Sciencemadness Discussion Board

Recovery of Pb and NaOH from Sodium Plumbite

almaslang - 18-3-2008 at 15:37

Hello There, anyone knows how to separate Pb from Na2PbO2... I was thinking maybe it is possible to extract Pb from Na2PbO2 and have a remaining solution of NaOH... help please

WizardX - 18-3-2008 at 16:07

http://en.wikipedia.org/wiki/Lead%28II%29_oxide

PbO is amphoteric, which means that it reacts with both acids and with bases. With acids, it forms salts of Pb2+ via the intermediacy of oxo clusters such as [Pb6O(OH)6]4+. With strong base, PbO dissolves to form plumbite(II) salts:[1] PbO + H2O + OH- → [Pb(OH)3]-

Na2PbO2ยท3H2O A toxic, corrosive solution of lead oxide (litharge) in sodium hydroxide; used (as doctor solution) to sweeten gasoline. The plumbite ion is Pb(OH)3−, or similar.

There are plumbite compounds, for example, sodium plumbite, Na2PbO2.

Plumbite ion may be formed by adding strong base to plumbous hydroxide.

Plumbite ion is a weak reducing agent.


Therefore adding a strong (concentrated) acid to a Na2PbO2 solution will force lead oxide, PbO to precipitate when pH is neutral.

[Edited on 19-3-2008 by WizardX]

almaslang - 18-3-2008 at 17:23

Thanks, I'm also thinking of adding elemental sulfur to precipitate the Pb as PbS, but I doubt if the PbS precipitate will be stable as solid in that solution. When added with acid, what will happen with the remaining solution? Is it possible to recover the NaOH?
I forgot to mention that I used NaOH to remove the PbO that adhered on some plastic tailings. Now I want to separate the NaOH and Pb from my resulting solution which is Sodium Plumbite. So I could reuse the NaOH for another cycle of treatment

chemoleo - 18-3-2008 at 17:30

You could convert the plumbite with HCl to PbCl2 and NaCl.
The PbCl2 dissolves badly in H2O, so you can filter it off (fine white crystals).
Then, dissolve the PbCl2 in NaOH, stoichiometric so as to generate Pb(OH)2 which again is insoluble. For this purpose the PbCl2 needs to be finely powdered in the first place to ensure complete conversion. The Pb(OH)2 can be roasted on a flame to PbO (and carbonate). From this you can make any Pb2+ compound. Do you seek to get metallic lead from Pb2+? Or just soluble, Na free Pb2+?

Alternatively you can use other acids than HCl. Such as HNO3, the lead salt of which is soluble. Precipitate the Pb(OH)2 with NaOH (stoichiometric) as before.

almaslang - 18-3-2008 at 17:40

I will be trying those reactions and do a cost estimate.

I just need a Na free Pb2+, and a nearly pure NaOH

WizardX - 18-3-2008 at 18:42

Quote:
Originally posted by almaslang
I will be trying those reactions and do a cost estimate.

I just need a Na free Pb2+, and a nearly pure NaOH


Either this reaction 3 PbO + 2 NH3 ==> N2 + 3 H2O + 3 Pb when you precipitate PbO

OR

Electrolysis of plumbite ion is Pb(OH)3−

almaslang - 23-3-2008 at 16:02

Quote:
Originally posted by WizardX
Quote:
Originally posted by almaslang
I will be trying those reactions and do a cost estimate.

I just need a Na free Pb2+, and a nearly pure NaOH


Either this reaction 3 PbO + 2 NH3 ==> N2 + 3 H2O + 3 Pb when you precipitate PbO

OR

Electrolysis of plumbite ion is Pb(OH)3−


How will Pb and NaOH separate thru electrolysis?

AJKOER - 18-5-2011 at 07:18

Are you sure about the reaction: 3 PbO + 2 NH3 ==> N2 + 3 H2O + 3 Pb

or is it possible: 3 PbO + 2 NH3 ==> Pb3N2 + 3 H2O

as an intermediate (or completely under certain conditions)?

That is, just Lead or Lead(II) Nitride!!? Both reactions are generic examples of the reaction of NH3 with metal oxides (MxO):

NH3 + MxO ==> H2O + M (or MN) + N (unless MN) + NO (unless N or MN formed)

There may, however, be a bang of a difference as the lead nitride is most likely unstable, possibly explosive?

AJKOER - 21-5-2011 at 17:52

Lead Nitride apparently does exists but per "Bretherick's Handbook of reactive chemical hazards", Pb3N2 is very unstable and explosively decomposes on vacuum degassing.

To return on topic, to recover Pb and NaOH, a creative suggestion, do NOT use HCl use HClO2 (or HClO3 and reduce the product with H2O2).

Logic, adding HClO2 to Na2PbO2 will yield either NaClO or NaClO2. This supposition is based on the following reaction in my notes:

Cl2O + PbO = Cl2 + PbO2

And, as the Cl2O, Dichlorine Monoxide, is the anhydride of HClO, by using HClO2 instead, we are more likely to produce some sodium hypochlorite (or chlorite) instead of the stable sodium chloride as implied by the above reaction.

Upon displacing into more unstable basic hypochlorites or chlorites (for example, Ag, Fe, Cu, Zn, NH4,..), one is more likely to recover NaOH more easily than from a stable chloride.

Pb recovery proceeds as previously suggested.

Problem solved, perhaps.

CAUTION: Some of the hypochlorites listed can be extremely unstable (even explosive). Take appropriate precautions.

Fluorite - 18-2-2021 at 14:01

Lead should behave similarly to zinc in sodium zincate solution and can be electrolysed to Zn and sodium hydroxide
Watch nurdrage zinc powder from zinc oxide video

Texium - 18-2-2021 at 14:58

Quote: Originally posted by Fluorite  
Lead should behave similarly to zinc in sodium zincate solution and can be electrolysed to Zn and sodium hydroxide
Watch nurdrage zinc powder from zinc oxide video
This thread is literally ten years old

njl - 19-2-2021 at 08:11

Fluorite loves 10 year olds I guess

zed - 19-2-2021 at 12:29

We grow older, the questions are answered only gradually.