Antibiotic removal by agricultural waste biochars with different forms of iron oxide
Pollution by antibiotics has become a serious threat to public health. In this study, agricultural waste, corn husk, in the form of biochar, was utilized for antibiotic removal from wastewater. Two kinds of iron-loaded biochars, impregnation–pyrolysis biochar (IP) and pyrolysis–impregnation biochar (PI), were synthesized to adsorb the typical antibiotics tetracycline (TC) and levofloxacin (LEV). PI contained amorphous hydrated iron oxide, whereas the major component of IP was γ-Fe2O3. Compared with IP, PI had a much higher adsorption capacity for both TC and LEV. This was because PI could provide more –OH, especially –OHads, to serve as the adsorption sites. In comparison with TC, –OH was prone to combine with LEV. FT-IR and XPS results indicated that the mechanisms of LEV adsorption included hydrogen bonding, F-replacement, electrostatic attraction and bridging bidentate complexation. TC adsorption may involve complexation, hydrogen bonding and electrostatic attraction.