Gold solution recovery

[Roberto Aleman]

I have a client with a cynide solution, pH= 11.2 and 30 ppm of gold, copper and silver. We have done AA assay, we have also evaporated and dryed a sample, ashed the salts and made a fire assay.

I ran a sample with zinc dust method, but gold did not precipitate, just copper and some silver. Is there any other chemical method for recoverying gold from this kind of solutions besides using zinc and alumminun? or how can i process this solution? I'm running a sample with an electrolityc cell with SS anode and cathode.

Thanks in advance

 

[anachronism]

Roberto

Please clarify that you mean 30ppm gold alone and the silver and copper is in addition to this.

If so then do remember that 30ppm gold equates to 3g per 100 litres of solution or 30g per 1000 litres. How much solution do you have?

Jon

 

[Roberto Aleman]

Yes, it has 30 ppm gold alone. We have 3000 liters of solution, so we expect around 90 g of gold.
I have used zinc method for similar solutions and left the solution with 4 ppm of gold after precipitation. But there's something in this particular one that doesn't let the gold to precipitate.

 

[4metals]

Perfect solution to build one of these to recover the metals;

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=24899

and since you have an AA, you're good to go!

 

[Lino1406]

Personally I can't see how copper will precipitate with out gold inside. However there is one chemical that can precipitate both, it is called sodium hydro sulphite and it comes from textile industry."30 and more recovery procedures"

 

[Roberto Aleman]

Thanks for the input. I think there's something like a chelating agent for gold, because the redox potential of cynide gold tells that it should be reduced by zinc or alumminum. I wil try the sodium hydro sulphite.

I've read Jon's topic about the electrolityc cell, it's very intresting, looks like a Zadra type cell:

 

[Lou]

It is also called sodium dithionite. It's cheap as chips.

You might not use zinc again. Likely your problem is needed more base because your zinc is old/oxidized.

 

[Lou]

OK I was feeling nice so I dug up this attachment for you.


this method works great and you won't use merril crowe again unless your gold is complexed.

 

[4metals]

The cell in Jon's thread is not unlike a Zadara cell but it uses a carbon fiber cathode, and the difference in surface area between the carbon fiber and the steel wool makes it more efficient. You will be able to set up a flow rate through the cell for single pass complete recovery by using your AA to analyze the discharge and setting the flow rate accordingly. The electrolyte does not need to be heated. Plus there is no steel wool in there to further add extra metal to your clean-up later on.

The down side to the method using hydrosulfite is the efficiency is best at 150ºC. Something about 5000 liters (or 24 full 55 gallon drums) is it isn't something you just pop on a hot plate to warm it up.

So unless you have a large jacketed vessel to heat your solution in, I still would favor a cell.

 

[Roberto Aleman]

OK I was feeling nice so I dug up this attachment for you.


this method works great and you won't use merril crowe again unless your gold is complexed.

Thank you so much Lou, I always learn something new from your posts.

 

[Roberto Aleman]

The cell in Jon's thread is not unlike a Zadara cell but it uses a carbon fiber cathode, and the difference in surface area between the carbon fiber and the steel wool makes it more efficient. You will be able to set up a flow rate through the cell for single pass complete recovery by using your AA to analyze the discharge and setting the flow rate accordingly. The electrolyte does not need to be heated. Plus there is no steel wool in there to further add extra metal to your clean-up later on.

The down side to the method using hydrosulfite is the efficiency is best at 150ºC. Something about 5000 liters (or 24 full 55 gallon drums) is it isn't something you just pop on a hot plate to warm it up.

So unless you have a large jacketed vessel to heat your solution in, I still would favor a cell.

I will definitely build a cell, I think it has a lot of potential for this one and further applications.

 

[Lou]

The cell in Jon's thread is not unlike a Zadara cell but it uses a carbon fiber cathode, and the difference in surface area between the carbon fiber and the steel wool makes it more efficient. You will be able to set up a flow rate through the cell for single pass complete recovery by using your AA to analyze the discharge and setting the flow rate accordingly. The electrolyte does not need to be heated. Plus there is no steel wool in there to further add extra metal to your clean-up later on.

The down side to the method using hydrosulfite is the efficiency is best at 150ºC. Something about 5000 liters (or 24 full 55 gallon drums) is it isn't something you just pop on a hot plate to warm it up.

So unless you have a large jacketed vessel to heat your solution in, I still would favor a cell.

You don't need jacketed stuff. You just need time and a way to decant all the liquid. Heat just makes it go faster.

 

[patnor1011]

It seems that sodium hydrosulphite and sodium dithionite are not the same. One is NaHS other is NaHSO3. Are they both acting the same in this instance or is there difference?
Is this one I found on ebay applicable?
http://www.ebay.ie/itm/Sodium-dithionite-dihydrate-Sodium-hydrosulfite-Na2S2O4-2H2O-600g-/221637810745?hash=item339aa49a39:g:EP8AAMXQRPRTJLH3