Sodium hypochlorite pretreatment for heap leaching gold ore
AdvisorHendrix, James L.
Mining and Metallurgical Engineering
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Laboratory leaching experiments were conducted to ascertain the effectiveness of sodium hypochlorite solution, NaOCl, as a pretreatment for oxidizing the carbonaceous matter and dissolving gold from finely disseminated gold ores. The ores tested were from the Jerritt Canyon ore body (oxide, carbonaceous) in Elko County, Nevada, USA and carbonaceous ore from the Carlin ore body in Eureka County, Nevada, USA. Extractions of greater than 70 percent were attained from three ores using sodium hypochlorite as a llxiviant. When the sodium hypochlorite pretreatment was followed by cyanidation, greater than 85 per cent gold extractions were achieved. Gold extraction was shown to be dependent on sodium hypochlorite concentration, heap leach flowrate, temperature and leaching time or bed volumes. Optimum leaching conditions were 10°C and below utilizing a 1.0 percent sodium hypochlorite solution at a flowrate of 15 gal/ft2 •day or greater for 2 to 13 bed volumes depending on the effluent hypochlorlte pH and ore type. These observations suggest that it would be beneficial to pretreat the heap during the colder months with sodium hypochlorite followed by cyanidation during the warmer months to achieve the best gold extraction at the lowest chemical costs.
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sodium hypochlorite solution
finely disseminated gold ores
Jerrit Canyon ore body
Carlin ore body
heap leach flowrate
effluent hypochlorite pH