Separating Alloys

[elementcollector1]

Is it possible to take an alloy (e.g. stainless steel, solder) and separate it into its components? Could you melt each metal out, or what?

Help is appreciated.

[Greg Boyles]

I don't think you can seperate any mixture of elements or componds based on melting point. The mixture has a composite of physical properties of the two subtsances forming the mixture, of which melting point is one. When heated the mixture melts at the composite melting point and not differentially.

 

 

It might be possible to fractionally distill the alloy as is done with oil based hydrocarbons but the temperatures required would make such a process economically unviable.

 

 

Might be more practical to use such methods as differential dissolution in acids, e.g. seperating zinc and copper in brass with sulfuric acid. Or perhaps differential electrolysis. But neither would be economically viable on a large scale I suspect.

 

It would be more viable to standardise and regulate alloys as much as possible and then recycle them differentially.

 

 

Same with plastics.

[insane_alien]

you seperate them with different acids as greg suggested.

[Greg Boyles]

you seperate them with different acids as greg suggested.

 

I assume that it is theoretically possible to seperate alloys via fractional distillation.

 

you seperate them with different acids as greg suggested.

 

I believe differential electrolysis would work as well. For example, if you made an anode out of a lump of brass then I assume the zinc would ionize preferentially into solution and the copper would precipitate and possibly corrode depending on the electrolyte.

[elementcollector1]

So, what if I wanted to separate mischmetal?

It's about 50% cerium and 25% lanthanum, with the balance being small amounts of praseodymium, neodymium, and magnesium/iron oxide.

Preferentially, I would extract the cerium first, if possible.

[John Cuthber]

How good are you at practical chemistry?

[elementcollector1]

Not very, mainly because I don't know the exact definition of practical chemistry, other than economic use.

[Enthalpy]

Distillation is commonly used as the economical way to produce magnesium. Heat is needed anyway when reducing the metal from its ore.

 

Differential electrolysis is the way copper and aluminium are produced from the ores. Zinc and the easily oxidized elements stay in the bath, copper deposits on the electrodes. But I "doubt" electrolysis would be used on metals already reduced.

 

Common alloys are very much recycled, and production methods tell "introduce the recycled metal here" and "put the new metal there". When a factory uses copper or nickel, it separates its garbage from steel; when valuable steel is used in big quantities, its garbage is separated from unalloyed steel as it resells better. Same for plastics, if big quantities are used and produce garbage. But at the consumer's garbage bin, alloys are less sorted.

[elementcollector1]

Okay. So, what exactly is distillation? That sounds the most promising of the group.

[Greg Boyles]

Okay. So, what exactly is distillation? That sounds the most promising of the group.

 

Cerium has the third-longest liquid range of any element: 2648 C° (795 °C to 3443 °C)

 

I don't think so. You would require a temperature in excess of 3443 degrees celsius in order to vapourise Cerium. Is it even possible for the average commercial furnace to reach such temperatures?

Edited September 13, 2011 by Greg Boyles

[elementcollector1]

Probably not. I thought distillation in this case meant the separation of liquids and solids.

[elementcollector1]

Probably not. I thought distillation in this case meant the separation of liquids and solids.

 

So, seeing as acids seem the best way to go, what would be a good procedure for getting the chlorides of lanthanum and cerium separated from the mix? I could probably reduce these with lithium.

[John Cuthber]

How good are you at practical chemistry?

[elementcollector1]

I'm okay at it, but it really depends on what needs to be done.

[John Cuthber]

Unless you have the background and a fair amount of equipment it's going to be tricky.

The major components of stainless steel are iron, nickel and chromium so let's focus on them.

Start by dissolving the metal in hydrochloric acid. That's rather slow unless you heat it. So you want to boil the acid under reflux with the metal. I'd strongly recommend using the azeotropic concentration (about 20%). You would also need to do this outside or in a fume hood of some sort.

 

That will dissolve the metals as (mixed) Cr(II) and Cr(III), Ni(II), and Fe(II) salts.

Carefully add H2O2 to the solution to oxidise the Fe and Cr to the (III) ions, then boil the solution to destroy excess H2O2.

Boil off most of the water then remove most of the remaining water on a steam bath or a rotary evaporator.

Take the salts up into solution in conc HCl and extract with ether repeatedly to remove Fe(III). Evaporate off the ether from that phase and you will get FeCl3. If you want to convert that to the element then you can do so by dissolving it in water, adding ammonia solution to precipitate "Fe(OH)3", drying that and heating it in a stream of hydrogen.

 

The Ni and Cr will still be in solution in the aqueous acid.

Is it really worth my time typing up how to separate them?

[elementcollector1]

Alright, so the end products of that seem to be CrCl3 and NiCl2 in solution. So, how do I get just chromium chloride in solution? Because once I have that, I should be able to put zinc in there and get chromium metal due to a single displacement reaction, correct?

 

EDIT: Also, where do I get ether?

Edited October 19, 2011 by elementcollector1

[John Cuthber]

where do I get ether?

You probably don't.

That's my point. It simply isn't very practical unless you are prepared to spend a lot of time and effort learning the ins and outs of chemistry.

 

A more interesting answer than usual to the question could be that you can reduce the Cr(III) to Cr(II) with zinc and acid then precipitate it as the acetate.

[elementcollector1]

So, could I precipitate chromium as the metal at all, or would this require something along the lines of a thermite?

[horsebox]

Yeah of course you can but you'd have to deal with insanely high temperatures to do that. A better approach may be to convert the metals into compounds 1 at a time. For example theres a technique you can use to purify nickel where you react it with carbon monoxide to form nickel tetracarbonyl which is a gas.

[elementcollector1]

Right, well, I found a way to make small amounts of Cr2O3 with stainless steel by placing the object in salt water (for some reason, the stuff only forms directly above the water level). Nonetheless, anyone got a faster way?

Also, I'd rather not deal with carbon monoxide, or collect a nickel-containing gas, no offense.

[hypervalent_iodine]

Yeah of course you can but you'd have to deal with insanely high temperatures to do that. A better approach may be to convert the metals into compounds 1 at a time. For example theres a technique you can use to purify nickel where you react it with carbon monoxide to form nickel tetracarbonyl which is a gas.

 

Nickel tetracarbonyl is a liquid, albeit a volatile one (boiling point is around 43^oC). I really would not recommend making it as it for the purposes that elementcollector needs it for, as it is incredibly toxic at low concentrations.

[elementcollector1]

Really, what I would need then is chromium (III) oxide. I can make some of it from steel, but the process is long and doesn't give me much. Could I just burn powdered stainless steel and magnetize out the impurities when cooled?

[elementcollector1]

Really, what I would need then is chromium (III) oxide. I can make some of it from steel, but the process is long and doesn't give me much. Could I just burn powdered stainless steel and magnetize out the impurities when cooled?

 

Actually, I just got a good amount of chromium chloride in solution. Wikipedia says this is largely inert to substitution (displacement?), but it also says that if I add zinc while there is still some HCl in there, it will reduce the CrCl3 to CrCl2, thereby "carrying out the rest of the reaction with ease" or something like that.

Would this make chromium metal powder?