Gravity Separation & Concentration Methods

Gravity Separation & Concentration Methods 2017-03-23T09:48:57+00:00
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Gravity and Intensive Leach Gold Processing (9 replies)

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

Could Gravity + Intensive Leach process the Gold in more cost effective manner? Some study in stopping the illegal miners using mercury claimed this opportunity too.

Some junior miners samples of Indonesia, showing > 100 ppm Au in the GRG concentrate, the problem is the GRG tailing is still have high base metal oxide content, even worst the deeper they go some base metal sulfide are present. Several junior who got alluvial type of deposit, use conventional CIL to handle their GRG/ Gravity Separation tailing, which are not very cost effective.

Thousands illegal miners around Indonesia use Mercury to recover the Gold. Some of them also run conventional cyanidation for the amalgamation tailing. The government is struggle stopping them. Share them a more cost effective way to recover the Gold, may reduce the use of Mercury.

It is very difficult to send sample out of the country at this moment, so any previous experience on test program or operation will help the situation. Furthermore, the concept can be introduced to the illegal miners to stop using mercury. 

Sandeep Bisht
1 year ago
Sandeep Bisht 1 year ago

I think the ILR should be the solution but the problem will be whether they will be technically equipped and skilled to run it efficiently without underutilizing it. The idea of hiring skilled technical laborers won’t be accepted by them anyway.

David Kano
1 year ago
David Kano 1 year ago

I'd suggest you visit Mintek in South Africa to view their "igoli" process and then get Geoservices to buy one and use it as a test model in Indonesia. I have no links to Mintek but they are great people and one of the best ways to assist that country is to build their marketing abilities http://is.gd/0jDQ2W

Hauptsturm
1 year ago
Hauptsturm 1 year ago

I agree that small-scale miners need alternatives to mercury and cyanide. Gravity separation has been suggested as an alternative to the use of mercury. However, many sites have pyrite and/or chalcopyrite. The gold is embedded in the ore in very fine particle sizes. That is not amenable to grinding using ball mills followed by gravity separation methods such as sluices or cyclonic concentrations. Consequently, there is a need for simple low-cost methods for leaching gold from sulfide-based ores. Some possibilities are the use of alkaline thiourea, iodine, bromine, and more recently the use of amino acids such as glycine. You should consider a pre-treatment stage in which the copper is leached from the ore. The ore then can be leached to dissolve the gold into solution.

Sudhirkumar
1 year ago
Sudhirkumar 1 year ago

Maximum gold recovery at a very minimal cost in a much safer way is the prime goal of any gold processing operation. Intensive cyanidation on gravity recoverable gold is the best for maximum recovery (cost on reagents), yet, it produces a pregnant solution which must go through electrowinning (cost), and finally through smelting (another cost). Mercury on the other hand gives an appreciable recovery with a minimal cost comparatively. The major issue associated is with its pollution on the environs and the health implications.

NB: The way forward is still the use of mercury, but in a manner that will absolutely minimize pollution, considering cost implications. A Scientist has designed a lantern retort that allows the mercury used in the recovery to be recompensed for another usage. No environmental issues.

Hauptsturm
1 year ago
Hauptsturm 1 year ago

While I would agree that rational decision makers would have tightened control on the use of mercury and made the use of retorts mandatory. However, there has been a worldwide campaign by the UNDP against the use of mercury by small-scale miners. This has led countries like the Philippines to ban the use of mercury without providing the miners with viable alternatives. One alternative tested at University of British Columbia is oxidative cyanidation of the ore in ball mills. But, Filipino decision makers are also considering banning the use of cyanide. So, alternative leaching methods must be developed. Most small-scale miners lack the education to apply such methods. The company I advise has developed processing centers using leaching methods to assist small-scale miners in Mindanao.

Sandeep Bisht
1 year ago
Sandeep Bisht 1 year ago

What leaching methods are being done in your processing center and how are the small scale miners coping with the methods technically?

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

The problem with Mercury is the effectiveness to amalgamated < 150 um(?) do you have different idea?

Paul Morrow
1 year ago
Paul Morrow 1 year ago

Curtin University in Western Australia has patented a new process that uses glycine, an edible cheap amino acid in alkaline medium to leach gold, silver and copper minerals (oxides, sulphides, carbonates and native copper). The metals form glycinates. Gold and silver glycinates are well adsorbed onto activated carbon. Unlike cyanide, which forms a range of WAD cyanides, thiocyanates, ferricyanide, etc., glycine can be recovered and reused as it is quite stable (as its sodium/calcium glycinate) in alkaline environment.

If there is copper in the system, the copper minerals can be leached first at ambient temperature, and the gold/silver later at elevated temperature (60deg C).

Copper can be precipitated using either NaSH or Na2S. The pH is adjusted with lime, although the start-up is with the caustic.

Positive aspects of the process:
Environmentally benign, non-toxic, low cost, (about USD2.00 per kg FOB) easily available, no transport issues, allows carbon adsorption, allows Cu and Au leaching in same pH range. Iron is essentially untouched in the leach residue.

The process therefore sidesteps both cyanide and mercury, whilst also not having the problems of most other novel leaching reagents (Cu-ammoniacal thiosulfate, halide leach, ammonia, etc.). Glycine and many of the transition metal glycinates are water soluble. Alkaline condition hives it high selectivity over siderphile and lithophile elements.

Hauptsturm
1 year ago
Hauptsturm 1 year ago

It is good to see you describe the research he has conducted concerning the use of glycine for leaching copper (1 paper) and for leaching gold and silver (2 papers). We look forward to their demonstrating the utility of glycine leaching with the mining industry.

As far as the processing facilities that AgriMer has established, we are still evaluating low-cost methods that can work with small-scale miners. In response, the leaching is being conducted by qualified chemists. The miners just need to bring their ore to the centers. We have good working relationships with the small-scale miners and are assisting them with registering People's Mining Areas and in forming Small-Scale Mining Cooperatives. The local, provincial, and federal officials are very supportive.

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