📖 ABSTRACT/OVERVIEW
The selective recovery of strategic and critical minerals including gold, palladium, indium, cobalt, and lithium from electronic waste using deep eutectic solvents represents a transformative direction in sustainable urban mining chemistry, offering potentially superior selectivity, lower environmental hazard, and reduced energy consumption compared to conventional hydrometallurgical acid leaching or pyrometallurgical approaches relevant to Nigeria's rapidly growing informal e-waste sector. This study develops original thermodynamic and kinetic models governing the selective dissolution of strategic metals from printed circuit boards, lithium-ion battery cathode materials, and liquid crystal display panels sourced from informal electronic waste recycling sites in Lagos and Kano States. A systematic library of twenty deep eutectic solvents based on choline chloride, glycerol, ethylene glycol, oxalic acid, and urea hydrogen bond donors is synthesised and characterised for viscosity, density, electrical conductivity, surface tension, and solubility parameter by standard physicochemical methods. Metal dissolution rate experiments are conducted at varied temperature, time, deep eutectic solvent water content, and solid-to-liquid ratios under inert atmosphere. Dissolution stoichiometry and complexation speciation are determined by UV-visible spectrophotometry, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure spectroscopy. Original Langmuir-Hinshelwood kinetic models accounting for surface speciation and deep eutectic solvent viscosity effects are developed and validated against experimental data. Thermodynamic parameters including Gibbs free energy, enthalpy, and entropy of metal complex formation in deep eutectic solvent media are determined by van't Hoff analysis. A selectivity coefficient framework enabling rational solvent design for targeted metal recovery is proposed as the central theoretical contribution. Keywords: deep eutectic solvents, electronic waste, strategic minerals, selective leaching, urban mining
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