Fabrication, characterization, and adsorption studies of thermally modified peanut shell charcoal for Orange G dye removal

This study explored the adsorption of Orange G dye using peanut shell charcoal (PSC) as an adsorbent. The effects of the concentration of the dye, adsorption period, and pH were investigated. The physical structure of the prepared PSC was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, transmission electron microscope, energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller analysis. PSC was prepared by thermal treatment at 500 °C in the absence of air and then used to remove the dye from an aqueous medium. The optimum conditions for maximum dye adsorption were established, with the highest capacity of 97.20 mg/g obtained using an initial dye concentration of 200 mg/L, adsorbent dose of 1.66 g/L, temperature of at 25 °C, and adsorption period of 75 min. Dye adsorption increased with higher adsorbent doses, with 96.2% of the dye adsorbed using an initial dye concentration of 50 mg/L, adsorbent dose of 3.33 g/L, and temperature of 25 °C. According to thermodynamic study, the adsorption process was exothermic and spontaneous. The adsorption kinetics followed a pseudo-second-order model. Both the Freundlich and Langmuir models could explain the equilibrium data, but the Freundlich isotherm model gave a better fit for the data, which suggested that Orange G adsorption on PSC was primarily physisorption with multilayer formation. Importantly, this method is a green approach that is free from harmful chemicals. PSC is a viable and sustainable alternative to activated charcoal in adsorption applications.