kamal
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Recovery of Catalysts
Hi friends ! 
I done a reduction reaction of a ketoxime using Zinc-Nickel couple to its amine. I made this couple insitu by dissolving first NiSO4 in conc. ammonia
solution & then adding zinc dust therein. According to the literature, nickel is reduced to a black precipitate while the zinc powder is oxidized
to soluble zinc salts (!!), and at the same time the finely divided nickel powder (!) reduces the organic substrate upon contact.
Here, I'm confused about the recovery of both of these catalysts..... I mean after the reaction, which salts I will get of Zinc & Nickel ? And how
can I recover both of these materials ? I actually don't know that which type of salt the Zn makes in this step & how it actually forms the couple
with Nickel........ 
Can you pls suggest me about proper recovery of both these catalysts ?
Awaiting your suggetions......
Regards, 
Kamal
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Nicodem
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They are not catalysts.
Zinc is used as a reducing agent and thus gets oxidized to its Zn(II) salts or in this case the salts of the [Zn(NH3)4]2+ complex. NiSO4 is reduced to
elemental Ni and thus is also consumed by the reaction. Most of the zinc salts and some Ni salts remain in the solution while its excess stays in the
solids together with Ni.
Catalysts are not reagents, that is, they do not get consumed or chemically modified in the reaction itself.
I'm curious on why you want to recycle such cheap chemicals?
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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kamal
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I want to recover these reagents because comparing to by wt. proportions for both, they are used over 6-8 times for complete conversion. And as I had
developed this proces for commercial scale, I have to recover them to set my economy due to the present severe hike in int'l prices of metals......
Again, I'm still confused after your reply.......
After the reaction completion, the solid metal particles remained in the reaction mixture (which I can filter out) would be of Ni & Zn metal both
? Which salts are present as soluble salts in the media ?
Pls revert......
Thanks,
Kamal
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Nicodem
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What you filtered off is mostly zinc coated with Ni (both elemental). These solid might be contaminated with some Zn salts, oxides and organic
remains. The salts and oxides can be removed by washing with dilluted ammonia and the organics with ethanol, isopropanol or whatever other apropriate,
cheap and inert solvent you have. Generaly you could use these remains for another reduction, perhaps even without adding another portion of NiSO4 or
adding less of it since there already is some. However, the yields might drop abruptly since this might be a system sensitive to small changes. You
would have to experiment a lot in order to devise a recycling methodology.
The mostly Zn and a little Ni salts/complexes in the filtrate are generaly not worth regenerating as this would require electrolysis and, due to the
low price of Zn powder, I suspect the process would not be worth unless on a really huge scale.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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