Polyethylenimine functionalized sulfur-containing POSS-based dendritic adsorbent for highly efficient and selective capturing of precious metal ions

A novel branched polyethylenimine (PEI) functionalized sulfur-containing polyhedral oligomeric silsesquioxane (POSS)-based dendritic adsorbent (POSS-S-PEI) has been synthesized for the highly proficient and selective capturing of precious metal ions such as platinum (Pt(IV)) and palladium (Pd(II)). The developed POSS-S-PEI exhibits not only highly proficient uptakes of 589.4 ± 23.9 mg/g for Pd(II) and 548.8 ± 19.6 mg/g for Pt(IV), but also high selectivity for these precious metal ions in the mixture of common, coexisting, and heavy metal ions, at pH 1. The adsorption studies accord with the Langmuir isotherm, and pseudo-second-order as well as intraparticle diffusion kinetic models. The uptakes of these precious metal ions were spontaneous and endothermic in nature. The electrostatic interaction, H-bonding, and chelation, between the protonated primary, secondary, and tertiary amino groups as well as the electron donor atoms (O-, S-, and N-) of POSS-S-PEI and these precious metal ions, are crucial factors during the adsorption process. The developed POSS-S-PEI not only exhibits a strong acid-resistance in very low pH, but also demonstrates outstanding reusability for these precious metal ions after five sorption cycles. This work clarifies the potential of POSS-S-PEI that can selectively eliminate precious metal ions from low pH medium, would be significant for the practical application in industry.