, -NH- functional groups on PGMA-N form stable, five-membered chelate rings through synergistic coordination with Pt(IV) or Pd(II), as determined by zeta potential, pH titration, XRD, FTIR, and XPS analysis.