# How can one reclaim isotopic cadmium from a solution of acid, i.e. H2SO4 or HCl etc.?

I have dissolved isotopic cadmium-114 with $$\ce{H2SO4}$$ and or $$\ce{HCl}$$. Now that I have the cadmium-114 in solution, precipitating out $$\ce{CdSO4}$$ and or $$\ce{CdCl2}$$, how can I reduce these simply to leave the pure cadmium metal isotope? I have dissolved $$\ce{^{114}Cd}$$ with acid in very complex electronic tubes and I wish to reduce the precipitated compound(s) to pure metal for reuse.

$$\ce{^{114}Cd}$$ or is running about \$ 1,500 per gram. So extremely useful to reclaim it. Can anyone tell me a simple way to do this?

• What is "isotopic" cadmium? – Karl Jun 6 '20 at 7:06
• What "isotopic cadmium"? There are several isotopes of cadmium. Which one? – Nilay Ghosh Jun 6 '20 at 7:37
• The usual way is electrolytic from a solution of the sulfate, Al as anode. – Karl Jun 6 '20 at 10:26
• Again, Thank you everyone for your responses. I am a Laser manufacture and also a plasma tube re-furbisher where possible. I make new tubes, however, they are very complex glass work. So, saving a tube when possible is economical. The Helium Cadmium Laser gains 30% more power by using a single isotope of Cadmium. Cd114 is the best option and produces the most usable power, especially on 325nm UV lines. 441.6nm lines are not as sensitive but do benefit. I have no need of Cd salts. Just pure metal. Cleaning the tubes for reuse is a standard process. So, dissolving the Cd out of the tube is on st – Dale Harder Jun 6 '20 at 20:01
• I´m not sure that you will find a procedure in the literature that is well suited to your application. But you surely have a lot of contacts into academia. Talk to one who has a wire into inorganic chemistry, convince them to write a small grant application for a one-year project to devise a safe and efficient small scale electrolytic Cd recycling process. There are a lot of good buzzwords in the subject. ;-) – Karl Jun 6 '20 at 22:41

Thank you everyone for the discussion. Sorry, I have been away for a few days, so was unable to follow up. Reading the ideas, it is a toss up on a procedure. Scraping the Cd off of an Aluminum electrode might work, but Al contamination would be very bad for the laser oscillation. It might work for awhile, but would die from contaminants in short order.

The Al oxide, though only a molecular layer, is extremely tough and can withstand a great deal of heat and abuse. I make Aluminum edge-wound voice coils for my speaker company and we depend on the oxide layer to act as an insulator from winding to winding. Our coils can withstand 600 degrees and will melt before they fail.

Stripping the oxide gives you only a few seconds before it reforms in the normal atmosphere. Any other thoughts? Perhaps reduction of the salt by heating?

Thanks Dale

• Perhaps the answer lies here...I understand a lot of it, but not everything. Please look. onlinelibrary.wiley.com/doi/pdf/10.1002/pip.402 Thanks, Dale. – user94922 Jun 15 '20 at 4:19
• The reference is paywalled. In the old days, electrolysis into a mercury cathode, followed by distilling the mercury off, might have been done. Of course, nowadays that would be something only for a specialist laboratory. But maybe use a glassy carbon cathode? Then no aluminum to contaminate the cadmium. – Ed V Jul 15 '20 at 12:26

From a solution of an aqueous cadmium salt ($$\ce{CdSO4}$$ or $$\ce{CdCl2}$$), try inserting a metal plate of say Aluminum.

With time and warming of the solution, a coating of cadmium should appear on the metal sheet.

Try scrapping off the deposited cadmium metal, per the replacement reaction:

[EDIT]$$\ce{2 Al(s) + 3 CdSO4 (aq) -> 3 Cd (s) + Al2(SO4)3 (aq)}$$

Note: depending on your tools for scrapping, you may induce some metallic impurities.

[EDIT] Importantly, my standard chemistry approach (based on a single-displacement reaction) is different from an electrolysis or electrochemical cell approach, employing an Aluminum electrode, as I suspect, that the electrode may quickly become coated and effectively inoperative. Also, an electrochemical cell with a large surface area anode (here Al) would require an even larger surface area cathode to operate efficiently. Further, the ability to facilely recover the Cd metal is key to the cadmium recycling process. My proposed process may fulfill these requirements.

• @ Ajkoer 1) Your equation is wrong ! You would need 3 CdSO4 to balance the equation. And it would produce Al2(SO4)3. 2) Are you sure that this reaction works ? Usually aluminum is covered by a protective layer of aluminum oxide, which prevents the metal from touching the solution. If it does it does not produce aluminum sulfite... – Maurice Jun 7 '20 at 10:25
• Thanks, I worked on it late and was originally thinking of using CdCl2. Will edit. However, more fundamental does my path work in practice? – AJKOER Jun 7 '20 at 14:03
• Why would cadmium ions not get reduced on a Cd cathode in electrochemical cell? And why should Al be used as a cathode in the first place? – Karl Jun 7 '20 at 17:12
• Cadmium can be reduced by metals like zinc and magnesium. With aluminum, it will be theoretically possible, if the protective layer of aluminum oxide would be removed. This protective layer is transparent, continuous and nearly insoluble in diluted acids. That is why for example Aluminum is used as container for handling concentrated nitric acid. The alumina layer protects the metals from corrosion. I don't know how aluminum behaves with cadmium salts. But I think there will be no reaction, because of the protective layer of alumina. Anyway cadmium may be reduced by electrolysis. – Maurice Jun 7 '20 at 19:25