product may precipitate just by adding water only .or make it basic

A recommendable method for such a reduction is like this:

Dissolve 0.2 moles of nitro compound in 1000 ml of 90% aqueous ethanol (90% water + 10% EtOH), add 60 ml of glacial acetic acid and 100 -150  g of iron filings (= an excess). Reflux for 4 hours. Filter off iron oxide formed. Add 2 l of water and enough Na2CO3 to come above pH 7 (attention: foaming due to CO2 liberated!), likely your product will precipitate now. If so, just cool (if necessary) to RT and filter off product.

If a liquid amine is formed it could at this point be extracted and worked up.

Caution! Check if your diamine is stable against air oxidation. Ths happens rather often, especially in case of aromatic diamines.

But our product gets precipitated in the solution therefore we cannot do the filtration, otherwise it will stick to the wall of the filter paper and then there will be loss of the product.

If your product precipitates already during reduction together with the iron oxide formed, then both should be filtrated together, if possible by suction, then this should be "dried" by further suction or an the air, the filter cake should be extracted with a hot suitable organic solvent that will dissolve the reduction product but not the iron oxide, then the solvent should be removed from the extraxct and the crude amine should remain. The iron oxide undissolved can be discarded, the amine obtained further purified.

Make sure that really your amine precipitates and not its sulfate (you used H2SO4!)

Try if ethyl acetate is suitable for dissolving your product. I do not know the structure of diamine so any hint is impossible. On principle a lot of organic solvents should be suitable. In this case, a solvent with a comparably low bp is recommendable for the ease of removal form the organic extract at the end.

@ Dieter.....I dont understand the sulfate issue, can you tell me more about it 

Along with it I am getting one more problem as now it is not soluble in organic layer (especially in ethyl acetate)

i got a green solution can you tell me what is that?

You should say what dinitro compound you tried to reduced to what (expected) diamine, if you may say that.

Discussing about "green" is useless if there is no more information.

And whre is the green? In aqueous solution? or in organic? if so, in what organic solvent?

it is in aqueous solution

Once again: You cannot expect to get a hint if you nearly give no chemical information WHAT you want to reduce!  Therefore: You should say what dinitro compound you tried to reduced to what (expected) diamine - if not, advices are impossible.

There are some 2-nitrophenols that in the presence of iron may form 2-nitrosophenols that are able to form iron complexes such as the dystuff Soliddruckgruen.

With no more details from you the consultation will have to stop at this point.

Thanks Dieter...I am attaching the image of the reactant

@ Dieter, I already follow the reduction protocol but observed that the reduced product is in aqueous phase and only some extend soluble in organic phase, which could make me afraid of lowering the yield. Can you provide me some advice on that!!

Likely, you have formed the sulphate of your amine by this step. This salt should be soluble in "acidic water", of course. If you add now a base, such as NaOH solution or Na2CO3 solution until the solution is slightly alkaline, pH 9 or so, your amine should become insoluble in thsi "basic water" and precipitate as a soild (hopefully!) or as an oil (happens sometimes. Then, you could filter it off or extract it and purify it.

Hint: If you take Na2CO3 to make it forst neutral and then alkaline, it will decompose and give a foam of carbon dioxide. Be careful and use a big beaker to prevent over-foaming.

NaOH will not give CO2 od course but should be added carefully under pH control.

@ Dieter I will definitely gonna try this and you are quite right as last time the beaker gets over flooded by adding Na2 CO3 and we lost some of the product.

Thanks!!