Utilization of acerola residue-derived biochars for methylene blue adsorption: effects of pyrolysis temperature

Adsorption is an effective method for removing various types of pollutants from aqueous effluents, and the production of adsorbent materials from biomass represents a sustainable alternative. In this study, biochars produced from the pyrolysis of acerola processing residues at temperatures ranging from 300 to 700 °C were evaluated as adsorbents for methylene blue dye. Batch adsorption tests revealed rapid adsorption kinetics, with equilibrium being reached within 30 min. The adsorption data were best described by the Langmuir isotherm and the pseudo-first-order kinetic model, indicating monolayer adsorption controlled by the availability of active sites. The biochar produced at 400 °C exhibited the highest adsorption performance, achieving a maximum adsorption capacity of 67.29 mg g^-1 and a dye removal efficiency of approximately 94% at an initial concentration of 100 mg L^-1. This superior performance was attributed to the optimal balance between surface area development and the preservation of oxygenated functional groups, which promote methylene blue adsorption through electrostatic interactions and hydrogen bonding. Overall, the results demonstrate the strong potential of acerola residue-derived biochars as low-cost and sustainable adsorbents for wastewater treatment, while also providing an environmentally sound destination for agro-industrial waste.