Adsorptive Removal of Oxytetracycline From Aqueous Solutions Using KOH‐Activated Biochar Derived From Grape‐Leaf Waste: Adsorption Properties and Mechanism

ABSTRACT

Oxytetracycline (OTC) was a kind of spectral antibacterial agent and widely used in livestock farming and disease prevention. It easily remained in the environment and was harmful to the health of humans and animals. Grape leaves, the waste of the grape production base in Beizhen, were used as raw materials to produce the biochar. The effects of adsorption time, temperature, adsorbent amount, pH, and OTC initial concentration on OTC adsorption capacity were investigated. The Box‐Behnken method was used to optimize the experimental design. The grape‐leaf biochar was modified with KOH for the efficient adsorptive removal of OTC in the wastewater. Compared with the unmodified biochar, the modified biochar can quickly adsorb low concentrations of OTC and has a better adsorption effect. The adsorption capacity of GLBC‐2OH (modified biochar) was calculated by the Langmuir isotherm as 116.96 mg/g. The OTC removal rate can reach over 85%. The adsorption mechanism of GLBC‐2OH for the OTC consisted of pore filling, π‐π interaction, electrostatic interaction, hydrogen bonding, and the complexation between the OTC and the biochar. The GLBC‐2OH adsorption was more suitable for pseudo‐second‐order kinetics and the Langmuir isotherm model, which was the chemisorption of monolayer adsorption. The analysis of thermodynamics showed that adsorption was a spontaneous, endothermic, and entropy‐increasing reaction. The grape leaves were waste, and the biochar made from them was an effective adsorbent material for the removal of OTC in wastewater. Reuse of grape waste can increase income and protect the environment.