I'd be using hydrochloric acid. There can be no universal recipe for concentration or temperature.  Health and safety considerations are paramount but HCl is decidedly less of a problem than HF.

I'd be using hydrochloric acid. There can be no universal recipe for concentration or temperature.  Health and safety considerations are paramount but HCl is decidedly less of a problem than HF.

I agree with Alan. You might want to try various HCl concentrations, up to about 6M.  If room temperature doesn't work after some stirring or other type of mixing, try gentle warming. Boiling (under a fume hood) might be needed for some samples.

BTW, I forgot to mention the obvious in my initial reply. HF digests silica....

The idea was to leave silica behind from the question...

Yeah, I tried it with several concentrations of HCl at several temperatures. It dissolves when concentration and temperature are moderately high. Thanks for the tips.

You could also try HNO3. The advantage of HNO3 over HCl is that it will decompose more easily in a possible calcination process of either your powder or in case you want to "concentrate" the Fe-solution at one point in time.

Yeah! An interesting Suggestion. Thank you Prof. Giesche. Ill try that too.

@ Sandun   BTW, the correct English is 'I want to' not 'I wanna' .  Nitric acid is also a possibility as Herbert indicates - however under certain circumstances one gets passivation of the iron and iron oxide surfaces resulting in reduced or zero rate of solubility.  This is hard to predict when or if it will occur but it's happened to me with ore analysis by AAS.

i agree with researchers/professors about HCl/HNO3 acids for iron remval from quartz.For lab studies it appears ok, where as from indutrial point waste acid disposal looks problamatic i feel.Converting these free acids to solid waste is expensive process.

If Fe in minor quantity, one can try dil. oxalic acid.

But, from EHS point of waste acid disposal, one can think of H2SO4 at certain concn. & heat if iron is in minor quantities in Quartz, acid can be easily converted to gypsum for disposal/ or finds use to some industry.

Sice it is powder material. The best way is to separate iron by simple physical separation such as magnetic separation technique, which can be dry or wet for bettter results.

This can give directly iron oxide product.

i recommend this method than chemical route.

Indeed we can try out magnetic seperation if only magnetite (Fe3O4) is available. But this material is non magnetic(Fe2O3). I have found a method for the digestion. HCl in higher concentrations is the most effective acid for digestion. Thank you for all your answers.

Hello Sandun.

I think you are facing problem to dissolve iron in efficient manner, as you have mentioned it is a rock powder sample.

Therefore, you are facing problem to dissolve those iron which are encapsulated with silica matrix.

I am not sure about the facilities of analysis you have. If you can, then use microwave digestion using 0.1 to 0.2 g sample in HCl of volume 10 to 15 mL (with optional 1-2 mL HNO3), temp. 120 to 150 degree C and apply power around 400 to 500 W for 1 h duration. Keep some holding time on that condition.

It is obvious that you must put a blank reference whenever you put your sample for digestion. Follow the operational manual.

It'll work and hopefully you'll get desired result.

i think mixes of HCl+H2SO4 can help you

CEA will dissolve hematite - citric acid, EDTA, ascorbic acid. See papers by Joseph.

Those interested at this discussion may possibly want to check also: https://www.researchgate.net/post/How_can_I_remove_iron_oxide_from_teflon_paddle_stirrer