RU_KLO - 29-12-2022 at 07:26
Hi,
Im trying to purify PbO2 taken from batteries.
Did not find anything in Internet. And as it is insoluble, recristalization is not possible.
From what I found, PbO2 "could" be oxidized to Pb3O4 from air.
So Im trying this route to purify it:
Pb3O4 + HNO3 = Pb(NO3)2 + PbO2 + H2O
(Pb(NO3)2 is soluble in H2O)
After doing this, the resulting precipitate has the same color as the starting material. (black)
PbO2 should be dark red (this color was seen when disassembled the battery in some parts)
This means:
1) the process did not work?
2) the solution (Pb(NO3)2) was treated with HCL to try precipitating PbCl2 (as lead qualitative analysis) but no precipitate was seen. (maybe Pb(NO3)2
was very diluted. (Im doing this procedure in test tube scale)
3) the PbO2 was pure? (I doubt this)
the solution generated some heat (very mild), but was not heated. Maybe should be heated?
[Edited on 29-12-2022 by RU_KLO]
Junk_Enginerd - 29-12-2022 at 09:32
Purify how? What is your goal? To have as pure PbO2 as possible, or do you actually mean that you want lead metal?
If it's PbO2, then isn't it pure enough already? Any lead exposed in electrolysis or such will be oxidized to PbO2 regardless.
If it's metal you want, then simple reduction with carbon works just fine. The temperature required means a significant vapour pressure though, so be
very careful.
RU_KLO - 30-12-2022 at 04:08
I want Pb02 as pure as posible starting from PbO2 from batteries.
Bedlasky - 30-12-2022 at 08:31
I think that PbO2 from batteries should be reasonably pure. Purification really doesn't solve problem with Mn2+ oxidation.
If you want do this anyway, I would reduce PbO2 by H2O2 in acetic acid, filter any insoluble crap, then add stoichiometric amount of HCl to
precipitate PbCl2, put suspension in to the fridge to crush out more chloride. Then you can do one or two recrystallizations from hot water, after
cooling down to room temperature put beaker again in to the fridge. Then you can precipitate Pb(OH)2 with NH3, add few drops of phenolphtalein and add
NH3 until indicator change the colour. Filter, wash and transfer in to another beaker. Add NaClO and heat the suspension, this way you'll obtain PbO2.
Be aware of lead aerosol. You also create some lead containing waste.
[Edited on 30-12-2022 by Bedlasky]
maldi-tof - 11-2-2023 at 10:12
I also struggle with PbO2... what i did add the PbO2 in hot water with nitric acid, and do washings... trying to dissolve any soluble impurity it may
have. Then wash again with water until pH=4 or % of the washing water. Filter and dry.
Take care because this product is not easy to filter (i use sintered glass funnels), it's always a challenge to take it out.
teodor - 16-2-2023 at 02:29
Sometimes getting pure product from unpure product doesn't worth the efforts. But if you know which impurities are critical for your experiments you
can test for them and check whether your method of purification works.
Washing with HNO3 generally removes most of impurities.
With the method of Bedlasky you can get very pure material indeed but at the last stage I think it requires HNO3 washing anyway - typical NaClO has a
technical grade. Also I don't think you need separate stages of recrystallizing PbCl2 and isolating Pb(OH)2 - when I was making PbO2 from batteries I
mixed PbCl2 with NaOH and added ClO- at the same time, you what you need is just good mixing. I think it worked well with other oxidizers also, I
will check my lab records.
Edit: if I recall it properly the big challenge in getting analytical grade PbO2 is drying ...
[Edited on 16-2-2023 by teodor]