Mechanical Activation in Metallurgical Processing: Mechanisms, Applications and Industrial Perspectives

Mechanical activation (MA) has emerged as an effective process-intensification strategy in metallurgical processing, modifying the structural and energetic state of solids through high-energy milling. Unlike conventional comminution, MA produces lattice defects, crystallite refinement, amorphization, and increased surface free energy, thereby significantly enhancing the reactivity of minerals and residues. This review critically examines the mechanisms of mechanical activation and its influence on hydrometallurgical and pyrometallurgical processes, including increased leaching rates, reduced reagent consumption, lower reaction temperatures, and improved reduction kinetics. Applications to primary ores, industrial residues, slags, tailings, and electronic waste are analyzed, with emphasis on the role of activation in enabling the treatment of refractory and low-grade materials. Particular attention is given to energy demand, process efficiency, and techno-economic feasibility, since the additional milling step may offset the metallurgical benefits if not properly integrated into the flowsheet. Emerging trends such as mechanochemistry, reactive milling, and hybrid activation routes are also discussed, highlighting their potential to improve selectivity and reduce overall energy consumption. The review identifies key research gaps, including the lack of standardized reporting of activation energy, limited correlation between specific energy input and metallurgical performance, and insufficient life-cycle and techno-economic evaluation. Mechanical activation is considered a powerful but energy-intensive tool, and its industrial application depends on an integrated assessment of kinetics, energy balance, scalability, and environmental impact.