MR AZIDE
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RECOVERY OF LEAD FROM CAR BATTERY SCRAPS.
Hi
This is my first post on this forum.
I remember reading from a very old school science review years ago, that lead(IV) oxide, PbO2, is insoluble in NaOH,, but interestingly if you add
sucrose, basically sugar , the PbO2 will dissolve in the solution, forming a
yellowy /brown solution.
Spongy lead can be obtained by electrolysis of the solution.
I did do this experiment, on a small scale from an old wrecked car battery i scavenged, and it does work.
The sponge of lead easily oxidised to yellow Lead (II) oxide when heated in an evaporating basin.
Wonder what sort of compound the Pb must be forming with the C12 H22O11 then.....?
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Hexavalent
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Do you have a reference for this?
http://www.sciencestuff.com/msds/C1694.html suggests that lead and lead oxide (albeit a different oxidation state of lead . ..would this matter
in this case?) will react with sodium hydroxide to generate sodium plumbite.
http://www.sciencestuff.com/msds/C1694.html suggests that this compound is soluble.
[Edited on 21-5-2012 by Hexavalent]
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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MR AZIDE
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I think the review was as old as 1986, i had only 4 of them, which i scavenged
from the science class bin, and that was about 10 years ago.
I think i still have them, in a cupboard. Ill need to look for them, look it up in whatever book it was.
Ill get back to this thread if i find them.
Whether or not the oxidation state of the lead in the oxide mattered in the dissolving into the NaOH....I dont know..... if lead oxides are amphoteric
enough to behave like Al and Zn oxides.
I suspect that the lead might have been forming some sort of soluble organic compound with the sucrose.
I think the main point of the article was that Pb was easily extracted from car battery scrap using very cheap, and readily available chemicals.
I mean you could scavenge lots of old lead/acid batteries and do this in BIG bulk in your back yard, very cheaply........ sell on the lead.
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blogfast25
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Any pictures or at least a more scientific description of what precisely you did?
PbO2 is a powerful oxidising agent, possible it oxidises the sucrose. The resulting Pb (II) oxide/hydroxide would dissolve in NaOH, as sodium
plumbite. That's one tentative explanation...
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Hexavalent
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I mentioned this upthread, could sodium plumbite be used as a source of lead in a reaction, e.g. for the formation of lead salt precipitates?
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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phlogiston
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In my experience, electrolysing sodium plumbite solution will result in deposition of lead dioxide on the anode. So some of the lead will go back to
the form you started with in the first place.
IMHO lead is one metal you should not desire to work with in bulk in your backyard, and especially not its water soluble salts.
[Edited on 21-5-2012 by phlogiston]
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MR AZIDE
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Quote: Originally posted by Hexavalent  | Do you have a reference for this?
I found the aforementioned SSR. Sep 1986, Volume 68, No 242, on page 91 to 93. ISSN 0036-6811.
It starts off by saying how lead gan be removed from accumulator scrap, and then goes on with some experiments concerning the solubility of lead salts
obtainable from accumulator scraps in NaOh soln.
PbSo4 + 4NaOH ---> Na2Pb(OH)4 + Na2So4
The lead sulphate dissolves in the 20% NaOH soln, with gentle heat to give a soln of lead hydroxy plumbate, and sodium sulphate.
Lead (II) Oxide dissolves also, but more slowly, BUT ONLY when the sugar is added.
The Lead (IV) Oxide will only dissolve as well when sugar is added, but also ( i forgot about this bit) with the evolution of H2 gas.......!
They go on to say , very interestingly that the solubility of these lead oxides improves as the number of hydroxyl groups on the polyglycols or sugars
increases.
They claim that the lead (ii) oxide forms complexes, and the lead (iv) forming lead (ii) as it oxidises the sugar.
They have listed that the recovery is as follows.
5g of PbO2 and 7g of PbSO4 are added to 200ml water which has has previously 45g cane sugar and 32 g NaOH dissolved.
The solution is heated to boiling, with stirring, until all had dissolved, with evolution of gases, untill a clear red solution forms.
After cooling the soln, is electrolyzed using graphite electrodes, while stirring, and the current is maintained at about 500mA throughout.
The Pb formingas a spongy mass at the Cathode, and O2 at the anode.
Says that the solution needs to be electrolizes ASAP as insoluble lead compounds crystallize.
Adding borax to the spongy lead allows it to be melted into solid lumps, and the borax protects from the oxidation .
I did try this much the same as described those years ago, but didnt add any of the lead sulphate, and was just done in small scale, without weighing
out etc.......
The interesting bit was that The sponge of lead produced easily oxidised in air while heating to form yellow lead(ii) oxide.........
but to its large surface area.
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blogfast25
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Well, I just had a quick attempt at this ‘soda/sugar/lead’ mixture even though for the life of me I can’t imagine what the sugar is doing in
there: sugars are mild reducing agents (see Fehling’s and Benedict’s reagents) at best.
About 7 g of battery lead pieces, 7 g of NaOH and 15 ml of water were first combined and the mixture heated. Predictably nothing happened. Then about
7 g of white sugar (sucrose) was added carefully and the mixture simmered for about ½ hour. I observed no reaction. The pieces of lead appeared not
to have dissolved or even slimmed.
It’s now cooling and I will test the supernatant liquid for lead tomorrow.
[Edited on 31-5-2012 by blogfast25]
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phlogiston
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The discussion above mentioned dissolving PbO2, not metallic lead.
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blogfast25
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Well, well, well.
After cooling, standing overnight, slight dilution and cold filtering I obtained a slightly syrupy liquid with a slight brownish tint (but clear). The
brown tint is caramelised sugar, I think.
To this filtrate about 10 ml of glacial acetic acid was added and low and behold a creamy white precipitate dropped out: ‘quite a bit’ too. See 3
TTs with that slurry in’em (sorry about the poor focus):
Below: the tubes above with:
a) Left: 70 % HNO3 added. Precipitate mostly dissolves but not all.
b) Middle: excess glacial acetic added, not much change noted
c) Right: with bleach added (NaClO): precipitate turns orangy/red
Below:
Here K2Cr2O7 solution was added to the supernatant liquid of the left tube in the photo right above. No lead (II) chromate formed because residual
sugar reacted with dichromate, hence the Cr3+ blue colour.
Additional tests (no images) on the straight slurry: 9 % H2O2 caused fizzing and precipitate turned brown. Adding 36 % HCl caused precipitate to
change texture: I believe white PbCl2 was being formed.
In conclusion, all this strongly points to significant (but not large) amounts of battery lead to have gone into solution as sodium plumbite (II)
[Na<sub>2</sub>Pb(OH)<sub>4</sub>].
Is all this explainable by lead's weak amphoterism alone?
[Edited on 1-6-2012 by blogfast25]
[Edited on 1-6-2012 by blogfast25]
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MR AZIDE
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the brownish tint, may be some sort of soluble complex of the sugar and lead.
you would expected lead acetate to form adding acetic acid, but lead acetates are very soluble, so you maybe made a very concentrated solution, and
hence a lead acetate slurry formed......or its something else.......
Have you tried recrystallizing the initial white slurry, to see if you can get lead acetate crystals?.
I think HNO3 would dissolve the lead acetate( or whatever that white slurry is) and make at least some lead nitrate, maybe it didnt all dissolve due
to some common ion effect.
did you get any fizzing / Cl2 when you added the hypochlorite.......? I think the hypochlorite has reaced with the white slurry, and produced a
precipitate of lead(ii) oxide....???
The H2O2 fizzing mustve been O2 gas, as it was oxisiding the white slurry, i think the brown precip was possible lead (iv) oxide (PbO2.
I agree with the texture chance...PbCl2......
Interesting things going on there blogfast.....
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blogfast25
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| Quote: Originally posted by MR AZIDE |
you would expected lead acetate to form adding acetic acid, but lead acetates are very soluble, so you maybe made a very concentrated solution, and
hence a lead acetate slurry formed......or its something else.......
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No, I think the litharge formed in these conditions just wasn't very soluble, that's why. I could have heated it up a bit but I didn't. Lead acetate
is far too soluble to form such a slurry.
I think the whole thing boils down to lead's amphoterism. I might have another go with NaOH + H2O2, see if that speeds things up a bit.
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