Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction 2017-04-04T06:57:36+00:00
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Carbonaceous Gold Ores Treatment Process (16 replies and 1 comment)

1 year ago
Gruppen 1 year ago

I'm working with carbonaceous gold ore at laboratory scale, now I’m doing at pilot test in two stage: gravimetric (shake tables) where I get concentrate (almost clean without carbonaceous material ready to cyanidation), the tail of shake table has the more carbonaceous material and 40% of gold, I’m doing test with kerosene (with different granulometry) as pre-treatment then cyanidation, even at small size (under 40 micron) of the final tail has gold values, what kind of species I have to difficult The dissolution of gold ? Maybe is refractory too and is necessary to reduce? (I did roasting test too with a material with d80 = 180 microns the recovery of Gold was 95%, so I think maybe is not refractory by size)

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

As a start I would recommend a diagnostic leach test to quantify the gold associations with carbon, sulphides, gangue, etc., and determine to what extent the ore is preg-robbing.

Victor Bergman
1 year ago
Victor Bergman 1 year ago

First you need a mineralogical characterization to determinate the amount of carbonaceous material in the ore.

1 year ago
Oberfuhrer 1 year ago

Application of IX resin can be beneficial in this case for two reasons, at least. IXR is resistant to organic fouling, including kerosene.

Having high affinity for aurocyanide the resin removes gold from the solution and so shifts leach equilibrium to favourable side. Thus, gold recovery from ore becomes few % higher. The resin of choice may be Purolite A194 either Dowex XZ91419. Both are commercially used products.

Zander Barcalow
1 year ago
Zander Barcalow 1 year ago

By carbonaceous I take it you mean that there is organic carbon in the ore which becomes "preg-robbing" in a cyanide leach circuit. I visited a plant in Malaysia (Penjom) where this was such a serious problem that they had to use kerosene to foul (blank) the organic carbon prior to cyanide leaching. They used a resin in pulp system then for the recovery of gold which worked very efficiently such that they were able to profitably treat the ore and recover the gold. I believe there are a number of plants around the world using this type of system.

Helena Russell
1 year ago
Helena Russell 1 year ago

The preg-robbing nature of the carbonaceous material present in gold ores is determined by its physical structure, for low preg-robbing ore the carbonaceous material or graphitic carbon has a structure similar to that of graphite. Generally speaking ore that contains this type of carbonaceous material can be economically treated by CIL under the right conditions. Highly preg-robbing ore that contains carbonaceous material with a structure similar to that of activated carbon requires blinding or roasting to achieve high recoveries. The physical structure of the carbonaceous material can be determined with Raman spectroscopy, I can send you some papers on this if required.

Also, as gold losses are often a result of preg-robbing and refractory gold it can be difficult to quantify how much is attributable to each and doing diagnostics analysis and mineralogy, as previously suggested, is required to gain a better understanding of this. To understand the preg-robbing nature of the carbonaceous material I would also suggest doing preg-robbing index tests to determine how much gold is being re-absorbed back onto the ore and also comparing the results from direct cyanide leach tests with CIL tests to assess how effectively activated carbon is recovering preg-robbed gold.

2 weeks ago

I would love to get the articles you have with Raman spectroscopy.
Thanks! handerson.asilva@hotmail.com

1 year ago
Standartenfurer 1 year ago

Try testing with paraffin oil (kerosene)

If roasting gave 95% recovery, then is not a size challenge but rather an oxidation challenge. We are about to test Ammonium Thiosulfate in Honduras.

1 year ago
Gruppen 1 year ago

Direct cyanidation has recovery 5%, about mineralogical characterization the sample is analyzing.
I heard about use of resins, but i couldn't read a paper, can you send me information, dosage, kinetics absorption, costs (more important) any supplier in South America. I read information about that plant, they apply many process (gravity, use of resin, flotation). I use kerosene to foul the organic carbon prior to cyanide and the results are good but not enough.

I was using a dosage 4 to 16 lts/m3 of pulp at 40% solids, can you suggest a time of residence to make contact to blank the carbonaceous material.

I was looking information about roasting, i did laboratory test with an electrical resistance furnace, the results area good at different size of particles. I think the ore has double refractory gold ore (sulphides have the locked up and the carbonaceous material which inhibits the recovery), I was doing test on a electrical resistance furnace, the recovery a different size was good, I'm still looking information about the design of reactor.

Thank you for let me know the results

Sugar Watkins
1 year ago
Sugar Watkins 1 year ago

What is the size of the resource? All the processes have a capex and opex. Is the resource large enough to justify a roaster? The gravity test had 60% gold recovery? Is this for the selective sample? Or has the resource been samples to show that a gravity circuit will produce high recoveries? The USBM did work over the years on carbonaceous ore.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

You have already received some good advice from members of the group. I recommend you stop doing any serious laboratory testing until you understand the problem. You can do this by diagnostic leach tests, preg robbing characterisation and mineralogical study of the material. You need to know how much gold is liberated for leaching, how much is locked in sulphides (typically pyrite or arsenopyrite), locked in gangue and how much of the gold that leaches initially is then locked up by carbonaceous material in the sample. Knowing the gold distribution and the reason why some gold is not leached (or not available for recovery) will allow you to define potential processes to overcome the problem.

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

I totally support your idea. It is important to understand what you are dealing with and do some investigations before getting into battle doing tests. If you like doing tests so much, do diagnostic leaching, 48h leaching kinetics tests, CIP (RIP) to prove how severe preg robbing effect is and how much you can actually leach. The end 5% recovery does not tell anything but the gold was still in solids. I can help you with the deportment study and give mineralogical base to the way to treat the ore most effectively.

1 year ago
Obersturmbann 1 year ago

There are two other less common options that I have seen used in the past to minimise preg robbing in CIL Circuits and have been shown to be successful.

You can use pre-flotation to remove the Carbon before the CIL circuit. The Carbon Conc. will contain about 15g/t Au, and this conc. can be processed further.

You can use post-flotation to remove the Carbon after the CIL circuit; This Carbon conc. can be processed further, and will tend to be even higher in Au Content then the pre-flotation concentrate.

The Carbon pre-flotation route would be the recommended method, as it reduces the operating complexity and operating costs of the CIL circuit.

Once you have a Carbon Concentrate you can oxidise the carbon to destroy it, using 2-3kg/t of hypochlorite and then put it back into the CIL to recover the Au. The process was used at Full Scale on-site at Pueblo Viejo in 1998, when we were involved in the operation.

Tony Verdeschi
1 year ago
Tony Verdeschi 1 year ago

Have you tried this http://is.gd/HQvkt8 it may result in a cheap and fast option.

Marshal Dienes
1 year ago
Marshal Dienes 1 year ago

You have received excellent comments for carbonaceous-refractory ores treatment. The economics to implement a successful plant will be related to recovery levels and treatment of effluents. As it has been mentioned, roasting provides highest recovery and the process will be well suited for both carbonaceous and refractory ores and the technology is also well known. I am working on a process including an advanced roasting approach and a non-cyanide route to gold recovery including controlling of all effluents for an environmental friendly process. This is a proprietary process.

1 year ago
Sturmbann 1 year ago

The mineralogy is the key. As is due diligence and asking the right questions. The new mill at Syama in Mali is processing an oxide ore containing traces of organic carbon. The testwork demonstrated a 5-15% increase in recovery after utilisation of a shear reactor/oxygenation device followed by CIL leaching. This appears to be at least partially true in the field (optimisations underway). I have never advocated the use of this type of reactor before as it is of value in niche applications only; but after commissioning I am pretty impressed by the DO levels staying high and the ore leaching almost completely (that which is liberated) by the third tank. 

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

Interesting comment! It sound alike Isa-mill-oxidation-leaching process at Kalgoorlie CGM that operated since 2002. They also use it at Las Lagunas (Dominican Republic) operating on tailings from Pueblo Viejo. It is also known as Albion process patented in 1993. It is good with fine gold in sulphides. Pyrite may not need to oxidize completely in this process. It works well with telluride gold ores such as at Certej in Romania. General mineralogy affects the process choice (sulfide content, carbonate content and composition, organic matter and so forth) as well as economics, infrastructure, climate, expertise.

Helena Russell
1 year ago
Helena Russell 1 year ago

There was a very good paper written for the World Gold Conference in 2013 entitled “A Historical Review of the Treatment of Preg-Robbing Gold Ores – What has Worked and Changed” by Rob Dunne et al. Well worth a read!

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