Electrochemistry Salt Water Electrolytic Cell

[butcher]

If you could use chlorine to dissolve the gold on one side of the split cell, adding salt as needed, I would think if current and conditions were in certain limits the gold chloride would form, instead of generating chlorine gas (or limiting chlorine gas that would evolve), once you had gold in solution it could be precipitated out of solution, or possibly plated out of solution, the membrane or salt bridge could keep gold on one side of the cell.

For ore the problem of base metals and all of the other chemistry involved in the ore, would possibly cause havoc with the electrolyte, but for ore maybe you could use the chlorine cell to generate chlorine and use the gas to volatize gold from ore in a roasting furnace where the suspended red hot powdered ore >900 degrees C is falling through the flue gases with chlorine gases rising through this flue, the ore could also be pre-roasted with NaCl, to help pre-chlorinate the ore, of course capturing these volatile metal gases in a scrubber, here the sodium hydroxide generated in the cell may come into play, although building a furnace and maintaining it safely would be difficult, it would possibly be easier to just bubble chlorine gas into a crucible fixed with an ability to capture volatized metals (such as gold chlorides), and try to chlorinate the gold in the gold left in the crucible (crushing the melt when cooled to powder and dissolving the now water soluble gold and other metal chlorides.

Even simpler would be to concentrate the finely ground powdered ore, roast it and use the chlorine generator to bubble chlorine gas into a hot solution liquid leaching process.

 

[Gratilla]

After having read the thread, together with all its side links and parallel threads, with interest, I'm wondering whether the long journey is nearing a destination?

The details so far:-

Electrodes: Platinum, Lead Dioxide, Titanium, Graphite?

Electrolyte: How many kg NaCl per 1,000 l water ... or does it matter?
a) Page 48: Seawater - approx 32kg,
b) Page 48: 1 mole/liter - 58kg,
c) Page 48: 100kg/ton of ore.
d) Chlor-Alkali cell - 260kg
e) Saturated soln - 359kg

Unit Design: Electrodes in same or separate containers? Pump? Convection currents? Membranes? Semi-porous ceramic/clay pots?

Voltage/Eh/pH/Temp: Pourbaix diagrams of Eh against pH would be useful.

In some ways this saltwater cell is an electrochemical equivalent of SSN (Saturated Salt Nitric leach), but with control over the voltage. And both are broad spectrum, that is they will leach the base metals before the Au and PGMs. (To specifically target Au in black sands, cyanide is probably the way to go.)

On the plus side though, both systems will also leach the PGMs ... and solvent extraction with butyl diglyme (or diethyl malonate) will extract close to pure gold (irrespective of base metals etc in the aqueous fraction).

 

[Traveller11]

Gratilla
There seems to be some question as to just how selective for gold this leaching method is. If you read the thread I started in "Prospecting, Mining, Ore Concentrates & Geochemical" which is titled "Recovery of gold from ores with chlorine in 1898", you will notice they are using a chlorine solution which should be almost identical to the chlorine solution produced electrolytically; namely, a solution of hypochlorous and hydrochloric acid in water at a ph of 5-6.

In this article from 1898, they described grinding ore to a fine pulp and roasting this ore in furnaces and then sending the ore to the leaching vats, with NO attempt to remove base metals such as iron. As iron is the 4th most abundant element on the planet and I am sure their ore had some iron in it, I can only assume this method did not put iron into solution.

Another article I read from the 1890's talked about why ores are roasted. It is not only to free gold up from sulphides. The article said that, by converting elements such as iron to its oxides, it made the iron far more resistant to the leach and prevented it from going into solution.

Once again, they said that copper in the ore, especially in its metallic state, was poison on the leaching process.

I would like to continue this discussion on the "Prospecting, Mining, Ore Concentrates & Geochemical" forum so as to avoid duplication of posting. Also, this has more to do with mining than anything else, so this might be a more appropriate place to discuss chlorine leaching.