A new absorbent technology that improves the efficiency of metal extraction and recovery in mining was recently invented by Dr. Eduard Guerra, Associate Professor at the Barthi School of Engineering, and doctoral student Nuri Hmidi. The technology is an adsorbent composition more durable than the activated carbon currently used in processes such as gold extraction. A patent application for the technology was filed by Goldcorp Inc., a Canadian company and one of the largest producers of gold in the world. The research was conducted at the Hydrometallurgical and Electrochemical Research Laboratory at Laurentian University as well as the Biomass Utilization Research Laboratory at Lakehead University. The work was partially funded by Goldcorp Inc. and the Natural Science and Engineering Council of Canada (NSERC) through its Engage Grant program.
The Science Behind the Invention
Certain adsorbent materials—that is, materials that hold a gas, liquid, or solid to their surfaces in a thin film—have been used in mining to extract metals from slurry during ore processing. One of the most common substances used is activated carbon. A particular challenge with activated carbon is that it wears down with use, breaking apart into fine particles that are hard to retrieve. These fine particles can accompany the waste rock that is disposed of in tailings ponds, carrying their load of valuable metal with them. As larger particles break down into smaller ones, fresh activated carbon surfaces are exposed, increasing the amount of precious metals they can absorb, which results in significant loss of precious metals to tailings.
Dr. Guerra and Mr. Hmidi’s solution was to create a two-part composite adsorbent—a durable plastic core with an activated carbon coating— that would avoid the generation of carbon fines. The core is resistant to wear and corrosion, making the composition less likely to break down than a piece of pure activated carbon. The composition is engineered in such a way so that even if it does break down and cannot be retrieved, the fracture surfaces will not contain activated carbon, so it will not result in an increase in adsorbent surface area, and less metal would be lost than with current methods.