Recently, green-prepared oxidized graphenes have attracted huge interest in water purification and wastewater treatment. Herein, reduced graphene oxide (rGO) was prepared by a scalable and eco-friendly method, and its potential use for the removal of methylene blue (MB) from water systems, was explored. The present work includes the green protocol to produce rGO and respective spectroscopical and morphological characterizations, as well as several kinetics, isotherms, and thermodynamic analyses to successfully demonstrate the adsorption of MB. The pseudo-second-order model was appropriated to describe the adsorption kinetics of MB onto rGO, suggesting an equilibrium time of 30 min. Otherwise, the Langmuir model was more suitable to describe the adsorption isotherms, indicating a maximum adsorption capacity of 121.95 mg g⁻¹ at 298 K. In addition, kinetics and thermodynamic analyses demonstrated that the adsorption of MB onto rGO can be treated as a mixed physisorption–chemisorption process described by H-bonding, electrostatic, and π $-$ π interactions. These results show the potential of green-prepared rGO to remove cationic dyes from wastewater systems.

The oxidative exfoliation of graphite is a promising approach to the large-scale production of graphene. Conventional oxidation of graphite essentially facilitates the exfoliation process; however, the oxidation procedure releases toxic gases and requires extensive, time-consuming steps of washing and reduction to convert exfoliated graphene oxide (GO) into reduced graphene oxide (rGO). Although toxic gases can be controlled by modifying chemical reactions, filtration, dialysis, and extensive sonication are unfavorable for large-scale production. Here, we report a complete, scalable, and green synthesis of GO, without NaNO₃, followed by reduction with citric acid (CA). This approach eliminates the generation of toxic gases, simplifies the washing steps, and reduces the time required to prepare rGO. To validate the proposed method, we present spectroscopical and morphological studies, using energy-dispersive X-ray spectroscopy (EDS), UV-visible spectroscopy, infrared spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Thermal gravimetric analysis (TGA) is used to analyze the thermal properties of GO and rGO. This eco-friendly method proposes a complete guideline protocol toward large-scale production of oxidized graphene, with potential applications in supercapacitors, fuel cells, composites, batteries, and biosensors.

In this study, we propose a novel approach to prepare few-layer graphene (FLG) dispersions, which is realized by exfoliating natural graphite flakes in a surfactant aqueous solution under hydrothermal treatment and liquid-phase exfoliation. In order to obtain stable and well-dispersed FLG dispersions, pristine graphite is hydrothermally expanded in a hexadecyltrimethylammonium bromide (CTAB) aqueous solution at 180 °C for 15 h, followed by sonication up to 3 h. In comparison to long-time sonication methods, the present method is significantly efficient, and most importantly, does not involve the use of an oxidizing agent and hazardous media, which will make it more competent in the scalable production of graphene.

A novel method is presented to prepare few-layer graphene (FLG) in N-methyl-2-pyrrolidinone (NMP) by using a simple, low-cost and energy-effective shear exfoliation assisted by zeolite and using a cappuccino mixer to produce shear. We propose that the exfoliation of natural graphite flakes can be achieved using inelastic collisions between graphite flakes and zeolite particles in a dynamic colloidal fluid. To confirm the exfoliation of FLG, spectroscopy and morphological studies are carried out using Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Additionally, the obtained graphene shows a linear flow of current and low resistance. The proposed method shows great promise for the industrial-scale synthesis of high-quality graphene with potential applications in future graphene-based devices, and furthermore, this method can be extended to exfoliate inorganic layered materials such as BN and MoS₂.