Kinetics, isotherms, and thermodynamics study on the dissolution-assisted conversion of plastic and biomass wastes into activated carbon

Abstract

Plastic and biomass wastes present persistent environmental challenges due to low recycling efficiency and limited value recovery. Polyolefin waste is particularly difficult to process, whereas palm fronds (PF) are an abundant lignocellulosic resource. This study focuses on the kinetics, isotherms, and thermodynamics of cationic dye adsorption using activated carbon (AC) derived from these wastes via a dissolution-assisted conversion route combining chemical activation and surface functionalization. The ACs were characterized for their morphology, surface area, pore structure, and surface chemistry, and their adsorption performance was evaluated. Equilibrium data were analyzed using six isotherm models, with the Langmuir model showing the best fit, reflecting monolayer adsorption with maximum capacities of 841 mg g⁻¹ and 707 mg g⁻¹ for Rhodamine B and Nile Blue, respectively. Kinetic studies revealed rapid initial uptake reaching equilibrium within 6 h, while thermodynamic evaluation confirmed a spontaneous and endothermic adsorption process. Overall, this work offers a sustainable and scalable route to convert mixed wastes into efficient adsorbents for dye-laden wastewater treatment.