Milad Norouzpour, Rafael M Santos, Yi Wai Chiang
Ultrasonic cavitation offers a powerful route to intensify leaching of refractory minerals, yet its effectiveness is often limited by persistent silica-rich transport restriction in silicate systems. Magnesium (Mg) extraction from serpentine is fundamentally constrained by incongruent dissolution and rapid formation of silica-rich alteration layers that suppress mass transport. Here, a coupled chemo‑sonic activation strategy is developed to elucidate how fluoride-mediated silicate destabilization and ultrasound‑driven transport intensification jointly redirect residue evolution toward transport-accessible pore architecture. Comparative leaching experiments were conducted under ambient, thermal, fluoride‑assisted, ultrasonic, and combined operating modes. Conventional acid leaching reached only ∼20% Mg2+ extraction, while thermal leaching accelerated early kinetics but plateaued near ∼50% due to silica‑controlled diffusion resistance. Fluoride activation destabilized silica-rich alteration domains, increasing extraction to >80%, whereas ultrasound-assisted leaching alone achieved near‑thermal performance at <40 °C, consistent with enhanced interfacial renewal. Synergistically, their coupled operation induced a non‑linear enhancement, reaching ∼86% extraction within 60 min at low temperature using reduced fluoride dosage. Space-time yield (STY) analysis confirmed genuine process intensification (20.23 g(Mg).L-1.h-1) rather than time‑shifted conversion. Integrated structural and textural characterization demonstrates that enhanced leachability arises from suppression of silica densification and the formation of a transport‑accessible pore architecture rather than surface‑area maximization. These findings demonstrate that chemo‑sonic activation suppresses silica-rich transport restriction and redirects residue evolution toward a transport-accessible, wide-mesopore-dominated architecture, enabling high Mg2+ extraction under low-temperature conditions.