Mesoporous activated carbon from Tabebuia aurea leaves for effective adsorptive removal of 2,4-dichlorophenoxyacetic acid

The extensive use of herbicides in agriculture contributes to water pollution, posing a significant environmental risk. This study focused on the H₃PO₄ activation of Tabebuia aurea leaves to prepare activated carbon. The resulting adsorbent was then tested for its capability to eliminate 2,4-dichlorophenoxyacetic acid (2,4-D), the heinous herbicide. The prepared activated carbon demonstrated a mesoporous nature with a high specific surface area (773.21 m²/g). Moreover, the existence of carbon and oxygen was proven using elemental analysis, and a post-adsorption chlorine signal confirmed 2,4-D presence. It was found that pH 2 provided optimal adsorption conditions, with an activated carbon dose of 0.45 g/L and 50 mg/L 2,4-D concentration. The process comprehended pseudo-second-order kinetics, as determined by kinetic modeling. The Langmuir isotherm model described the adsorption equilibrium, indicating a maximum adsorption capacity of 158.28 mg/g. Thermodynamic tests indicated physisorption and exothermicity. The prepared activated carbon also demonstrated substantial regeneration capacity up to five cycles. Consistent adsorption capacity proves its efficacy across diverse water matrices. Adsorption efficiency remained largely unaffected by inorganic ions at 0.1 and 1 mM concentrations. This confirms the viability of the synthesized adsorbents and their affordable use for 2,4-D removal in water remediation.