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Cyanide Alternatives (6 replies and 2 comments)

Alan Carter
11 months ago
Alan Carter 11 months ago

What is the best alternative way to replace cyanide in gold heap leaching. I am looking for an industrial method. Laboratory methods used for gold Leach know as thiosulfate and thiosulfate urea to replace very toxic cyanide.

If an industrial method that can be used instead of cyanide will be very good

John Koenig
11 months ago
John Koenig 11 months ago

There are alternative leaching methods that we are presently evaluating in the Philippines. Which one is the best remains to be determined. Best may mean different things to different people. Does it mean the lowest cost or the most environmentally safe? Some alternative methods include the use of halides such as chlorine, bromine, or iodine. Others that can work are thiourea, thiosulfate, and combinations of several agents. Numerous patents exist that one can consult to see what has been evaluated.

Victor Bergman
11 months ago
Victor Bergman 11 months ago

To date there is nothing more effective on a great variety of ores, at lower overall cost, or safer and more environmentally friendly.

John Koenig
11 months ago
John Koenig 11 months ago

There are about 6 companies (two with patents) selling a Gold Dressing Agent (also called separation agent and other names) that state their products are an alternative to cyanide. We have tried two products with success. So, they are a viable alternative. The main constituent is either thiourea or urea.

See also the posting about the use of glycine for leaching copper and also leaching gold and silver (at a higher temperature).

John Koenig
11 months ago

While cyanide use is widespread it cannot be considered safe either for the workers or local communities in underdeveloped countries where regulations concerning safety measures are not enforced. Governments have and some will continue to ban the use of cyanide. So, alternative methods need to be considered. The mining companies are not the ones who ultimately decide whether cyanide leaching is allowed.

Maya Rothman
11 months ago
Maya Rothman 11 months ago

The alternatives to date are not as friendly as anticipated and sometime much worse to environment and safety. Chlorine for example was used as battle gas killing soldiers during I WW - just one breath was enough to kill. Chlorine is used safely but it requires well trained crews and properly maintained equipment. One good thing about cyanide is that it breaks down into C and N, both abundant and safe. So with good detox it does not creates danger to environment. However safety awareness, training how to handle are requirements .

Bob Mathias
11 months ago
Bob Mathias 11 months ago
  • Step 1: perform detailed mineralogical anlysis of the ore
  • Step 2: conduct a series of detailed studies comparing alternative lixivants, flotation and gravity separation
  • Step 3: perform alternative feasibility studies of the options from step 2
  • Step 4: complete detailed feasibility study of the most viable option
  • Step 5: present this to alternative funding sources

If you obtain funding build the plant

11 months ago
Philroy 11 months ago

HI. I am posting here since I have similar question. 

I've been thinking about heap leaching of porphyry copper tailings dam for getting gold in the tails which is around 0.100 ppm. I've tried lab tests using gravity and magnetic separation but results are not very satisfactory. The tails are already fine (P80=90microns)  but would still need re-grind to obtain acceptable concentrate grades and recoveries, which is obviously power-consuming. As to heap leaching, cyanide would not be a good option since it is highly toxic to the environment.

I have researched on heap bioleaching process instead but I don't really know much it could really cost, and I'd need to have it tested in very capable labs such as SGS. Would it be viable for processing gold tails? Are there mines which do so? Thanks a lot.

11 months ago

Hi Philroy, and welcome here.

0.1 ppm Au? Any Cu?

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