Mesoporous carbon from Vateria indica fruit for efficient 2,4-D herbicide removal: Mechanistic insights from double-layer statistical physics modelling and regeneration studies

The widespread application of herbicides like 2,4-Dichlorophenoxyacetic acid (2,4-D) poses significant environmental risks due to their persistence and toxicity. This study presents a sustainable, chemical-free synthesis of mesoporous activated carbon (AC) from Vateria indica fruit, utilizing hydrothermal treatment followed by physical activation. The resulting AC exhibited a high specific surface area (327.46 m²/g) and a mesoporous architecture, contributing to enhanced adsorption performance. Adsorption experiments demonstrated maximum 2,4-D removal capacity of 226.23 mg/g at 323 K, with optimal conditions observed at pH 2 and an adsorbent dosage of 0.25 g/L. Kinetic analysis indicated adherence to a pseudo-second-order model, while isotherm and thermodynamic studies suggested a physisorption-dominated mechanism. Advanced double-layer statistical physics modelling further revealed a dual-layer adsorption mechanism governing the process. Notably, the AC retained approximately 80 % efficiency after five regeneration cycles using 0.01 N NaOH, surpassing many conventional adsorbents reported in literature. These results highlight the potential of V. indica fruit-derived AC as a cost-effective and eco-friendly material for herbicide removal, with significant implications for sustainable water treatment technologies.