The conventional Fe(III)/H 2 O 2 system is of low efficiency on the removal of most organic pollutants. However, we discovered that the Fe(III)/H 2 O 2 system was robust on remediating tetracycline (TC) in water (0.109 min −1 for the pseudo-first kinetic constant), and the reaction was even slightly faster than that in the conventional Fe(II)/H 2 O 2 system (0.105 min −1 ). The addition of TC could also initiate the degradation of other refractory pollutants in the Fe(III)/H 2 O 2 system. Complexation between Fe(III) and TC with the stoichiometric ratio of 1:1 was observed. Electron transfer from TC to Fe(III) gave rise to the slight production of Fe(II), which served as the initiator of the following Fenton reaction. •OH was ascertained as the main reactive species through quenching experiments, EPR tests and the probe method, while O 2 • − /HO 2 • was also a subsidiary contributor. Hydroquinone intermediates were proved to be generated through the hydroxylation of the benzene ring of the TC molecule by •OH and thus facilitate the reductive transformation of Fe(III) to Fe(II). This study analyzes the relationship between molecular structural features of TC and the catalytic efficiency of ferric Fenton-like reactions. We expect to shed light on new mechanistic insights on autocatalysis in the Fenton-like catalytic processes.
Hydroxylated fullerene, Fullerol, has applied in many areas because of its high electron affinity and antioxidant potential, while it was few used in wastewater treatment. In this study, the mechanism involved that Fullerol accelerated the regeneration of Fe(II) in the Fe(III)/H 2 O 2 system under dark condition, which was investigated with chloramphenicol (CAP) as a model pollutant. In Fullerol/Fe(III)/H 2 O 2 system, CAP removal was completely achieved at 60 min via a non-photochemical pathway. In addition, the quenching experiments and electron spin resonance (ESR) results indicated that hydroxyl radical ( OH) was the main reactive oxygen species (ROSs). The Fullerol/Fe(III)/H 2 O 2 system had a rate constant of CAP degradation about 5.0 × 10 −2 min −1 , which was about 22 times higher than it in Fe(III)/H 2 O 2 Fenton-like system (2.3 × 10 −3 min −1 ). Fe(II) was ascertained the effective component that was responsible for H 2 O 2 activation to produce OH, which derived from 1) the first pathway: Fullerol complexed with Fe(III) and the redox potential of the complex is much lower than Fe(III)/Fe(II); 2) the second pathway: Fullerol acted as an electron donor to reduce Fe(III) into Fe(II). Moreover, CAP degradation intermediates were identified and its degradation pathways were proposed. This study suggested a new approach for improving the Fe(III)/H 2 O 2 system by accelerating Fe(III)/Fe(II) cycles with Fullerol.
Hao Xu,Qian Ye,Jing Zhang,Qiansong Li,Meijing Wang,Peng Zhou,Guanyu Zhou,Qingguo Wang
In response to the inherent restriction of low Fe(II) regeneration in the Fenton process, this study demonstrated a mutual-promoting configuration, where oxygen functionalized g-C 3 N 4 (OCN) was applied in Fe(III)/H 2 O 2 system to utilize mild natural solar light (SL) for persistent Fe(II) generation. The constructed OCN/Fe(III)/H 2 O 2 /SL system exhibited strong adaptability to various pollutants, and it well outperformed the g-C 3 N 4 (GCN) modified system and the traditional Fenton system in pollutants degradation efficiency. Compared with GCN, OCN could significantly promote the Fe(II) generation under solar light (SL), leading to more efficient H 2 O 2 activation. The characterization analyses revealed the larger surface area and enhanced charge separation of OCN, which were considered to take main responsibility for its enhanced photoactivity. The complexation of Fe(III) with the carboxyl groups of OCN also benefited the Fe(II) generation. ·OH was detected as the dominant radical responsible for metronidazole (MNZ) degradation, and its production in the OCN modified system was about twice that in the GCN modified system and the Fenton system. Moreover, the precipitation of FeO x on the OCN surface benefited the charge separation of the OCN, so that the improved OCN enabled a slight enhancement of MNZ degradation in the reuse experiments. The intermediates of MNZ degradation were analyzed based on the results of LC-MS, which provided insight into MNZ degradation pathways. This work highlighted the concept of self-improving photocatalyst, the ingenious combination of photocatalysis and Fenton-like system formed a mutual-promoting situation where the OCN and the Fenton-like system could both be improved, which endowed the configuration great potential for green and economical oxidation in environmental remediation.
危险品化学品经营许可证（带存储）