chief
National Hazard
Posts: 630
Registered: 19-7-2007
Member Is Offline
Mood: No Mood
|
|
Separating Chromium out of electrolytically corroded stainless steel
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
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
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
National Hazard
Posts: 630
Registered: 19-7-2007
Member Is Offline
Mood: No Mood
|
|
The washing-machine alloy is said to contain up to 20 or 30 % chromium ...
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
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
National Hazard
Posts: 630
Registered: 19-7-2007
Member Is Offline
Mood: No Mood
|
|
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
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
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
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
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.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
