High adsorption capacity of Rhodamine B dye on bio-activated carbon derived from sugarcane bagasse

This paper details the synthesis, characterisation, and adsorption efficacy of bio-activated carbon (BAC) generated from sugarcane bagasse for the effective elimination of Rhodamine B (RhB) dye from aqueous solutions. Sugarcane bagasse, an accessible agro-industrial byproduct, was chemically activated with HCl and subsequently carbonized to yield a porous carbon material rich in surface functionalities. Structural and surface analyses validated the formation of a hierarchical mesoporous framework, as demonstrated by SEM, FTIR, XRD, EDX, and nitrogen adsorption–desorption tests, including predominant pore sizes within the 2–5 nm range and intact oxygenated groups conducive to dye adsorption. Batch adsorption tests exhibited fast elimination of RhB, reaching equilibrium in 20 minutes and sustaining removal efficiencies over 95% across a broad concentration spectrum. Kinetic modeling indicated that the pseudo-second-order model most accurately represented the adsorption process, emphasizing chemisorption as the primary mechanism, with heterogeneous surface interactions and pore diffusion effects. Isotherm analysis revealed that the Freundlich model exhibited the optimal fit (R² = 0.9950), indicating multilayer adsorption on energetically heterogeneous sites, with a maximum adsorption capacity (qmax) of 30.36 mg g⁻¹ as determined by the Langmuir model. Further fittings to the Temkin, Elovich, Henry, and Dubinin–Radushkevich models corroborated a synthesis of physical and chemical adsorption mechanisms. The findings validate that sugarcane-bagasse-derived BAC is an economical, sustainable, and efficient adsorbent, presenting considerable promise for practical wastewater treatment applications while facilitating the valorization of agricultural residues into valuable environmental remediation materials.