Mechanistic insights of 2,4-D sorption onto biochar: influence of feedstock materials and biochar properties

Objective of this study was to investigate the mechanisms of 2,4-Dichlorophynoxy acetic acid (2,4-D) sorption on biochar in aqueous solutions. Sorption isotherm, kinetics, and desorption experiments were performed to identify the role of biochars’ feedstock and production conditions on 2,4-D sorption. Biochars were prepared from various green wastes (tea, burcucumber, and hardwood) at two pyrolytic temperatures (400 and 700 °C). The tea waste biochar produced at 700 °C was further activated with steam under a controlled flow. The sorption of 2,4-D was strongly dependent on the biochar properties such as specific surface area, surface functional groups, and microporosity. The steam activated biochar produced from tea waste showed the highest (58.8 mg g⁻¹) 2,4-D sorption capacity, which was attributed to the high specific surface area (576 m² g⁻¹). The mechanism of 2,4-D removal from aqueous solution by biochar is mainly attributed to the formation of heterogeneous sorption sites due to the steam activation.