Vat Leaching and Box Leaching in Hydrometallurgy: Process Principles, Industrial Applications, and Future Perspectives
Vat leaching and box leaching are proven percolation-based hydrometallurgical methods that provide a controlled alternative to traditional heap and tank leaching. Unlike heap leaching, which works under large-scale, low-control conditions, and tank leaching, which involves fine grinding and intensive agitation, vat and box leaching systems process crushed ores in confined reactors. This allows for better distribution of solutions, faster recovery rates, and a smaller environmental impact. These methods are widely used to extract gold, copper, uranium, and, more recently, rare earth elements from both primary ores and secondary resources. Their main benefits include greater control over leaching parameters (such as residence time, irrigation rate, and solution chemistry), reduced reagent losses, and improved handling of effluents and emissions. However, limitations such as low throughput, the need for prior crushing and sizing, potential channeling effects, and higher capital costs per unit capacity hinder wider adoption. This review explores the fundamental principles of fluid flow, mass transfer, and reaction kinetics in vat and box leaching systems, assesses their industrial use across different commodities, and discusses recent technological developments, including modular setups, hybrid flowsheets, and digital process monitoring. It also highlights key knowledge gaps related to scale-up, modeling multiphase flow in packed beds, and integrating sustainable resource recovery strategies, providing a guide for future research and industry implementation.