Gravity Separation & Concentration Methods

Gravity Separation & Concentration Methods 2017-04-04T06:57:23+00:00
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Cheap Gold Recovery Process (9 replies)

JohnnyD
2 years ago
JohnnyD 2 years ago

Do we finally have a viable efficiency low-cost "Cheap" Gold Recovery Process that most can afford?

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

Some junior miners samples 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 sent 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.

David Kano
2 years ago
David Kano 2 years ago

I think the ILR 'in-leach-reactor' should be the affordable solution but the problem of this gold recovery process will be weather they will be technically equipped and skilled to run it efficiently without under utilizing it. The idea of hiring skilled technical labourers wont be accepted by them anyway.

Helena Russell
2 years ago
Helena Russell 2 years 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 marketting abilities. They invented many great technology in mineral processing area.

Victor Bergman
2 years ago
Victor Bergman 2 years 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 are 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 pretreatment stage in which the copper is leached from the ore. The ore then can be leached to dissolve the gold into solution.

Maya Rothman
2 years ago
Maya Rothman 2 years 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). Mecury 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 foward is still the use of mecury, but in a manner that will absolutely minimize pollution, considering cost implications. A man has designed a lantern retort that allows the mecury used in the recovery to be recondensed for another usage. No environmental issues.

Victor Bergman
2 years ago
Victor Bergman 2 years 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 by Dr. Veiga 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. 

David Kano
2 years ago
David Kano 2 years ago

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

JohnnyD
2 years ago
JohnnyD 2 years ago

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

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years 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 leach d 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 startup 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 therefor 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.

Victor Bergman
2 years ago
Victor Bergman 2 years ago

It is good to see somebody describe the research conducted with 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 to Ofori, 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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