Plant Sources-Based Facile Synthesis of Reduced Graphene Oxide (rGO) as an Efficient Adsorbent for the Removal of Organic Dyes

Graphene and its derivatives are currently a highly popular subject of research in the field of carbon nanomaterials. Reduced graphene oxide (rGO) is a form of graphene oxide (GO) that has been reduced, resulting in a few layers with minimal functionalities. There is a growing need for sustainable synthesis of reduced graphene oxide (rGO) because of its remarkable properties and wide range of potential applications in different fields. This study presents a simple and environmentally friendly method for producing reduced graphene oxide (rGO) by reducing graphene oxide (GO) with the help of Citrus Sinensis peel extract as a natural reducing agent. To enhance the synthetic conditions, the authors conducted the reactions by modifying various reaction parameters, specifically, time and pH. Following that, the ideal condition was utilized to create the most effective material for further examination. The synthesized material underwent various characterization techniques including UV-Vis spectrophotometry, FT-IR spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, and Thermogravimetric (TG) analysis. The successful removal of oxygen-containing functionalities in GO was verified through the analysis of UV-Vis, FT-IR, and XRD. Through the successful reduction of GO, the formation of rGO was confirmed by restoring the C=C group and reducing various oxygen-containing groups. The SEM analysis confirmed the successful formation of exfoliated and separated few layers of rGO nano-sheets. The adsorption efficacy of the obtained rGO was evaluated using Methylene Blue (MB) as a model dye. The dye removal activity and adsorption efficiency were monitored using UV-Vis spectroscopy. For the study of the adsorption kinetics of MB on rGO, two different models were used: the pseudo-first-order, and pseudo-second-order. The obtained data showed that the pseudo-second-order kinetic model provided the best fit. Furthermore, the analysis of kinetics revealed that the adsorption of MB onto rGO can be considered as a mechanism involving chemical bonding. This can be attributed to the increased surface area of the obtained rGO, as well as the presence of H-bonding, electrostatic, and π − π interactions. All of these factors contribute to the effective removal of Methylene Blue (MB) dye. Similarly, for the isotherm study, the Langmuir, Freundlich, and Temkin isotherm models were employed. It was found that the Langmuir model exhibited the best fit. In the case of Langmuir isotherm, a high adsorption capacity of 89.23 mg/g was found. The result suggests that the surface of rGO is uniform, allowing for the adsorption of a single layer. It is anticipated that the environmentally friendly approach could serve as a viable alternative to traditional chemical methods. Additionally, the synthesized rGO shows great potential as a material for effectively cost-effectively treating industrial wastewater. With its immense potential, this environmentally friendly and affordable method offers a promising opportunity for the mass production of rGO.

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