Thiosulfate Reagent Interchangeability

[chawimac]

I was wondering about the thiosulfate leach chemistry and have a major doubt. Is Sodium Thiosulfate (Na2S2O3.5H2O) and Ammonium Thiosulfate ((NH4)2S2O3) interchangeable reagents? How about the ammonia used? Ammonium Hydroxide (NH4OH) and Ammonia (NH3)????



I am going to attempt a thiosulfate leach of a gold bearing ore which I had posted about elsewhere. The ore chemistry is the following:

Au 616.7 g/t
Ag 196.78 g/t

(Gold and silver are the assay of a concentrate produced, the rest is ICP of the ore.)

Al 5.07%
S Total 0.05%
(Sulfide 0.02%)
(Sulfate 0.03%)
Ca 0.74%
Fe 3.55%
K 1.35%
Mg 0.18%
Ti 0.03%
As 19,722 PPM
Ba 272 PPM
Mn 543 PPM
Sr 125 PPM

I will leach 1,000 grams of material under the following conditions:
(I am taking into account high As in the sample so adjusted based on public research)

Leach Time: 3 Hrs.
Target PH: 10
Agitation: 400 RPM (seems fast right?)
Temperature: 50 Celsius
Pulp % of Solids: 40%
Gas: Air injected via aquarium pump
Ammonia: NH3 at 3M
Copper: CuSO4.5H2O at 1.2mM
Thiosulphate: Na2S2O3.5H2O at 0.2M and expect to use 7.7 Kg/ton

Might also try this if all goes well:

Gas: O2 at 0.2 Liters per minute
Lye NaOH at 0.4M
Calcium Hydroxide Ca(OH)2 at 0.11M

Reagents will be prepared to appropriate concentrations, mixed, poured into beakers with ore, heated, stirred for 3 hours. Then they will be washed twice with tap water, and the leach will be filtered with filter paper. Leach will be precipitated using Zinc Powder. Electrowinning is also in the future if all goes well.

 

[chawimac]

Update:
No luck. The leach did not work or perhaps I did something wrong. Tried to drop gold first by electrowinning, next with steel wool and last with zinc. Nothing worked thus far.

 

[Lou]

If it assays that high, I would consider it a smelting prop.


Lou

 

[chawimac]

Update:

Turns out the problem was grind size. This particular ore has gold in something called electrum, which if you wiki it says that its basically gold, silver and a couple other posibilities and in this ore it is found in extremely fine particles. It needs to be finely ground for the chemicals to do their magic. I opted out of Thiosulfate since it is much more difficult than NaCN. Here is a picture of the mineralogy in case anyone is curious.