I'm not completely understanding your question, but:

If the components do not crystallize from the water, you should consider using a different solvent, but if you really need to recovery the material from the water, azeotropic distillation with benzene or toluene will remove the water.

If they are crystals in an aqueous mother liquor, I would just collect them by filtration and wash the filter cake with cold isopropanol and then keep under high vacuum, over P2O5 for a couple hours. 

Brennan is right if your salt is not well soluble in water and just precipitates upon formation. However, if it is soluble, you will need to remove water. The best way is to use a vacuum rotary evaporator; you can use also a freeze-drier, but in this case drying process will be much longer. After the solvent is evaporated, you can remove the last traces of water. Instead of drying over P2O5, you can do that  by co-evaporating the residue 2-3 times with organic solvent able to form an azeotropic mixture with water, for example, acetonitrile. If you want, then you can obtain your salt in convenient crystalline form (or as amorphous, but still solid powder) by precipitation procedure, say, precipitate it from methanol into ether (it depends on solubility).

You could try two things:

1) Dissolve threonine and picric acid in minimal amount of hot water and then cool the solution so that the salt crystalizes.

An experimental procedure can be found here:

http://www.sciencedirect.com/science/article/pii/S1386142510002404

You could try to ask the authors of this paper for more details.

(the link is also attached to the post)

2) try preparing the salt in an organic solvent like dichloromethane or ethyl ecetate - the salt could precipitate easier from organic solvent and evaporation/drying would be easier than for water. However this can be hard because threonine can be poorly soluble in organic media.

http://www.sciencedirect.com/science/article/pii/S1386142510002404

You can take small portion of solution, add MeOH or Acetone to see if you can precipitate the salt.

Add until it begins to precipitate and then reheat to get clear solution and cool it. It should crystallize. Else refrigerate it.

you can only crystallize them for separation & drying purposes of both compounds.

If your means you want to omit solvents  you can use rotary instrument.

you can use Na2SO4 or MgSO4

you can use Rotary Evaporator and dry your material.

can i use heating mental for drying the solution?

 Jaydeep It is still not clear what do you mean by drying the solution.

Do you mean that you want to remove the solvent which can be done by simple distillation or vaccum distillation on heating mental or oil bath. Or simply by rotatory evaporation.

Or you want to crystallize your product. If you want to crystallize, you need to use minimal solvent. Simple method is suspend your compound in water (may be 2 times or 5 times of your compound like 2-5ml for 1 g) and heat it (usually reflux but varies from compound to compound).  And check if all the compound is dissolved or not. If not add little more solvent. Once you get the clear saturated solution. Remove the heating and let your compound stand at room temperature for the slow evaporation of the solvent (This may take days even month, if you want to get the good crystal). Your compound will crystallize out, which you can isolate by filtration.  

Find the attachment for your case of L-threonium picrate. They just dissolved the compounds in distilled water to get saturated solution, covered with aluminium foil (with few holes) and left at room temperature to grow the crystals

Best luck!

Do you mean that you want to remove the solvent which can be done by simple distillation or vaccum distillation on heating mental or oil bath.

use of drying agent as sodiyum sulphate or magnesium sulphate ahyd. for shaking filtering, in portions as possible,

recrystallise following the organic chemistry practical book (Vogel) for suitable solvents and crystals formation.