Seperating Silver from Tellurium or Telluirium-silver

[lazylightning]

Hi!

I have some leftover ore concentrate given to me for analysis that contains mostly metal. 60% lead, 14% tellurium, 12% silver and 12% antimony.

Though the ore initially yielded 7 grams of gold per kilogram of ore by treating it with caustic soda in an induction oven, a spectral analysis of the ore concentrate showed it contained only 120 grams per ton instead of the expected 7000 grams. The owners have decided not to work with the material.

Since I need a bit of silver for some experiments and I have about a 20 kilo bag of the ore, I'm trying to figure how to get the silver out. At least a hundred grams or so. Both silver and tellurium are dissolveable in nitric acid, which will also dissolve the lead and leave the antimony behind, if of course I'm not dealing with antimony-glass at least in part. Antimony glass is an alloy of silver and antimony which is quite resistant to attack. If antimony is best dissolved with hot aqua regia (while quickly saturating the acid and dissolving little antimony per bath), the antimony glass can be more resistant.

Assuming only part or none of the silver is combined in such a way with the antimony and it is free with the lead and tellurium or is as tellurium-silver, then how do I go about getting the silver and tellurium apart?

The ore concentrate is not simple. When I only add HCl to it, large plumes of red gas - nitrogen dioxide/tetroxide come off and it boils by itself for a long time. Perhaps the lead or other elements are as nitrates and nitric acid forms. Perhaps something electrochemical is going on with all that metal in there. So just by adding HCl I end up with boiling aqua regia. Therefore I will have to hit it first with dilute nitric washes to get out the lead, tellurium and silver, leaving at least the antimony behind.

Then I suppose after cementation or evaporation I can incinerate and then properly remove the lead (and zinc) with HCl. Then I will have tellurium and silver or tellurium -silver left. What should I do next? Any ideas?

Thanks,
Paul

 

[Harold_V]

Yes, I have one idea. Use the 20 kilos of concentrate as fill, and buy the required silver.

I realize that doesn't answer your question, but unless your objective is the experience, you're going to find that small amount of silver is going to end up costing you a small fortune. There's a real good reason the rightful owner abandoned the project. If he can't make it work in volume, you're surely going to take a bath in small increments by chemical extraction, and you still won't have pure silver.

Assuming the tellurium is free, it can be eliminated by roasting. It comes off as a brown gas. I have done so with slimes from a copper parting cell, where several precious metals were contained within.

Incidentally, a recent post by a new member was making reference to a slag that was reputed to be loaded with values. A quick estimate of the slag resulted in a value around ½ million dollars/ton. I expect, just as in this case, it won't be there in reality.

I don't know that the hell is going on with assaying these days, but they manage to come up with totally unreasonable numbers, but the ore, slag or concentrate doesn't produce. I always say place your trust in a fire assay.

Harold

 

[lazylightning]

Thanks for the idea about roasting! I'll give it a fry!)))

Yes, the silver will be expensive to get out. Actually it's impossible to even buy silver here in Russia, except as coins from the government bank or silverware))). I would have to have some kind of industrial liscence to be able to buy it as technical 99.9% silver and it would be at least twice the world market price. The upside is that some people are ready to pay the world market price for precious metals that aren't exactly pure)

I've read about some gold that's been studied which is spectrographically invisible yet assayable. I hope it wasn't that gold, then I have misinformed that gentleman as whether the material is profitable or not. I simply informed him about the prospect of hydrometallurgical methods. At 120 grams per ton, it would be useless. If it really has 7000 grams per ton , then the 100 tons he has would be worth working with somehow.....

I used 1 liter of 35% nitric, that's four boiling baths, to get the lead, tellurium and perhaps silver out of 200 grams of the material. I used the same amount of conc. AR(40%HCl plus 70% nitric) to dissolve the remaining antimony, with four seperate long boil downs. Yes nitric supposedly dissolves antimony, ha ha ha, however after reading a well informed text describing antimony from the 19th century, I knew that AR is the solvent of choice, though that text warned that it quickly saturates the AR and the material seems hardly dented. The remaining material seemed invincable until I used the leach with sodium hydroxide plus sulfur( creates sodium thiosulfate and sulfur nitride to boot- a patented process), after ten hours of boiling(replentishing w/ water) nothing was left but a little sand and light sulfide(transformed to sulfides) mass. It was then that I got the call informing me that there was only .012% of gold in the material instead of the waited .7%.

The owner informed me that they had to abandon the induction oven at the industrial level due to the oven's owner refusing to allow sodium hydroxide to be volatilized in his oven due to corrosion. Otherwise, they were consistently getting 7 grams of gold from each kilo of ore concentrate at experimental levels.

 

[Harold_V]

Damn, I hope my mental lapse wasn't misleading. I spoke of tellurium, but it was selenium that I eliminated. Sorry for the error. Had I not read your most recent post, I wouldn't have given it another thought. Still, for all I know it will work, so please comment, good or bad, after your experience.

I wasn't aware that you were in Russia. Didn't look at your information before responding. Sounds like you folks don't have any trouble acquiring nitric acid there.

Good luck with the project. I think I understand. There's often times I do things because it seems like the things to do. That's how we learn.

Harold

 

[OMG]

This was on webelements.com
(I don't know what would happen with the silver, but its information anyway. webelements.com is a good website.)

TELLURIUM
Isolation: it is not usually necessary to make tellurium in the laboratory as it is commercially available. While there are some tellurium ores, most tellurium is made as a byproduct of copper refining. Extraction is complex since the method employed will depend upon what other compounds or elements are present. The first step usually involves an oxidation in the presence of sodium carbonate (soda ash).

Cu2Te + Na2CO3 + 2O2 → 2CuO + Na2TeO3 + CO2

The tellurite Na2TeO3 is acidified with sulphuric acid and the tellurium precipitates out as the dioxide (leaving any selenous acid, H2SeO3, in solution). Tellurium is liberated from the dioxide by dissolving in sodium hydroxide, NaOH, and electroytic reduction.

TeO2 + 2NaOH → Na2TeO3 + H2O → Te + 2NaOH + O2

 

[Lino1406]

I would try precipitating Te with SnCl2 (like Se). What
you have to lose by trying?
If AgCl results, you may dissolve it with
Na2S2O3 (after good water rinse)
and prooceed from there

 

[lazylightning]

Here's a new twist to that story. So, I decided to go ahead and do a broad analysis of that ore concentrate. It seemed so strange that they got .7% gold with an induction oven while the analysis said .012% gold. The general analysis reads: 54% lead, 11% antimony, 3% copper, 2% silica, 1% silver, 1% iron, 1% sulphur and lots of oxygen(oxides). Hhhmmmm. Well, though I was begining to consider they had a fortunate combination for alchemical transmutation ;-) I now feel it is something more akin to the nutshell and marble trick. After all, hey, a hundred tons can fit into just a couple of trucks)))) At 7 kg a ton, maybe somebody went through the trouble to "exchange" the material with something that was somewhat similar. Theft. The owner doesn't even answer my messages, I guess he's the silent type in these matters)))

Well, with only a percent of silver in it))) I'm not going to bother. I have a friend that's offered me some old banged up silverware, that sounds much better.

I can buy 67% nitric at one chemicals and lab equipment shop here in Moscow. About $3 per liter. The 70% stuff is available in .5 liter bottles at the radio parts flea market. I get my 40% HCl there, it's rockin stuff! Makes great AR with the 70% Nitric. I can buy as many bottles as I want if I agree in advance for them to bring it. They say that the canisters and tanks of it require special liscences to transport and they don't deal with them. My projects are quite small though and a backpack full is quite enough for me. I always bring extra newspaper and pack the bottles myself)))

Here's a copy of that patent which I refered to. It dissolved that last antimony material that the AR wouldn't. It did turn it partially into solid sulfides, which dissolved easily in AR leaving behind only very fine silica sand which it had alomost completely dissolved. It dissolved all the black sand too, easily.

http://www.patentstorm.us/patents/5290338/fulltext.html