Enhancing Graphene Oxide Production and Its Efficacy in Adsorbing Crystal Violet: An In-Depth Study of Thermodynamics, Kinetics, and DFT Analysis

Abstract

The textile industry’s waste often contains excessive amounts of crystal violet (CV), leading to environmental concerns. Graphene oxide has been studied as a promising adsorbent for removing crystal violet, a cationic dye, from aqueous solutions. The study involved a comprehensive analysis of various experimental parameters, including initial concentration, pH, adsorbent mass, contact time, and temperature. Graphene oxide underwent thorough analysis using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and specific surface area determination via the Brunauer–Emmett–Teller (BET) method. Energy-dispersive X-ray spectroscopy (EDS) was also employed. This study aimed to optimize the synthesis yield of graphene oxide from graphite using the Hummers method and response surface methodology (RSM), achieving a yield of 106.14% with 5 g of KMnO4 and 1 g of NaNO3 for 8 hours. The graphene oxide was analyzed via FTIR, XRD, SEM, BET, pHpzc, and EDS. Optimal conditions for maximal adsorption included 0.016 g of graphene oxide, 18 minutes of contact time, pH 10, and a temperature of 25°C, resulting in a 97.38% reduction in crystal violet with a monolayer adsorption capacity of 470.78 mg/g. Kinetic data were best fitted by the pseudosecond-order model, and the Langmuir isotherm accurately depicted adsorption. Thermodynamic analysis indicated spontaneous (ΔG° < 0) and exothermic (ΔH° < 0) crystal violet adsorption. Density functional theory (DFT) explored interactions between graphene oxide and crystal violet, supporting experimental findings and confirming graphene oxide’s efficacy as an adsorbent for crystal violet removal from aqueous solutions.