# Selectively precipitate Ag, Cu, Ni, Zn, ...



## Swissgoldrefiner (Dec 9, 2021)

Hello,
I have mixed solution of nitric acid with Ag, Cu, Ni, Zn.
With reactivity table of metal, i am able to selectively remove each of them.
However, i wounder if it's possible with chemical to remove them selectively.
For example, with DMG maybe precipitate Ni...however i wounder if it will precipitate copper as well.

Thank you guys.


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## butcher (Dec 9, 2021)

With DMG the pH is a major factor of which metal it will precipitate, or with which metal it is used as an indicator.

HCl would convert silver to insoluble AgCl (forming a type of aqua regia with even slight excess.

Copper can be recovered using Iron in a displacement reaction.

The remaining metals, along with the iron can be removed as oxides or hydroxides as you treat the solution for waste before proper disposal.


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## Swissgoldrefiner (Dec 10, 2021)

butcher said:


> With DMG the pH is a major factor of which metal it will precipitate, or with which metal it is used as an indicator.
> 
> HCl would convert silver to insoluble AgCl (forming a type of aqua regia with even slight excess.
> 
> ...


But at which pH do you work? for example to remove Ni and not copperand what you do with Zn?


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## butcher (Dec 10, 2021)

What is your goal?

We do not normally separate all of these metals from each other, not all will separate selectively or sometimes even well, yes it can be done but cost and trouble are big considerations, not to mention the education and practice along with practical expierience needed to succeed in that type of endeavors...

Are you studying how to recover and refine precious metals or are you trying to learn how to mine and recover base metals?

Copper can easily be recovered from your waste.

Note recovery processes are not refining processes and may not be very selective.

Copper can be recovered from solutions by different means, insoluble CuCl cuprous chloride or even carbonates, or by other chemical means, the difficulty of that and not profit and no reasons for doing so, it is not something we would normally study or do.

We normally recover copper from solutions using iron, this process also displaces a mixture of copper and other metals depending on what metals are in solution, this copper can be reused in many applications chemically and for our use as a lab reagent, as a collector metal, or in smelting and in the different recovery processes of more valuable metals...

Or if for some reason we wished to lose money on it we could further refine it or put it through something like a flotation process and smelting process or other complicated costly processes for a metal that is thrown in the trash daily we could find in most trashcans of almost any country today, why waste time with it?

Study, Study I repeat the study, dealing with waste if you have not done this extensively and continue to study dealing with waste and safety as long as you work in this field you have no business even touching what we do.

Within that study, you will learn the answer to many of the questions you are asking now, and those study's if continued will lead you to answers to so many questions you did not even think to ask yourself or others...



The more reactive the metal or the more related chemically with other metals involved the more difficulty in recovery or refining it generally becomes.

Did you come here to learn to refine zinc or gold and silver?


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## Geo (Dec 10, 2021)

It can't be done in one go. Nickel and zinc will not cement from solution in any effective way. The silver is easiest to separate. Copper will cement on iron. The rest will only come down after PH adjustments. DMG will precipitate nickel salt but the cost outweighs any advantage. It would be cheaper to buy nickel and zinc.


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## butcher (Dec 10, 2021)

Iron will displace copper from the solution, as well as a host of other metals, such as the more valuable metals we are normally after if we have not already recovered them from the solution using copper or by some other means.

Iron will displace from solutions precious metals such as silver palladium, mercury, platinum, and gold, we normally separate these by other means, 
Iron as well as displacing the copper from the solution it will also displace other metals, which are also reduced to elemental metallic form along with the copper, including bismuth, arsenic, antimony, lead, tin nickel, cobalt, and cadmium if they also happen to be included in this soup...

Metals higher in the series of reactivity, more reactive than Iron, like chromium, zinc, aluminum, and a host of other even more reactive metals would remain in the solutions as ionic compounds.

PH adjustment (sometimes along with sulfides in water treatment) can help to remove the iron and most of the more dangerous reactive metals from the waste solutions...

Study dealing with waste.


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## Jado (Dec 11, 2021)

Personally I’d drop the Ag, then take Cu & Ni out electrolytically, then scrub the NOx from the remaining Zn. Success would be highly dependent on purity though (Mn would help, but add extra steps). It really depends on the goal. Any time you add an ingredient to a solution, you have more work to get it separated again.


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## butcher (Dec 11, 2021)

Solubility product constants.


http://www2.chm.ulaval.ca/gecha/chm1903/6_solubilite_solides/solubility_products.pdf




This can help with understanding dealing with waste, very useful in the chemistry we work with, as well as being useful in the separation or even crystalization or recrystallization of different ionic metal compounds...
Much depends on how much of what in many aspects, take crystalizing a salt through evaporation of two metal ionic compounds for example in a sulfate-based compound, much depends on the concentration of what.
For example, in an ideal world, our solution would only have one main product say FeSO4 with a small amount of CuSO4 and a low concentration of sulfate ions, and we would get some pretty green iron sulfate crystals to use to precipitate or test for gold in solution.

If we had mostly CuSO4 we could easily get some pretty blue crystals of copper to grow with a purity that could be improved upon with re-crystalization of these salts.

but if we have more of a mix of both CuSO4 and FeSO4 in more balanced proportions with an excess of sulfate ions we will crystalize both from solution.

Electrode potentials and solubility as well as concentrations of other metals play a large role in the chemistry involved...


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## nickvc (Dec 11, 2021)

We seem to encounter these sort of questions fairly often as members seek to extract as much value as possible from their materials but and it’s a very big but we do not have the massive plant and equipment needs to refine base metals in huge amounts to make it cost effective , copper and nickel refiners have massive set ups to refine the base metals and small labs in comparison to process the values so for us we need the reverse


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## butcher (Dec 11, 2021)

If you have a solution of copper nitrate even if it is mixed with nickel in solution, you can reuse it in a recovery process as is, or make other salts or make other useful reagents out of it for our recovery processes.

What many here would call a waste I see as a useful byproduct. one man's trash is another man's treasure.

I have many uses around the lab for copper or other nitrate salts or solutions, for example, I will use the copper nitrate by adding gold plated copper such as pins, cut into small pieces and add sulfuric acid, then distilling the mix, ending up with nitric acid distilled off (and concentrated through evaporation), of the copper sulfate and gold foils that remain behind, the copper sulfate is used several ways, such as in the recovery of silver, or copper electrolysis, the gold after refining is put back in the ground. 

There are numerous ways you can reuse your byproducts of recovery or refining before you declare them waste solution, and actually treat it a waste to treat for disposal. A little studying goes a long way to saving you money and coming up with ways to reuse a useful byproduct.

Sulfuric acid is a waste byproduct, companies used to let go up in smoke causing acid rains.

To clean the environment they had to capture it, and pay to dispose of it, so what did they do, well they did not want to pay to dispose of it and they couldn't dump it.

So the went to work to find and market, a way to make money from the waste, find new or other ways to sell their waste product or sulfuric acid world wide, drain cleaners and other products from their waste is on our store shelves today.


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## orvi (Dec 11, 2021)

butcher said:


> I have many uses around the lab for copper or other nitrate salts or solutions, for example, I will use the copper nitrate by adding gold plated copper such as pins, cut into small pieces and add sulfuric acid, then distilling the mix, ending up with nitric acid distilled off (and concentrated through evaporation), of the copper sulfate and gold foils that remain behind, the copper sulfate is used several ways, such as in the recovery of silver, or copper electrolysis, the gold after refining is put back in the ground.


Very interesting and clever idea. I was using this approach a lot, but without the distilling "part" of the process  Just added plated scrap to copper/nickel/iron nitrate solution, adding bit of HCl and then sulfuric to make the metals go into the solution. After the reaction, all nitrate content was used up to oxidize the metals. Saving (for me) precious nitric feed.
Base metals nitrates have an advantage over say sodium or potassium nitrate in the means of greater solubility of the corresponding sulfates.


Swissgoldrefiner said:


> Hello,
> I have mixed solution of nitric acid with Ag, Cu, Ni, Zn.
> With reactivity table of metal, i am able to selectively remove each of them.
> However, i wounder if it's possible with chemical to remove them selectively.
> ...


Ag, Cu, Ni and Zn solution could be recovered in more "scientific" approach.
1. drop silver with chloride solution/HCl or by cementing it on copper. as cementing on copper put more of the copper to the solution, maybe HCl/NaCl could be preferred.
2. then cement the copper on iron. this will leave nickel and zinc mostly in solution. and add iron in as well... 
3. to the mainly nickel/zinc and now also iron nitrate solution, add base such as sodium hydroxide, which will precipitate iron and nickel hydroxides/oxides. zinc, when this is done carefully with excess base, will form soluble zincate, which will stay dissolved.
4. (painfully) filter/decant the voluminous oxohydroxides of iron and nickel, leaving zinc and nitrate in the solution. 
5. acidify the solution near neutral pH. this will precipitate most of the zinc as hydroxide, leaving nitrate solution with whatever acid you used as a sodium salt.

to the nickel/zinc solution it is fairly simple to perform, but from there, things get more complicated. 
you can also perform electrolysis on the nickel/zinc solution to get mostly nickel with zinc contamination. zinc could be then removed by treating with hydroxide, leaving nickel undissolved.

but i will rationally stop at the copper removal. from there, it will be painful, unless you have big and optimized facility processing tons and tons a day. just my opinion


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## Swissgoldrefiner (Dec 11, 2021)

butcher said:


> What is your goal?
> 
> We do not normally separate all of these metals from each other, not all will separate selectively or sometimes even well, yes it can be done but cost and trouble are big considerations, not to mention the education and practice along with practical expierience needed to succeed in that type of endeavors...
> 
> ...


I am trying to recover Silver. However, after reaction, i have all this metal in the solution. 
So, the aim is to separate them selectively. Actually, i have a paper which separate Ag, Ni and Cu.
However, i need to read it better and try it, but it looks too long.
If the process that you propose is not cost effective, it s not usefull...adding Iodide, etc...is too expensif to recover.
I am here to learn new thing, related to PM, however to refine silver i prefere use my refiner, as i have good price with my annual volume.
Actually i sent 1800 kilo of pure silver last year to refine.
My aime to all question is to find an industrial way to recover all metal and recyle and get more value for my wast.


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## Swissgoldrefiner (Dec 11, 2021)

Geo said:


> It can't be done in one go. Nickel and zinc will not cement from solution in any effective way. The silver is easiest to separate. Copper will cement on iron. The rest will only come down after PH adjustments. DMG will precipitate nickel salt but the cost outweighs any advantage. It would be cheaper to buy nickel and zinc.


Why nickel will not cement out if you add iron? it should be as it's more reactive than iron. Off curse, zinc will not as it's less reactive, but why not nikel?


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## Swissgoldrefiner (Dec 11, 2021)

butcher said:


> Solubility product constants.
> 
> 
> http://www2.chm.ulaval.ca/gecha/chm1903/6_solubilite_solides/solubility_products.pdf
> ...


Nice paper for the solubility, thank you!


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## Swissgoldrefiner (Dec 11, 2021)

butcher said:


> If you have a solution of copper nitrate even if it is mixed with nickel in solution, you can reuse it in a recovery process as is, or make other salts or make other useful reagents out of it for our recovery processes.
> 
> What many here would call a waste I see as a useful byproduct. one man's trash is another man's treasure.
> 
> ...


Actually my nitric acide purshasing price dosent worth to do all this. I ask quote to a german company who can recycle copper nitrate and nickel nitrate, i am waiting their quote.


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## orvi (Dec 11, 2021)

Their potentials are in very close proximity. Influence of other ions in the solution play important role in this process. Standard electron potential is one thing, real world with aqua-coordinated metal ions and plentiful of nitrates, other metals and stuff is different.
Silver easily plates on copper, because the gap in the reduction potential of the mentioned two metals is relatively big (in theory silver 0,8 V, copper 0,34 V). As butcher said, pH control could help to precipitate it with iron in terms of controlling which ionic species are in the solution. Another option what comes to my mind is precipitating these on aluminium. This could work to some extent, leaving mostly nickel in the solid form-but also zinc could mess things up redissolving back to the solution. Altough the aluminium has reducing properties, which are much more powerful than iron. This could cause problems in nitrate solutions, but i never done this personally. This is only an "educated" guess.
If you are recovering nearly 2 tonnes of silver a year, i think you could work it up with someone, who put your ideas in perspective of industrial application. Everything what was covered here is already existing in the industry, it must work, because we have supply of these metals for whole world market in vast quantites. Folks out there found the best ways to do this many years ago. And folks who designed or invented such procedures aren´t that often on forums like this. They are often busy to keep vast industrial operations running, so their time is precious and valuable. Consulting such things with top experts will yield top results for you, but probably it will cost a lot of money.
This is more of a metallurgy/advanced hydrometallurgy task, not precious metals recovery/refining. We should give you our best opinions, but i dont think eg my viewpoint on this problem is of any value for processing tons of material at price, which is competing with big metal manufacturers/recyclers


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## Geo (Dec 11, 2021)

Nickel is a very peculiar metal. As a salt, it is very resistant to ionic exchange. Zinc metal will cement a very small amount of nickel compared to the amount of nickel salt present. Aluminum does not cement nickel at all, relatively speaking. Iron does not cement nickel in any meaningful amount. Only trace amounts.


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## orvi (Dec 11, 2021)

Geo said:


> Nickel is a very peculiar metal. As a salt, it is very resistant to ionic exchange. Zinc metal will cement a very small amount of nickel compared to the amount of nickel salt present. Aluminum does not cement nickel at all, relatively speaking. Iron does not cement nickel in any meaningful amount. Only trace amounts.


Good to know that, very interesting informations. Pointing out my idea with aluminium is theoretically correct, but in the real world useless  
Never tried to recover nickel from anywhere, altough i maybe had a good bit from processing metal cap transistors (casing is mostly nickel). I´ve just electroplated nickel on copper in early days to make nickel electrode That went pretty well with nickel sulfate with a bit of boric acid, layer was very compact and shiny. I used it a lot for producing zinc powder from zinc oxide dissolved in NaOH electrolyte. Very easy and straightforward process, nice spongy deposit, which crumbles and washes easily from traces of hydroxide.


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## Geo (Dec 11, 2021)

The best electrolyte for electrorefining nickel is acetic acid. I can't think of a process to go to nickel metal in one step. Nickel acetate is fairly easy to create. Pure nickel anode and cathode. The solution will balance itself after a short time under current.


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## Jado (Dec 12, 2021)

Geo said:


> The best electrolyte for electrorefining nickel is acetic acid. I can't think of a process to go to nickel metal in one step. Nickel acetate is fairly easy to create. Pure nickel anode and cathode. The solution will balance itself after a short time under current.


I’d argue for sulphamate/chloride. Acetate plating is user friendly, but doesn’t come close to 70 year old bumpers and trim back when they used the good 3-step chroming


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## Geo (Dec 12, 2021)

For industrial plating, I agree. I am talking about electrorefining. Forming an acetate could be as simple as adjusting PH to neutral and dropping all of the salt as oxides. Rinse and dissolve the salt in acetic acid. This creates an acetate of what ever metal salt was there. Using the electromotive series can get some metal out without too much overlap.


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## nickvc (Dec 12, 2021)

We had a valued member , Irons , who had a saying he loved to use 
‘ everything but the oink’ 
You are now trying to get that oink, if your business needs that oink you really are not operating properly and could spend more time and effort than you will ever recover chasing it, if you can find someone to take your waste and pay on it that’s great, any more effort or time and it will cost you more than you will receive for that waste, if you produce huge volumes then perhaps a deal is possible but the profit loss line might be very very fine


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## Jado (Dec 12, 2021)

Geo said:


> For industrial plating, I agree. I am talking about electrorefining. Forming an acetate could be as simple as adjusting PH to neutral and dropping all of the salt as oxides. Rinse and dissolve the salt in acetic acid. This creates an acetate of what ever metal salt was there. Using the electromotive series can get some metal out without too much overlap.


Sorry, I misrepresented my point. “Best method” for anything should have the least number of steps (opportunities for error or worse) from the input to the (most valuable) output. Anhydrous Acetate is difficult, Aqueous Acetate is unfinished, and it’s not a valuable end product in any quantity. Chloride is “better,” but still requires pH swinging or oxidation from it’s input state to achieve. Sulphate is a single step from Nitrate and is high value as a Sulfamate ingredient in bulk.


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