Comprehensive insights into aqua regia-based hybrid methods for efficient recovery of precious metals from secondary raw materials

The increasing scarcity of precious metals necessitates the development of sustainable recycling strategies to fulfill industrial requirements while mitigating environmental impact. Aqua regia has emerged as a key leaching agent for precious metal recovery from secondary raw materials due to its economic viability, swift leaching kinetics, and straightforward implementation. Due to synergistic benefits such as enhanced recovery rates, improved selectivity, and increased environmental sustainability, aqua regia leaching integrated with sorption, solvent extraction, and biohydrometallurgical techniques. This review article provides a comprehensive overview of aqua regia-based hybrid approaches for recovering Au, Pt, and Pd from diverse secondary sources, including waste electrical and electronic equipment, spent catalysts, industrial effluents, and others. The study evaluates a wide range of functional sorbent and extractant materials for their effectiveness in recovering precious metals from acidic environments, and aqua regia settings. Evaluating various factors that affect precious metal sorption, this study emphasizes the need for acid-resistant and highly selective sorbents. The review also addresses the challenges associated with aqua regia and evaluates potential solutions like selective leaching and diluted aqua regia applications. Finally, the review outlines future directions, focusing on advancements in hybrid methods to achieve superior precious metal recovery with minimal environmental impact.