Preparation of biochar from tea waste and its adsorption of bispyribac-sodium

Biochar is a kind of highly aromatic carbon rich solid with high porosity and large specific surface area. Its surface contains abundant chemical functional groups. And it has been widely used in many fields because of its strong adsorption capacity. Bispyribac-sodium is a high-efficiency pyrimidine salicylic acid herbicide, which is commonly used to control weeds in paddy fields. It is easy to cause water pollution and affect the ecological environment because of its high solubility in water. In view of this, the tea waste was selected as raw material to prepare biochar (BC-500 and BC-700) by pyrolysis at 500 ℃ and 700 ℃ in this work, and then treated BC-500 with KOH solution and pyrolyzed at 700 ℃ to obtain activated biochar (TBC-700). The X-ray diffraction (XRD), scanning electron microscope (SEM), surface area measurement (BET) and Zeta potential were applied to characterized the obtained biochar and studied the adsorption mechanism. The difference of adsorption effect between BC-700 and TBC-700 was compared, and the adsorption kinetics and adsorption isotherm of activated biochar were fitted. These results showed that the surface of activated biochar had abundant pore structure, and the specific surface area of TBC-700 was 768.07 m²/g, which was increased by 143 times comparing with BC-700. In addition, the removal rate and adsorption capacity of BC-700 were 0.95% and 0.66 mg/g, respectively, while the maximum removal rate and adsorption capacity of bispyribac-sodium by TBC-700 ware 98.67%, and 65.97 mg/g respectively. The adsorption effect was increased by 100 times. The fitting results indicated that the adsorption behavior of TBC-700 met the pseudo first order kinetics and Langmuir isotherm. this work can provide the research ideas and theoretical basis for the efficient removal of bispyribac-sodium in the environment and the sustainable utilization of the tea waste.