Hi Suraj,

Unfortunately there's not a great deal else you can do. If you attempt to evapourate the solution you'll just concentrate both the acid and the dissolved solids until they start to precipitate, which leaves you in the same position you're now in. It may reduce the overall volume of solution to be treated but you'll still need to neutralise something, likely with a similar amount of base and deal with a similar amount of solids generated in the practice. There would also be significant equipment required and you run the risk of generating hazardous vapours if trying to evapourate from solutions of increasing concentration.

You can control the neautralisation to produce solids with better solid/liquid separation characteristics if you control the neutralisation process (temperature/saturation of various phases/etc.), but there's no way of simply evapourating the entire solution without other treatment. Even if you could the vapour produced would be hazardous to the Environment as well.

If you want to improve the handling properties of the solid generated, look at literature around the precipitation of the various species you're generating for information on the best method for control.

Hope this helps.

Cheers,

Laurence

Thanks for your suggestion.

Thanks Laurence. kindly elaborate solid/liquid separation characteristics which I can use for minimum sludge generation during neutralization.

Hi Suraj,

Sorry, I'll clarify. If you control the neutralisation you can produce a solid that is much easier to handle and separate from the solution. By heating the solution and slowly neutralising the reaction you can improve the physical properties of the solids that you generate.

Cheers,

Laurence

We've used neutralization and precipitation of iron hydroxide solids followed by nano-micro bubble floc-flotation.  We do the whole process in a single-pass high shear reactor followed by a specially designed flotation column.  Dr. Rubio in Brazil has published articles on this method, even to the degree that he specifies bubble generator types and flocculants.  The shear reactor enables the iron solids chemical reaction to occur nearly instantaneously.     

Hi Suraj,

What are the iron and acid concentration? Perhaps I may give you little information on the use of sludge. 

regards,

Navneet

In our effluent (Spent Pickling Acid) acid content is 3-4% and Iron is 13-15%. 

Perhaps you can perform the neutralisation-precipation in suspended sand reactor.

I have had several thesis students that worked with this method in cooperation with Veolia. In this method iron precipitates in grains which are very dense compared to sludge. 

http://technomaps.veoliawatertechnologies.com/metclean/en/

Hi Suraj,

The following paper may be of some use to you for getting an overview on topic you asked about.

http://www.ipublishing.co.in/ijesarticles/thirteen/articles/volfour/EIJES41027.pdf

Further you can find more information on utilization of pickle liquor for making useful products as well as recovery of acid that has been carried out in our laboratory. Some of the publications made out of this work are given below.

Article Development of an Efficient Process for the Recovery of Zinc...

Article Investigation of a novel ionic liquid, Cyphos IL 104 for the...

Article Recovery of high value copper and zinc oxide powder from was...

Article Low temperature hydrothermal synthesis and characterization ...

Article Solvent extraction and separation of zinc and iron from spen...

Article Effective separation and recovery of hydrochloric acid and i...

All the best,

Navneet

If the Si content is low, you can use the Ferrite process (“P. Hererra et al., 2010. Minerals Engineering”) to recover something valuable from AMD. For sludge management, you can also opt to use the “high-density” sludge process. Good Luck!