I extracted about 0.5L of black gunk from several dry cells.
I then washed the gunk by shaking it vigorously with about its volume of water three times. Letting it settle each time to pour off the water. However
significant quantities of zinc and chloride remained to the extent that adding NOH produced a strong white precipitate and adding 16% sulphuric acid
to the gunk produced a strong smell of chlorine.
If I load the gunk in to a tall filter funnel and elute the soluble contaminates with a volume water equal to the volume of the gunk will that remove
more soluble contaminates than vigorously washing (as above) it with a volume of water equal the volume of the gunk?
Fidelmios - 24-11-2016 at 14:04
Multiple small washes beat out single washes of equal volume.BromicAcid - 24-11-2016 at 20:29
Multiple small washes beat out single washes of equal volume.
When I read this I pretty much nodded and agreed but then I realized that is only relevant for washing an insoluble phase to remove a component where
a partition coeffiecent balances the soluble component between the phases. In this case you're just washing a solid to remove zinc chloride. I have
to think that if you wash with 4 x 250 mL or 1 x 1L you're still dissolving the same 420 g of material if that is how much you have.
WG48, in your case I would ask if your solids are completely broken up so that you have the best contact with the washes (and don't trap any ZnCl2).
I think the washes should work fine, ZnCl2 is very soluble afterall. The only hangup is that you're going to have a little liquid in the solids every
time you decant, if you could filter the solids it would be good just for the sake of removing the small amount of liquid but it shouldn't matter that
much. Just don't skimp on the washes, the MnO2 is insoluble and thankfully water is cheap.
