When I had synthesized graphene oxide by improved Hummer's method I had got black precipitated at the residue.I think this may be graphite or potassium permanganate.How can I remove this?
Yes, you are right in Improved hummer's method , it may be due to potassium permanganate. Add More amount of Hydrogen Peroxide (H2O2) to remove the excessive KMnO4. So you get good dark brown colour GO precipitate.
You may want to check out the following article :
1. A Simple Approach to Stepwise Synthesis of Graphene Oxide Nanomaterial
Article A Simple Approach to Stepwise Synthesis of Graphene Oxide Nanomaterial
2. Synthesis and Characterization of Reduced Graphene Oxide (rGO) Started from Graphene Oxide (GO) Using the Tour Method with Different Parameters
Article Synthesis and Characterization of Reduced Graphene Oxide (rG...
3. Graphene Oxide: Strategies for Synthesis, Reduction and Frontier Applications
Article Graphene Oxide: Strategies for Synthesis, Reduction and Fron...
I hope this articles help and clear your doubts. Good luck with your research!