Instead of typing here, type in GOOGLE. You will get humpty number of  papers on GO synthesis.

Quite simple. Just follow Tour's method using phosphoric acid. This is even better and simpler than Hummers' method.

Hi Md Osim Aquatar

Please, find in attach a paper on: A Simple Approach to Stepwise Synthesis of Graphene Oxide Nanomaterial Paulchamy B1, Arthi G2 and Lignesh BD3. Paulchamy B1, Arthi G2 and Lignesh BD3.Paulchamy et al., J Nanomed Nanotechnol 2015, 6:1

http://dx.doi.org/10.4172/2157-7439.1000253

Best wishes

modified hummer method is prevalent procedure for synthesis of GO . you can follow attached file.

 How to purify Graphene Oxide if don't have centrifuge?

Dear er Jaafar

You find below an abstract of this paper: Scale-up and purification of graphite oxide as intermediate for functionalized graphene Folke Johannes Tölle, Karlheinz Gamp, Rolf Mülhaup.Published in Carbon, Volume 75, August 2014, Pages 432–442

Abstract

High purity graphite oxide (GO) and scale-up of GO synthesis is in high demand for enabling GO applications in catalysis and the synthesis of functionalized carbon nanomaterials. Although Hummers method, which involves oxidizing graphite with KMnO4 in sulfuric acid, is highly attractive with respect to its cost-effective raw materials and low energy demand, still purification, scale-up and safety problems prompt numerous challenges in large scale production. Conventional dead-end-filtration (DE) is difficult, owing to the severe plugging of the filters by water-swollen GO, whereas dialysis requires massive amounts of water. Plugging problems are solved when using membrane separation with average membrane pores smaller than the lateral micrometer dimensions of GO nanoplatelets. In contrast to DE and dialysis, a short DE prefiltration of acidified GO dispersions, combined with subsequent cross-flow filtration (CF) enables easy GO scale-up and production of high purity GO. Equipped with on-line monitoring of waste-water, this CF process is automated and enables concentration of GO dispersions in the final stage. In GO purification, pH switching represents the key to removing Mn and S impurities.

Best wishes

Very easy way for Graphene Oxide synthesis,

http://instanano.com/nanomaterial-synthesis/carbon-nanomaterial/easy-synthesis-of-high-quality-graphene-oxide-new-method/

The answer added by Dheeraj Kumar is useful.