Turnkey system for cyanide removal from electroplating wastewater

A. 1. OZONE 2. ION EXCHANGE (especially if someone else does the regeneration)

A. Ricky,

If ferric and chromium ions exist in the wastewater, it is really hard to eliminate cyanide by oxidation process with chlorine, hypochlorite, even ozone. This is because the oxidation process should be carried out in basic solutions with pH>10.2, in which cyanide strongly tends to complex ferric and chromium ions. The complexed cyanide is hardly destroyed by regular oxidation processes.

Ion exchange technology is helpful to remove all the free cyanide and complexed cyanide ions in neutral wastewater. Of course the ion exchanger needs regularly regeneration and the discharged solution containing concentrated cyanides has to be destroyed using special process. It is very important to avoid ferric and chromium ion contamination of cyanide wastewater. Otherwise it is costly to treat it. Ling

A. I run a plating company specializing in Chrome, Black Chrome, Nickel, Cadmium, Zinc, (Cyanide), Electroless Nickel, Copper (acid & cyanide), Gold, Silver. My cyanide consumption is approx. 200 kg per month and is mostly for Cadmium. Govt. regulation here demand very low levels of all contaminants.

• CN <0.025
• Cd <0.05
• Cr <0.5
• Ni <0.025
• Cu <0.5
• Zn <0.05

I achieve low levels of all heavy metals by precipitation and plating out cells and cyanide destruction using electrolytic salt water chlorination.

A. Re. cyanide residue, I suggest you might investigate the use of high intensity UV light to break down the cyanide as there probably would not be any interaction with the other heavy metals. Possibly you could concentrate the residue (without the cyanide)with a RO system and then evaporate to produce a solid, there may be a market for the dry residue hope these thoughts are of some use.