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 kobs 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.

Effect and mechanism of norfloxacin removal by guava leaf extract in the ZVI/H2O2 system.

To overcome the bottlenecks of the conventional zero-valent iron Fenton-like (ZVI/H2O2) process, such as low reagent utilization, low applicable pH, and iron sludge contamination, guava leaf extract (GLE) was used as a green promoter to enhance ZVI/H2O2 process in this study. Compared with the ZVI/H2O2 system, the removal rate and kobs of norfloxacin by the ZVI/H2O2/GLE system were increased by 33.76% and 2.19 times, respectively. The experimental investigation of the mechanism showed that the attack of reactive oxygen species was the main pathway for the removal of pollutants, and three types of reactive oxygen species (1O2, O2-,·OH) generations in the ZVI/H2O2/GLE system were effectively promoted by the introduction of GLE. The reactivity improvement was mainly due to the decrease of pH. At the same time, the chelation of iron ions by GLE promoted the Fe(III)/Fe(II) cycle on the catalyst surface was also a minor mechanism to improve the reactivity. This study provides a crucial reference for the practical application of guava leaf to promote the ZVI/H2O2 process in environmental pollution control.