cyanide and ferricyanide wastes

[100tific]

hello,
I have been reading something on the forum about cyanide and ferricyanide waste used in chemical electropolishing, or in gold extraction from minerals, but I have not found any post where it is written in detail how to dispose of this waste safely.

I spent some time researching how to do it. First, those that contain free cyanide, which are blue in color. It seems that using the hydrogen peroxide method and a copper catalyst works, but I have a problem with ferricyanides, and that is that they interfere with the potentiometric titration with silver nitrate. That is, I cannot measure them.
In order to destroy that free cyanide, I must first break down the ferricyanide into free cyanide and iron. For this I am using persulfate and UV light.
I have carried out cyclic voltammetry tests on ferricyanide to verify that I can effectively eliminate it with persulfate and UV light, but although I can lower its concentration after 10 hours of exposure to light, I cannot completely eliminate it.
Does anyone have experience with this? Could you give me some advice?
Thanks

 

[anachronism]

The blue you're referring to is also known as Prussian Blue and it's used as a die. Isn't that Ferric Ferricyanide that's come from whatever they were leaching? I've not come across free cyanide in a solution presenting as a blue colour myself.