So, I have been puzzling over this for the past couple of days. I have a 50/50 mixture of Hydrofluoric acid (48% wt) and Nitric acid (68% wt) and an
unknown amount of cobalt dissolved in the solution. I want to recover the cobalt as crystallized Cobalt Fluoride and Cobalt Nitrate and make it safer
for handling as an electrolyte solution (pH about 6). How would I achieve this? Thank you very much for your help!!! In a perfect world I would like
to re use the same acid solution to continue to use my process over and over, so if I could recover the cobalt in another manner that would leave the
acid unharmed and the cobalt removed I would be ok with that. Is there a liquid liquid extraction I could perform?elementcollector1 - 10-4-2014 at 11:28
With HF? Not too likely, it's nasty stuff. I would suggest distilling off your acids, as that would allow you to recover your cobalt and your acid,
but you need special equipment to distill HF - it'll just eat your glassware otherwise.
I would suggest adding more cobalt until the pH is roughly neutral, evaporating or boiling the mix of cobalt fluoride and nitrate down, and collecting
the assorted crystals.Brain&Force - 10-4-2014 at 16:26
Cobalt fluoride is only slightly soluble in water (14 g/L), so it would most likely crash out of solution. I don't know if cobalt(III) fluoride will
form, but it's a highly oxidizing brown solid that will produce oxygen in water.Dr.Bob - 11-4-2014 at 11:19
CoF3 will not form easily. It requires CoF2 + F2 to produce (or CoCl2). And it is very reactive, so not so easy to handle as some books suggest.
The good part is that you can recycle the CoF2 produced during fluorinations back to CoF3 with more fluorine, so it acts almost like a catalytic
source of F2.
And the hydrates are soluble, which is the likely salt form in water.
Cobalt(II) fluoride is a chemical compound with the formula (CoF2). It is a pink crystalline solid compound[1][2] which is antiferromagnetic at low
temperatures (TN=37.7 K)[3] The formula is given for both the red tetragonal crystal, (CoF2), and the tetrahydrate red orthogonal crystal,
(CoF2·4H2O). CoF2 is used in oxygen-sensitive fields, namely metal production. In low concentrations, it has public health uses. CoF2 is sparingly
soluble in water. The compound can be dissolved in warm mineral acid, and will decompose in boiling water. Yet the hydrate is water soluble,
especially the di-hydrate CoF2·2H2 O and tri-hydrate CoF2·3H2O forms of the compound. The hydrate will also decompose with heat.
So you might be able to ppt the Cobalt as the carbonate by titrating in sodium carbonate until the ppt stops, that would remove the cobalt, but your
acid strength will get weaker as well.
So, I have been puzzling over this for the past couple of days. I have a 50/50 mixture of Hydrofluoric acid (48% wt) and Nitric acid (68% wt) and an
unknown amount of cobalt dissolved in the solution.
Wow. Some guys have all the fun. I hope you realise just how potentially lethal 48 w% HF is. Some refuse to handle it without complete respiration
apparatus and full body protection.
