UV light irradiation combined with nitrate for degradation of bisphenol A: kinetics, transformation pathways, and acute toxicity assessment

As an endocrine disruptor, bisphenol A (BPA) is a severe threat to human health. In this study, nitrate (NO3-) photolysis with a low-pressure UV lamp (LP-UV) was employed to degrade...

UNDERSTANDING THE PHOTODEGRADATION MECHANISM OF GASEOUS ACETALDEHYDE OVER BI2WO6 — MODIFIED ZNWO4 PHOTOCATALYST UNDER UV LIGHT IRRADIATION

Indoor air quality has a significant impact on human health as people spend more time indoors. As a common indoor air pollutant, acetaldehyde is considered toxic when exposed to it for a prolonged period. The aim of this study is the enhancement of the photocatalytic activity of ZnWO4 with a monoclinic wolframite structure for degradation of gaseous acetaldehyde by modifying its surface with Bi2WO6 layered structure. The mechanisms behind the enhanced photocatalytic activity and the pathways for acetaldehyde photodegradation over the Bi2WO6-modified ZnWO4 photocatalyst are discussed

Synthesis and application of g-C3N4/Fe3O4/Ag nanocomposite for the efficient photocatalytic inactivation of Escherichia coli and Bacillus subtilis bacteria in aqueous solutions

Contamination of water with bacteria is one of the main causes of waterborne diseases. The photocatalytic method on the basis of bacterial inactivation seems to be a suitable disinfectant due to the lack of by-products formation. Herein, g-C3N4/Fe3O4/Ag nanocomposite combined with UV-light irradiation was applied for the inactivation two well-known bacteria namely, E. coli and B. subtilis. The nanocomposite was prepared by a hydrothermal method, and subsequently it was characterized by XRD, FT-IR, SEM, EDX and PL analyses. The optimum conditions established for the inactivation of both bacteria were as follows: nanocomposite dosage 3 g/L and bacterial density of 103 CFU/mL. In the meantime, the efficient inactivation of E. coli and B. subtilis took 30 and 150 min, respectively. The results also revealed that inactivation rate dropped with an increase in the bacterial density. It is also pointed out that OH˚ was found out to be the main radical species involved in the inactivation process. Finally, the kinetic results indicated that the inactivation of E. coli and B. subtilis followed the Weibull model. It is concluded that C3N4/Fe3O4/Ag nanocomposite along with UV-light irradiation is highly effective in inactivating E. coli and B. subtilis bacteria in the aqueous solutions.

MOFs Derived Hetero-ZnO/Fe2O3 Nanoflowers with Enhanced Photocatalytic Performance towards Efficient Degradation of Organic Dyes

It is still a challenge for wastewater treatment to develop efficient yet low-cost photocatalysts on a large scale. Herein, a facile yet efficient method was devised to successfully synthesize ZnO/Fe2O3 nanoflowers (NFs) by using metal organic framework ZIF-8 as the precursor. The photocatalytic activities of the as-prepared hetero-ZnO/Fe2O3 NFs are purposefully evaluated by photocatalytic degradation of methylene blue (MB) and methyl orange (MO) under UV light irradiation. The resulting ZnO/Fe2O3 NFs display even higher photocatalytic activities than those of single-phase ZnO and Fe2O3 as a photocatalyst for the degradation of both MB ad MO. Particularly, nearly 100% MB can be photocatalytically degraded in 90 min under UV light irradiation using the hetero-NFs photocatalyst. The enhanced photocatalytic properties are probably ascribed to the synergistic contributions from the suitable band alignment of ZnO and Fe2O3, large surface area, and strong light absorption property. Radical scavenger experiments prove that the photogenerated holes, ·OH and ·O2-, play key roles in photocatalytic degradation process of organic dyes. Accordingly, the photocatalytic degradation mechanism of hetero-ZnO/Fe2O3 NFs towards dyes is tentatively proposed. The work contributes an effective way to rationally design and fabricate advanced photocatalysts with heterojunction structures for photocatalytic applications.

Facile Preparation of Oxygen-Vacancy-Engineered MoOx Nanostructures for Photoreversible Switching Systems

Photochromic materials have attracted increasing attention. Here, we report a novel photo-reversible color switching system based on oxygen-vacancy-engineered MoOx nanostructures with water/N-methyl-2-pyrrolidone (NMP) as solvents. In this work, the system rapidly changed from colorless to blue under UV irradiation (360–400 nm) and slowly recovered its colorless state under visible light irradiation. The obtained oxygen vacancy-engineered MoOx nanostructures exhibited good repeatability, chemical stability, and cycling stability. Upon UV light irradiation, H+ was intercalated into layered MoOx nanostructures and the Mo6+ concentration in the HxMoOx decreased, while the Mo5+ concentration increased and increased oxygen vacancies changed the color to blue. Then, it recovered its original color slowly without UV light irradiation. What is more, the system was highly sensitive to UV light even on cloudy days. Compared with other reported photochromic materials, the system in this study has the advantage of facile preparation and provides new insights for the development of photochromic materials without dyes.

Fabrication and Characterization of Cobalt-Pigmented Anodized Zinc for Photocatalytic Application

Population growth and urbanization have led to water scarcity and pollution, which is a health hazard not only to humans but also to the ecosystem in general. This has necessitated coming up with ways of treating water before consumption. Photocatalysis has proved to be one of the most promising cheap techniques that involve chemical utilization of solar energy. TiO2 widely used in photocatalysis absorbs a narrow range of the solar spectrum compared to ZnO. In this regard, this study aimed at preparing and optimizing cobalt-pigmented ZnO, which is applicable in photocatalytic water treatment. The objectives in this study were to fabricate zinc oxide (ZnO) thin films by anodization, pigment the fabricated films with varying cobalt concentrations, characterize the fabricated films optically, and investigate the cobalt-pigmented ZnO’s performance in the methylene blue degradation under UV light irradiation. Mirror-polished zinc plates were sonicated in ethanol and rinsed. Anodization was done at room temperature in 0.5 M oxalic acid at a constant voltage of 10 V for 60 min, and cobalt electrodeposited in the films. Post-deposition treatment was done at 250°C. Optical properties of the films were studied using a UV-VIS- NIR spectrophotometer in the solar range of 300–2500 nm. The photocatalytic activity of the fabricated films was studied in methylene blue solution degradation in the presence of UV light irradiation for 5 h. Cobalt pigmenting was observed to reduce reflectance and optical band gap from 3.34 to 3.10 eV indicating good photocatalytic properties. In this study, ZnO film pigmented with cobalt for 20 s was found to be the most photocatalytic with a rate constant of 0.0317 h−1 and hence had the optimum cobalt concentration for photocatalytic water treatment. This can be applied in small-scale water purification.

Electrospun Poly(methyl methacrylate)/TiO2 Composites for Photocatalytic Water Treatment

Electrospinning was successfully used for the one-step fabrication of poly(methyl methacrylate) (PMMA) fibers loaded with an inorganic photocatalyst—titanium oxide (TiO2). By tuning the PMMA/TiO2 ratio and the electrospinning conditions (applied voltage, needle tip-to-collector distance, and flow rates), PMMA/TiO2 composites with selected organic/inorganic ratios, tailored designs, and targeted properties were obtained. The morphology of the electrospun composites was affected by the amount of TiO2 incorporated into the PMMA fibers. In addition, the inorganic photocatalyst had an impact on the wettability, thermal stability, and optical properties of the electrospun composites. In particular, the surface wettability of the composites was strongly influenced by UV light irradiation and from hydrophobic became superhydrophilic. Moreover, PMMA/TiO2 composites had enhanced tensile strength in comparison with those of bare PMMA mats. The electrospun PMMA/TiO2 composites showed excellent photocatalytic efficiency against the model organic pollutant—methylene blue—which is very promising for the future development of membranes that are highly efficacious for photocatalytic water treatment.