Adsorption Behaviour of Selected Acid Herbicides on Activated Carbon: Equilibrium, Kinetic and Laboratory—Field Assessment

The present study evaluates the adsorption behaviour of selected acid herbicides (MCPA, Mecoprop-P, 2,4-D, and Triclopyr) on activated carbon under controlled laboratory conditions and assesses the relevance of this behaviour to aquatic environmental protection. Batch adsorption experiments were conducted to investigate the influence of contact time, adsorbent dosage and initial herbicide concentration. Adsorption equilibrium data were analysed using Langmuir and the Freundlich isotherm models, while adsorption kinetics were evaluated using pseudo-first-order and pseudo-second-order models. Freundlich modelling showed better agreement with the experimental data, suggesting heterogeneous surface interactions during adsorption. Langmuir modelling demonstrated high intrinsic adsorption capacities, reaching 116.82 mg g^-1 for MCPA. Kinetic analysis revealed that the pseudo-second-order model provided the best fit (R² up to 0.996), suggesting that it adequately describes the adsorption kinetics. Regression analysis indicated a statistically significant preliminary relationship (R² = 0.933, p ≤ 0.05) between intrinsic adsorption capacity and field removal efficiency. The findings highlight the practical relevance of laboratory-derived adsorption parameters for preliminary assessment of the performance of activated carbon in agricultural water treatment systems and contribute to ecological protection by supporting improved management of herbicide contamination in water resources.