Is this carbon adsorption?

[Traveller11]

From "Getting Gold: A practical treatise for prospectors, miners and students" by J.C.F. Johnson, F.G.S. (1898)

"Great improvements on this slow and imperfect method have been made of late years, among the earlier of which was that of Messrs. Newbery and Vautin. They placed the pulp with water in a gaslight revolving cylinder, into which the chlorine was introduced, and atmospheric air to a pressure of 60 lb. to the square inch was pumped in. The cylinder with its contents was revolved for two hours, then the charge was withdrawn and drained nearly dry by suction, the resultant liquid being slowly filtered through broken charcoal on which the chloride crystals were deposited, in appearance much like the bromo-chlorides of silver ore seen on some of the black manganic oxides of the Barrier silver mines. The charcoal, with its adhering chlorides, was conveyed to the smelting-house and the gold smelted into bars of extremely pure metal. Messrs. Newbery and Vautin claimed for their process decreased time for the operation with increased efficiency."

Mr. Johnson talks about filtering the gold in solution through broken charcoal, depositing the auric chloride crystals there, and then smelting the charcoal with its adhering auric chloride crystals.

Is this a basic form of the carbon adsorption method? Is it really as simple as filtering gold in solution through activated carbon (charcoal)? What becomes of the carbon during smelting, does it all get burnt off?

 

[g_axelsson]

I don't know anything about this method but whenever you smelt anything with an excess of oxygen the charcoal will burn and go away as carbon dioxide.

But I would be very careful to smelt anything with auric chloride in it, around that time they didn't really knew how volatile auric chloride could be. I would suspect that you would have large losses going away as gas if you tried this process. Unless carbon monoxide could serve as a reducer and turn the auric chloride into pure gold, then it would work quite good.

Anyone know if carbon monoxide could reduce gold chloride into gold?
I'm also wondering if it could reduce silver chloride into silver?

/Göran

 

[butcher]

Good advice /Göran, I agree a lot more study or better understanding of the chemistry would be needed here.


I do not understand how the carbon would react with the chlorides, or if it would reduce the gold and drive off chlorides in a slow heating process at lower temperature,before burning off carbon and then before melting the gold.

I would need to study more before trying to deal with something like this.

But my first thought would be to try and reduce the gold to metal, and converting the gold chloride to gold, converting the chlorides to NaCl saltwater using caustic washes in sodium hydroxide, and then washing the carbon and reduced gold with boiling hot water to wash out all of the salt water that formed from the reaction, before drying the gold and carbon, then heating gently to drive off any remaining chloride salt before raising the heat to combust carbon to CO2 gas then raising the heat again to melt the gold.

Carbon will reduce metals in a melt, but I do not know enough about its reaction with chlorides to see how it would react with the gold chloride, or if you may be able to drive of chloride with a lower temperature before burning the carbon without making the gold volatile, with the use of a mild heating step, then roasting, then melting process alone, or if a flux might also help to reduce the gold.

I would need to do a lot more studying before I would try to melt, I think I would begin the study by looking at the temperature needed to reduce gold chloride to gold with heat to drive off chloride (without lose of gold), and where carbon reduction to CO2 gas would come into play.

 

[Traveller11]

Good advice /Göran, I agree a lot more study or better understanding of the chemistry would be needed here.


I do not understand how the carbon would react with the chlorides, or if it would reduce the gold and drive off chlorides in a slow heating process at lower temperature,before burning off carbon and then before melting the gold.

I would need to study more before trying to deal with something like this.

But my first thought would be to try and reduce the gold to metal, and converting the gold chloride to gold, converting the chlorides to NaCl saltwater using caustic washes in sodium hydroxide, and then washing the carbon and reduced gold with boiling hot water to wash out all of the salt water that formed from the reaction, before drying the gold and carbon, then heating gently to drive off any remaining chloride salt before raising the heat to combust carbon to CO2 gas then raising the heat again to melt the gold.

Carbon will reduce metals in a melt, but I do not know enough about its reaction with chlorides to see how it would react with the gold chloride, or if you may be able to drive of chloride with a lower temperature before burning the carbon without making the gold volatile, with the use of a mild heating step, then roasting, then melting process alone, or if a flux might also help to reduce the gold.

I would need to do a lot more studying before I would try to melt, I think I would begin the study by looking at the temperature needed to reduce gold chloride to gold with heat to drive off chloride (without lose of gold), and where carbon reduction to CO2 gas would come into play.

It seems, from further reading I have done, the biggest problems they had in those days (1890's) was the low quality of the activated carbon they were using and the large amounts of ash that ended up in the gold.

There is no mention, from articles of that time, of the gold losses to the atmosphere Goran mentions but, if they weren't aware of the losses, they wouldn't mention them, I guess.

 

[g_axelsson]

In "The Metallurgy of Gold" by M Eissler he talks about the volatization of gold in chloride roasting on page 216. That book was printed in 1896.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=54&t=14107&p=167038#p141655

Göran

 

[Richard NL]

There is no mention, from articles of that time, of the gold losses to the atmosphere Goran mentions but, if they weren't aware of the losses, they wouldn't mention them, I guess.

Volatilisation of gold, page 5 till 9 and page 22 in this book.

Please correct me if I'm wrong or made a mistake,i am still learning.