Cyanide is one of the most common commercially used and efficient reagents to leach gold. However, many mine operators still struggle to efficiently manage their cyanide concentrations due to limitations of traditional measurements methods such as manual titration. Challenges in measurements range from user bias, unknown interference in the samples, to errors in calibration and extensive maintenance of equipment. To help mine operators understand where they stand with regards to their current cyanide monitoring process, here is a checklist we have developed based on our experience working with mine operators.
The framework focuses on neuralgic points in the cyanide monitoring process where users can understand whether they might require strategic overhaul or if process can be fixed with immediate measures. Going through this list not only helps to highlight causes for elevated variability in measurements but also allows mine operators to understand where they need to take action and close the gaps with respect to cyanide consumption, gold recovery rates and turnaround time for corrective actions. When all items along the checklist can be answered with “YES”, you are right on track with your cyanide monitoring process.
But do not be discouraged if some items in the checklist are answered with “NO”. As the saying goes, “Feedback is the breakfast of champions,” we have prepared a list of quick fixes that you can easily implement immediately and we are here for you if you have any further questions.
Evaluate your choice of the endpoint indicator – The composition of your sample influences which endpoint indicator is more efficient for your application. For instance, using potassium iodide instead rhodanine might be helpful if your sample carries high concentration of copper – cf. Research paper
• Determine your possible interference – What other metals or chemicals exist in your ore? Having this information at hand will allow you to assess potential interference and understand the variability occurring in your measurements.
• Revisit your sampling regime – Are measurements taken at the same point with the same procedures? How much time is between sample collection and measurement? Is sampling equipment properly cleaned?
• Use reference solutions to examine your accuracy – Benchmarking your current measurement process can be done using cyanide standards which can be purchased from reference labs or suppliers. This helps to get a better understanding of how accurate your measurements are and identify sources of variability. Alternatively, you can try out the spiking method.
• Check your reagents – Re-examine expiry date and concentration of your titration reagents. Use properly cleaned glassware of appropriate size that fits your desired measurement range. For instance, the resolution of measurements can be improved by using lower concentration of silver nitrate or a laboratory burette with a lower volume.