Electrochemistry Tin recovery from Dore bar

[kjavanb123]

All,

Once motherboards are smelted, copper can be recovered in copper cell, and PMs are at the anode sludge, what happens to Tin, Nickel? Are they in anode slime or still on the Dore anode? In solution?

Considering its high price it would be valueable to recover.

Best regards,
Kevin

 

[solar_plasma]

Nickel will form soluble sulfate. Tin is somewhat special and I hope, some of the chemists will join in. When I look at wikipedia, I guess also soluble, acidic tin sulfate will be formed. But it is not stable in H2O. As far as I read, it can be cemented with zinc.

Someone on the forum once said that nickel will not cement on zinc. If this is true, it would be a possiblity to recover the tin from the solution, after copper is recovered.

But that's assuming. If no better informations are availlable, small scale experiments are necessary.

edit: are your boards lead free?

edit: okay, I've found it: Extractive metallurgy of copper, page 270: Pb forms sulfate, Sn forms SnO2 (!!!), both are found in the anode slimes. you can find a free link to the book on the forum.

 

[goldsilverpro]

Much of the gold on the Earth is in the oceans but it's not cost effective to recover it. I put a lot of those base metals in the same category.

 

[Geo]

you can part tin in an electrolytic cell but the same principals and rules apply. it has to be very high content of the target metal before parting.

 

[Geraldo]

Someone on the forum once said that nickel will not cement on zinc. If this is true, it would be a possiblity to recover the tin from the solution, after copper is recovered.

Nickel can most definitely be cemented from sulfate solution using zinc dust. It is the basis of the RLE (Roast-Leach-Electrowin) zinc process, by which about 90% of the world's zinc is made. Nickel (and cobalt and germanium) interfere with zinc electrowinning and must be controlled to extremely low levels.

In that process, nickel and cobalt are cemented in the "hot" purification step. At the industrial level, this cementation is done with "activation" ions to increase the rate and reduce zinc dust usage. There are arguments about whether this is catalytic activation or just co-cementation, but the most common activators are arsenic and antimony ions, added at very low levels. Personally I suggest antimony and not arsenic, as stibine gas is much harder to make than arsine and is less toxic. Antimony activation is also faster.

Hot purification is done at around 60C, with a residence time typically 20-60 minutes, at pH 5.2 or higher (depending on the solution contents).

The problem in this case is trying to cement nickel from a copper sulfate solution, if I read the OP correctly. Raising the pH to sufficient levels results in copper precipitating to form basic copper sulfate. The copper will also be cemented preferentially to the nickel.

In industrial copper refineries, they will typically treat a bleed stream using some form of bulk cyrstallization or solvent extraction in order to control nickel impurity levels. Alternately, they will use solvent extraction on their impure copper feed solution to produce a pure copper solution for electrowinning and then recycle the leach solution.

Best Regards, Geraldo

 

[solar_plasma]

Thank you, Geraldo! Very interesting and lots of notes for further internet research for those, who are interested in this field.

 

[Geo]

i may be totally off base here but a copper parting cell would use either copper nitrate or copper chloride as the electrolyte as ive seen cells use both. ive never seen a copper parting cell that used sulfuric acid. i suppose the diluted sulfuric would work but if it were me, i would use the cheaper (and for me, safer) hcl to make my electrolyte.

 

[g_axelsson]

i may be totally off base here but a copper parting cell would use either copper nitrate or copper chloride as the electrolyte as ive seen cells use both. ive never seen a copper parting cell that used sulfuric acid. i suppose the diluted sulfuric would work but if it were me, i would use the cheaper (and for me, safer) hcl to make my electrolyte.

I think you are totally off base here...
https://www.google.se/search?q=site:goldrefiningforum.com+%22copper+sulphate%22+cell

That's the way the big boys have done it the last 150 years.
http://en.wikipedia.org/wiki/Refining_%28metallurgy%29#Copper

Göran

 

[solar_plasma]

Extractive metallurgy of copper, chapter 16.5, describes several plants around the world using CuSO4/H2SO4 for copper refining. And in my opinion it is even safer, since the only gasses that can occur are H2 and O2 plus some acid aerosoles from bubbles, but not if the system runs at proper parameters.

 

[Geo]

ahh, so dilute sulfuric acid which attacks copper would make the best electrolyte. i have had good deposits of copper using copper chloride myself but it was on a very small scale. i believe Rusty was using copper nitrate in his parting cell. perhaps it just depends on the scale at which you are working. i am going to have to try the copper sulfate electrolyte in a small cell to see the difference it makes.

my faulty memory strikes again. rusty WAS using copper sulfate as his electrolyte. for some reason (i would have sworn in court) that i read he was using copper nitrate. oh well, no damage done i hope. sorry about that.

 

[solar_plasma]

I am far from understanding it completely, but it seems to me, that CuSO4/H2SO4 has some benefits when it comes to the rejuvenation of the electrolyte.

 

[goldsilverpro]

Every industrial copper electrorefining system and most every (some use fluoboric acid) acid copper plating system I've ever seen was a sulfate system using dilute sulfuric acid and copper sulfate. I've played around with other matrices that work, sort of, but sulfuric is, by far, the best, with fluoboric a close second. Anytime you want to know what to use for most anything, find out what is used commercially. Industry has already attempted and weeded out the inferior methods.

 

[kjavanb123]

All,

Interesting responses here, I just got an email from a Chinese woman working in ewaste and she claims 16% of weight of printed circuit bosrds is Tin? Any confirmation on this?
Tin prices as of today $22,000 per metric tonne or $10 per lbs. assuming 16% of weight is correct, then 2207 lbs of PCBs would have 335 lbs of Tin??????

Regards,
Kevin

 

[rusty]

ahh, so dilute sulfuric acid which attacks copper would make the best electrolyte. i have had good deposits of copper using copper chloride myself but it was on a very small scale. i believe Rusty was using copper nitrate in his parting cell. perhaps it just depends on the scale at which you are working. i am going to have to try the copper sulfate electrolyte in a small cell to see the difference it makes.

Geo my cell used a copper sulphate electrolyte.

I had the anode dead center with a cathode positioned at both sides of it.

 

[goldsilverpro]

All,

Interesting responses here, I just got an email from a Chinese woman working in ewaste and she claims 16% of weight of printed circuit bosrds is Tin? Any confirmation on this?
Tin prices as of today $22,000 per metric tonne or $10 per lbs. assuming 16% of weight is correct, then 2207 lbs of PCBs would have 335 lbs of Tin??????

Regards,
Kevin

Sounds way too high to me. Maybe Sn makes up 16% of the weight of the total metals after depopulating. I found one study that gave about 24% for Cu and 2.3% for Sn. That seems more realistic.

This company sounds interesting
http://www.ultromex.com/

Their patent
https://www.google.com/patents/WO2013104895A1?cl=en&dq=inassignee:ultromex&hl=en&sa=X&ei=bREaUuCvBYqd2gXOxYGAAQ&ved=0CDYQ6AEwAA

A search brought up several similar schemes using weak leach solutions of various combinations of H2SO4, HCl, and HNO3 and then precipitating the various metals as hydroxides by pH control.

 

[rusty]

Page's 25 to 31 are of interest re: tin recovery.

 

[solar_plasma]

Very interesting! But I guess both fluoroboric acid and methanesulfonic acid as an alternative for dissolving tin are nothing for hobbyists or school experiments? Fluoroboric acid surely NOT. Has anyone experience with methanesulfonic acid?

 

[goldsilverpro]

Here's the patent mentioned on the link Palladium gave.
https://www.google.com/patents/EP1159467B1?cl=en&dq=%22EP+1+159+467+B1%22&hl=en&sa=X&ei=WjYaUpSLAurK2gWwj4HIBw&ved=0CDQQ6AEwAA

I used fluoboric acid (HBF4) daily, in large quantities for several years, with no mishaps. To me, it's one of those wonderful universal miracle chemicals (I put cyanide in that same category). Just about any common metal can be plated from a fluoborate matrix. It's especially good for tin, lead, and tin-lead solder plate. A mix of HBF4 and H2O2 is probably the best Pb, Sn, or Sn-Pb solder stripper there is. The MSDS gives it a 3 Hazard rating, mainly for burns, but I can't ever remember being burned by it. To compare other acids, HNO3, HF, and H2SO4 (I've been burned by all 3 of those) have a 4 hazard rating and HCl is a 3.

 

[solar_plasma]

But german wikipedia states that there will form HF in the electrolytes? Yeah, sounds wonderful....in the right hands at least.

edit: I read the msds on Gestis Stoffdatenbank, and hey, that fluoroboric is quite ugly.

 

[snail]

I work at a tin plating facility that uses a methanesulfonic bath. We keep stannous tin at 20-24 g/l, methanesulfonic acid at 18-20 g/l, 2-4 g/l sulfuric acid, and a grain refiner. 200-300 A/sq ft current @ 110 Fahrenheit.
Seems relatively beneign to handle, no outstanding health issues in people exposed daily for 20 years.
Dale