My home-made elution / carbon stripper

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oro-del-sur
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My home-made elution / carbon stripper

Post by oro-del-sur » December 8th, 2018, 8:41 pm

I’m wondering if I’m in the ballpark with this and how scaleable it might be.

2.5 L of solution
1% cyanide
1% sodium hydroxide
2% alcohol

- 700g of activated carbon w/ aprox 2-3 g of gold
- carbon is wrapped in mosquito netting
- anode is a carbon / graphite rod
- cathode is steel wool wrapped in a coffee filter
- power supply is 1 amp - either 6 or 12 volt (?)
- heat at 80 C

It’s a bit cramped in the Pyrex as you can see in the photo. Does position of the electrodes matter? Can they touch the carbon without issue?

The pH started out at 13 and dropped to 11 after 2 hours

The solution started to turn yellow within 15 minutes

I read it can take 30-40 hours or more to reach optimum recovery.

Am I on the right path?
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oro-del-sur
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Re: My home-made elution / carbon stripper

Post by oro-del-sur » December 9th, 2018, 1:12 pm

Next day...unfortunately the whole thing evaporated overnight! ...but seems like it worked, nice gold wool.

I assume a single vessel to heat and electrowin can only be done using non conductive ceramic / porcelain or similar material, therefore a limited capacity, more or less 1 kg of of activated carbon. Yes? A 5-10 kg capacity would need to be two vessels, a steel pot on a burner and then pump / or manually transfer the liquid to a second stage electrowin cel and then pump / transfer back to steel pot...more or less yes?
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FrugalRefiner
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Re: My home-made elution / carbon stripper

Post by FrugalRefiner » December 9th, 2018, 2:11 pm

oro-del-sur wrote:
December 9th, 2018, 1:12 pm
a steel pot on a burner and then pump / or manually transfer the liquid to a second stage electrowin cel and then pump / transfer back to steel pot...more or less yes?
Trying to balance two pumps would be frustrating. Let gravity help. Put one vessel lower than the other. Use one pump to pump liquid from the lower vessel to the higher vessel. Then have an outlet near the top of the upper vessel that allows the liquid to flow back down to the lower vessel.

Dave
Printer friendly copy of C. M. Hoke's Refining Precious Metal Wastes.
Screen readable copy of C. M. Hoke's Refining Precious Metal Wastes.

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oro-del-sur
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Re: My home-made elution / carbon stripper

Post by oro-del-sur » December 9th, 2018, 3:35 pm

Thanks Dave. So a slow drip to lower electro cell, then slow pump back to heated pot. Considering the 80-90 C caustic solution is a special type of pump rquired? Whats the best material to use for the electro cell?

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Re: My home-made elution / carbon stripper

Post by oro-del-sur » December 12th, 2018, 7:35 am

Here's a drawing I did, please comment. I have Ammen's book, Hoke, The Chemistry of Gold Extraction but sparse info about Elution and EW from cyanide solution. Google searches don't render much either. I want to learn. A few questions.

What is best material for the anode (I have some stainless mesh)

proper arrangement of cathodes (steel wool) and anodes

Heating methods for stripping solution, column / pot

how much steel wool x estimated gr of gold?

how much solution x kilo of carbon?

pH 11 until the end?

treat steel wool with HCL?
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Deano
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Re: My home-made elution / carbon stripper

Post by Deano » December 12th, 2018, 5:55 pm

At a temperature of 80C all of the elution of gold from the carbon is being done by the alcohol.

All alcohol based stripping systems recycle the alcohol in a permanent loop through a column of carbon which is wetted by cyanide solution.

These systems only operate while alcohol or alternative organic complexes are present.

In an unsealed system the organic component will volatilise out of the system and gold desorption will cease.

The main advantage of the organic type stripping systems is the speed of operation, the main disadvantages are the presence of organic fumes on fire safety and personal health.

The basic Zadra strip will get a lower residual level of gold on the carbon but at a time and energy penalty.

There are a lot of papers on many types of stripping systems available on the internet, if you read them you will see that you are not working on something new but are starting at the base level of a process which was very quickly made quite sophisticated in order to have a system which was efficient and safe for commercial use.

Deano

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