Purifying Lead with Caustic Soda

[Bent Ramrod]

I would imagine that efforts have been made to bypass the roasting process. Environmental laws made it necessary to add a sulfuric acid plant to the roasting operation to capture and recycle the sulfur dioxide emissions. If they couldn't sell the sulfuric acid at a competitive rate, the operation ran at a loss. A direct reduction of sulfide would be the solution.

By the way, that foaming and fizzing you see is hydrogen being released as the zinc is converted to zincate by the molten sodium hydroxide. When the gas evolution stops even though sodium hydroxide is still available, it means you have pretty much removed all the zinc. Antimony and bismuth should similarly form antimonates and busmuthates, albeit more slowly, tin should eventually form stannate, and lead should react the slowest of all.

[B.C.Jay]

Teck has always had a fertilizer plant that uses up most of their acid streams.
They are actually a pretty clean operation and they have been working pretty hard in recent years to get their remaining emissions down.

From what I gather from this info, bismuth doesn't react in this part. Any bismuth containing lead goes to electrolysis.

The four metals discussed in this paper are arsenic, tin, antimony and tellurium, and they get reacted with the sodum nitrate to form sodium based metallic salts.
So here's my question to the chemistry gurus, can these tin and antimony salts be recovered back to metals easily? For example, can they just be fluxed back into the next lead smelt, or do they have to be turned to oxides before they can be reduced by the fluxing?

[B.C.Jay]

And one final thing for those of you who ARE going to try this at home....

What do we do with the bucket of caustic solution?
Apparently adding lime (calcium cabonate) will precipitate out any remaining dissolved metal salts.

Three things can be done with the caustic

1) Dispose of it. The proper way is to neutralize it with muratic acid to a ph of 7 (you've just created NaCl and water - essentially table salt) then it can be dumped.
2) Use it. Drain cleaner, Wash your garage floor, soak your greasy car parts in it... just don't use it as mouthwash or shampoo.
3) Dehydrate it totally back to crystals and start all over again with it.

Be Smart, Be Safe

[NikA]

It's probably worth mentioning that if Sb or As remain in the solution when you go to neutralize the base with an acid, there's a real possibility of creating stibine or arsine gas, which are toxic at levels below scent detection. Apparently the lime reaction has been proposed before for cleaning mine tailings and is not typically used because it is slower and less complete than other reactions. You can further separate the metal salts by completely oxidizing them and precipitating them from solution and then play with the oxides if you're really just interested in industrial level separation processes.

[B.C.Jay]

https://www.youtube.com/watch?v=1ZMxW5UKRFA

An interesting video, mostly concerned with the making of Coke from coal. The last couple of minutes reference using coke in the lead smelting operations. Of interest is a very brief mention of the lead refining process were they use vacuum distillation to remove zinc as well as the addition of caustic soda to remove the last of the impurities before casting.

The title of the video is "Illawarra Coke"

[bruce381]

interesting read BUT please note that NAOH WILL dissolve skin, eyes face etc.

Even washing skin it will still be there longer than you think that slippery feel is you SKIN being dissolved.

Eye, face skin protection (like my picture) and a pail of maybe vinegar of some mild acid to neutralize your skin if you get it on you.

Nasty stuff if you know how fine I do but will not try this.

Very interesting non the less.

[shaggybull]

You neutralize a base with acid. I used to run di plant we neutralized caustic with vinegar.

[B.C.Jay]

interesting read BUT please note that NAOH WILL dissolve skin, eyes face etc.

Even washing skin it will still be there longer than you think that slippery feel is you SKIN being dissolved.

Eye, face skin protection (like my picture) and a pail of maybe vinegar of some mild acid to neutralize your skin if you get it on you.

Nasty stuff if you know how fine I do but will not try this.

Very interesting non the less.

The sky is falling! the sky is falling!

I use NaOH all the time. Its not nearly as bad some internet quarterbacks make it out to be.
It's part of an industrial process. Let's SHARE interesting information, not PANIC about it.

[shell70634]

B.C.Jay,
This has been a very educational thread and the information is much appreciated. I'm quite familiar with hazardous materials and aware of the safety precautions. I don't have any need currently to refine my lead but I now know it can be done away from an industrial environment. Thank you.

Shelly

[B.C.Jay]

One of things I found interesting with the few seconds of video dealing with the caustic was that the lead mass seemed to be heavily agitated. I expect that whatever reaction that goes on is only occurring at the surface of the metal so stirring/circulation is probably a very important part of this process.

[B.C.Jay]

B.C.Jay,
This has been a very educational thread and the information is much appreciated. I'm quite familiar with hazardous materials and aware of the safety precautions. I don't have any need currently to refine my lead but I now know it can be done away from an industrial environment. Thank you.

Shelly

And Thank You, for the comments!
I've played with this concept, and honestly, I don't really think it has a lot of usefulness to us 'boolit casters' but this site has so much good information that I think it's worth throwing ALL the information into one place.

Someone down the road may thank us.

~Jason

[bruce381]

Fully agree BUT some guy will get driano crystal and get it in his hair eyes and as happened to a friend then blind in that eye.

As I said if you know how to handle this material fine but 99% of most here do not, thats all.

Now that I think about it some people are so sloppy that they should not even be reloading.