# gold refining methods



## Tahmoures (Feb 12, 2022)

Hello everyone

I was searching about gold refining methods
I found this:
1. aqua regia (the method that im using currently)
2. thiourea
3. iodine (this method is expensive)
4. cyanide ( very dangerous method and must be very carefull)
5. electrolysis

I was thinking about which method is better?
my work space is small and im doing it outdoor but im designing a acid resistant fume hood.
and im working on WEEE like computer rams, cpu, telecom boards, ic chips and etc.

(I didn't mention some of the methods and i'll be happy if you point them)

best regards
Tahmoures


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## nickvc (Feb 12, 2022)

To be successful you need to concentrate on your recovery methods and processes , that really is the most important part to master, if you are just dissolving all metallics in AR you are wasting chemicals and time , producing huge amounts of toxic waste and probably losing some of the values.
If you are working on e scrap in most cases you do not need to use AR as the gold is either in flakes from recovery or very thinly plated where cyanide can be king but comes with its own problems, learning to use it successfully and safely is a whole new process and it rarely recovers all the gold but if used properly you get 90%+.


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## orvi (Feb 12, 2022)

If you are going to recover the gold, which is exposed as gold plating, then in larger scale, any metod which dissolve the base metal and rest of the material is wasteful.
Cyanide is dirt cheap if you can get it (legally) as bulk chemical, and also other chemicals needed for the whole process. As it was issued, efficiency is not always the greatest, but with little knowledge and slightly more effort you could go higher.
AR is good only for very rich scrap. When used on low grade material, immense waste stream is produced (practically unnecessary) which need to be treated and properly disposed - and this is problematic.
If you have no problem with smelting your material, then electrorefining could be considered - it is relatively cheap, you do not produce barrels of liquid waste and copper byproduct is easily sellable.
If you are scared of cyanide, eco-goldex is maybe good considering as an alternative option, but it have it´s own problems. 
Everybody in "small sector" is using AR process, because of simplicity. I see that you are from Middle East... So price of the acids is not a biggest concern. And so it´s not the hazardous nature of the process (correct me if I´m wrong), evolving clouds of nitrogen dioxide and chlorine.
No big facility in the world which process hundreds of tons of e-waste is doing it with AR.
Main route is pyrometallurgy and more pyrometallurgy  bit more difficult processes, but extremely efficient in terms of energy consumption and waste production.


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## cejohnsonsr1 (Feb 13, 2022)

You might want to check out Sreetips on YouTube. He has very detailed videos showing recovery and refining of various materials using several methods.


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## Tahmoures (Feb 13, 2022)

nickvc said:


> To be successful you need to concentrate on your recovery methods and processes , that really is the most important part to master, if you are just dissolving all metallics in AR you are wasting chemicals and time , producing huge amounts of toxic waste and probably losing some of the values.
> If you are working on e scrap in most cases you do not need to use AR as the gold is either in flakes from recovery or very thinly plated where cyanide can be king but comes with its own problems, learning to use it successfully and safely is a whole new process and it rarely recovers all the gold but if used properly you get 90%+.


dear nickvc
Thank you so much for your answer.
i didn't catch one of your sentences.
you told: that really is the most important part to master, if you are just dissolving all metals in AR you are wasting chemicals and time.
at first in my process I'm using nitric acid for dissolving base metals and then with dropped gold foils i do Aqua regia reaction. for the dissolving base metals I'm aware of the NOx gas hazards and im building a scrubber for it.
are you saying that the Aqua regia process is waste of time and materials if i use aqua regia individually and without nitric acid or the Aqua regia process is wrong at all?

and would you please give me a advice for correcting my gold refining process or a sign for my searching?
you are very kind in answering and i appreciate it.

thank you so much


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## Tahmoures (Feb 13, 2022)

orvi said:


> If you are going to recover the gold, which is exposed as gold plating, then in larger scale, any metod which dissolve the base metal and rest of the material is wasteful.
> Cyanide is dirt cheap if you can get it (legally) as bulk chemical, and also other chemicals needed for the whole process. As it was issued, efficiency is not always the greatest, but with little knowledge and slightly more effort you could go higher.
> AR is good only for very rich scrap. When used on low grade material, immense waste stream is produced (practically unnecessary) which need to be treated and properly disposed - and this is problematic.
> If you have no problem with smelting your material, then electrorefining could be considered - it is relatively cheap, you do not produce barrels of liquid waste and copper byproduct is easily sellable.
> ...


Dear Orvi,
thank you so much for your time. so about what i got about your answer is that i should go for a process that i just have reactions with gold and not other base metals from the first step or last; Am I right?
because I'm dissolving base metals in nitric acid in the first step and then I dissolve gold plated parts in AR.

about the NOx you are right and I'm my country its not being controlled correctly but it is my concern and I'm going to reduce it step by step and I care about it. my dissolving system is a closed flask system that the NOx gas is being trapped in gas washing glass; i can do it for the dissolving base metals system that im doing it with nitric acid but the material should be crushed and i don't have the machine. the problem in this step is if I crush the scraps, i should dissolve all of the base metals except gold and then i can do aqua regia with solid that separates with filtering.

pyrometallurgy is good but its toxic i think because of burning manufactured fibers and polymers that is dangerous.

I'll check about the electrorefining process too and thanks for your advice.
and at the end I wanna know which process is the best choice? because im doing refining in lab scale and i have to decide for doing large scale too; so if its not a big request, would you please guide and help me about this?
i just want a process name and I will search for it and study. I was looking for this question in other topics but I couldn't find it.

Thank you so much for your help.


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## Tahmoures (Feb 13, 2022)

cejohnsonsr1 said:


> You might want to check out Sreetips on YouTube. He has very detailed videos showing recovery and refining of various materials using several methods.


dear Cejohnsonsr1
thanks for your guide; I'll check it out.
​


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## Tahmoures (Feb 13, 2022)

Tahmoures said:


> dear Cejohnsonsr1
> thanks for your guide; I'll check it out.
> ​


and I have to say wow, that helps me a lot. thanks again.


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## Martijn (Feb 13, 2022)

Aqua regia is fine to refine your recovered gold.
Nitric for recovery is expensive, may cause problems with tin and creates a lot of waste as copper nitrate and more. 
Any silver and palladium will dissolve in the nitric as well. 

You could look into the Cupric Chloride leach also known as Acid Peroxide (AP).
The copper that is leached as Cuprous Chloride becomes a copper oxidizer itself and is not waste but becomes more etchant. 

Recovered foils and other thin gold can also be dissolved in HCL and bleech or in HCL and H2O2, i prefer AR. 
Its how pure the gold is that you dissolve to refine, and how well you wash your gold powder that makes the big difference in purity. 

Trash in, trash out. 

Martijn.


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## orvi (Feb 13, 2022)

Tahmoures said:


> Dear Orvi,
> thank you so much for your time. so about what i got about your answer is that i should go for a process that i just have reactions with gold and not other base metals from the first step or last; Am I right?
> because I'm dissolving base metals in nitric acid in the first step and then I dissolve gold plated parts in AR.
> 
> ...


Yes. But we need to clarify one thing. 
If we are talking about stripping gold from base metal like copper or some other alloy, you need to have it exposed to the solution. If pins are still in the sockets, no gold would leach as solution cannot get to the covered gold.

And also shredding whole PCBs and then soaking it in nitric is very wasteful practice, which is in turn quite low yielding.

Processing bulk scrap on semi-automated line is very complicated with hydrometallurgy. Values are often hidden and not easily liberated. That is why most of the refineries use pyrometallurgy as first step. Coarsly shred material goes to the magnetic separator, where ferrous metallic parts are removed. Then it is shred to the finer diameter and subsequently smelted. Only flux in small proportion is added. Oxidizing atmosphere help keeping iron and zinc content down - they pass to the slag.
Metal is poured and then electrorefined. PM are recovered from anode slimes.

Toxicity of smelting is quite low if done properly and materials are contained. 
You need to first incinerate the material to ash - with plenty of oxygen in hot furnance to burn the toxic gasses properly. And only then you can smelt the metal.

Best choice for bulk PCBs is pyrometallurgy (my opinion) - but you need proper setup, build the incineration furnance, and smelting furnance capable of operating at temperatures as high as 1200-1400°C to properly liquify the fiberglass boards (with some flux of course). If you have enough "hands" to pick through the boards and remove only valuable parts, often you can go with AP or AR, as the material is richer. You could sell stripped boards for low price, to eliminate the waste.
If you can separate the pins and plated material, you can strip them with cyanide or something like eco-goldex. Or strip the gold in sulfuric acid electrolytic cell.
You can also melt the pins with some flux and pour anode bars for electrorefining - you get copper and slimes with values. Divide pins and material with magnet to magnetic and non-magnetic before this operation.

Everything is on the forum here, well discussed. Just browse tutorial section and search for keywords.

Stay safe


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## Martijn (Feb 13, 2022)

In stead of incineration you can also depopulate the board of their components in a burner trommel, shred and hammer mill the pcb's to a fine powder and separate the (gold plated) copper traces and solder on a shaker table. Then melt into copper anode bars for the sulfuric cell, a HCL bath for the solder wont hurt. If you dont cut the contact fingers off for Ebay goodie bags and sell the boards as low grade. 
The IC's will need pyrolizing and incinerating. 
Plastic sockets with pins inside can go in the shredder or in AP. 
Less toxic fumes in the air if you don't burn the pcb's with components and plastic sockets. 

But i think the OP is operating on a small scale. And burning pcb's will not give him much good vibes in his neighborhood. 
Neither will a hammer mill


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## cejohnsonsr1 (Feb 14, 2022)

Tahmoures said:


> dear Cejohnsonsr1
> thanks for your guide; I'll check it out.
> ​


It’s not mine. Just a very good source of information. Probably the best since he demonstrates every step of the process and doesn’t edit out his occasional mistakes so you can benefit from them.


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## orvi (Feb 14, 2022)

Martijn said:


> But i think the OP is operating on a small scale. And burning pcb's will not give him much good vibes in his neighborhood.
> Neither will a hammer mill


Burning PCBs will not give him much good vibes in his neighborhood... Yeah, so true   

If you have tuned-up working furnance with cyclone, well air-feeded afterburner and temperature at least 1000°C... Do not recommended


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## nickvc (Feb 14, 2022)

Tahmoures said:


> dear nickvc
> Thank you so much for your answer.
> i didn't catch one of your sentences.
> you told: that really is the most important part to master, if you are just dissolving all metals in AR you are wasting chemicals and time.
> ...


Using nitric on e scrap as a first process is not usually the best choice due to the amount of tin that can be present which will impact on your yield unless you incinerate your recovered material and then use HCl to remove it before going on to dissolve the values. As the material you recover is in small fractions I’d use either bleach or peroxide with HCl to dissolve your gold and then heat the solution to drive off any excess oxidizer before precipitating your gold.
I can’t tell you what processes you need to use for your recoveries as I don’t know what you process or what you have to aid the recoveries as in equipment or chemicals, I can advise you you to read here on the forum about the materials you have to process and what other members advise to use on them, there are many methods available for many products but you have to find the ones that suit your circumstances and only you can do that.
If you research and find a process that you feel will work for you and what you have the resources to follow post that idea with full details and any faults will be pointed out fairly quickly.


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## kurtak (Feb 14, 2022)

orvi said:


> If you are scared of cyanide, eco-goldex is maybe good considering as an alternative option, but it have it´s own problems.


Orvi --- I NEED to make a correction here !!!

eco-goldex is IN FACT a cyanide process !!!

the foundation of eco-goldex uses potassium ferri or ferro cyanide (can't remember if it's ferri or ferro)

So it's a potassium/iron/cyanide complex

The iron complexed with the cyanide in it's self makes it a safe product (the cyanide is not "free" to act as cyanide) so the potassium/iron/cyanide complex is actually use in the food industry

In order for the cyanide to work as cyanide - the iron needs to be disassociated from the cyanide thereby freeing the cyanide to work as cyanide

What eco-goldex has done is complexed the potassium ferri/ferro cyanide with something like 6 or 7 other chemicals

It is something in (&/or combination) of their own complex that disassociates the iron from the cyanide *allowing the cyanide to be cyanide*

In other words - once the iron is disassociated from the potassium ferri/ferro cyanide what you in fact have is *potassium cyanide *

In other words - eco-goldex - is in fact - nothing more then potassium cyanide & therefor *MUST* be treated/handled exactly the same as if you started with potassium cyanide in the first place

The problem with eco-goldex is that because of the other chems in their complex - used to disassociate the iron from the cyanide - it also makes it *very difficult* to recover the gold from solution after the cyanide has dissolved the gold

You can use straight up potassium ferri/ferro cyanide (instead of the eco-goldex) with less problems to recover your gold

With straight up potassium ferri/ferro cyanide you (again) just need to disassociate the iron from the cyanide

You can effect this disassociation by exposing the dissolved potassium ferri/ferro cyanide to UV

The bottom line is that once you disassociate the iron from potassium ferri/ferro cyanide complex - *you in fact have potassium cyanide* & therefor *MUST* be treated/handled as potassium cyanide --- regardless of whether your potassium ferri/ferro cyanide comes from the eco-goldex product or you start out with straight up potassium ferri/ferro cyanide

I have in fact worked with all three (eco-goldex - straight up potassium ferri/ferro cyanide & potassium cyanide) --- all three result in a flat out potassium cyanide process & MUST be handled as a potassium cyanide process

As a matter of personal experience - & due to the difficulty getting your gold back from the eco-goldex product - *I will never ever again use their product* - & the only reason I would consider using straight up potassium ferri/ferro cyanide (exposed to UV) is if I couldn't get actual potassium cyanide (or sodium cyanide)

The important thing to understand is that they are all a potassium cyanide process - having ALL the same dangers & therefore MUST be treated as such

Eco-goldex makes the claim that it is a safe product - that just is not true - it is only safe up to the point you dissolve it - once it is dissolved - it is in fact potassium cyanide (which is why it dissolves gold) & must be handled as such

Edit to add; - if you are afraid of (&/or do not understand) the cyanide process then be just as afraid of eco-goldex - AND have a FULL understanding of working with cyanide - at which time you are best served to go get actual potassium or sodium cyanide instead of working with "work arounds" that complicate the cyanide process

Kurt


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## orvi (Feb 14, 2022)

kurtak said:


> Orvi --- I NEED to make a correction here !!!
> 
> eco-goldex is IN FACT a cyanide process !!!
> 
> ...


I was always told that eco-goldex do not work with cyanide. Locally, guys working in mining tested this in lab, just to measure no free cyanide in the solution in their facility.
Thanks for clarification. I did not consider it this will be the case.




This is from their official website. Now I can see it


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## kurtak (Feb 15, 2022)

orvi said:


> I was always told that eco-goldex do not work with cyanide. Locally, *guys working in mining* tested this in lab, just to measure no free cyanide in the solution in their facility.
> Thanks for clarification. I did not consider it this will be the case.


Per the bold print --- Eco-goldex (at least back in 2016 when we here on GRF first became aware of it) had two products

One was their eco-goldex O product the other was their E product

the O product was their product for leaching Ore

the E product was their product for leaching E-waste

The leaching mechanism in the O product was (I believe) a thiourea leach

The leaching mechanism in the E product is the one using the potassium ferri/ferro cyanide

Hence the different equations you posted yesterday --- the first three being the O product (or thiourea leach) the fourth being the E product (or cyanide leach by way of potassium ferri/ferro cyanide)

here is a link to a thread where GRF members first became aware of the eco-goldex product(s)

It's 13 pages long -----------









Eco-goldex CYANIDE Leach


Does anyone have experience with this process? It looks interesting, what do you think about it? It may be solution for processing pins and plated material from electronics, it looks like cyanide leach but bit more on safer side of things. http://eco-goldex.com/...




goldrefiningforum.com





eco-goldex (mostly the E product) has been discussed *extensively* here on GRF (there a number of other threads beside the one I provided a link to)

It was not until we exposed the truth about eco-goldex in fact being a cyanide process that eco-goldex posted this on their web site (bold print)

"What makes Eco-Goldex successfully accepted in commercial production is that it is a simple system, *which has exactly the same operational procedures and conditions as cyanidation. It is easy to use and can seamlessly replace sodium cyanide in most gold leaching operations*

Until we exposed the truth about it being a cyanide process they were promoting it as a safe process

For what it's worth Deano posted a lot of info about (straight up) potassium ferri/ferro cyanide

For what it is worth - here on GRF the general opinion is that - like Shor products - eco-goldex products are complete B.S. --- we have exposed both companies/products for their B.S. - but it's a big world so it does not stop them from selling their B.S.

Edit to add; - here on GRF we do not endorse ether Shor products or eco-goldex products - in fact we warn against them 

Kurt


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## galenrog (Feb 15, 2022)

Long ago, when the world was young, I once thought about using one of these systems. Then I found the Gold Refining Forum, read Hoke, and became enlightened. Time for more coffee.


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## Tahmoures (Feb 16, 2022)

Martijn said:


> Aqua regia is fine to refine your recovered gold.
> Nitric for recovery is expensive, may cause problems with tin and creates a lot of waste as copper nitrate and more.
> Any silver and palladium will dissolve in the nitric as well.
> 
> ...


dear martjin

for problems of using Nitric acid as you said, what if I separate the solter and tin with weak acid and then filter it for nitric acid process and for nitric acid waste, i recycle that for my next process when I'm using my base metals dissolved in nitric acid for copper refining with Sulfuric Acid?

I was searching and learning about CuCl2 process, I couldn't find lazersteve website but as I learned, this process makes much more time than the process that I do, but more safe and controllable than nitric acid that produce NO2 gases.

I'll study more about AP and thanks for your advice and thanks for your time.


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## Tahmoures (Feb 16, 2022)

orvi said:


> Yes. But we need to clarify one thing.
> If we are talking about stripping gold from base metal like copper or some other alloy, you need to have it exposed to the solution. If pins are still in the sockets, no gold would leach as solution cannot get to the covered gold.
> 
> And also shredding whole PCBs and then soaking it in nitric is very wasteful practice, which is in turn quite low yielding.
> ...


dear nikvc
as i was reading your answer, I couldn't understand one sentence and it's because of not knowing some phrases in English.
in the sentence: If you have enough "hands" to pick through the boards and remove only valuable parts, often you can go with AP or AR, as the material is richer.
i couldn't understand what "hands" means.

and that was my mistake about toxiticy of pyrometallurgy process and I understood what you said.
I'll check about electrolysis process too and thanks for your advice.
i appreciate your help.


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## Tahmoures (Feb 16, 2022)

Tahmoures said:


> dear nikvc
> as i was reading your answer, I couldn't understand one sentence and it's because of not knowing some phrases in English.
> in the sentence: If you have enough "hands" to pick through the boards and remove only valuable parts, often you can go with AP or AR, as the material is richer.
> i couldn't understand what "hands" means.
> ...


that was good if I could correct the names,
sorry orvi about that. I'm a little sick and my focus is a little low right now.


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## Tahmoures (Feb 16, 2022)

Tahmoures said:


> dear nikvc
> as i was reading your answer, I couldn't understand one sentence and it's because of not knowing some phrases in English.
> in the sentence: If you have enough "hands" to pick through the boards and remove only valuable parts, often you can go with AP or AR, as the material is richer.
> i couldn't understand what "hands" means.
> ...


that was good if I could correct the names,
sorry orvi about that. I'm a little sick and my focus is a little low right now


Martijn said:


> In stead of incineration you can also depopulate the board of their components in a burner trommel, shred and hammer mill the pcb's to a fine powder and separate the (gold plated) copper traces and solder on a shaker table. Then melt into copper anode bars for the sulfuric cell, a HCL bath for the solder wont hurt. If you dont cut the contact fingers off for Ebay goodie bags and sell the boards as low grade.
> The IC's will need pyrolizing and incinerating.
> Plastic sockets with pins inside can go in the shredder or in AP.
> Less toxic fumes in the air if you don't burn the pcb's with components and plastic sockets.
> ...


I have a small space i industrial zone that is for one of my friends, I think its not a big deal with the sound and burning. I'll check it out too


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## Tahmoures (Feb 16, 2022)

nickvc said:


> Using nitric on e scrap as a first process is not usually the best choice due to the amount of tin that can be present which will impact on your yield unless you incinerate your recovered material and then use HCl to remove it before going on to dissolve the values. As the material you recover is in small fractions I’d use either bleach or peroxide with HCl to dissolve your gold and then heat the solution to drive off any excess oxidizer before precipitating your gold.
> I can’t tell you what processes you need to use for your recoveries as I don’t know what you process or what you have to aid the recoveries as in equipment or chemicals, I can advise you you to read here on the forum about the materials you have to process and what other members advise to use on them, there are many methods available for many products but you have to find the ones that suit your circumstances and only you can do that.
> If you research and find a process that you feel will work for you and what you have the resources to follow post that idea with full details and any faults will be pointed out fairly quickly.


thank you so much Nikvc, I'm so happy that I found this forum and I can learn and find my mistakes. I'll check out acid peroxide process and study about it. 
thanks for your time.


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## Tahmoures (Feb 16, 2022)

kurtak said:


> Orvi --- I NEED to make a correction here !!!
> 
> eco-goldex is IN FACT a cyanide process !!!
> 
> ...





orvi said:


> I was always told that eco-goldex do not work with cyanide. Locally, guys working in mining tested this in lab, just to measure no free cyanide in the solution in their facility.
> Thanks for clarification. I did not consider it this will be the case.
> 
> View attachment 48343
> ...


 dear Kurt and Orvi
thank you so much for the information and I have to study a lot about this process for feeling safe about it. I'll do study as soon as possible.


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## orvi (Feb 16, 2022)

Tahmoures said:


> dear nikvc
> as i was reading your answer, I couldn't understand one sentence and it's because of not knowing some phrases in English.
> in the sentence: If you have enough "hands" to pick through the boards and remove only valuable parts, often you can go with AP or AR, as the material is richer.
> i couldn't understand what "hands" means.
> ...


By saying "if you have enough hands to pick through" i meant that "if you can hire enough labor force to manually depopulate the boards and pick just most valuable components off them". Sorry for unclear formulation.

No worries


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## Tahmoures (Feb 19, 2022)

orvi said:


> By saying "if you have enough hands to pick through" i meant that "if you can hire enough labor force to manually depopulate the boards and pick just most valuable components off them". Sorry for unclear formulation.
> 
> No worries


thanks for your explanation.


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## dpgold (May 21, 2022)

nickvc said:


> To be successful you need to concentrate on your recovery methods and processes , that really is the most important part to master, if you are just dissolving all metallics in AR you are wasting chemicals and time , producing huge amounts of toxic waste and probably losing some of the values.
> If you are working on e scrap in most cases you do not need to use AR as the gold is either in flakes from recovery or very thinly plated where cyanide can be king but comes with its own problems, learning to use it successfully and safely is a whole new process and it rarely recovers all the gold but if used properly you get 90%+.


What would the difference be from the remaining waste from AP and AR, I have seen some refiners put the remaining waste in stockpot for further recovery via cementation. Could you elaborate a bit on this aspect? I have asked a refiner if he puts all the AR toghether with other filtrates and he said yes.


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