Affordable and Clean Energy (SDG 7), Responsible Consumption and Production (SDG 12)
Selective recovery of precious metals from printed circuit board with a novel scavenger of thiocarbamate functionalized filter paper M. K. Mohammad Ziaul Hyder* Department of Chemistry, Chittagong University of Engineering & Technology, Raozan, Chittagong Precious metals are extensively used in various applications such as catalysis, electronics, automobiles, jewelry, and so on. The advanced technology has great impact on the consumption of the precious metals. However, the natural deposits and occurrences of the precious metals are limited. In recent decades, the technological innovations on electric and electronic equipment are rapidly changing our lifestyles, and as a result, resulting in discharging a large amount of waste electric and electronic equipment at a quick pace. 1,2 The quick production is accelerating the consumption of valuable metals like gold, silver, and palladium. Consequently, waste electric and electronic equipment is the essential resource for convalescing valuable metals. 3 Printed circuit board is the key component of electric and electronic equipment where high amounts of valuable metals are used, and hence, these are considered as the greater source of precious metals than natural high-grade ores. Thus, it is crucial to develop economically practicable and sufficiently selective methods and materials for the recovery of precious metals. Low-cost adsorbents with excellent selectivity toward target precious metals are expected to provide a beneficial solution for this problem. Modified cellulose materials have been attracting significant attention as efficient and cost effective bio- based adsorbents. Cellulose is the most abundant biopolymer with outstanding physical and chemical properties. Selective collection of precious metals such as Ag(I), Pd(II), and Au(III), requires appropriate designs of ligands. We have focused on soft thiocarbonyl moieties with the lower contribution of harder tautomeric thiol groups. As the support of the sulfur ligand, we used cellulose filter paper (CFP) that is advantageous in abundance, inexpensiveness, accessibility, mechanical strength, and high surface area. The scavenger was found to adsorb only Ag(I), Pd(II), and Au(III) from an aqueous media in the presence of coexisting ions of different base and precious metals at wide ranges of pH and acid concentrations. The adsorption reached equilibrium within 60 min. Regeneration experiments indicated that the adsorbent maintained 97% of its initial efficiency even after five adsorption/desorption cycles. The developed scavenger was successfully applied to recover Ag(I), Pd(II),and Au(III) from an aqua regia solution of waste printed circuit boards. References 1. Liu, Y.; Song, Q.; Zhang, L.; Xu, Z. Targeted Recovery of Ag-Pd Alloy from Polymetallic Electronic Waste Leaching Solution via Green Electrodeposition Technology and Its Mechanism. Sep. Purif. Technol. 2022, 280, 118944. https://doi.org/10.1016/j. seppur.2021.118944. 2. Barragan, J. A.; Alemán Castro, J. R.; Peregrina-Lucano, A. A.; Sánchez-Amaya, M.; Rivero, E. P.; Larios-Durán, E. R. Leaching of Metals from E-Waste: From Its Thermodynamic Analysis and Design to Its Implementation and Optimization. ACS Omega 2021, 6 (18), 12063–12071. https://doi.org/10.1021/acsomega.1c00724. 3. (3) Xolo, L.; Moleko-Boyce, P.; Makelane, H.; Faleni, N.; Tshentu, Z. R. Status of Recovery of Strategic Metals from Spent Secondary Products. Minerals 2021, 11 (7), 673. https://doi.org/10.3390/min11070673.
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