Synthesis, Modification, and Comprehensive Characterization of Lavender-Derived Activated Carbon for Adsorptive Removal of Pharmaceutical Pollutant.

Abstract

Pharmaceutical contaminants in aquatic environments require sustainable and efficient treatment strategies, while biomass residues provide promising renewable precursors for adsorbent production. In this study, lavender residue generated after essential oil extraction was valorized as a precursor for porous activated carbon through ZnCl₂ impregnation followed by chemical activation under N₂ at 550°C, 650°C, and 750°C. Structural and morphological analyses confirmed the progressive transformation of the lignocellulosic precursor into a porous carbonaceous structure, while nitrogen adsorption-desorption analysis demonstrated that Lavender AC750 possessed the highest BET surface area (646.39 m²/g) and pore volume (0.239 cm³/g), with a developed micro/mesoporous structure. Consequently, Lavender AC750 was selected for adsorption studies. The experimentally determined point of zero charge (pH_pzc) was 4.33, and adsorption performance was influenced by solution pH, contact time, adsorbent dosage, initial flutamide concentration, and temperature. Nonlinear equilibrium analysis showed that the Langmuir model provided the best fit (R² = 0.9164, RMSE = 1.540 mg/g), yielding a maximum monolayer adsorption capacity of 32.23 mg/g. Nonlinear kinetic analysis showed that the pseudo-first-order model satisfactorily described the adsorption kinetics (R² = 0.9435, RMSE = 0.545 mg/g), with a calculated equilibrium capacity (5.943 mg/g) close to the experimental value (5.83 mg/g). The combined results suggest that flutamide adsorption involves pore filling and surface adsorption accompanied by π-π interactions, hydrogen bonding, and pH-dependent electrostatic contributions. Overall, this study demonstrates a dual environmental benefit by valorizing lavender-processing residue into a functional porous adsorbent and providing a promising material for the removal of flutamide from aqueous systems.