Sciencemadness Discussion Board

My zinc oxide not pure, have carbonate, can ZnO absorb CO2?

TmNhRhMgBrSe - 3-9-2021 at 05:56

people gived 2 parts ZnO me, I tryed mix ZnO and sulphuric acid to make zinc sulphate, have bubles come out, 1 part out more bubles, other part out less bubles, so I guess ZnO have zinc carbonate, not pure, and 1 part have more zinc carbonate, other part less zinc carbonate, so I guess only 2 possibility, one is people made ZnCO3, then burned it but not yet burned finish, so had ZnCO3 left, other is people made ZnO, then ZnO absorbed CO2, like lime water, then which more possible?

woelen - 3-9-2021 at 06:23

Both are possible.

Any really basic oxide can absorb CO2 from air. I have similar experience with CdO (a brown powder, which turned somewhat lighter on storage and now bubbles a little when added to acid).

ZnCO3, when heated insufficiently, or for a short time, certainly can have left-over carbonate in it.

Pumukli - 14-9-2021 at 08:18

I have old (20+ years) pharmacy grade ZnO stored in a paper bag. So it could have absorbed CO2 from air if wanted. But did not. So I assume ZnO does not absorb CO2 from air or not readily for sure.

Tsjerk - 14-9-2021 at 09:58

I think it depends on whether the oxide reacts with water from the air to form hydroxide, which would absorb CO2.

Triflic Acid - 14-9-2021 at 18:16

Might also be some sulphide contamination, did it smell like rotten eggs?

AJKOER - 1-12-2021 at 11:35

Be mindful on the source of your ZnO. For example, a paper "Cost-effective large-scale synthesis of ZnO photocatalyst with excellent performance for dye photodegradation" at . The abstract, to quote:

"Zinc oxide with excellent photocatalytic performance for the photodegradation of dyes (superior to Degussa P25 TiO2) could be easily prepared in large quantity by direct calcination of zinc acetate (Zn(Ac)2·2H2O)."

So, in the presence of a light source (especially UV rich) your ZnO may be a quite good photocatalyst depending on how it was prepared.

Implications, typically for a photocatalyst per a source (see where in the presence of any water, for example, to quote:

"Photocatalysts can produce hydroxyl radicals (OH•) and superoxide (•O2-) which are scavenger radicals produced from water when in contact with the photocatalyst. These scavenger radicals then nonselectively attack organic pollutants and degrade them ..."

Possible reactions include:

CO + OH• → CO2 +  H• (see )

So, CO2 also from any CO presence which leads to Zinc Hydrogen Carbonate (see discussion in this thesis ) and yes, eventually a carbonate (actually, per Wikipedia on Zinc carbonate, a "basic zinc carbonate (Zn5(CO3)2(OH)6)", see

[Edited on 1-12-2021 by AJKOER]

theAngryLittleBunny - 6-12-2021 at 15:14

From my experience it doesn't. I had like 150g of ZnO in a 1L container which isn't even air tight for probably 3 or 4 years. Recently I dissolved it in dilute H2SO4 to make some ZnSO4, when adding the ZnO it just disappeared with the solution heating up, no gas was evolved. To avoid any excess acid I would just use a bit of excess ZnO and add small amounts of acid until it was almost clear, then it could be filtered to get a clean solution. You could just assume that it is all ZnCO3 and add the stochiometric amount of acid to it, and then just add small portions of acid until it is almost gone (wait for 2 or 3 minutes between additions, ZnO seems to take a bit to fully react).