Thermally reduced graphene: Synthesis, characterization and dye removal applications

Since its recent discovery, graphene has emerged as a promising material for a variety of applications. In this article, thermally reduced graphene (TRG) was produced by thermal exfoliation of graphite oxide; characterized using XRD, SEM, TEM, FTIR, XPS, BET, and elemental analysis; and used as an adsorbent to remove methyl orange (MO) dye from aqueous solution. Langmuir and Freundlich isotherm models are used to examine the nature of the adsorption process and the results indicate that MO adsorption on TRG can be described as monolayer type (Langmuir) adsorption. Moreover, the adsorption process is physical, spontaneous, and follows a second order kinetics as revealed by the analysis of the thermodynamic and kinetic data. Furthermore, the sorption capacity and the removal percentage strongly depend on the adsorbent-to-dye ratio, the solution pH and temperature. The current study indicates that graphene could be a very efficient adsorbent for removal of MO dye from colored-waters with a maximum sorption capacity of 100 mg of dye per g of TRG and a removal percentage of 98%. In addition, more than 80% of the adsorbed dye can be recovered and TRG can be regenerated and reused with no significant change in its sorption capacity.