Sciencemadness Discussion Board

Platinum Group Metal extraction from Galena ore

Shamase - 18-4-2013 at 02:11

Hi

I have galena ore with the following composition;

90% PbS
5% FeS
3% Ir
1.5% Rh
0.9% Pt
0.5% Ag

My objective is to remove as much of the lead as possible , leaving me with pure PGMs from the material, so here are the steps I have taken, but still I am not getting the results that I hoped for.

step 1) Floatation with PAX as collector and Potassium Dicromate as depressant
step 2) Roasting of the concentrate with 15% charcoal at 650 deg for 12hours
step 3 Sulphuric leach for 2 hours-to dissolve base metals
step 4-The residue has 5 hour Aqua regia leach, pH adjusted to 6.5, filtered
step 5- To the filtrate 5 hour formic acid leach, Sodium carbonate used to adjust Ph to 5, filtered
step 6- residue again leached in Aqua Regia, cooled and filtered,
step 7- to the filtrate I added ammonium chloride to precipitate PGM's and also added oxalic acid to the AR solution but no noticeable precipitate was formed.

The XRF analysis indicates between 20-40% Ir in the residue after step 7, but still very high Pb. The question is what am I doing wrong why can't I get rid of all or most of the Pb and where am I losing the Ir, Rh, Pt in the process?

Anyone have an idea? :(

Edited for spelling and grammar.



[Edited on 18-4-2013 by ScienceSquirrel]

plante1999 - 18-4-2013 at 03:58

Check your U2Us.

I sent you a message.

plante1999 - 18-4-2013 at 08:21

Using sulphuric acid to leach base metal is not a good idea, lead sulphate is insoluble and will precipitate during leaching, a better alternative would be to use nitric acid for the leach. It would remove bases metals and silver. The silver can be obtained by neutralysing the solution, removing excess nitric acid and adding a copper sheet in the solution. The silver will precipitate on the copper sheet. The residue after the leaching can then be leached using aqua regia, and they should have way less lead, and be very concentrated in PGMs.

Second point, you migth want to revise your mean of precipitating the PGMs. Ammonium chloride is selective for platinum and iridium, but there is better precipitants for other PGMs.

[Edited on 18-4-2013 by plante1999]

unionised - 18-4-2013 at 10:43

You have a rock that's 3% Ir ?
Iridium is a lot rarer than gold: where did you get this ore?

blogfast25 - 18-4-2013 at 10:46

Quote: Originally posted by unionised  
You have a rock that's 3% Ir ?
Iridium is a lot rarer than gold: where did you get this ore?


If he tells you he'll have to kill you! ;)

Adas - 18-4-2013 at 10:47

Quote: Originally posted by unionised  
You have a rock that's 3% Ir ?
Iridium is a lot rarer than gold: where did you get this ore?


The same question. I've never heard about that. :O You are gonna be rich :D

plante1999 - 18-4-2013 at 16:26

Ah, I love metallurgy! Such an interesting topic to extract metals out of ore! 3% Ir ore is very concentrated, but I got a question.

Is the 3% Ir after, or before the flotation?

If I were you, I would probably roast the ore in oxygen, to get "poor" metal oxide, take this mixture and leach it with nitric acid. Precipitate the copper as said. Then, take your residue and toughly leach them with very hot aqua regia, decant, a lot of rhodium will not have dissolved in the aqua regia, and will be in the precipitate. Keep the precipitate for future processing and boil down your leach to powder and make it analyse. Fallowing the results of the analysis, you should have a pretty much concentrated PGMs salt mixture. The PGMs can be process as a normal PGM scrap.

12AX7 - 19-4-2013 at 13:11

Quote: Originally posted by plante1999  
Ah, I love metallurgy! Such an interesting topic to extract metals out of ore! 3% Ir ore is very concentrated, but I got a question.

Is the 3% Ir after, or before the flotation?

If I were you, I would probably roast the ore in oxygen, to get "poor" metal oxide, take this mixture and leach it with nitric acid. Precipitate the copper as said.


+1

All that sulfur will be awful to treat with acid directly. It certainly doesn't need to be smelted, either (and I'm guessing Ir isn't soluble in Pb, so you probably wouldn't want to).

After getting the lead, iron and other things in solution, PGMs will be left as dross. A mild reducer (like cementation with copper, is that what you meant plante?) will precipitate silver from solution for a quick buck. The remainder of the solution can also be precipitated, perhaps with a sulfate (precipitating PbSO4, insoluble and easy for hazmat to dispose of) and base (everything else).

The only thing I know of with an absurd amount of Ir is asteroids, and even then, it's in the ppm range, which is still high as PGMs go, but certainly not a percentage. Asteroids also aren't subject to the hydrothermal differentiation which produces PbS deposits here; in asteroids rich with sulfur, FeS would be much more common.

Tim

ElectroWin - 22-7-2013 at 11:39

3% Ir is way too rich; even in iron asteroids, where it is relatively abundant, it is thought to be in ppm.

if the above analysis is true, this "ore" must be coming from some post-industrial waste process

[Edited on 2013-7-22 by ElectroWin]

unionised - 22-7-2013 at 12:53

Then someone has a weird idea of "waste".
Let's face it. the guy posted once and never came back.
Pipedream I think.

[Edited on 22-7-13 by unionised]

jock88 - 23-7-2013 at 14:02

Going way off topic......

Seen a report on BBC news that street sweepings had a significant noble metal content. When all the plastic, paper, stones, grit, shit, glass etc etc was removed (recycled) they were left with dust and when analyzed was found to contain a useful amount of Pt and Ir. It comes from car exhausts they reckoned.

ElectroWin - 30-7-2013 at 10:52

ok, interesting! and not so far off topic. the company is Veolia, who announced a plan circa 2011 and is written up in a few places:

http://www.scrap-ex.com/news/waste_management/veolia_extract...
http://www.dailymail.co.uk/news/article-2041699/From-roads-r...

but notice, the yields seem very low. £80,000 from processing 30,000 tonnes of street sweepings, is a
yield of £2.66 per tonne


[Edited on 2013-7-30 by ElectroWin]

froot - 30-7-2013 at 23:16

Something's wrong with that analysis, adds up to 100,4%.

ElectroWin - 3-8-2013 at 11:49

Quote: Originally posted by froot  
Something's wrong with that analysis, adds up to 100,4%.


remember significant figures; it's an artifact of rounding.