Analysis and Prospects of Cyanide-Free Methods for In Situ Borehole Leaching of Precious Metals

The declining quality of primary mineral resources necessitates the development of new approaches to the recovery of precious metals. One promising approach is in situ borehole leaching (ISL), which has been successfully applied to the recovery of uranium and copper. However, the use of toxic cyanide for precious-metal leaching under ISL conditions is impractical, primarily due to environmental concerns. In this context, halogen-, thiourea-, and thiosulfate-based reagent systems are among the most promising alternatives. This review examines various leaching systems based on these reagents, with particular emphasis on their advantages and limitations. The most promising approaches for the application of ISL to gold recovery are highlighted, and potential directions for further research and development in this field are discussed.