Enhanced platinum and palladium recovery from aqueous solutions : a comparative study of acylthiourea and amine-modified silica gel adsorbents
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Royal Society of Chemistry
Abstract
The recovery of precious metals from secondary sources is becoming increasingly important due to their natural scarcity and rising industrial demand. This study introduces a novel adsorbent, N-triethoxysilylpropyl-N′-benzoylthiourea-modified silica gel (TESP-BT-SG), developed for the selective recovery of platinum (Pt) and palladium (Pd) from aqueous solutions that simulate refinery wastewater. The extraction capabilities of TESP-BT-SG were compared with those of an amine-bearing adsorbent, (3-aminopropyl)triethoxy-silane-modified silica gel (APTES-SG), previously recognized for Pt and Pd recovery. Under optimal conditions, TESP-BT-SG achieved extraction efficiencies of 97% for Pt and 99% for Pd. Both adsorbents demonstrated rapid adsorption kinetics for Pd relative to Pt, reaching equilibrium within 3 hours for Pd and within 6 hours (TESP-BT-SG) and 24 hours (APTES-SG) for Pt. In solutions with elevated competing ion concentrations (5–100 mg L−1), both adsorbents retained high selectivity (>97%) for Pt and Pd. Adsorption isotherms and kinetic models were applied to elucidate the adsorption mechanisms, with the Langmuir isotherm and pseudo-second-order models providing the best fits, indicating monolayer coverage and chemisorption, respectively. Notably, the APTES-SG sorbent demonstrated enhanced performance with an increased loading capacity of 2.45 mmol g−1 compared to the previously reported 1.15 mmol g−1, achieved through our improved synthesis method. This modified APTES-SG showed significantly higher affinity for Pd (98%), Pt (97%), and iridium (Ir) (89%) compared to previous values of 8%, 33%, and 42%, respectively. The exceptional efficiency and selectivity of these silica-anchored adsorbents underscore their potential as cost-effective solutions for industries seeking to recover precious metals.
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DATA AVAILABILITY : The data supporting the findings of this study are available within the article and the ESI.
Keywords
N-triethoxysilylpropyl-N′-benzoylthiourea-modified silica gel (TESP-BT-SG), Platinum, Palladium, Aqueous solutions, Wastewater, 3-aminopropyl)triethoxy-silane-modified silica gel (APTES-SG)
Sustainable Development Goals
SDG-12: Responsible consumption and production
SDG-06: Clean water and sanitation
SDG-06: Clean water and sanitation
Citation
Mphahlele, M.R.R., Mosai, A.K., Tutu, H. & Kotze, I.A. Enhanced platinum and palladium recovery from aqueous solutions: a comparative study of acylthiourea and amine-modified silica gel adsorbents', RSC Advances, vol. 15, no. 6, pp. 4607-4618, doi : 10.1039/d4ra07935c.