Hi All,

 

I mixed bauxite (aluminum ore contained 50% Al2O3 and 13% Fe2O3) with strong Sulfuric Acid/H2SO4. We all know both Al2O3 and Fe2O3 soluble in Sulfuric Acid. My question is : how to precipitate Fe2O3 alone, and let Al2O3 be soluble in sulfuric acid??

 

What to add?? Or how to treat??

 

Thanks in advance for your kind helps.

Anyone willing to help??

willing, but not able, in my case. I don't know the relative solubilities of Fe2O3 and Al2O3, although if you look up their Ksp values, that'd help you calculate which one will precipitate first and how much will be left when the second one starts to precipitate.

 

Look up "solubility product constant" on wikipedia and see what you get. if it seems to be something you want to persue, let me know and i'll try to help you along the way. i should warn you, though, sometimes it's not feasible to separate mixtures like this.

I can`t think of anyway to get the Oxide out with a single wet chem rxn.

Hydroxide or Carbonate perhaps, and then heating the dry ppt to decompose seems to be the only route I can think of right now.

although Iron Sulphate will undergo ariel oxidation and decompose directly into the oxide given time.

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should have used HCl instead of sulphuric, it would have been loads easier

If you carefully add an excess of NaOH you will disolve the Al as sodium aluminate and leave the iron as "Fe(OH)3".

It would have been easier to dissolve the bauxite in NaOH to begin with.

why dont remove Fe by complexing with CNS etc and converting it to Fe2O3 later after seperation

Thanks, but would you please elaborate how to CNS it??

 

 

why dont remove Fe by complexing with CNS etc and converting it to Fe2O3 later after seperation

Do you mean thiocyanate complexation? That will only keep the iron dissolved. The thiocyanate is quite expensive too. John Cuthber has the right idea I think.

By dissolving it in caustic soda, NaOH, it is true that Fe will not soluble. But this Bayer process will take time, energy and cost. I want to be more economic way...

 

 

Do you mean thiocyanate complexation? That will only keep the iron dissolved. The thiocyanate is quite expensive too. John Cuthber has the right idea I think.

one can use simple centrifuge machines to seperate thiocyanide complex along with unsoluble impurities. now solid mass obtained can again be addded in appropriate solvent to remove unsoluble impurities. i dont know the cost related factors as i havent brought any chemicals till now . college lab does it for us. what about some electrochemical way to get iron or aluminium out.

reduction potentials:-

Fe2+ to Fe =-.044v

Fe3+ to Fe =-.036v

Al3+ to Al =-1.66 v

hence take the solution containing both Al and Fe take Al electrode as anode Fe electrode as cathode and apply potential difference greater then 1.5 v. i think iron will seperate out by depositing on Fe electrode.

though expert comments invited

amit , don't you think so that these is highly exothermic reaction .

nope as i believe its in aquous medium

Excellent....

But any cheaper way??

 

 

one can use simple centrifuge machines to seperate thiocyanide complex along with unsoluble impurities. now solid mass obtained can again be addded in appropriate solvent to remove unsoluble impurities. i dont know the cost related factors as i havent brought any chemicals till now . college lab does it for us. what about some electrochemical way to get iron or aluminium out.

reduction potentials:-

Fe2+ to Fe =-.044v

Fe3+ to Fe =-.036v

Al3+ to Al =-1.66 v

hence take the solution containing both Al and Fe take Al electrode as anode Fe electrode as cathode and apply potential difference greater then 1.5 v. i think iron will seperate out by depositing on Fe electrode.

though expert comments invited

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Just curious and need your opinion.

If I add excess iron sulfate salt, to make iron to be saturated. Will it be (iron) be precipitate??

dont rush on any thing i will be more than happy if some expert comment on above method(electrolysis). i dont think we can precipitate iron as such as after some time FeSO4 will be no more soluble. or crystallization may follow but ppt of iron i dont think so

If there were an easier, more ecconomical way of doing it, they wouldn't use the Bayer process.

The electrochemical process might work reasonably well but you need to realise that as the concentration of iron in the solution falls the voltage needed to reduce it will rise. At some pont you will reach a potential where it's easier to reduce water to hydrogen so you won't remove all the iron