Photocatalytic Degradation of Fluoroquinolone Antibiotics in Solution

The photocatalytic degradation of two quinolone-type antibiotics (ciprofloxacin and levofloxacin) in aqueous solution was studied, using catalysts based on ZnO nanoparticles, which were synthesized by a thermal procedure. The efficiency of ZnO was subsequently optimized by incorporating different co-catalysts of gC3N4, reduced graphene oxide and nanoparticles of gold. The catalysts were fully characterized by electron microscopy (TEM and SEM), XPS, XRD, Raman, and BET surface area. The most efficient catalyst was 10%Au@ZnONPs-3%rGO-3%gC3N4, allowing to obtain degradations of both pollutants above 96%. This catalyst has the largest specific area, and its activity has been related to a synergistic effect, involving factors as relevant as the surface of the material and the ability to absorb radiation in the visible region, mainly produced by the incorporation of rGO and gC3N4 to the semiconductor. The use of different scavengers during the catalytic process, was used to establish the possible photodegradation mechanism of both antibiotics.

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

Kinetics and Mechanism of Aniline and Chloroanilines Degradation Photocatalyzed by Halloysite-TiO2 and Halloysite-Fe2O3 Nanocomposites

The kinetics of photocatalytic degradation of aniline, 2-chloroaniline, and 2,6-dichloroaniline in the presence of halloysite-TiO2 and halloysite-Fe2O3 nanocomposites, halloysite containing naturally dispersed TiO2, Fe2O3, commercial TiO2, P25, and α-Fe2O3 photocatalysts, were investigated with two approaches: the Langmuir–Hinshelwood and first-order equations. Adsorption equilibrium constants and adsorption enthalpies, photodegradation rate constants, and activation energies for photocatalytic degradation were calculated for all studied amines photodegradation. The photodegradation mechanism was proposed according to organic intermediates identified by mass spectrometry and electrophoresis methods. Based on experimental results, it can be concluded that after 300 min of irradiation, aniline, 2-chloro-, and 2,6-dichloroaniline were completely degraded in the presence of used photocatalysts. Research results allowed us to conclude that higher adsorption capacity and immobilization of TiO2 and Fe2O3 on the halloysite surface in the case of halloysite-TiO2 and halloysite-Fe2O3 nanocomposites significantly increases photocatalytic activity of these materials in comparison to the commercial photocatalyst: TiO2, Fe2O3, and P25.

Preparation of Activated Carbon/TiO2 Nanohybrids for Photodegradation of Reactive Red-35 Dye Using Sunlight

Activated carbon/titanium dioxide (AC/TiO2) nanohybrids were synthesized by a hydrothermal technique using various weight percent of commercial AC and were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). The synthesized nanohybrids were applied to photodegradation of Reactive Red-35 (RR-35) dye in aqueous solution using sunlight. Due to the synergistic effect of adsorption and photodegradation activity, AC/TiO2 nanohybrids were more efficient in treating the aqueous dye solution than that of AC and TiO2. The maximum (95%) RR-35 dye removal from the water was obtained with 20 wt% AC/TiO2 within 30 min at natural pH of 5.6. The possible photodegradation mechanism of RR-35 dye with AC/TiO2 was discussed from the scavenger test. Moreover, AC/TiO2 was found to be suitable for long-term repeated applications through recyclability experiments. Therefore, AC/TiO2 nanohybrid is a promising photocatalyst for treating azo dyes especially RR-35 from water.

Photochemistry of 1-Phenyl-4-Allyl-Tetrazol-5-One: A Theoretical Study Contribution towards Mechanism Elucidation

The photodegradation mechanism of 1-phenyl-4-allyl-tetrazol-5-one has been studied using (time-dependent) density functional theory with the M06-HF, B3LYP, and PBE0 functionals and the VDZ basis set. All calculations have been carried out using the polarizable continuum model to simulate the solvent effects of methanol. The reaction pathway evolution on the triplet state has been characterised to validate a previously postulated experimental-based mechanism. The transition states and minimums have been initially located by local scanning in partial constrained optimisation, followed by a fully relaxed search procedure. The UV spectra has shown to be better described with PBE0 functional when compared with the experimental results, having the M06-HF a shift of 40 nm. From the energetic point of view, the postulated mechanism has been validated in this work showing a concerted photoextrusion of the N2 molecule. The intramolecular proton transfer occurs at a later stage of the mechanism after cyclization of the allyl group on a triplet biradical intermediate. The photoproduct observed experimentally, a pyrimidinone, has been characterised. The infrared spectroscopic reaction profile has also been proposed.

New Insights into Cd2+/Fe3+ Co-Doped BiOBr for Enhancing the Photocatalysis Efficiency of Dye Decomposition under Visible-Light

Uniform flowerlike microspheres Cd2+/Fe3+ co-doped BiOBr were prepared with the aid of the microwave hydrothermal process. The results indicate that the degradation performance of Bi1−xCdxOBr and Bi1−xFexOBr are 1.31 and 2.05 times that of BiOBr for RhB, respectively. Moreover, the novel Cd2+/Fe3+ co-doped BiOBr photocatalysts with ~0.42 eV impurity bands presented remarkably enhanced photocatalytic activities with being 3.10 times that of pure BiOBr, by achieving e−/h+ efficient separation and narrowed bandgap with the ions synergistic effect of Cd2+ and Fe3+. Based on DFT insights, the photodegradation mechanism was systematically studied that the conversion of multivalent Fe3+ ions promoted the production of •O2−, and Cd2+ ions worked as electron transfer mediators, which elucidated that the •O2− and h+VB mainly participated in the catalytic reaction. The experimental and theoretical results show that the synergistic effects of multi-ion doping have great potential in the field of photocatalysis.