Sulfuric acid mainly intercalates into graphite layers and also helps to form diamanganese heptoxide (Mn2O7) when potassium permanganate reacts with sulfuric acid. This Mn2O7 is the active oxidizing species for graphite oxidation.

Sodium nitrate further enhances the oxidation on the basal plane of graphitic sheets

Hydrogen peroxide is used to remove/neutralize the potassium permanganate from the reaction system.

Check the following papers for details:

http://pubs.rsc.org/en/content/articlelanding/2014/ra/c4ra01019a#!divAbstract

http://pubs.acs.org/doi/abs/10.1021/nn500606a

Here in Egypt I hardly find Sodium nitrate , may I use another salt ???

You can use potassium nitrate......

i mean any thing rather than nitrate ...