Oxytetracycline degradation and toxicity evolution by catalytic oxidation process over sludge derived carbon

The degradation behavior of oxytetracycline (OTC) in aqueous solution using sludge derived carbon (SC) was investigated in this paper. SC treated with different kinds of acids were characterized by BET and thermogravimetric analysis. The results showed that SC-H ₂ SO ₄ exhibited higher catalytic activity than SC-HCl and SC. The maximum removal of OTC and total organic carbon (TOC) after catalytic oxidation process at 60 °C was 92.6% and 70.2%, respectively. The safety of antibiotics after advanced oxidation processes (AOPs) has attracted much attention due to the possibility of toxicity increasing. Seven intermediate products were identified by GC-MS and four pathways were proposed. Furthermore, the toxicity of OTC degradation was investigated by zebrafish embryos for the first time. Zebrafish incubated with OTC solution (TE2) had haemagglutination, pericardial edema and showed significant changes in heartbeat, body length, and roaming frequency compared with the normal nutrient solution (TE1). Moreover, all zebrafish embryos had condensation phenomenon and did not hatch out in the treated OTC solution (TE3). In contrast, the zebrafish could hatch out without abnormality cultured with the treated OTC solution adjusted to the neutral pH (TE4). Results indicated that the treated OTC solution after catalytic oxidation process should be adjusted to the neutral pH to reduce the toxicity to the ecology.