The OI Analytical CNSolution™ 9310 On-line Cyanide Analyzer is capable of measuring cyanide present in precious metal leaching solutions using U.S. EPA Method OIA-1677 and ASTM D 6888-09. The gas-diffusion amperometry process in these standard methods has been shown to be free of interference due to metallic sulfides and copper that weaken the accuracy of traditional methods such as titration.
The utilization of CNSolution 9310 On-line Cyanide Analyzers allows silver and gold mills to measure and monitor cyanide levels at significant points in the cyanidation process in an accurate manner. A dynamic view of the process is obtained through consistent on-line monitoring rather than periodic snapshots received through laboratory analysis and grab sampling. The use of cyanide is strictly monitored by enhanced accuracy, leading to the operating cost of a plant being reduced.
Measuring cyanide present for leaching precious metal ores containing copper and metallic sulfides is considered a problematic process. Copper complexes with cyanide reducing the cyanide available for leaching.
Commonly used titration methods to control the process in gold leaching poorly estimate the quantity of cyanide available when copper is available. Various other reaction products, such as sulfur (IV) oxides, ammonia, nitrite, nitrate and thiocyanate interfere with most cyanide analysis techniques.
The OI Analytical CNSolution™ 9310 On-line Cyanide Analyzer is custom designed to measure the cyanide that exists in precious metal leaching solutions by U.S. EPA Method OIA-1677 3 and ASTM D 6888-09 4. The gas-diffusion amperometry method in these techniques has shown to be free of interferences from copper and metallic sulfides available in precious metal leaching solutions.
On-line monitoring with the CNSolution 9310 allows silver and gold mills to decrease cyanide consumption and operating costs linked to the cyanidation process.
Reliable Data for Process Control
During the operation process, a filtered slurry sample is introduced into the CNSolution 9310 to fill a volume loop that is fixed. A base reagent is constantly pumped through one side of a gas diffusion module consisting of a hydrophobic membrane and out through an amperometric detector’s flow cell.
The sample present in the loop is injected into an acidic carrier stream. The acidic conditions transform CN– in the sample to hydrogen cyanide (HCN) gas, which spread all over the hydrophobic membrane and into the base reagent where it transforms back to CN–and enters the amperometric detector’s flow cell.
Cyanide ions respond with the silver electrode and deliver a current proportional to the cyanide concentration. The response of the detector for every single sample is displayed in real-time as a peak on the touch-screen display and is also capable of being output to a supervisory control and data acquisition (SCADA) system. It is possible to output data to a LAN network in a Microsoft® Excel® – ready .csv format or a USB memory stick can be used to retrieve the data.
The main features of the OI Analytical CNSolution™ 9310 On-line Cyanide Analyzer are listed below:
- Offers accurate measurement of cyanide present in precious metal leaching solutions
- Analyzer measurement ranges support use during the cyanidation process
- Uses well-established gas-diffusion amperometry process in ASTM D 6888-09 and Methods USEPA OIA-1677