Romix
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Lead recovery from glass, theory and practic.
Hello Dear forum members.
Is any of you here, worked with crt glass?
Recomend me lead recovery methods.
Ok, dry sodium hydroxide, with clean crt glass.
Melting point near 300C. On hot plate, straight of the mains.
Silicon, alkali metals and lead will dissolve. Unsure about others.
After hour boiling in base, with breakes, wearing all protective PPE.
Then boil it in water, few times, see what dissolves and drops out.
For example metalic aluminium dissolved in basic hydroxide solutions and drops out on dilution. Can similar happen with these complexes?
Then wash all in hydrochloric acid, it will remove all the alkali metals. And base by weight that were added.
What next?
[Edited on 21-5-2017 by Romix]
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unionised
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Why?
There are easier ways to get lead.
There are probably better ways to recycle CRT.
Molten/ boiling NaOH is nasty stuff.
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alive&kickin
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Why? For the fun of it.
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Sulaiman
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maybe if you could melt the crt glass into slabs there would be eBay buyers of 'lead glass radiation shield blocks' ?
CAUTION : Hobby Chemist, not Professional or even Amateur
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Praxichys
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Here is how I would try it:
Use a clean steel container. Powder the glass first with a hammer and then with a mortar and pestle. Grind the NaOH and glass powder together, then
heat to about 350°C for an hour or two.
What's left will be hard and glassy. Pulverize to a powder and stir this with boiling water for a while to dissolve aluminates and silicates. Filter,
but keep in mind paper filters will be dissolved by strong NaOH and fritted glass + NaOH is a no-no. I'd recommend a felted polypropylene cloth filter
with multiple passes.
Left in the filter will be unreacted glass and lead/aluminum hydroxides. Stir this with dilute HCl and the lead and aluminum hydroxides will dissolve
as the chloride salts, leaving behind the residual glass, which is filtered from the solution. Addition of sodium bisulfate solution to the filtrate
will cause the lead to precipitate as lead sulfate while any aluminum remains dissolved.
Filter and dry the lead sulfate. If you want to recover the lead metal from this, I'd suggest strongly heating a mix of the lead sulfate and aluminum
powder with extra aluminum added as a reaction moderator. (The reaction is thermitic in nature and you want to minimize the vaporization of the lead.
You can achieve this by using excess of either reagent, but aluminum is easier to deal with from a wastewater standpoint and has a higher heat
conductivity which will help the reaction complete). The resulting cake can be crushed and stirred with hot, weak HCl to recover the lead nodules,
which can be melted together and cast into ingots. Keep in mind that aluminum sulfide will form during the thermal reduction and subsequently the
digestion will probably give off some H2S, which is dangerous.
Alternatively, you can use electrochemistry to plate the lead out of the initial lead/aluminum chloride solution onto a lead anode.
Leaded glass can be as low as 18% PbO. This gives it a little over 16% recoverable lead by weight. I understand this is probably a pedagogical
exercise but keep in mind that this is in no way economical. It also creates a lot of waste with traces of soluble lead in it, which needs to be
disposed of properly.
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Romix
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Quote: Originally posted by Sulaiman  | | maybe if you could melt the crt glass into slabs there would be eBay buyers of 'lead glass radiation shield blocks' ? |
Yes, good idea.
How much they're paying per kg?
If price low, better melting some sort of a radiotion blocking containers for rare radioactive minerals or compauds. But melting point of it higher
then aluminium, and it's less safe. Today I melted one shard, something smelly evaporated from it, reminded me of old soviet medication.
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Romix
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Can it block thorium brake down? How thin glass have to be?
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Boffis
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The easiest way is to simply melt the glassy with or without a flux and add a reducing agent such as charcoal or potassium hydrogen tartarate etc.
This is the basic principle behind fire assaying for gold except in that process the lead that forms is used to collect the gold and silver present.
To ensure that the lead coalesces into a single bead the glassy melt needs to be as fluid as possible so you either need to work at high temperatures
or add extra Li and Na salts as a flux. As suggested above sodium hydroxide is probably the best for you though borax might help too.
Providing there is enough reducing agent the process is practically quantitative and rapid. The melt is simply poured into a mold and when cold the
lead bead separated by hammering with a small hammer.
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unionised
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| Quote: Originally posted by Praxichys | Here is how I would try it:
Use a clean steel container. Powder the glass first with a hammer and then with a mortar and pestle. Grind the NaOH and glass powder together, then
heat to about 350°C for an hour or two.
What's left will be hard and glassy. Pulverize to a powder and stir this with boiling water for a while to dissolve aluminates and silicates. Filter,
but keep in mind paper filters will be dissolved by strong NaOH and fritted glass + NaOH is a no-no. I'd recommend a felted polypropylene cloth filter
with multiple passes.
Left in the filter will be unreacted glass and lead/aluminum hydroxides. Stir this with dilute HCl and the lead and aluminum hydroxides will dissolve
as the chloride salts, leaving behind the residual glass, which is filtered from the solution. Addition of sodium bisulfate solution to the filtrate
will cause the lead to precipitate as lead sulfate while any aluminum remains dissolved.
Filter and dry the lead sulfate. If you want to recover the lead metal from this, I'd suggest strongly heating a mix of the lead sulfate and aluminum
powder with extra aluminum added as a reaction moderator. (The reaction is thermitic in nature and you want to minimize the vaporization of the lead.
You can achieve this by using excess of either reagent, but aluminum is easier to deal with from a wastewater standpoint and has a higher heat
conductivity which will help the reaction complete). The resulting cake can be crushed and stirred with hot, weak HCl to recover the lead nodules,
which can be melted together and cast into ingots. Keep in mind that aluminum sulfide will form during the thermal reduction and subsequently the
digestion will probably give off some H2S, which is dangerous.
Alternatively, you can use electrochemistry to plate the lead out of the initial lead/aluminum chloride solution onto a lead anode.
Leaded glass can be as low as 18% PbO. This gives it a little over 16% recoverable lead by weight. I understand this is probably a pedagogical
exercise but keep in mind that this is in no way economical. It also creates a lot of waste with traces of soluble lead in it, which needs to be
disposed of properly.
|
That works right up until the point where the lead dissolves (as plumbite) in the NaOH and disappears through your filter. (Oh, BTW, lead chloride's
not very soluble).
However, I think you could take that plumbite solution and add a sulphide to ppt the Pb as PbS.
Then it's essentially the same process as the smelting of galena.
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Texium
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Thread Split
23-10-2022 at 05:29 |
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