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·g–1, respectively, at 298 K and pH ∼ 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.