Selective Recovery of Palladium (II) from Acidic Solutions Using Dithio- and Benzimidazolylthio-Functionalized Resins

Adsorbents derived from Merrifield’s resin and a reaction with three functionalizing ligands namely 1,2-ethanedithiol (M-EDT), 1,2-benzenedithiol (M-BDT), and 2-benzimidazolylmethylthio acetic acid (M-BITAA) were synthesized for the recovery and separation of PGMs from simulated solutions. M-EDT, M-BDT and M-BITAA resins were characterized by the FTIR, UV-Vis, TGA, CHNS and SEM techniques, which confirmed significant structural modifications in these resins. A batch adsorption study revealed that M-BITAA exhibited the highest capacity for Pd(II), with about 0.244 mmol·g−1, while that of both M-EDT and M-BDT resins was below 0.094 mmol·g−1. The adsorbents obeyed the Langmuir isotherm in 0.8 M HCl solution. Batch adsorption further showed, in a competitive study, that M-BITAA was not selective for Pd(II) but an attractive sorbent for other PGMs such as Pt(IV), which may be advantageous for solutions containing these PGMs.