Adsorption of Methylene Blue Using As-Developed Binderless Hot-Pressed Granular Activated Carbon Derived from Sugarcane Bagasse Residues

Abstract

This study aims to develop sugarcane bagasse-derived granular activated carbon (SCB-GAC) as a biobased adsorbent for methylene blue (MB) adsorption in an aqueous solution using a binderless hot-pressed (HP) technique. HP conditions, i.e., mechanical pressure, temperature, and holding time, were systematically fine-tuned to first produce HP-SCB pellets. HP pellets were further carbonized at 500 °C for 1 h to obtain biochar pellets, which were cut into granules prior to activation with steam under the optimum conditions of 850 °C for 30 min. The mechanical pressure showed the most significant influence on the yield and textural properties of the as-developed HP-SCB-GAC. The optimal HP condition of 20 MPa at 270 °C for 30 min resulted in a substantial yield (53.7%) of the developed HP-SCB-GAC with uniform surface texture possessing the highest strength and specific surface area (804.6 m²/g). The MB adsorption using the selected HP-SCB-GAC showed minimal sensitivity to pH adjustments. The maximum MB adsorption capacity at approximately 138 mg/g could be achieved and fitted with the pseudo-second-order kinetic model and Langmuir equilibrium isotherm behaviors. The selected HP-SCB-GAC could reach as high as 87–92% of MB adsorption efficiency for at least five consecutive cycles using ethanol as the regenerant.