From Waste to Resource: Characterization, Management, and Resource Recovery of Electrocoagulation Sludge in Mine Tailings Water Treatment: A Structured Review

Electrocoagulation (EC) treatment of mine tailings water transfers metals, metalloids, and suspended minerals into sludge, creating a secondary waste stream whose resource potential requires rigorous qualification. This structured review synthesizes 105 eligible studies selected from 850 Scopus records published during 2006–2026; search and screening records are documented in Supplementary Material S1. Evidence from mine-affected waters is distinguished from non-mining wastewater studies, whose recovery outcomes require matrix-specific validation before transfer to tailings-derived sludge. Investigated pathways include sludge conditioning, adsorption, catalysis, construction materials, pigments, and selective mineral recovery. Across these applications, aqueous contaminant removal, solid-phase formation, functional performance, and environmental safety represent distinct evidentiary requirements. We propose a source–phase–function–risk (SPFR) framework linking feedwater and electrode provenance, mineralogical and chemical phase identity, application-specific performance benchmarks, contaminant mobility, and life-cycle and techno-economic comparisons. SPFR provides a transparent, staged qualification approach rather than a validated predictive score. Key research priorities include dry-solid mass balances, phase-resolved characterization, product durability, realistic leaching and aging tests, and consistent functional-unit comparisons. These requirements support evidence-based decisions on responsible resource recovery from EC sludge generated during mine tailings water treatment.