cyanide destruct with INCO process

[rpclayman]

Is it possible to do a batch treatment for CN destruct in a single tank using the INCO process? If so how long is a typical reaction time for each sequence. By way of reminder here is a post from krea0824 on February 8, 2008.

"One of the environmental management controls of our mining plant is a detoxification plant for free cyanide management. Process utilizes INCO process, using Sodium Metabisulphite and copper sulfate for the destruction of cyanide complexes to free cyanide. Operation is at 1:8 mixing ratio for CN:Sodium Metabisulphite. We employed two tanks with a retention time of 30 minutes in each tank.1) Before we discharge, we conduct colorimetry tests using Free Cyanide Test Kit, as concentration is expected to be low. During this time, Free Cyanide concentration at the effluent of the Detox Plant is 0 ppm. The effluent is further conveyed through a 2-km pipeline to its final outfall to a surface water. When we monitored along the 2 km tailings pipeline, we noted increased concentrations of Free Cyanide in the effluent within the tailings pipeline, and much higher concentration when it reaches the surface water... Is the INCO process reversible? Why is it that the free CN concentration increases even when we read it as O ppm at the effluent of our DEtox Plant. We tried titration analysis as well and got similar results. Pipeline is isolated from other potential cyanide contamination."

 

[moltenmetal]

Does the INCO process convert cyanide complexes to cyanate? If so, it may be reversible.

If the metabisulphite and copper sulphate are intended to destroy metal-cyanide complexes to liberate free (uncomplexed) cyanide ion, you would then need a process to destroy the free cyanide. What is that process?

The "free cyanide" colourimetric analysis is absolutely FRAUGHT with difficulties and interferences. Send samples for free cyanide detection by ion chromatography. If those show no free cyanide, you may have an interference with the test.