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

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

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Electrowinning difficulties/pre-acid washing carbon to remove Hg (2 replies)

H
CA
6 years ago
CA 6 years ago

We've recently encountered some problems with electrowinning from carbon that has high Hg loadings.  We are doing an alcohol Zadra strip with carbon loaded from a non-cyanide leach. 

When using alcohol, we usually see high Au recoveries within 24hrs when there is not much Hg loading.  However, we are seeing very low Au recoveries even after 48hrs of alcohol stripping with this carbon that is highly loaded with HG. 

The gold seems to be coming out of the carbon as our liquid is testing at up to 57ppm Au, but we are having difficulties pulling it out of solution and onto our cathodes.  We are, however, getting large amounts of Hg loaded onto the cathodes and forming as a sludge inside our e/w cell.  

Someone recommended that we do a cold hydrochloric acid wash prior to stripping in order to remove the Hg from the carbon.  Any thoughts on this?  What % of acid should we use and for how much time?  

Thanks in advance for any ideas you may have.  

 

R
Richard S
6 years ago
Richard S 6 years ago
Like

It would help to know what the non cyanide leach you used and are you stripping in a cyanide alcohol solution?  However, you could certainly try using a hydrochloric acid strip of the carbon prior to your Zadra leach.  I would try a 10% solution of HCl first and see what your results are using a say 1 kg sample.  You should be able to test the carbon for residual Hg content.  If not very effective, increase the HCl strength. 

Heating the carbon would also remove the Hg.  Hg has a very high vapor pressure with increasing temperature.  You would need to recover the Hg in the vapor using a sealed system and a condenser.

http://www.kuntermetallurgy.com/

J
jfernando
6 years ago
jfernando 6 years ago
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          It would be possible to remove Hg from solution depending on your operating conditions.

 


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