Timely and accurate chemical analysis is a critical part of safely and effectively managing cyanide’s use in gold mining. Cyanide measurement is challenging – particularly at low concentrations – because it is chemically reactive and easily affected by changes in acidity, temperature, trace metal content, and the presence of sulfur or sulfur compounds.
Common methods for testing the presence of cyanide in precious metal process solutions and treated water involve distillation, oxidization or modifying the pH. Additionally, these methods generally require that the sample be sent to a lab for testing, and it may take several days to get the results. Because chemical or biological reactions can change the composition of test samples when removed from their natural environment, the accuracy of the testing can be questionable.
Newmont has been working with a proven technology – called gas-diffusion – and adapting it to slurries and complex gold process solutions so monitoring can be done at the critical points in the field for real-time results. Along with analysis times at just over a minute, gas-diffusion allowed samples show a high degree of accuracy without the sample degradation problems often associated with other testing methods.
Newmont deployed this technology at a number of sites in 2015, and this work continues across our operations. While ISO and ASTM – two international voluntary standards organizations – have certified the gas-diffusion testing method, Newmont is working with regulatory authorities to recognize the method as the standard for cyanide testing and reporting.