Review of Diverse Strategies Practiced for Gold (Au) Recovery (2000-2025) from Various Primary and Secondary Sources

Gold (Au) recovery from ores, metallurgical residues, industrial catalysts, and e-waste has emerged as a strategically important research domain due to the increasing global demand for precious metals and the rapid generation of secondary waste streams. This review presents a comprehensive chronological overview of the diverse recovery strategies reported between 2000-2025 for the extraction and purification of Au from conventional and unconventional sources. The disclosed review segment was systematically compiled from major scientific repositories, critically analyzed, and organized according to process type, source material, leaching chemistry, extraction methodology, recovery efficiency, and technological significance. The review highlights the evolution of pyrometallurgical, hydrometallurgical, biometallurgical, and integrated hybrid recovery routes, with specific emphasis on environmentally benign and high-selectivity processes. Considerable attention is devoted to Au recovery from e-waste, where alternative lixiviants such as thiourea, thiosulfate, halide systems, ionic liquids, functionalized adsorbents, ion-exchange resins, and advanced nanostructured materials have progressively replaced the conventional cyanide based technologies. The review even highlights the role of process optimization, selective adsorption, electrowinning, solvent extraction, and emerging sustainable materials in improving recovery yield and operational feasibility. By consolidating 25 years of scattered research disclosures into a unified chronological framework, this article provides an extensive reference platform for researchers, industrial practitioners, and policy developers aiming to design sustainable, economically viable, and environmentally responsible Au recovery technologies for future resource circularity