Blog Post

November 2, 2022

How to measure WAD Cyanide in a fast, safe and a reliable way

To verify environmental compliance and safety, mines need to monitor WAD Cyanide (Weak Acid Dissociable). WAD cyanide is important for water management, and it is a major indicator of the cyanide toxicity level.

Recently CyanoGuard’s development team has developed an innovative solution to measure specifically WAD.

What is the difference between WAD Cyanide and Free Cyanide?

Free cyanide is cyanide not bound in any ion association or complex.  

Weak acid dissociable cyanide (WAD) is a term used for cyanide that can be determined as free cyanide after a decomposition distillation from an acetate/acetic acid buffer.

Cyanide Species

Our existing measurement method quantifies free cyanide, but now we can detect WAD cyanide with our new method.

What the correlation is between different cyanide measurement methods?

Let's look at the graph below, where you can see the correlation between WAD cyanide measurements, free cyanide measurements, and silver nitrate titration.

 different cyanide measurement methods
The correlation between different cyanide measurement methods

What we discovered during our product development was:  

1. The higher the cyanide-to-copper ratio is, the closer the measuring results of Silver Nitrate Titration are to CyanoGuard’s measurements, meaning that with decreasing copper concentration (relative to cyanide) the effects of the well-known copper interference is weakened.

2. The lower the cyanide-to-copper ratio is, meaning the more copper is present, the less accurate Silver Nitrate Titration results are compared to CyanoGuard’s Free Cyanide measurements.  

3. CyanoGuard’s test results show the same results as W. van der Merwe and P. Breuer literature have suggested in 2011.

4. When the ore has a lot of copper, Silver Nitrate Titration always underestimates the concentration of cyanide in the tanks.  

5. CyanoGuard's free cyanide method shows more accurately the amount of available cyanide, which is the amount of cyanide that is effectively available to leach gold.  

6. Our test results have shown more than 95% of recovery rate when measuring WAD cyanide.

7. The gap shown between the WAD cyanide and Free cyanide is the amount of cyanide that doesn’t leach gold.  

How CyanoGuard helps gold mines

Our new solution helps you simplify environmental monitoring, achieve compliance with respective regulations more efficiently and thus better serve the interests of communities. On top, the added measurement capabilities allow for fast and easy cyanide speciation.

CyanoGuard measures WAD Cyanide 10x faster than the reference method “The Picric Acid Method for Determining Weak Acid Dissociable (WAD) Cyanide”.  

Our method is orders of magnitude safer than the Picric Acid Method. Picric acid is explosive and challenging to store and procure. CyanoGuard’s  WAD measurement solution is as easy as our proven method for Free cyanide.  

How do we measure WAD cyanide?  

The determination of WAD cyanide is done in 4 steps.  

1. The first step is sample preparation. In case the sample contains a high amount of solids, you can easily filter it in an instant with our provided syringe filters.  

2. The second step is mixing the sample with the special WAD buffer solution according to the expected WAD cyanide concentration.  

3. The third step is adding a diluted sample with the buffer and flushing it through the cartridge. Which is then inserted into the CyanoSmart device.  

4. In the fourth step the device displays WAD cyanide concentration in ppm and uploads the data to a cloud-based and device-independent platform.

You can choose WAD method measurements ranging from 0.1 ppm to 4000 ppm.

One of the key benefits of the measurements with the CyanoGuard’s WAD method is a short time to result. One sample measurement takes about 3 minutes or less.  

The sensor used for the CyanoGuard WAD method is highly selective and has shown no interaction with hypersaline matrixes.

The WAD measurements are easy and safe to use. Operators receive the appropriate training and are examined by CyanoGuard’s Swiss engineering team to verify high measurement quality.

Why does the mining industry need to measure WAD cyanide?

To optimize cyanide process control, mines measure free cyanide. To verify environmental compliance and safety mines need to monitor WAD cyanide.

Using CyanoGuard’s WAD cyanide technology, mine operators achieve compliance with the Cyanide Code in a simpler, more efficient and safer way. Monitoring WAD cyanide in tailings is a key Cyanide Code requirement to make sure that the water released back into the environment is safe. Consequently, we also want to help mining sites improve their ESG score.

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