chief - 14-4-2009 at 03:36
Suppose one would want chromates or other chromium-compounds, and the chromium-source would be the parts of some old washing-machine.
==> Those parts could be corroded by using them as anode in a saltwater-solution (just abusing the chlorate-cell ..)
Then a maybe black fine powder would settle on the ground, containing the Iron/Chromium oxides/hydroxides ...
How would one now work this up, to get the iron out and keep the chromium-oxide/hydroxide (or the other way around) ?
[Edited on 14-4-2009 by chief]
not_important - 14-4-2009 at 04:00
What type of stainless steel? this determines the alloying elements and their amounts, so SS aren't worth processing for alloy metals.
There was a paper in Refs wanted-xlate some weeks ago, on making nanoparticles of Ni, Cu, &ct, using sugar as the reductant. Iron is in the
activity range of metals they used, chromium is much higher, so it might be practical to get everything into acid solution and ppt out the Fe &
Ni.
Or dump everything as hydrated oxides, mildly roast, extract with HCl to remove most iron, then use woelen's bromate process to get Cr as chromate
with Fe staying as hydroxide/oxide.
chief - 14-4-2009 at 04:02
The washing-machine alloy is said to contain up to 20 or 30 % chromium ...
not_important - 14-4-2009 at 04:11
Sounds a little high, 20% sounds to be maximum to me, and you need to know how much nickle and molybdenum is in the steel.
chief - 14-4-2009 at 04:45
There is a table at the bottom of this page:
http://en.wikipedia.org/wiki/Stainless_steel
So 16-20% Cr is a common figure. Have you any better source of chromium than old stainless steel ? One washing-machine may give easily 0.5-1 kg worth
of pure chromium.
not_important - 14-4-2009 at 21:14
Note the nickle concentrations. Either the sugar reduction or oxidation with NaOCl if you can control the conditions correctly might selectively
remove nickle as well as iron. The point is that there are several alloying elements that need to be considered in the purification process, it does
help to know the exact alloy.
The alloys with high amounts of Cr and Ni might present passivation difficulties, although halides help prevent that.
Sedit - 14-4-2009 at 22:09
There is some brass fittings used for traps and faucets that IIRC is chrome plated. The joy of that would be it could be run as the electrode until
the plating wares to minimize contamination from the brass. It is relatively thick compared to most forms of plating but still probably not worth it
if you need large amounts of chromium product.