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The finishing.com Hotline: Serious Education ... plus the most fun you can have in metal finishing. Ted Mooney, Webmaster

Gold Recovery, Cyanide, Electrowinning, details needed




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Q. I have been tasked with setting up a gold retrieval system, that which I have limited experience with. I am a electromechanical engineer, not a chemist. Our company cleans equipment that is gold contaminated. The proposed plan is to build a holding tank that will contain ~50 gallons of techni-strip, a cyanide based gold extraction solution. (Our system designs include exhaust, waste treatment, and life safety.) The parts will then be placed into the solution for the gold removal process. The next item will be a winning cell that is powered by a rectifier. The solution will then be pumped thru the winning cell. The winning cell is configured with alternating anode/cathodes so that the gold will plate out onto them. I need some help with the details. Voltage and current settings, plate design, plate spacing, solution concentrations, and what ever else that would support the project. I have reviewed the health safety aspects and have systems in place to perform the work.

James W [last name deleted for privacy by Editor]
- Dallas, Texas


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A. Hi, James. In a way your question is a bit like saying that you've inherited a Chevy that is presently up on jack stands and you want to know how to design auto wheels so you can drive it again :-)

Because the thing is, electrolytic recovery cells for plating wastes, like car wheels, are a long-established and readily available off-the-shelf technology. You don't have to figure out how to safely fuse the cells, or how to keep it from shorting out as the deposit grows, or how to keep the recovered dust from catching fire, or how to provide enough agitation that you can plate out the metal efficiently, or the cathode spacing, and all that stuff. You just buy an electrolytic recovery cell and you get the benefit of the experience of people who have designed and installed them for decades -- it's really that easy. Best of luck.

Regards,

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


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A. I agree with Ted, I don't need to know how a mobile phone operates, I just use it. I would suggest that you use ion exchange, then all you need to do is to let your wastewater through the resin, and send the resin for rewin. Not take care of plating technique.

Best regards,

Bo Kønig
- Denmark


(2007)

Q. What resin are you referring to? And how do you mean send "through it".

Frank Pressly
- Greenville, South Carolina


The Nalco Water Book

(2007)

A. Hi, Frank. Bo is talking about the ion exchange process. A capsule-shaped canister (often made of fiberglass, sized anywhere from a couple of liters to a couple of hundred ) is packed with cationic ion exchange resin (looks like a large grained powder) and contained in screening; wastewater is pumped into one end and flows out the other. As the solution passes over and through the ion exchange resin particles, the gold is left behind on the resin (a chemical reaction releases hydrogen in its place). The resin is then sent to a refinery where it is either regenerated for use again (with the gold released into a much smaller quantity of water in place of the large quantity that was treated) or (more likely) the resin is burned, leaving the gold behind.

Normally electrolytic recovery might be applied on highly concentrated solutions and ion exchange used for low concentration solutions. Good luck.

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


June 8, 2008

Q. What is the easiest way to precipitate gold and or silver from spent cyanide plating solutions? I can refine whatever precipitates out with aqua regia.

Chris Rossiter
Engineer - Danville, California, USA


June 16, 2008

A. Hi, Chris. If the metal content is high you can start by electroplating the precious metal out. If it's low, or after the plating step, I think you will find ion exchange greatly superior to any chemical precipitation method from almost every possible perspective. Then the ion exchange resin can be burned for recovery of the metal. Good luck.

Regards,

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


June 19, 2008

Q. Where would I look for precious metal recovery resins?

Chris Rossiter [returning]
- Union City, California, USA


June 20, 2008

A. Hi, Chris. Rohm & Haas is a major supplier of such resins. However, rather than buying resin and having to design your own ion exchange system, you might consider just getting the Gold Bug package from PMPC, or a recovery system from companies like Eco-Tec. Patient Googling to filter out the hits related to consumer and other unrelated applications will get you there. Good luck.

Regards,

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


June 18, 2008

Q. Hi sir,
I'm from Malaysia. I'm trying refine the precious metals which is contained inside the resin.
I have tried thiocyanate with the resin by doing electroplating but still failed. Please guide the proper method to process this resin.

gary raj
- malaysia


June 18, 2008

thumbsup2 Hi, Gary. Any reader is welcome and encouraged to help you, but the site focuses on metal finishing ... so most of our readers are familiar with using the resin in an ion exchange canister in a plating shop to capture the gold values and sending it to a refiner, but generally unfamiliar with the operations inside a precious metal refinery.

My understanding is that the resin is burned, leaving the gold behind, but I would not know the operational parameters. Sorry.

Regards,

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



August 4, 2016

Q. Is there any other alternative cathode rather than steel wool that can be used in the electrowinning of gold?

tafadzwa matshiya
- kadoma, midlands, zimbabwe


August 2016

A. Hi cousin tafadzwa. Without understanding your situation, the best I can say is that almost any metal in almost any shape can probably be used, but steel wool is cheap because steel is cheap, and steel wool has a very high surface area, which can be vitally important for cathodic efficiency if you are dealing with low concentration wastes.

Please give us the details of your own situation. Abstract questions involve a dozen "ifs, ands, & buts" which can take several pages to cover. Forums like this are best suited to very carefully detailed situations because readers are unlikely to offer responses of more than a paragraph or two, and can't get involved in all those "ifs, ands, and buts". Best of luck!

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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