In situ microwave-assisted oxidation of graphite into partially oxidized graphite nanoparticles for microwave-sorptive removal of anionic and cationic dyes

Abstract

In this work, partially oxidized graphite nanoparticles (POG-NPs) have been produced by the action of a green, fast, efficient and microwave-assisted heating process. In this approach, in situ etching of the carbon atoms on the surface of graphite was accomplished with hydrogen peroxide to produce POG-NPs and this was analyzed by SEM, HR-TEM, FTIR, TGA, XRD and BET. The HR-TEM analysis confirmed the conversion of graphite into nanosized range (21.8–34.18 nm). Removals of anionic congo red (CR) dye and cationic malachite green (MG) dye have undergone in very short time periods (5–25 s) with efficient microwave sorptive removal. The removal of CR and MG were found 56.94–98.74% using 5–25 s microwave heating time. Other parameters affecting on the microwave sorptive removal process of CR and MG were operated to reach the optimum removal conditions. The adsorption kinetic followed the pseudo-first-order (R2 = 0.941) for CR and pseudo-second-order (R2 = 0.985) for MG. The adsorption isotherm obeyed the Langmuir model (R2 = 0.968) for CR and Freundlich model (R2 = 0.952) for MG. Excellent removal adsorption capacities in real water specimens with high percentage >90% recovery from tap, sea and wastewater.