Recovery of Au(III), Pt(IV), and Pd(II) Using Pyridylethyl-Containing Polymers: Chitosan Derivatives vs Synthetic Polymers

The sorption properties of <i>N</i>-2-(2-pyridyl)­ethylpolyethylenimine (PEPEI), <i>N</i>-2-(2-pyridylethylpolyallylamine (PEPAA), and <i>N</i>-2-(2-pyridyl)­ethylchitosan (PEC), synthesized via the aza-Michael reaction with 2-vinylpyridine and cross-linked with epichlorohydrin, have been investigated. It was shown that sorption capacities toward Pd­(II) and Pt­(IV) changed in the order PEPEI > PEC > PEPAA, with the maximal capacity of 4.6 mmol Pd/g for PEPEI. All the derivatives showed comparable efficiencies in Pt­(IV) uptake, with sorption capacities within the range 2.4–2.7 mmol/g. PEC was found to be the most efficient sorbent for Au­(III) recovery, with the sorption capacity equal to 4.9 mmol/g. XPS investigations have revealed that sorption of Au­(III) and Pt­(IV) by polymer precursors and all pyridylethyl derivatives is accompanied by changes in metal oxidation states. No direct correlation between sorption capacities and total ion-exchange capacities of the polymers was found, showing that noble-metal ions were recovered by pyridylethyl derivatives via chelation and/or redox sorption mechanisms rather than ion exchange. Pyridylethylation was beneficial to increase the efficiency of platinum and palladium elution after the sorption on PAA and PEI derivatives and of gold elution after sorption on the chitosan derivative, which enhances the potential of the application of these polymers in sorption/regeneration cycles

Data

The Data.zip consists of the data of Figures (from Figure 1 to Figure 9). The files can be opened by specific software such as Diffrac Plus 1.01 for XRD, SpecsLab 2.23 for XPS, SigmaPlot Workbook 12.0 for Raman, TA60 2.01 for TGA, ZView 3.4c and Origin 8.0 for electrochemical data