Eco-Friendly Large-Scale Production of Reduced Graphene Oxide (rGO) from Dry Coconut Shells for the Removal of Direct Blue 86 Pollutant

Abstract

In the current study, reduced graphene oxide (rGO) based on coconut shell waste was successfully synthesized using the carbonization method to remove Direct Blue 86 (DB86) pollutant dye from an aqueous solution. As per our knowledge, this is the first report where coconut shell-based rGO was used to remove DB86. Several state-of-the-art analytical techniques like XRD, XPS, UV–Vis, FTIR, Raman spectroscopy, BET, and TEM were performed to thoroughly characterize as-prepared rGO. The XRD analysis shows dominant peaks at 2θ of 23.39°, 43.15° and 46.40°. FTIR spectroscopy shows compounds' functional groups. XPS C1s spectrum shows a major peak at 284.6 eV corresponding to graphitic carbon and the sp²C shows a major peak at 283.2 eV. Raman spectra show the I_D/I_G intensity ratio of 0.73. Through HRTEM analysis the interplanar distance comes out to be 0.29 nm. The obtained specific surface area of rGO was ~273 m²/g using BET analysis. These analytical outcomes confirmed the formation of rGO. Further, the synthesized rGO was assessed for its dye removal efficacy using DB86 aqueous solution. The as-prepared rGO samples showed a significant dye removal efficiency of approximately 76% after 60 min of incubation, which might be due to the chemical interactions with dye molecules. The result of post-adsorption characterization study demonstrates that rGO almost retained its chemical properties, indicating its stability after adsorption. Subsequently, rGO can be successfully synthesized on a large scale using this renewable natural waste material (i.e., coconut shell waste) by carbonization method which could be used for wastewater treatment.