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Removing Carbonates from a silver potassium Cyanide bath


I need to remove carbonates from a silver potassium cyanide bath. I am aware that carbonate can be frozen out in a sodium cyanide bath but will this still work with potassium cyanide? If not is there any other way to remove this?

Andrew Wilde


Everything that I have read is NO, because of the much greater solubility of the potassium salt. No idea on any other methods that are commercially available.

James Watts
- Navarre, Florida


Letter no. 473 offers some ideas, Andrew. Regards,

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


Hi Andrew ,

you can remove Carbonates from Silver Potassium Cyanide bath by the use of Barium Cyanide , the carbonates are precipitated as Barium carbonate , you would need to do the precise calculations based on the chemical reactions yourself , However , of late in the USA & Australia Barium Cyanide has become very scarce and you may wish to try the other method , that is the addition of Calcium Hydroxide

However here to there are problems , lime is readily available but what you can buyis of very poor quality, ( it is full of impurities )you would need to talk to a lime manufacturer about which type of lime is the purest in terms of metals & organic materials , once again you would need to do the math to find out exactly how much to add


John Tenison-Woods
John Tenison - Woods
- Victoria Australia


Calcium Nitrate also can precipitate carbonates.

In my establishment, we intentionally allow the level of Silver to drop. Take out a calculated volume of bath, dump out carbonates by treating with calcium Nitrate and then precipitate single Silver Cyanide from that bath using Silver Nitrate. Wash the precipitate and then add it back to the electrolyte along with required free cyanide. In effect the carbonate in the bath taken out for reaction is dumped off. If this is carried out as a routine, It is possible to control level of carbonates.

Yashawant V. Deval
electroplaters - Pune, maharashtra, India


Does anybody have experiences with ozone for the removal of Cyanide at a waste water with the following parameters ?

Waste Source = CN Metal Plating
Capacity = 142 lpm / 8.52 m3/h
CN in = 100 ppm
CN out = 0.1 ppm

Thank You very for any suggestions!

Bernhard Baumgaertner
- Heidelberg, Germany

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