Dissolve and recover Base metals (copper)

[Ardibash]

Hello guys,

I'm experimenting with a method to bring the acid costs down and recover the coper from refining process.
Please advise and comment if this is a good idea and or I'm missing something.

First of all I strip the boards from SMDs and connectors in plain HLC, after 2-3 days everything falls off.
Then some of the boards that have gold plating (some sound and video cards are all gold plated) got to sodium hydroxide bath to remove protective coating.

Then I take
3 L of distilled or deionized water, add
500 ml of 98% sulphuric acid, and
300 ml of Nitric acid

and put everything that has a bare metal on it into a solution. The solution should dissolve 600g of copper.

The reaction is pretty slow but with no fumes (very faint smell of nitrogen dioxide), in 3-4 day the solution turn into very nice blue colour (copper sulfate CuSO4) with fold flakes and some other metals depositing at the bottom.

After filtration (pretty hard to do) and removal of values, I boil the solution till only 30% of the liquid is left. A few hours later I have nice blue CuSO4 crystals and solution turns to very very light blue (almost clear).

I plan to extract copper from CuSO4 via electro wining, and as far as I understand I would need Platinized Titanium or Lead Oxide anode to recover the copper.

ANY TOUGHS?

 

[butcher]

Ardibash,
You may get some idea's from a process I use, it is different than yours, but is related.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=48&t=11945&p=121417&hilit=kill+two+birds#p121417.

The copper sulfate crystals once made are harder to dissolve (to recover gold), than if you dilute the copper sulfate solution before crystals form


You do not mention heat, but I suspect your heating solution to get the crystals to form.

Maybe a grafite anode will recover copper from the copper sulfate solution.

You can use iron to cement copper from the copper sulfate solution (making ferrous sulfate, this can be used to test for gold in solution or precipitating gold from aqua regia).

 

[Ardibash]

Hi Butcher,

"The copper sulfate crystals once made are harder to dissolve (to recover gold)" can you explain what you mean by "(to recover gold)".
In this process gold will not dissolve as some other base metals such as lead (or tin, not sure which is falling down as slug).

You're right, I do heat the solution, in fact I boil it to evaporate 60-70% of the solution which is water, this also helps to decompose any nitric that might have been in the solution for future HCL boil, and the remaining solution is sulphuric acid (of unknown concentration .

The graphite anode falls apart in CuSO4 solution during the electro wining and makes a big mess.

The main idea is to use cheapest acid, which is the sulphuric @ £0.75 a litter, and avoid hazardous waste disposal companies, who charge £450 + VAT to dispose of 100L of spent acid.

 

[Ardibash]

I also noticed that this combination of acids will not dissolve nickel, I place a piece of nickel plated bras, after 3 days there was thin nickel layer left.

Harold, what are your toughs on this process?

 

[Harold_V]

I also noticed that this combination of acids will not dissolve nickel, I place a piece of nickel plated bras, after 3 days there was thin nickel layer left.

Harold, what are your toughs on this process?

It's beyond anything I ever experienced, so I have no opinion.

I question your reasoning in forming copper sulfate crystals, however. If you intend to recover the copper electolytically, why not do so directly? Seems the evaporation, driving the solution to the point of forming crystals, isn't necessary. Did I miss something?

Harold

 

[Ardibash]

Thank you Harold,

I was thinking of not using the H2SO4 in electro wining, to keep the decomposition of cathode to a minimum and reuse the H2SO4 that is left after the boiling (may be I'm in a wrong direction, and the electro-wining can be done right there if correct anode is used).

I would dissolve CuSO4 in water, recover the copper, and boil the remaining solution into Sulphuric acid (after electro-wining the sulfur goes into solution and makes dilute H2SO4 ). Or just sell the CuSO4, that is if I find any buyers

BTW are you up this early or haven't slept yet

 

[samuel-a]

Like Harold, I don't really understand your reasons for creating solid copper salts (nitrate/sulfates).

Anyho... if you are dealing with these salts and want the metal, calcining at excess of 1200F might prove the most efficiant way to go.
Then smelt the oxides with soda (bicarbonate/carbonate)

 

[Anonymous]

Then I take
3 L of distilled or deionized water, add
500 ml of 98% sulphuric acid, and
300 ml of Nitric acid

and put everything that has a bare metal on it into a solution. The solution should dissolve 600g of copper.

I like this.

The reaction is pretty slow but with no fumes (very faint smell of nitrogen dioxide), in 3-4 day the solution turn into very nice blue colour (copper sulfate CuSO4) with fold flakes and some other metals depositing at the bottom.

After filtration (pretty hard to do)

I do not like this.

 

[butcher]

Maybe I misunderstood, I thought you were recovering gold, what I thought is your basically making a nitric acid solution (nitric and sulfuric acid), (to save on nitric acid consumption). and I thought you were using this solution to remove base metals from gold (copper mainly), the gold will not dissolve in this solution (maybe I did not read where you had separated the two?), now your evaporating water and the nitric acid as fumes of NO, NO2, NOx gases, leaving you with copper sulfate salts, and other salts of sulfate base metals.

You may have some very fine gold carried through to these salts, depending on how well you filtered the solution and other conditions.

I assumed this was a question of a process, and not just asking how to recover copper from a waste solution.

Did you read the link I posted? it is doing something very similar, but there I make nitric acid from the fumes, separate my gold (from copper base metal, gold plated), and make copper sulfate, all in one reaction, also reading it can explain some of what your trying to do, and may give you ideas to adapt your process.

The copper sulfate salts, once formed, are much harder to dissolve back into a liquid, it will take much more water and heat to get them back into a liquid state, than it did to form the salt (heat to evaporate, and amount of water(and acidic fumes) removed).

if you are just treating waste (mainly copper nitrate with high sulfuric content), and want to recover copper powders, I agree with Harold, just cement copper with Iron, (no need to waste heat evaporating to crystals, putting NOx gases in air, and trying to get crystals back into solution to recover copper) neutralize acid and precipitate the other metals (read the dealing with waste in safety section).

Edit: to me your not cutting down your acid cost, but wasting acids, evaporating them off into the air (read links I posted to see what I mean).

 

[Harold_V]

BTW are you up this early or haven't slept yet

Up early?

Heh! Not even at gun point.

Susan and I are night people. We generally turn out the lights about 5:00 AM.

I hate mornings. :lol:

Harold

 

[Ardibash]

Sam,

I don't really understand creating solid copper salts myself

I gave it a try just out of my curiosity, and then thought of refining it just like copper producers. I'll try the calcining and melting the salts and post results.
But, I was thinking which one would be more energy efficient electro-wining or melting, advantage of electro-wining will be recovery of sulphuric acid. I will also try to recover copper from acidic solution without creating salt crystals as suggest by Harlod (just bought a platinized titanium anode, and let me say, it was not cheap ).

Butcher,

This is a question of a process.
I use Whatman 113 Filter Paper so no gold particles should escape.
The chemical processes here are a little different than what is in your post.
This can be done in 2 ways:
1 - 100 Ml of 30% Hydrogen Peroxide, 30 Ml of 98% (18M) Sulphuric acid which will dissolve 30 g of copper (simple but not efficient as a lot of H2O2 will decompose)
2. - 3 L water, 500 ml of 98% sulphuric acid, 300 ml of Nitric acid, where nitric acid acts just as an oxidizing agent but the dissolving is done by sulphuric acid, hence creating sulphates not nitrates. Nitrogen oxide formation is very little, and it can be scrubbed very easily with a simple fume scrubber (I will post the drawings and detailed description of a scrubber I'm building).
The advantage is that this will dissolve all metals above Cu in reactivity series, however Lead and tungsten are resistant to sulfuric acid so they will fall as fine slime.

The reason for me to try to electro wine it is that, during this process at the cathode the water is split into oxygen and hydrogen, oxygen will bubble out but the hydrogen ions will combine with sulfate to form sulphuric acid which later can be reused and copper collected. I have read a lot about "dealing with waste" and right now I'm just dropping everything with iron shavings.

Can you explain why do you think this is a waist of acids? The only acid that is practically irrecoverable is nitric as there are very few fumes and they will be really hard to catch and dissolve to make nitric acid. Also the sulfuric acid is the cheapest £0.75 a liter.

My be I'm wrong I don't know ...

 

[Ardibash]

I hate mornings. :lol:

Harold

Same here

 

[butcher]

Here is my thinking, you have 500ml H2SO4, 300ml HNO3, which dissolve base metals (usually high copper content), you remove gold flake (not attacked by solution).

Your final product (beside gold flake) is mainly copper sulfate, this means you used 300ml HNO3 (escaped solution as fumes).

The sulfuric acid will not come out of solution (even with a reasonable high heat), water will, and eventually so will nitric acid.

the 300ml of nitric will form NOx gases, first in solution to oxidize base metals (some NO, and NO2 gas can escape while attacking copper, depending on conditions), then as you proceed to heat the rest of nitric will escape as NOx gas (driven off by heat and with sulfuric acid taking the copper to make copper sulfate crystals).

In my mind there is no need to scrub your NOx fumes (unless you wish to make sodium nitrate for reuse).

You could recapture a good portion of the nitric fumes (NOx), to make nitric acid with these fumes (by slight modification's to your reaction vessels, and bubbling these NOx fumes into a little water with some hydrogen peroxide you could get back much of that 300ml of expensive nitric acid for reuse).


As far as recycling copper, to me cementing it from solution with iron will give you copper you could reuse (it can be cleaned up somewhat) and not that expensive to get back the copper, this may actually give you just about as good of a copper powder as you would get from using electrolysis to push copper out of solution, but then again you would not reclaim the sulfuric your talking about, for me sulfuric acid is cheap, and easy to get (nitric acid is not).

Electro refining the copper you will run into problems because of purity, electro refining and melting copper you will most likely find you could buy copper (and sulfuric acid) cheaper than you could recover copper, and sulfuric acid it in usable or saleable form (time, equipment, electricity, fuel, and other expense may not be worth it), (I feel this will cost you more than you can make, and give you much trouble trying to make it work, you can do it, but your cost may make the copper and sulfuric you produce worth more to you than gold.

But do not take my words try it and see, keep us posted of results.

 

[Geo]

it is my experience that scrap yards will buy copper powder but at a reduced price. to receive #1 copper prices the copper needs to be a certain gauge as well as oxide free. the material that i recovered from my spent AP was 85% copper 11% tin 2% nickle and 2% other base metals but no PM's. i can lower the tin by hcl acid wash and maybe get bronze prices from the scrap yard if i melt it into ingots. from what i have now it would cost $85.00 worth of propane to fire the furnace and i may clear $250.00-$275.00 for the metal. not a great profit but as my grandpa used to say "its better than a poke in the eye with a sharp stick"

 

[jimdoc]

from what i have now it would cost $85.00 worth of propane to fire the furnace and i may clear $250.00-$275.00 for the metal. not a great profit but as my grandpa used to say "its better than a poke in the eye with a sharp stick"

If you could setup some sort of waste oil furnace it may pay off.

Jim

 

[Geo]

ive thought about waste oil, but im concerned about spills and/or incomplete combustion causing smoke or even residue in the furnace. used motor oil has some nasty stuff in it. ive even considered collected cooking oils, i can get this stuff by the drum full but ive never dealt with it before and have no idea how it will behave in a furnace.