Striking Gold with Online Cyanide Monitoring

Veladero-Mine_Scenic.JPGApproximately 374 kilometers from the city of San Juan, Argentina (located approximately 4,850 meters above sea level), one can literally strike gold. Barrick Gold Corporation’s Veladero Gold Mine is located in the highly prospective Frontier District and produced 432,000 ounces of gold in 2017.

The Veladero Mine is a conventional operation where ore is crushed by a two-stage process and transported by way of overland conveyor and trucks to a leach pad area. Large quantities of cyanide are used for the extraction of gold. To take proactive measures that cyanide is used, treated, and contained in a safe manner, the Veladero team has initiated a monitoring program for all ground and surface water sites for any possible cyanide contamination of the environment.

Barrick chose to partner with OI Analytical in pursuit of operating its mines in a safe and responsible manner, taking a forward-thinking approach to the management of social, economic, and environmental impacts. OI Analytical’s CNSolution 9310 Online Cyanide Analyzer was determined the instrument for the job.

A Golden Opportunity
 

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The CNSolution 9310 Online Cyanide Analyzer measures cyanide and reports results that not only correlate, but are equivalent to results by laboratory analysis.  The analyzer is deployed near the sampling point enabling analysis within minutes, eliminating holding time concerns that complicate the laboratory analysis of cyanide. Results are available immediately, allowing plant operators to make on-the-spot decisions rather than waiting hours or even days. Continuous monitoring yields a dynamic view of the process (or the environment) rather than periodic snapshots obtained by grab sampling.

In the case of the Veladero Mine, 14 sites are maintained where surface and/or ground water are monitored. Barrick chose this site for its existing shelter, available power, and proximity to the surface water stream and data logger.

Barrick_J.-Welsh_CN9310.jpgThe CNSolution 9310 was installed in a shelter that is typically used as a refuge shelter during dangerous thunderstorms. The sample point in the stream was 25 meters from the shelter and upstream from an existing flume and monitoring station. Sample input and return lines were inserted into heavy rubber tubing to protect them from the environment and connected to the 9310 sample pump. Concentration data was sent via 4-20 mA output from the CNSolution 9310 to an existing Campbell Scientific data logger and ultimately transmitted to the Veladero data acquisition system.

The CNSolution 9310 was configured for the determination of Total Cyanide. In many applications, the determinations of free cyanide or cyanide from compounds that can be dissociated by a weak acid are sufficient. However, in this application the possibility existed for the presence of heavy metal cyano-complexes of gold, silver, and other heavy metals. This configuration required the addition of an in-line UV Digester to insure complete conversion of the heavy metal cyano-complexes to HCN.

Cyanidation and the CNSolution 9310

Cyanidation is a hydrometallurgical process used to extract gold and silver from low grade ores by converting them to water soluble metal cyanide complexes for recovery by precipitation on zinc dust, activated carbon, or ion exchange resins. Leaching solutions may contain cyanide in concentrations ranging from about 50 ppm to 2,000 ppm. Tailings discharges must contain less than 50 mg/L cyanide for compliance with the International Cyanide Management Code.

OI Analytical developed the CNSolution 9310 Online Cyanide Analyzer based on the gas-diffusion amperometry technique employed in USEPA methods OIA-1677 and ASTM D 6888-09. These methods have been demonstrated to be free of interferences from copper and metallic sulfides in precious metal solutions, providing a far more reliable solution to cyanide analysis.

Gas Diffusion Amperometry

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For more information on how OI Analytical’s CNSolution 9310 Online Cyanide Analyzer provides reliable and accurate monitoring while cutting cyanide consumption and operating costs, click here.

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