Waste Streams as Sources of Precious Metals: An Updated Review of Cost-effective and Environmentally Friendly Recovery Methods (2016–2026)

Abstract

This review examines recent advances in the recovery of precious metals (PMs) from waste streams during the period 2016–2026, with emphasis on recovery methods reported as cost-effective and environmentally friendly. Precious metals, including gold, silver, platinum group metals and associated elements, are increasingly required for electronics, catalysis and other technology-dependent sectors. At the same time, depletion of high-grade ores and growth in waste generation have strengthened interest in secondary resources such as wastewater, electronic waste leachates, industrial effluents, sewage sludge and mining residues. A structured literature-based approach was used to identify and analyse studies from major scientific databases, including Scopus, Google Scholar, ScienceDirect, SpringerLink and SciFinder. The review synthesises evidence on adsorption, ion exchange, biohydrometallurgy, biosorption, bioleaching and plant-assisted recovery systems. Adsorption-based processes, particularly those using magnetic nanoparticles, metal-organic frameworks, graphene-like carbon materials and functionalised polymeric adsorbents, showed strong selectivity, operational simplicity and reusability under reported laboratory conditions. Ion exchange systems, including natural and synthetic resins, also demonstrated potential for selective and simultaneous recovery of gold, silver, platinum, palladium and rhodium when operational parameters were optimised. Biological approaches, including microbial biosorption, bioreduction and bioleaching, offer lower-energy alternatives and reduce reliance on harsh chemical reagents. Plant-based systems provide an emerging route through the reducing and chelating activity of phytochemicals, although their development remains at an early stage. Overall, the reviewed evidence indicates that integrated and hybrid recovery strategies may improve efficiency and sustainability in complex waste streams. Further work is required to address scalability, techno-economic feasibility, process standardisation and environmental assessment before broader industrial implementation can be achieved.