Gold extraction from ore concentrate

[crazycolor786]

Dear all,

I am new to this forum but professionally well qualified to perform chemical reactions following safety protocols. I have received an ore samples having following composition determined through EDXRF. In order to verify the compositions i carried our XRD diffraction as well of this ore and the spectra of gold and platinum is popping up there. To my surprise this concentrated ore posses good amount of precious metals and worth trying. i am looking for advise from experienced hobbyist and professionals for a suitable process to start with for initials lab scale extraction of the Au and Pt. just to add, i have access to a good standard labs having fumehoods, chemical and glassware. I also posses DC-AC based power supplies for electrowinning process as well. our labs also posses good characterization equipment like Raman, FTIR, UV-vis, SEM-EDX as well. Actually my area of research is something else but this project seems interesting to me so i took up this challenge and want you guys to help me in getting towards right direction.

looking forward to your advice and help

Iqbal

elements wt %
Gold 0.23
Platinum 0.27
Silver 0.21
Zinc 0.43
Copper 0.19
Manganese 0.62
Vanadium 0.11
Titanium 3.04
Sulphur 3.13
Silicon 31.72
Aluminum 7.25
Magnesium 0.24
Potassium 2.72
Calcium 1.24
Tungsten 0.93
Germanium 0.36
Strontium 0.11
Iron 46.96

 

[nickvc]

My advice for what it is worth is have an assay done before attempting anything, the next question you need an answer to is how much of the precious metals you can recover, just because they are there doesn’t mean they are recoverable economically.

 

[crazycolor786]

My advice for what it is worth is have an assay done before attempting anything, the next question you need an answer to is how much of the precious metals you can recover, just because they are there doesn’t mean they are recoverable economically.

Thanks a lot @nickvc
Could you please elaborate which assay you are refering to. Definatley, you raised the right question and at first i am also interested into to know the economical recovery for any possible scale-up. I am looking for a way forward as the presence of a lot of counter ions make recovery difficult. Any recomendation on the possible process to start with e.g. cyanidation or aqua-regia ?
Regards

 

[anachronism]

I wish I could find some of these ores with 2.3Kg/tonne Gold and 2.7Kg/tonne Platinum.

That's truly exceptional.

 

[Lino1406]

Free the PM's from iron sulfides with concentrated H2O2 or roasting at 700C. Then aqua regia

 

[nickvc]

I believe you need two or three assays done, a full assay of all the materials, an aqua regia digest assay and possibly a cyanide leach assay if I remember correctly. This should tell what’s actually there and what is actually recoverable.
I may be wrong on the assay methods so do further research to be sure.

 

[crazycolor786]

I wish I could find some of these ores with 2.3Kg/tonne Gold and 2.7Kg/tonne Platinum.

That's truly exceptional.

Indeed @anachronsim when i first see the composition i was skeptical about its composition but it contains pretty now the challenge is to get it recovered.
regards

 

[crazycolor786]

Free the PM's from iron sulfides with concentrated H2O2 or roasting at 700C. Then aqua regia
[/quote

any suitable parameters or reference on using conc. h202 for freeing PM's from H2O2?

regards

 

[crazycolor786]

I believe you need two or three assays done, a full assay of all the materials, an aqua regia digest assay and possibly a cyanide leach assay if I remember correctly. This should tell what’s actually there and what is actually recoverable.
I may be wrong on the assay methods so do further research to be sure.

Thanks @nickvc. i will definitely try both as the big question is how much is recoverable. regards

 

[Lino1406]

The reference is personal knowledge. Just pour H2O2 (20%-30%) on the ore, let it self boil until done. It can take few hours. It can be reboiled by adding a little H2SO4

 

[Deano]

The industry standard for gold is fire assay, this will tell you the total gold present in your concentrate.

If you see real values in the fire assay you then get aqua regia assays done to determine the available gold by wet chemistry.

If you again see real values in the aqua regia assays, usually lower than the fire assay values, then you get rolling bottle cyanide assays done.

The rolling bottle assays will tell you the gold levels recoverable from your concentrates without having to go through expensive pretreatments.

Testwork on a new ore body is always done in this sequence.

Always keep in mind that some sulphide ores will give higher gold results from the head ore than from concentrates when cyaniding.

Also remember that you will always have some losses when making your concentrate, so the concentrate grade is usually lower than the mathematical theoretical grade based on the head ore.

Deano

 

[crazycolor786]

The reference is personal knowledge. Just pour H2O2 (20%-30%) on the ore, let it self boil until done. It can take few hours. It can be reboiled by adding a little H2SO4

Thanks Lino1406. How much of H2O2 & H2SO4 and Ore should be tested. Any details? What would be the end result and conclusions from such an assay.

Thanks dude

 

[crazycolor786]

The industry standard for gold is fire assay, this will tell you the total gold present in your concentrate.

If you see real values in the fire assay you then get aqua regia assays done to determine the available gold by wet chemistry.

If you again see real values in the aqua regia assays, usually lower than the fire assay values, then you get rolling bottle cyanide assays done.

The rolling bottle assays will tell you the gold levels recoverable from your concentrates without having to go through expensive pretreatments.

Testwork on a new ore body is always done in this sequence.

Always keep in mind that some sulphide ores will give higher gold results from the head ore than from concentrates when cyaniding.

Also remember that you will always have some losses when making your concentrate, so the concentrate grade is usually lower than the mathematical theoretical grade based on the head ore.

Deano

Thanks @ Deano for your detailed response. I definatyely have some directions now. Will try to dig more about stndarized procedures to fire, aqua and cyanide roll tests and perform them.
Can you suggest any literature or book to follow?

Best regards

 

[Lino1406]

Ore 30ml H2O2 100ml H2SO4 20 ml end result Fe+++ in solution maybe Ag2SO4

 

[Deano]

If you are looking at putting money into the project then you should get the assays done by a commercial lab rather than try to develop the skills and techniques yourself.

If you are happy to put your money at extra risk by developing your own assay systems that is your decision.

There are Australian Standards for various assay elements, unfortunately no comprehensive books covering the full range of assays you will need.

Most of the assays are simple to do if you are familiar with the techniques, not quite so simple if learning the basics.

Deano

 

[crazycolor786]

If you are looking at putting money into the project then you should get the assays done by a commercial lab rather than try to develop the skills and techniques yourself.

If you are happy to put your money at extra risk by developing your own assay systems that is your decision.

There are Australian Standards for various assay elements, unfortunately no comprehensive books covering the full range of assays you will need.

Most of the assays are simple to do if you are familiar with the techniques, not quite so simple if learning the basics.

Deano

Dear Deano,

I think these assays are not that complicated as i got a good lab facility at my work place which includes all facilities of an advanced chemistry lab as well as furnaces etc. basically i am a metallurgist with a PhD degree and taking up such challenges is my hobby. I do a lot of stuff with harsh chemicals for cleaning gemstones and now i came across this ore which seems quite promising to me.
I am just looking for advise from experienced person like yourself to stay on the track. luckily i have all the consumables available for cyanidation including a setup which i made for something else but i am sure it will work well for cyanide assay. the only thing worrying me is that how platinum will behave in the cyanide assay and how to check its content.
Now i am just shortlisting the protocols of these assays and then i will be in a position to execute the tests. Planning to do aqua-regia and cyanide assay this week.
I have just question what is the proportion of zinc power required for a good cementation? and how the counter ions like platinum can be detected and extracted through these assays.
I red in a thread that you are the most experienced person here on this forum with extraction of gold from ores so your advice for me would be really important.

best regards,

 

[crazycolor786]

Ore 30ml H2O2 100ml H2SO4 20 ml end result Fe+++ in solution maybe Ag2SO4

Thanks a lot.

 

[Deano]

If you do not run fire assays then you are working from an unknown base, this is important when looking at grind sizes for your ore for the leaching stages, especially for cyanide.

Best of luck developing a repeatable fire assay from scratch, it is an art as much as a science.

The big commercial labs use specialist fluxes which are not available to the small operator so you have to develop this side of the process as well.

The amount of zinc needed to cement out the precious metals depends on the level of these metals in the leach liquors.

Basically zinc is cheap so use a multiple of the theoretical amount shown in your solution assays.

Platinum group metals are read in AAS using the respective lamps, unless you are working with a Western Australian ore you are unlikely to have commercial levels of these metals.

Deano

 

[crazycolor786]

If you do not run fire assays then you are working from an unknown base, this is important when looking at grind sizes for your ore for the leaching stages, especially for cyanide.

Best of luck developing a repeatable fire assay from scratch, it is an art as much as a science.

The big commercial labs use specialist fluxes which are not available to the small operator so you have to develop this side of the process as well.

The amount of zinc needed to cement out the precious metals depends on the level of these metals in the leach liquors.

Basically zinc is cheap so use a multiple of the theoretical amount shown in your solution assays.

Platinum group metals are read in AAS using the respective lamps, unless you are working with a Western Australian ore you are unlikely to have commercial levels of these metals.

Deano

Thanks a lot!

 

[DarkspARCS]

I wish I could find some of these ores with 2.3Kg/tonne Gold and 2.7Kg/tonne Platinum.

That's truly exceptional.

=)