Investigation of tetracycline degradation by activating persulfate with lotus leaf biochar: source of active substance and toxicity evaluation

ABSTRACT This study withered lotus leaves as a precursor to prepare lotus leaf biochar (LLBC) as an activator for persulfates (PDS), targeting the oxidation and degradation of tetracycline (TC). Under neutral conditions, LLBC (LLBC = 20 mg, PDS = 4 mM, TC = 10 mg/L) exhibited the best catalytic degradation effect within 180 min, achieving 86.58% degradation. The LLBC/PDS system was tested in various water matrices, all achieving over 70% TC removal. In continuous flow column experiments, the TC removal efficiency was 61.56%. The results indicate that the LLBC/PDS system can efficiently degrade TC in real water bodies and has potential for use in continuous flow engineering. Additionally, an in-depth analysis was conducted on the active sites and reactive oxygen species (ROS) involved in the degradation of TC by the LLBC/PDS system. By analyzing the changes in the functional groups (C = O, C–O, and C = C) using XRD, FT-IR, and XPS before and after the reaction, it was determined that the primary active sites for generating ROS from activated PDS in LLBC were the C = O and C = C groups. Quenching experiments, electrochemical tests, and ESR confirmed that the ROS responsible for degrading TC in the LLBC/PDS system included both radical and non-radical pathways, with 1O2 playing the dominant role.