Adsorption of Tetracycline and Sulfamethoxazole on Crop Residue-Derived Ashes: Implication for the Relative Importance of Black Carbon to Soil Sorption

摘要

The main objective of this study was to investigate the key factors and mechanisms of antibiotic adsorption on crop residue-derived black carbon, as well as the relative importance of black carbon to the overall sorption to soil. Batch sorption experiments were performed for two reference antibiotics (sulfamethoxazole and tetracycline) on wheat- and maize-residue-derived black carbon. After removal of the mineral fraction from the raw black carbon by acidification, tetracycline exhibited less enhanced adsorption than sulfamethoxazole, implying stronger complexa-tion of tetracycline on the mineral components. The antibiotic adsorption on the demdneralized black carbon was very strong (The measured iQ was in the order of 103-105 L/kg). The adsorbent surface area-normalized adsorption of sulfamethoxazole was higher on the demineralized black carbon than on nonporous graphite due to the micropore-filling efFect. The opposite trend observed for bulky tetracycline was attributed to the size-exclusion efFect. Owing to the strong surface complexation and/or cation exchange reaction, sorption of tetracycline to Na+-exchanged montmorillonite, soil mimic acids, and bulk soil was remarkably stronger than sulfamethoxazole. It was estimated that the contribution of Hack carbon to the overall sorption to bulk soil was important for sul&methoxazole, but negligible for tetracycline.