recovering valuables from used solder

[vgecas]

hi,

i have some (~1kg) used solder, that i am playing around. i shot poured it and ran through electric cell (1.2V). i got lot of nice crystals i suppose tin, leftovers became dark and brittle, so i grounded them to mud consistency. i suppose this mud should consist mainly silver and lead chlorides plus copper and small amount of gold.

i would be very thankful if someone could advice how to separate them apart. one way to separate silver chloride could be using ammonia. if i add ammonia to the mud, silver would take water soluble form, so i could filter everything out. i understand explosive danger, everything should be kept wet and immediately after processing acidified.

maybe there is some other, safer method?

 

[g_axelsson]

Here is a good thread about solder.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=22889

Göran

 

[clearsteam]

Not wanting to hijack the thread, but in a similar vein, on some of the high end boards I am getting ready to process, there is visibly gold in the solder especially around items with gold brazing. Im assuming the best way to get this simply is to dissolve the tin in hydrocloric , leaving silver and gold residues for further processing. I appreciate that it would cost more in acid and create too much waste to process all the solder in this way.

But I cant send off gold that is winking at me from the solder, so I was thinking of buying a desoldering iron as I have time on my hands, and just processing the rich seams.

Can I ask why sodium hydroxide doesnt seem to be used by anyone to remove the tin? the resulting waste looks to be easier to dispose of safely and the cheap cost of sodium hydroxide woud possiby make recovering gold and silver from solder economically viable.

Would processing whole boards in cold NaOH just dissolve the lower metals, or would it turn the soldermask to mush and make a mess?

Thanks in advance
Phil

 

[vgecas]

thank you Göran, i have read that post before, but after your encouragement i took more time to get into these pdf's, especially this one:
2175.pdf

i will try to leach solder with HNO3 later, but now i have to deal with mix of lead and silver chlorides... maybe you could give an advice how to separate them?

 

[goldsilverpro]

Lead chloride is soluble in water but is about 5 times more soluble in hot water (30g/l) than cold water (6g/l). The solubility of silver chloride in hot water is only about .02g/l.