[mikeolesen]

This is an edit to my previous posting on the same subject.  I removed this topic from other sites to comply with rules for posting.  I feel this area may be best.

I am using heated (~140C) concentrated (98%) sulfuric acid to clean a part of organic films.  I follow this by rinsing with hot deionized water.  I end up with a mixture of H2SO4.H2O, with > 10% H2O.  My need is to remove as much of the water as possible by heating the mixture.  I would like to achieve < 10% H2O in the H2SO4. 
I originally thought I needed to get to 98%, however, that may not be possible by heating only. 

I can calculate the amount of wattage required to evaporate, for example, 1 liter of water per hour.  Using the same calculations, can I assume to be able to evaporate the same 1 liter/hr?  Or do the rules change, since I have a mixture where the temperature can be much hotter than water only?

I am considering two methods to do this, one would be to heat the full volume of acid and water mix and evaporate the water from the surface.  There would be a nitrogen flow above the bath to carry off the moisture.  The other would be to use heated plates where a thin film of the mixture would flow across the plate in the nitrogen atmosphere into a pool below at the correct concentration.  Give me your thoughts.

If someone can shed some light on this please do so and respond.

Thanks, Mike Olesen

[ARGOS++]

Dear MikeOleson;

In my opinion I would try to remove the water by heating the mixture in the vacuum.
Already a Water-Jet could do it to come close to 98% (= the azeotropic mixture), and you don’t need any Nitrogen for. For this method the required energy should also be less, but you have to try.
If I remember correctly already in earlier times Sulphuric acid (SA) was used as a generator for middle till high vacuum (also in a Jet but for SA!).
I’m not able to get all the necessary references at the moment.

Otherwise you could use a “Thin-film-Short-way”-Distillation and reuse as much energy as possible (Of course in the vacuum.).

I hope this will be of any help to you.

Kind Regards
                   ARGOS⁺⁺