Valorization of Butia Endocarp via Hydrothermal Liquefaction: A Novel Activated Carbon for Emerging Contaminant Removal

Abstract Hydrothermal liquefaction of biomass generates fermentable sugars for the second-generation ethanol industry, bio-oil as a fuel for combustion, and hydrochar, which can be used for adsorptive processes. This study aimed to prepare and characterize an activated carbon (AC) through chemical activation with phosphoric acid (H₃PO₄), using hydrochar derived from the hydrothermal liquefaction of butia endocarp as the precursor material. The obtained material was applied for the removal of emerging contaminants, paracetamol and 2,4-dichlorophenoxyacetic acid (2,4-D), from aqueous solutions. The activated carbon exhibited a predominantly mesoporous structure, with a specific surface area of 1045 m² g⁻¹ and a total pore volume of 0.139 cm³ g⁻¹. Its adsorption-favorable morphology was confirmed by electron microscopy and pore size distribution analysis. In adsorption studies, the general-order kinetic model best described the experimental data, while the Sips isotherm model provided the best fit for equilibrium, with maximum adsorption capacities of 99.5 mg g⁻¹ for paracetamol and 116.0 mg g⁻¹ for 2,4-D. The adsorbent also demonstrated high removal efficiency (over 90%) at various concentrations for both contaminants, highlighting its potential as a promising alternative for treating effluents containing emerging contaminants. These results indicate that the carbonaceous material produced from agro-industrial waste has significant environmental potential, combining high adsorption performance with sustainability.