Mechanochemical synthesis of graphitic carbon nitride/graphene oxide nanocomposites for dye sorption

The nanocomposites of graphitic carbon nitride supported on graphene oxide (g-C3N4/GO) were synthesized using the mechanochemical method, effectively leveraging the synergistic benefits of mechanical energy and chemical reactions. The sorption performance of g-C3N4/GO for methylene blue (MB) was explored using the Langmuir adsorption isotherm. The g-C3N4/GO nanocomposite exhibited a maximum sorption capacity (qmax) value of 116.41 +/- 5.46 mg g-1 for MB at pH 7, while GO and g-C3N4 displayed qmax values of 55.71 +/- 3.11 and 17.01 +/- 1.65 mg g-1, respectively. The superior qmax value of g-C3N4/GO was attributed to the mechano-chemical exfoliation of both GO and g-C3N4, resulting in its increased surface area and favorable surface char-acteristics. The highest sorption of MB on g-C3N4/GO was achieved at pH 10, with the qmax value of 191.20 +/- 9.94 mg g-1. Furthermore, g-C3N4/GO demonstrated good reusability, maintaining a removal efficiency of 92% after five consecutive sorption cycles of MB. The sorption process was spontaneous at all the tested temperatures. A positive Delta H0 value of 18.8 kJ mol-1 suggests that the sorption process is predominantly physisorption. In the case of the negatively charged methyl orange (MO), no sorption occurred on the g-C3N4/GO. A red shift of 22 nm in the lambda max of MO was instead observed due to the protonation of the azo group.