# How to conveniently separate Cd impurities from ZnO without contaminating it?

How could I separate Cd impurities from ZnO without contaminating it and without using overly expensive equipment or extremely dangerous solvents?

I don't want to contaminate it by introducing other heavy metals or being left with more than trace levels of undesired solvents.

I'd be fine losing some amount (say max 10-20%) of my ZnO in the process, if necessary.

Please ask me for any further clarity I could bring to this question.

I know nothing about this so I'd be happy with any contributions on how to easily separate any reasonable portion of $$\ce{Cd}$$ salts from $$\ce{ZnO}$$ in general (precipitating it out or solving it away from $$\ce{ZnO}$$ for instance). Cycling the zinc through a series of reaction and then back to ZnO would be fine also (if not leaving trace levels of anything biologically harmful).

• Have you thought of using a calutron? – A.K. Jun 27 at 22:23
• Purity of $\lt \pu{26 mg}/\pu{100 mL}$ of $\ce{Cd}$ salt in solution is okay? – Mathew Mahindaratne Jun 28 at 2:25
• @A.K. Hello A.K! I had actually never heard of calutron. I'll read about it! (though I'm not sure I can get access to the necessary equipment) – Veritas Jun 28 at 4:52
• @MathewMahindaratne 26 mg/100 mL may be a little bit too high. My target end result should at the very minimum be under 5ppm of dry product, preferably <0.5 ppm. Though this doesn't need to be a one step process, and I welcome any measure that can allow me to conveniently separate some amount of Cd salts from my ZnO samples (I can then look at all the separation possibilities and make up the right process based on the equipment I need and my requirements) – Veritas Jun 28 at 4:57
• Think about treating it with caustic to form a zincate ... crystallise to remove Cd dwc.knaw.nl/DL/publications/PU00011954.pdf add the pure zincate to water to dissolve and adjust pH of slurry / solution to return zinc oxide. That's how I'd start, there are most probably cleverer ways of doing it. And if you keep your waste liquors it may be worth attempting a different purification of them. Hope this helps. – user1945827 Jul 2 at 12:35