Gold Recovery Breakthrough Opens New Horizons for Refractory Ore Processing
Researchers at Ural Federal University have advanced a processing technology for so-called refractory gold ores, which traditionally require complex and costly treatment methods. Their new approach increased gold recovery from 68% to 90%.
Refractory ores are deposits from which gold is extremely difficult to extract using conventional techniques such as standard cyanidation. The gold is locked inside mineral structures at extremely fine, sometimes nanoscale, dimensions, making it effectively invisible under an optical microscope. Another major obstacle is organic carbon, which absorbs dissolved gold complexes before they can be recovered. In effect, conventional processing rarely achieves recovery rates above 80%, while some ore types remain uneconomic to process altogether. Yet these refractory deposits account for roughly one-quarter of the world's geological gold reserves.
Researchers from the Laboratory of Advanced Technologies for the Integrated Processing of Mineral and Industrial Raw Materials of Non-Ferrous and Ferrous Metals at Ural Federal University have developed an integrated hydrometallurgical process based on atmospheric nitric acid leaching enhanced with proprietary process additives. Notably, the nitric acid is regenerated and reused repeatedly, significantly reducing operating costs.
One of the key additives is lignosulfonate, a byproduct of wood processing generated by the pulp and paper industry. The technology also deactivates compounds that interfere with gold recovery, including organic carbon, while converting toxic elements such as arsenic and mercury into forms that can be safely disposed of. As a result, the process delivers both environmental and economic benefits.
Technology Patented
The method has already been validated at industrial scale using ore from the Malomyr deposit in Russia's Amur Region. It is currently undergoing evaluation on double-refractory sulfide gold ores in Uzbekistan at the Navoi Mining and Metallurgical Company, one of the world's largest gold producers.
The technology has already received a Russian patent, and an application has been filed for a Eurasian patent. Researchers plan to continue refining the process, including the introduction of neural network models capable of tracking how mineral characteristics and operating parameters influence recovery efficiency with greater precision. The laboratory is also developing methods to recover valuable metals from industrial waste streams, including sludges and legacy tailings.
According to the developers, bringing these technically challenging resources into production could generate economic benefits measured in tens of millions of dollars. Preliminary estimates place the technology's payback period at between five and ten years.
A Broader Industry Impact
Approximately one-quarter of the world's geological gold reserves and resources remain only partially developed because of high processing costs and technological complexity. The new technology could expand the resource base available to the gold mining industry without requiring the discovery of new high-grade deposits. It would also make processing portions of refractory ores and accumulated mining waste economically viable while reducing dependence on expensive autoclave equipment and mitigating environmental risks traditionally associated with gold extraction.
The technology's long-term potential is closely tied to the development of neural network models. These models could uncover hidden relationships between mineral composition, process parameters, and final metal recovery. In practice, AI would become a tool for continuous optimization, transforming the process from a set of fixed operating conditions into an intelligent processing management system. Neural networks could automatically optimize reagent consumption, leaching duration, and other operating parameters for the specific characteristics of each ore feed.
Back in 2022, Polyus became the first company in Russia to deploy the BIONORD bioleaching technology at its Olimpiada deposit. In that process, bacteria oxidize sulfide mineral shells, making gold accessible for subsequent extraction. The underlying version of the Ural Federal University technology was presented by the university's researchers in 2024, when they introduced a non-autoclave acid leaching process capable of recovering more than 90% of the gold contained in double-refractory ores.
Earlier this year, industry representatives also highlighted the growing use of big data analytics, video analytics, and digital geological models to improve metal recovery, optimize production control, and identify new reserves. In that context, Ural Federal University's planned integration of neural networks closely aligns with the mining industry's broader digital transformation.
