Cost-saving nanotechnology set to disrupt gold processing industry
Mining.com reported that for over a century the gold processing industry has been dominated by one primary material that is used in the cyanide leaching process: activated carbon.
Put simply, gold-bearing ore is crushed into fine particles before being mixed into a pregnant leach cyanide solution that is filtered through activated carbon sourced mostly from burnt coconut shells. The gold adsorbed by the activated carbon is then recovered through elution, before being regenerated (baked) in a rotary kiln at around 700 degrees Celsius.
While it is a popular material for gold recovery, activated carbon has its limitations. The capacity for gold adsorption depends on the metallurgy of the ore, the quality of the activated carbon, the pH of the pregnant solution and other factors. About 10% of the carbon is lost during the process, which adds to the producer's input costs. Moreover, activated carbon is not highly selective, meaning that other minerals in the pregnant leach solution become trapped within the activated carbon a problem known as organic fouling. There is also the fouling and adsorption of other metal ions that compete for adsorption with the gold and are also difficult to elute.
There had to be a way to make the process more efficient. The challenge was taken on by Dr. Glen Southard, an expert in molecularly-imprinted polymers and their applications, who has authored over a dozen technical peer-reviewed journal articles on the subject and has several patents.
In 2014 Southard joined 6th Wave Innovations as chief scientific officer. The Utah-based company was formed a year earlier and one of its first products to enter commercial production was an explosive detection technology that was purchased by the US Navy’s Explosive Ordnance Disposal teams. 6th Wave Innovations took the basis of that knowledge and started looking at other commercial opportunities. Having spent the last three years developing an application for gold processing, 6th Wave Innovations recently launched a product it calls IXOS® – a nanotechnology bead for the gold mining industry.
The company estimates that its molecularly imprinted polymer ion exchange resin can increase gold mining profits by about $100 per ounce in processing savings and extra gold recovered in direct comparison to activated carbon, the most widely-used extraction medium today. Widespread adoption of IXOS could add billions of dollars in profits to an industry that produces about 90 million ounces of gold each year, according to 6thWave Innovations.
President Sherman McGill told MINING.com that “It's a nanotechnology resin that was specifically designed to recover dicyanoaurate from alkaline cyanide processing of gold-bearing ore. It has a very high capacity and selectivity which is independent of other metals in the pregnant leach solution. Our molecular pocket rejects all of those other metals and that is why our purity is so high.”
Each patented IXOS® bead is imprinted at the molecular level to attract gold and ignore the other elements leached off in mining operations. Unlike conventional ion exchange resins, the IXOS® resin has a long life (>50 loading/unloading cycles), high capacity (~30g/kg) and selectivity for gold (>95%) and greater than 98% gold recovery (no solution losses). Moreover, the capacity and selectivity does not degrade with successive cycles. The unloading (“elution”) process is simple, straightforward and inexpensive when compared to activated carbon. The beads require no activation step for re-use. The resin is supplied ready-to-use, with a range of particle sizes available to accommodate heap leach and resin-in-leach/pulp circuits.
Source : Mining.com