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

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.

Interface coupling effect in biomass-derived iron sulfide nanomaterials triggering efficient hydrogen peroxide activation

Slow electron migration in iron sulfide nanoparticles (C-FeS NPs) synthesized by co-precipitation severely limits the activation performance of hydrogen peroxide (H2O2). Herein, a biofunctional FeS NPs (P-FeS NPs) derived from Pinus massoniana Lamb biomass, with interface coupling effect, was used for enhanced H2O2 activation and norfloxacin (NOR) degradation. It was discovered that P-FeS NPs exhibited superior catalytic activity (100%) compared to C-FeS NPs (53.1%). Fe atoms of FeS NPs and hydroxyl groups (-OH) of Pinus massoniana Lamb biomass were mutually coupled to produce Fe-OH interfacial sites, which significantly increased the generation of multi-reactive species by accelerating the transfer of electrons across interfaces. Additionally, radical quenching tests elucidated that singlet oxygen (1O2) (66.6%) played a leading role, while hydroxyl radicals (•OH) (14.5%) and superoxide radicals (•O2-) (18.9%) were secondary oxidants. Finally, P-FeS NPs showed a high tolerance to a wide range of pH conditions and could remove 96.4% NOR from wastewater. Overall, this work generates important insights into understanding how green sustainable interfacial catalysts can accelerate catalytic activity.