Mercaptoacetic acid-functionalized reduced graphene oxide for methylene blue removal

Chlorine in chlorine-functionalized reduced graphene oxide (ClRGO) was substituted by the mercaptoacetic acid, and mercaptoacetic acid-functionalized reduced graphene oxide (MRGO) was formed. Some chlorine atoms in the central of sheet were eliminated, and then the sheet was sequentially reduced. The sulfur content of MRGO is obviously lower than the chlorine content of ClRGO. Although mercaptoacetic acid is bigger than the chlorine, the average interlayer space of MRGO is smaller than ClRGO. The average interlayer space of graphitic material should be influenced by pillaring agent. The crystallization degree of MRGO is higher than ClRGO. The carboxylic group provides the graphene sheet with extra efficiency to accommodate adsorbate by providing extra binding sites on sheet to hold methylene blue between graphene sheets. The adsorption capacity for methylene blue is 180.4 mg/g, which is higher than that (78.2 mg/g) of RGO.