Effect and mechanism of norfloxacin removal by Eucalyptus leaf extract enhanced the ZVI/H₂O₂ process

The conventional ZVI/H₂O₂ technology suffers from poor reagent utilization, excess iron sludge generation, and strong low pH dependence. Therefore, eucalyptus leaf extract (ELE) was introduced to improve ZVI/H₂O₂ technology, and the efficacy and mechanism of ELE promoting ZVI/H₂O₂ technology were deeply explored. The results showed that the norfloxacin (NOR) removal and k_obs of the ZVI/H₂O₂/ELE process were enhanced by 35.64 % and 3.27 times, respectively, compared to the ZVI/H₂O₂ process. In the ZVI/H₂O₂ process, the production of three reactive oxygen species (ROS: ¹O₂，·O₂^-，·OH) was effectively promoted by ELE so that the reaction efficacy was significantly enhanced. Moreover, the attack and degradation of pollutants by ROS was the main way to remove pollutants. With the introduction of ELE, the reactive sites on the catalyst appearance were increased to some extent, and the Fe(III)/Fe(II) cycle was improved. The analysis showed that ELE is rich in titratable acids and the ZVI/H₂O₂ technology is promoted mainly by lowering the pH of the process. In addition, the chelation of ELE and the reduction in pH by the ELE synergistically enhanced the ZVI/H₂O₂ technology, which significantly improved the reagent utilization (4.70 times for ZVI and 3.03 times for H₂O₂), broadened the pH range of the technology (6-9) and was able to effectively reduce the iron sludge contamination (30.33 %) of the process. Therefore, the study offers an important value to study eucalyptus leaves in micron-scale ZVI-Fenton technology.