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Separating Copper from Gold (electroplating) (8 replies)
There is a process to remove copper from carbon prior to stripping gold called a "cold cyanide strip". I think it will be difficult to remove Cu from Au in the electrolyte solution.
You can find it the paper on Onemine. It is called "Control of Copper in Carbon Adsorption and Gold Recovery Circuits - American Girl Mining Experience" dated 1993 authored by C. L. McKenzie.
The American Girl operation did not remove the Cu from the operation only the strip. It will build up and must be removed from the solution. The USBM published work on the EW of Au, Ag & Cu using square wave pulse of 2.5 V for 10%-30% of a period of 100 to 1000 milliseconds. The remaining time was 0 V. This resulted in plating of gold and silver and minimal plating of Cu. But the Cu needs to be removed from the circuit. A separate EW for the high Cu low Au & Ag solution would be used.
But the use of a Zadra circuit instead of an AARL impacts the use. Zadra circuit has the elution and EW directly connected. AARL separates the two. Contact me if you are interested in discussing more on this subject.
The cold cyanide soak prior to elution of about 1 hour @1% cyanide is a good start- this is followed by a cold rinse--BUT-- the rinsed solution must be kept out of the circuit - about four bed volumes of rinse will remove most of the soluble copper on the carbon- we used to spray that water on old heap leach pads and active cyanide broke down there leaving copper behind to a large degree where the process was just circulating -- do lab work on the ore and see where the copper comes from or whether this is a case of small amounts of copper in the ore that had just built up because of the way you are dealing with elution practice now and that the copper now ends up in the bullion- to optimize results take samples for AA every 15 minutes and monitor strip period and efficiency to make decisions
Look at your contract with the refinery, you may be sailing closely to getting your bullion treated as base metal due to copper content and that can cost a lot in revenue for treatment and penalty- more reason to get the copper off the carbon.
Have no idea this will work but was just looking at some old work on precipitation of metals from solutions. The following came to mind.
- (Aux+CNy + AgCN + CuCN Solution
- Add NaCL precipitate AgCl
- Filter then melt with NaCO3 to produce pure silver metal
- To solution add NaS
- Precipitate Copper Sulfide
- Filter and discard
- Electrowin Au metal
Looks simple, would it work?
The "Cold Strip" mentioned by Mark Gorman, also known as "Cold Cyanide Soak" as mentioned by Willem de Klerk is the way to deal with the problem reported. But the cold strip works up to a certain limit that should have been detected with proper mineralogical characterization. If the amount of copper is such that the ore really corresponds to "low grade copper with traces of gold", then a copper removal step employing for instance the SART process might be mandatory, in addition to the cold strip.
I am currently separating and extracting gold from margin ore dump (Mod) using the following processes: leaching, carbon in pulp, elution (zadra process) and electro winning. My final product (sludge gold) is contaminated with excessive copper. What method should I apply in order to make sure that copper does not electroplate with gold? Or what method should I apply to separate copper from gold? My elution column Temperature is 135 degree Celsius.