Significant enhancement of photo-Fenton degradation of ofloxacin over Fe-Dis@Sep due to highly dispersed FeC6 with electron deficiency

3D printed monoliths: From powder to an efficient catalyst for antibiotic degradation

To improve the effectiveness and durability of wastewater treatment technologies, researchers are showing a growing interest in 3D printing technology. This technology has attracted significant interest owing to its ability to fabricate challenging complex geometries using different material compositions. This manuscript is focused on the development of 3D monoliths from noncommercial filaments, i.e., a powder blend of iron oxide and polylactic acid (PLA) at 15 wt% of the former. Different monolith designs have been prepared to improve the fluid dynamics of the process, so a simple cylinder (15-Fe3O4@PLA) and a cylinder with double the length and an internal mesh (15-Fe3O4@PLA-DM) were used. These monoliths were characterized by Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC) and Mössbauer spectroscopy, then used for water-based ofloxacin degradation in a continuous down-up flow configuration. Additionally, computational fluid dynamics simulations were performed to estimate the degradation rate constants and analyze the distribution of fluid velocity and pollutant concentration along the 15-Fe3O4@PLA-reactor. The oxidant dose was also optimized to develop the highest degradation rate. The degradation of the target pollutant for those monoliths was 55 and 82 % under optimized conditions. In addition, the 15-Fe3O4@PLA-DM monolith was operated for long term experiments, keeping the degradation performance at a good 67 % for up to 120 h. Finally a fixed-bed reactor was mounted with printed pellets of the mixture (15:85), Fe3O4:PLA, after being ground in a range of 125-200 μm. Under this setup configuration, we observed the total degradation of ofloxacin. 3D printing technology is cheap, reproducible and time saving in the development of supported catalysts in comparison with conventional deposition techniques. Moreover, the leaching of active sites on streams was largely diminished. In fact under continuous operation the leached Fe concentration is below 0.1 ppm, corroborating the good adhesion of the catalyst in the PLA support.

Amorphous ferric oxide-coating selenium core-shell nanoparticles: a self-preservation Pt(IV) platform for multi-modal cancer therapies through hydrogen peroxide depletion-mediated anti-angiogenesis, apoptosis and ferroptosis

A self-preservation Pt(IV) nanoplatform, amorphous ferric oxide-coating selenium core-shell nanoparticles (iAIO@NSe-Pt), was developed for H₂O₂ depletion-mediated tumor anti-angiogenesis, apoptosis, and ferroptosis. Upon entry into the blood, the ferric oxide shell effectively blocked the contact Pt(IV) prodrug with reduced molecules, then avoided the inactivation of the Pt(IV) prodrug and increased its accumulation in the tumor. After entering cancer cells, iAIO@NSe-Pt caused a series of cascade reactions: (1) AIO on the surface of iAIO@NSe-Pt quickly dissolved, released an abundance of Fe(II) because of the weakly acidic tumor microenvironment, and then catalyzed cellular H₂O₂ into highly toxic ˙OH, resulting in cellular H₂O₂ deficiency and cell ferroptosis. (2) The platinum(IV) prodrugs were exposed and quickly reduced to highly toxic Pt(II) by depleting GSH. This process inactivated GPX4, promoted ROS accumulation, and further accelerated ferroptosis. In addition, the generated Pt(II) quickly inhibited DNA replication, achieving effective apoptotic cell death. Meanwhile, Pt(II) inactivated SOD1, which blocked the synthesis of cellular H₂O₂ and accelerated ROS (superoxide anion radical) accumulation. (3) The deficiency of cellular H₂O₂ significantly inhibited the expression of vascular endothelial growth factor-A (VEGF-A), blocking tumor angiogenesis and then improving the anticancer effect. (4) After such a cascade reaction, the exposed NSe successively disrupted mitochondrial respiration and inhibited cancer angiogenesis, further inducing cancer cell death. Collectively, our functional and mechanical investigation suggested that iAIO@NSe-Pt exhibits excellent tumor targeting, biocompatibility and anti-tumor efficiency in vitro and in vivo, and provides a novel example of a self-preservation Pt(IV) nanoplatform for H₂O₂ depletion-mediated tumor anti-angiogenesis, apoptosis, and ferroptosis, showing great promise for future clinical use.

New Insight into a Fenton-like Reaction Mechanism over Sulfidated β-FeOOH: Key Role of Sulfidation in Efficient Iron(III) Reduction and Sulfate Radical Generation

Sulfidation can greatly improve the efficiency of utilization of reducing equivalents for contaminant removal; however, whether this method benefits Fenton-like reactions or not and the possible mechanism are not well understood. In this study, we revealed that surface sulfidation can greatly promote the heterogeneous Fenton activity of β-FeOOH (Fe₃S₄@β-FeOOH) by 40 times, in which not only the ^•OH formation was enhanced but also SO₄^•- as a new oxidation species was generated. Moreover, their contribution to metronidazole (MTZ) degradation was 52.5 and 37.1%, respectively. In comparison, almost no HO₂^•/O₂^•- was detected in the Fe₃S₄@β-FeOOH/H₂O₂ system. These results were different from some previously reported Fenton counterparts. Based on the characterization and probe experiments, sulfur species, including S^2-, S⁰, and S_n^2-, as an electron donor and electron shuttle were responsible for efficient conversion of Fe(III) into Fe(II) other than via the Haber-Weiss mechanism, leading to excellent ^•OH generation via a Fenton-like mechanism. Most importantly, HSO₅^- can be generated from SO₃^2- oxidized by ^•OH, and its scission into SO₄^•- was not dependent on the extra electric potential or Fe-O₂-S(IV) intermediate. These findings provided new insight for utilizing sulfidation to improve the activity of iron-based Fenton catalysts.

Recent progress in Fenton/Fenton-like reactions for the removal of antibiotics in aqueous environments

The frequent use of antibiotics allows them to enter aqueous environments via wastewater, and many types of antibiotics accumulate in the environment due to difficult degradation, causing a threat to environmental health. It is crucial to adopt effective technical means to remove antibiotics in aqueous environments. The Fenton reaction, as an effective organic pollution treatment technology, is particularly suitable for the treatment of antibiotics, and at present, it is one of the most promising advanced oxidation technologies. Specifically, rapid Fenton oxidation, which features high removal efficiency, thorough reactions, negligible secondary pollution, etc., has led to many studies on using the Fenton reaction to degrade antibiotics. This paper summarizes recent progress on the removal of antibiotics in aqueous environments by Fenton and Fenton-like reactions. First, the applications of various Fenton and Fenton-like oxidation technologies to the removal of antibiotics are summarized; then, the advantages and disadvantages of these technologies are further summarized. Compared with Fenton oxidation, Fenton-like oxidations exhibit milder reaction conditions, wider application ranges, great reduction in economic costs, and great improved cycle times, in addition to simple and easy recycling of the catalyst. Finally, based on the above analysis, we discuss the potential for the removal of antibiotics under different application scenarios. This review will enable the selection of a suitable Fenton system to treat antibiotics according to practical conditions and will also aid the development of more advanced Fenton technologies for removing antibiotics and other organic pollutants.

Accelerated Redox Cycles of Fe(III)/Fe(II) and Cu(III)/Cu(II) by Photo-Induced Electron from N-CQDs for Enhanced Photo-Fenton Capability of CuFe-LDH

Layered double hydroxide (LDH) materials have shown charming photo-Fenton capability for the treatment of refractory organic wastewater. In this study, CuFe-LDH hybridized with N-doped carbon quantum dots (N-CQDs) was investigated to further enhance the photo-Fenton capability. The results showed that the assembly techniques of coprecipitation and the hydrothermal method could synthesize the target material, CuFe-LDH/N-CQDs, successfully. CuFe-LDH/N-CQDs could possess a 13.5% higher methylene blue (MB) removal rate than CuFe-LDH in 30 min due to the accelerated redox cycles of Fe(III)/Fe(II) and Cu(III)/Cu(II), resulting from the photo-induced electron transfer from N-CQDs to CuFe-LDH via a d–π conjugation electronic bridge. Moreover, CuFe-LDH/N-CQDs has excellent photo-Fenton capability in the pH range of 2–11, even after being reused five times. This study would provide an efficient and stable photo-Fenton catalyst for the treatment of refractory organic wastewater.