Tin

[bswartzwelder]

I have seen all the posts lately on how tin can be the biggest enemy of the gold refiner. I have been wondering how tin refiners remove unwanted metals to produce pure tin. Is there a simple answer to this? If so, can we just make pure tin by removing all the unwanted things and then remove the gold from whats left? I sincerely don't have any ideas on how tin is prepared, but possibly there is a backdoor approach to getting rid of it. Just a thought.

 

[Geo]

tin is refined and purified through the same electro-chemical processes used for most other metals. electrowinning is the process.

http://en.wikipedia.org/wiki/Electrowinning

 

[kashiffat]

see Gold refining help from e scrap thread.... you will get help if you read the procedure.... do some experimentation after that...

PM me after that i will tell any confusion if appeared..

 

[bswartzwelder]

Geo, Thanks for the reply. I have read the Wiki article on electrowinning, but did not see tin mentioned. I then read what Wiki says about tin. Do not think it says much about electrowinning. I assume that the electrowinning process is used for almost any metal where they want extremely high purity.

Kashiffat, I have 6 or 8 buckets filled with scrap cell phone circuit boards. Once the weather warms up, I need to depopulate the boards. Once that has happened, I would like to get rid of as much lead and tin as possible. Presently, the method I am considering would be to dunk them in a crock pot with warm HCl.

My questions about tin were to see if there is any method used in industry which could possibly be used more effectively for doing this. I was also thinking about getting all the tin out and then if possible, selectively removing the other valuables starting with gold. I was thinking that if we could get rid of the tin first, then getting everything else might not be quite as challenging. Just trying to look at it from a different angle. If that's not possible, then it will have to be the old tried and proven method. At least I didn't lose any values by exercising the thought process.

Thanks to all.

 

[Geo]

this is clean solution but it should work with dirty solution. [youtube]http://www.youtube.com/watch?v=Af9GAUYDrlQ[/youtube]

 

[bswartzwelder]

Geo,

I watched the video and saw an Anchor Hocking glass baking dish with a liquid in it. On the right was a piece of coat hanger wire or copper wire. I couldn't make out the other terminal. Something was growing on the wire on the right hand side. It must have been something in the solution "plating" onto the wire. What were the anode and cathode metals? What was the solution? How can this help get rid of tin? If this will work, it could save hours of sitting over a crock pot full of hot HCl not to mention having a lot less contaminated solution to have to deal with.

THANK YOU

 

[kashiffat]

Bswartwelder you can easily remove tin by dissolving it in Hcl and then filter to remove the clear solution of sncl2 which is also helpfull in detection later on

 

[butcher]

What other base metals did you just dissolve in this same solution, that you plan on using as stannous chloride or use to detect precious metals with?

Aluminum, iron, zinc, nickel, cobalt and so on, what other oils grease or glues or trash would this solution contain?

Do you plan on trusting this dirty solution to use as a test solution , on a solution which could hold considerable valuable metals to determine if you will dispose of that solution or not?

Not me.
Fairly pure tin is very cheap, stannous chloride is a very easy to make, I would not want to lose values trusting a dirty waste solution for my stannous chloride test solution, when I can very easily make clean stannous chloride in just a few minutes, with a clean pure piece of tin metal, and have a test solution I can depend on.

 

[Geo]

in the video (from what i can gather) the anode was a block of solder consisting of 95/5 tin/antimony. the cathode was a piece of stainless steel wire and the electrolyte was stannous chloride. the tin crystals are pure tin metal.

in an AP solution, tin gets converted into stannous chloride which is in the solder. a graphite anode and a stainless steel cathode will remove metals through electrolysis. what you will need to know is the correct current (volts/amps) to apply to remove the tin. as tin has a specific resistance, with a little trial and error, you should be able to remove the tin from solution. it wouldnt be pure because it is an exact science and would be contaminated with other base metals that was close to it in the frequency range of tin. you would need a rectifier with a wide range of settings on both the volts and amps.

this is also a viable method of removing other metals from solution when not needed like copper. theres a couple of metals that cant be removed by this method (like nickel) so its not a good method for waste removal. copper can be removed from solution relatively pure by electrolysis because it has a wider range of frequency compared to some other metals.

 

[bswartzwelder]

Many THANKS, Geo. WOW! The more I study on this forum, the dumber I feel. I thought I was starting to become slightly educated by what I read here, but it's becoming painfully obvious that the more I learn, the more I don't know. Hopefully, at some time, I will learn enough to be confident and competent to work at recovery and refining on a hobbyist level and to do it safely.

I have a laboratory type power supply where the amps are completely adjustable from 0 to 10 amps DC, and the voltage is completely adjustable from 0 to 30 volts DC. There are a number of things which will determine what current would work. Resistance of the solution, separation between the anode and cathode, as well as the surface area of the anode and cathode. Larger anodes and cathodes will allow for more current to pass through them and greater distance between them will decrease current flow. Also, the strength of the AP solution will enter into the equation. As more and more copper gets dissolved into the AP, resistance will go down and amps will go up assuming the voltage stays constant.

Thankfully, graphite and stainless steel are relatively easy to get. I am also confident I can make a pretty good batch of AP as I have 2 buckets used to remove foils from printed circuit boards. If I read this correctly, I can just put my printed circuit boards into AP (which I was going to do eventually) and by applying an electrical current, get rid of the tin (and possibly lead?) and leave the gold plated foils ready to process. It appears that by doing it this way, I can avoid the step whereby I have to soak the circuit boards in warm or hot HCl to get rid of the tin (and hopefully lead).

THANKS again, Geo. You, Butcher, Harold V, Lasersteve, Patnor, and any of the others I can't think of off the top of my head are just too awesome to believe.

 

[butcher]

Unless the solution is fairly pure with the target metal in solution as the electrolyte, not a mixture of metals in solution , I do not see plating out one metal and not another, unless conditions were favorable, the standard electrode potential determines which metal will plate out in the cathode vicinity, many metals can be close to each other in their electrode potential, also if the metal is in solution as a majority it will plate better if the other metals are limited to a very small percentage of the mix, if the electrolyte contains a wild mix of metals, then a wild mix of metals would be reduced at the cathode.

 

[bswartzwelder]

Thanks. I wouldn't mind a wild mix of things in what I plated out as long as it doesn't contain gold. I know there is a chart with the metals listed. I believe it even lists them in order of their electrochemical activity. If you were to pick out the metal at the bottom of the chart and start at the lowest voltage, it seems you might be able to slowly increase the voltage and continue selectively precipitating out the metals. Don't know for sure if this will work, so it will take a lot of experimentation. Starting too high would precipitate everything below that vaolage at once. I will give a lot of thought and reading before I try this. For now, I'll stick to the soak in warm HCl to get rid of tin and hopefully lead.

 

[FrugalRefiner]

Selective electrowinning of metals from a mixed metal solution works a lot better in theory than it does in practice.

One reason is that electrons move easily through a solution as they can "jump" from one ion to the next between your anode and cathode. The metal ions themselves, on the other hand, have to move physically through the solution. So once your target metal is depleted in the vicinity next to your cathode, other ions will be acted upon by the electrical forces and your target metal will become contaminated by other ions that are close to the cathode. There's a lot more to it than that, but you can see the problem.

Dave

 

[Geo]

not really sure the purity of the reduced metal is as important as not removing noble metals such as PM's. if i were working at this, reducing base metals is the objective. if you pull excess copper or lead, or even a little silver, i would consider it a success as long as it didnt reduce any gold. just my opinion.

 

[FrugalRefiner]

Geo,

You're right that if the purpose is just to remove base metals, then it doesn't matter if they mix on the cathode as long as the noble metals aren't included. My response was directed towards bswartzwelder's comment about selectively separating the metals by controlling the voltage as each metal was "selectively" removed.

Dave

 

[hatemelborai]

Hi all
I want to remove all components from PC motherboards using chemicals to remove soldering and then removing components will be easy.
can any one help.
thanks and best regards

 

[jimdoc]

Hi all
I want to remove all components from PC motherboards using chemicals to remove soldering and then removing components will be easy.
can any one help.
thanks and best regards

How will you deal with all your waste?

Jim

 

[hatemelborai]

Hi all
I want to remove all components from PC motherboards using chemicals to remove soldering and then removing components will be easy.
can any one help.
thanks and best regards

How will you deal with all your waste?

Jim

I will recycle the PCB using crusher and separator. I will refine ICs and connector for precious metals
Hatem

 

[FrugalRefiner]

Hatem,

I think you missed Jim's point. When he asked how you would deal with the waste, he was referring to all of the ground up bits of materials and the gallons of contaminated acids that will now contain a variety of poisonous heavy metal ions in solution.

Here are a few things to think about when you're considering recovery and refining:

• What are the hazards of the chemicals you intend to use
  How can you minimize the risks of these chemicals (engineering controls and PPE)
  What chemical compounds will be created during the reaction
  What are the hazards of those chemicals
  How can you minimize the risks of these compounds
  What wastes will be left when you finish your process
  How will you treat the waste to make it less hazardous
  How will you dispose of the waste that is left

That is just a short list. You should be able to answer every one of those questions before you start any process.

The first rule is to be safe in everything you do. Read EVERYTHING in the Safety section of the forum, especially the Dealing with Waste topic. No amount of precious metal is worth jeopardizing your health or the health of those around you.

Dave