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separating mixed metal oxide fines (2 replies)

3 months ago
spanner 3 months ago

We are producing a mixed metal hydroxide cake principally containing magnesium, ferrous iron, aluminium, zinc, copper and manganese. There are also smaller volumes of chromium, barium, cadmium, nickel, Beryllium, cobalt, strontium. We need help to separate these metal hydroxides, preferably to high purity metals.

Can anyone assist us.

metal oxides
3 months ago
Wayne 3 months ago
1 like by David

Hi spanner,

What about dissolving in H2SO4 and doing selective pH and precipitate the hydroxides individually?

This may not work for all species as things like nickel and cobalt are very close in pH at precipitation although we have had some success with nickel cobalt separation using a solvent extraction post precipitation and re acidification.

I am thinking and although you can start to separate using pH not all will separate into the purities that I believe you would like. and unfortunately you will still run the gamut of a huge number of steps and techniques including sulfide precipitation, Pyro-metallurgy etc.

You can separate them but the question is at what cost?

Sorry I can't be of more help at this time.

Cheers, Wayne


3 months ago
jpearcy 3 months ago
1 like by David

This is a very complex problem, for which it is unlikely that an economical process could be proposed, because there are no noble metals that could justify the expense in a multistage metallurgical separation process. However, here are some ideas on a possible theoretical route to separating the metals.

1.- I would think that Aluminum powder could be added to the mixed metals oxides, so that at high temperature the aluminothermal reduction of all metal oxides, with the exeption of the Al2O3 and MgO would take place. Reduced metals and oxides would form two inmiscible liquid phases and a gas phase, so that Mg and Al oxides could be removed as slag, pure Zn would distill off as vapor and could be recovered by cooling and condensation, and the other metals would remain in the melt.

2.- The mixed molten metals could then be subject to chlorination, which would facilitate the fractional distillation of the various metal chlorides (chlorides boiling points are very different for different metals). These metal chlorides could be reduced to the respective metals by known processes. Need to check Ellingham diagram to decide which best applies for each one of these.

3.- The slag consisting of mixed Mg and Al oxides could be subject to reaction with HCl to selectively convert MgO into MgCl2, which is soluble, and could be separated from the Al2O3. Electrolysis of MgCl2(s) is a known commercial process. Note that HCl would be produced in case H2 was used for reduction for some of the metals in step (2) above.

Hope this helps, or at least serves to stimulate further thinking on this challenging problem.

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