Photodegradation Rate Research Articles

Mesoporous I-doped-g-C3N4 with C Vacancies as Superior Visible-light-driven Photocatalyst for Removal of Tetracycline Antibiotic

The discovery of g-C3N4 (GCN) has attracted great attention for antibiotic pollutants from wastewater. Nonetheless, photocatalytic performance of GCN suffers from rapid recombination, limited surface area, and restricted under visible light irradiation. In this work, different concentrations of mesoporous I-doped GCN were synthesized. Mesoporous I-doped GCN with 0.50g of I dopant (GCN-I0.50) manage to photodegrade 99.8% of TC within 150min under visible light (λ > 420nm). The tetracycline (TC) antibiotic photodegradation rate increased by 2.64 times than that of parent GCN. It is proven that I-dopant and generation of C vacancy provides extra electrons to reconstruct the GCN network. This led to a stronger driving force in photo-oxidation photodegradation. The C vacancy also acts as a trap to prevent fast charge recombination. Subsequently, the substantial surface area and mesoporous nature of GCN-I0.50 (63.76 m2/g) facilitate the breakdown of a greater quantity of TC pollutants. In addition, the structural distortion of GCN-I0.50 has promoted n-π* transition, extended photoactivity to visible light region due to smaller band gap (2.45eV). The GCN-I0.50 photocatalyst significantly improved the TC photodegradation rate with good stability.

Differential photoaging behaviors of different colored commercial polyethylene microplastics in water: The important role of color characteristics

Upon entering the environment, plastics would undergo photoaging and forming microplastics (MPs). However, information on the photoaging behavior of colored MPs and how the color characteristics (wavelength, lightness, and saturation) influence their photoaging process is still lacking. Thus, attention was paid to comparing the photoaging process of transparent and five-colored MPs. To reveal the degree of photodegradation and photooxidation, physicochemical changes (e.g., surface morphology, functional groups, and the leaching of intermediates) of transparent and five-colored MPs were explored. Photodegradation rates and photooxidation degrees ranked transparent > yellow > red ≈ orange > green > blue. However, transparent and five-colored MPs exhibited a different photoaging sequence and eluted different photodegradation products from each other. Pearson correlation analysis was used to describe the relationships between color characteristics (wavelength, lightness, and saturation) and their photoaging properties, and the results indicated that MPs (yellow, red, and orange) with longer color wavelength, higher lightness, and lower saturation are more susceptible to UV light than MPs with shorter color wavelength, lower lightness and higher saturation (green and blue). The findings demonstrate that the photoaging process of colored MPs is correlated to their color characteristics, highlighting the important role of color in MPs' environmental fate.

Introducing a prediction method for the photodegradation of p-cresol, a phenolic contaminant of emerging concern, in wastewater effluent

Despite extensive efforts to understand the photodegradation of phenolic contaminants of emerging concern (PhCECs) in aquatic systems, prediction methods, especially in waters containing effluent organic matter (EfOM), remain underdeveloped. This study introduces a prediction method for p-cresol, a representative PhCECs, based on correlations between EfOM optical parameters and p-cresol kinetic parameters. We examined p-cresol photodegradation in various EfOM samples, characterized by their optical properties, and used the reaction rate coefficient between EfOM and p-cresol, α3EfOM⁎, to quantify and predict p-cresol degradation in different wastewater effluent samples. Results showed significant correlations between p-cresol's photodegradation rate constant (0.144 to 0.441 h−1) and EfOM characteristics, with α3EfOM⁎ values ranging from 4 × 1011 to 10 × 1011 M−1 s−1. The method was validated with p-cresol at concentrations ranging from 25 to 100 μM and multiple EfOM samples. The method's applicability was further evaluated using propranolol, a pharmaceutical contaminant of emerging concern, demonstrating its versatility for predicting the degradation behavior of other contaminants in different wastewater samples. The method accurately predicted p-cresol and propranolol degradation across diverse wastewater samples, suggesting its potential for expansion to other classes of contaminants, aiding in water quality management, improving wastewater treatment processes, and enhancing environmental risk assessments.

Enhancement of the photocatalytic efficiency of ZnO utilizing luminescent Y2O3 particles

Abstract This study explored the superior photocatalytic performance of the nanoscale zinc oxide-yttrium oxide (ZnO-Y2O3) based composite over ZnO nanoparticles (NPs). We investigated this by following the photocatalytic degradation efficiency of methylene blue (MB). The sol–gel synthesized Y2O3 and ZnO NPs were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The spectral behaviour and photocatalytic efficiency of the proposed composite were investigated by UV–vis spectrophotometry, steady-state and time-resolved photoluminescence (PL) measurements, respectively. The results indicated the successful formation of Y2O3 and ZnO nanoparticles with desirable structural properties. The photocatalytic degradation efficiency of the MB solution was evaluated for different concentrations of the counterparts of the ZnO-Y2O3 composite. In particular, the ZnO-5Y2O3-based composite showed superior photocatalytic activity after 150 min of UV irradiation, achieving 98.4% degradation of the MB solution compared to the 77% degradation achieved by pure ZnO. Although Y2O3 alone does not exhibit photocatalytic activity, its combination with ZnO significantly enhances the photocatalytic performance of ZnO. This improvement was attributed to the luminescence properties of Y2O3. By elucidating this unique mechanism, the performance of photocatalytic materials can be significantly enhanced. In our study, the improvement of the photodegradation rate constant (kapp) of ZnO from 0.009 min−1 to 0.0242 min−1 demonstrated the promising photocatalytic efficiency of the ZnO-5Y2O3 based composite, opening up exciting possibilities for further applications in environmental remediation and other fields.

Optimal Suppression of Photocatalytic Activity of Hybrid TiO2 Particles in Epoxy Thin Film by Using Taguchi Method

In this study, two different Al2O3-TiO2 and SiO2-TiO2 hybrid TiO2 particles were synthesised by using silica (SiO2) and alumina (Al2O3) to suppress the photocatalysis of TiO2. Key variables such as the concentration of the hybridization material (C), heating temperature (Th), and calcinating temperature (Tc) were selected with performance measured by photodegradation rate. The Taguchi L9 orthogonal array, a systematic approach used in the design of experiments (DOE), confirmed A333 (Al2O3-TiO2) achieved 99% photodegradation suppression with photodegradation rate reduced significantly from 0.01305 min−1 to 0.00009 min−1 and improved yellowing resistance by 63%, while S323 (SiO2-TiO2) achieved 75% suppression with photocatalysis activity decreased from 0.01305 min−1 to 0.0033 min−1 and 42% improved resistance. X-ray Diffraction (XRD) analysis showed A333 had a higher rutile phase (40.1% vs. 10.2% for S323), and Fourier Transform Infra Red (FTIR) and Field Emission Scanning Electron Microscopy (FESEM) analyses revealed A333's rougher surface and lower surface area compared to S323 and pure TiO2. Overall, A333 effectively suppressed photocatalysis and improved yellowing resistance of epoxy thin film. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Synthesis of Mesoporous ZnO•SiO2 Nanocomposite from Rice Husk for Enhanced Degradation of Organic Substances Including Janus Green B under Visible Light

Rice husk (RH) is often mentioned as an agricultural by-product, often used in the pass as fertilizer and for raw burning. With modern science, RH have been researched and found many new potential benefits and applications. In this study, RH were used to synthesize amorphous SiO2, which was used to prepare the ZnO•SiO2 nanocomposites by a hydrothermal method. The as-synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and N2 adsorption/desorption isotherm. Their photocatalytic properties were studied by an ultraviolet-vis spectrophotometer and a fluorescence spectrophotometer. The ZnO•SiO2 nanocomposite has an excellent ability to degrade organic substances such as dyes, antibiotics, caffeine, etc. The effects of operating parameters on the photo-degradation reaction progress, including catalyst dosage, initial dye concentration, and pH of the initial dye were investigated in detail. In addition, the photodegradation rate of the dye on the ZnO•SiO2 nanocomposite was evaluated using the pseudo-first-order model. The ZnO•SiO2 nanocomposite can be used as a photocatalyst for wastewater treatment as it detaches much more easily from the solution. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Roles of direct and indirect photodegradation in the photochemical fates of three 3rd generation fluoroquinolones

Fluoroquinolones (FQs) are widely prescribed antibiotics that are commonly detected in aquatic environments, but the persistence, fates, and ecotoxicities of new generation FQs have yet to be fully investigated. We investigated the direct and indirect (hydroxyl radical (·OH), singlet oxygen (O21), and excited stated of organic matter (3CDOM*)) photodegradation of three 3rd generation FQs, moxifloxacin (MOX), gatifloxacin (GAT), and sparfloxacin (SPAR). The photodegradation rates and photolytic quantum yields (ΦFQ) of the FQs depended on their dissociation species at different pH in a range of 1×10−4 to 1×10−3 M mol-photon-1. Unlike MOX and GAT whose zwitterions had the highest ΦFQ, the anionic form of SPAR had the highest ΦFQ. The k·OH,FQ values were in the order of: k·OH,SPAR > k·OH,GAT ≈ k·OH,MOX with the 1010M−1s−1 order of magnitude. The kO21,FQ values were in the order of: kO21,SPAR (∼108M−1s−1) > kO21,MOX (∼107M−1s−1) > >> kO21,GAT (insignificant). Higher kLC*3,FQ values were observed for MOX (109 to 1010M−1s−1) compared to GAT and SPAR (108 to 109M−1s−1). The zwitterions had the highest reactivities with ·OH and the lowest reactivities with O21 and 3CDOM*. Reactions with ·OH enhanced the formation of transformation products (TPs) from decarboxylation and sidechain oxidation pathways, whereas reactions with O21 and 3CDOM* enhanced the formation of TPs from sidechain oxidation pathways. Some of the TPs were predicted to exhibit aquatic ecotoxicity and environmental persistence. The half-lives of the FQs were estimated to be 0.42 to 0.67 h for MOX and SPAR, and 4.6 to 4.9 h for GAT. Their half-lives and main photochemical fates depended on the surface water pH and water column depth. These results highlight the key roles that photodegradation plays in removing new generation FQs from aquatic environments, though this might lead to the formation of TPs that are harmful to aquatic ecosystems.

Investigating the efficacy of Palladium Doped Ceria for the Photodegradation of Azo Dyes

Ceria (CeO2) was prepared by microwave assisted precipitation method while sonothermal method was utilized for the synthesis of palladium doped ceria (Pd-CeO2) photocatalyst. HR-TEM analysis confirms the face centered cubic geometry (FCC) of CeO2. The particle size of Pd-CeO2 calculated from HR-TEM analysis (7.6 ± 2.18 nm) is in close relation with XRD (8.25±0.25 nm). The SAED pattern of Pd-CeO2 shows the poly crystallinity where the d-spacing was 0.31 and 0.30 nm which corresponds to CeO2 and Pd crystal facets 111 and 100 respectively. The amount of dopant and existence of Pd, Ce and O was confirmed from EDX spectra and elemental mapping. BET surface area analysis of CeO2 (64.45 m2/g), Pd-CeO2 (60.20 m²/g) revealed that the decrease in the surface area of CeO2 due to Pd loading which is confirmed by pore volume (0.079 cm³/g) for CeO2 and pore volume for Pd-CeO2 (0.073 cm³/g). The photocatalytic activity of Pd-CeO2 was screened against a model azo dye Acid red-4 (AR-4). The fluctuation of the rate of photodegradation (PD) of AR-4 was observed under different reaction conditions. Therefore, the reaction parameters were optimized to achieve best catalytic activity up to PD; 98 %. The kinetic study suggests that the PD of AR-4 follows 1st order kinetics with regression coefficient (R2=0.973) and rate constant (k = 0.024/min). Recycling study revealed the prolong use of catalyst without significant loss of activity. DFT study and experiments revealed the synergism of Pd on the photo response of CeO2. Perhaps this synergistic effect due to metal support interaction, causes redistribution of charges and Fermi energy levels. The synthesized catalyst showed potential application for the treatment of textile industrial effluents.

Effect of magnesium doping on the structure, optical properties and photocatalytic efficiency of ZnO nanostructures deposited by atmospheric pressure MOCVD

ZnO nanostructures doped by magnesium impurity were grown on Si substrates by atmospheric pressure MOCVD deposition using Zn and Mg acetylacetonates as initial precursors. XRD patterns confirm the successful incorporation of Mg ions into ZnO lattice. Room-temperature photoluminescence spectra of Mg-doped ZnO nanostructures demonstrate near-band edge emission and visible deep-level emission with ratios 2.9, 1.3 and 0.3 correspondingly for 1, 2.4 and 5.7 at. % of Mg in ZnO nanostructures. Raman measurements showed decreasing in intensity for ZnO modes with increasing Mg content. The best photodegradation rate constant was observed for ZnO NS with 2.4 at. % of Mg.

Upconversion Phosphor-Driven Photodegradation of Plastics.

Plastic waste poses a profound threat to ecosystems and human health, necessitating novel strategies for effective degradation in nature. Here, we present a novel approach utilizing upconversion phosphors as additives to significantly accelerate plastic photodegradation in nature via enhancing ultraviolet (UV) radiation. Pr-doped Li2CaGeO4 (LCGO:Pr) upconversion phosphors readily converting blue light into deep-UV radiation, dramatically improve photodegradation rates for polyethylene (PE) and polyethylene terephthalate (PET) microplastics. In situ spectroscopic studies show that upconversion fluorescence initiates the photophysical cleavage of C-C and C-O bonds in the backbones of PE and PET, resulting in plastic degradation. Moreover, incorporating LCGO:Pr into polypropylene (PP) sheets realizes markedly enhanced photodamage, with the cracking area increasing by nearly 38-fold under simulated sunlight for 10 days. This underscores the potential of employing this approach for the construction of light-driven destructible polymers. Further optimization and exploration of material compatibility hold promise for developing sustainable photodegradable plastics.

Enhanced catalytic activity of modified g-C3N4 heterojunction for photocatalytic degradation of methylene blue from wastewater

Rapid recombination of photoinduced charge carriers and poor photocatalytic degradation performance greatly hinder the large-scale application of g-C3N4 photocatalysis. Therefore, the g-C3N4 is modified by BiPO4 to overcome its poor photocatalytic performance, which is investigated by methylene blue (MB) removal. The S scheme heterojunction is constructed by modifying g-C3N4 with BiPO4, which can effectively preserve the redox activities of holes and electrons on VB and CB, exhibiting good photocatalytic activity. Therefore, the modified g-C3N4 exhibits excellent photocatalytic activity with efficient separation of the photoelectron-hole, compared to pure g-C3N4 and BiPO4. The modified g-C3N4 exhibits large MB degradation removal of 96.7 %, which is significantly larger than the pure g-C3N4 (46.3 %) and BiPO4 (3.3 %) owe to synergy, respectively. The photodegradation rate constant of the modified g-C3N4 is 4.8 and 43 times larger than that of the pure g-C3N4 and BiPO4, respectively. The modified g-C3N4 still has large MB removal of 92.9 % after 5 cycles, indicating excellent stability and recyclability. The fractal density calculation of the modified g-C3N4 is investigated combined with LUMO and HOMO analysis. The MB photocatalytic degradation process follows the S scheme charge transfer mechanism, based on degradation mechanism analysis combined with semiconductor energy band and density functional theory calculation analysis. The MB photocatalytic degradation path is systemically analyzed based on MS-UPLC result analysis, which indicates that MB is finally decomposed into CO2 and H2O, achieving the degradation of MB.

Ag induced plasmonic TiO2 for photocatalytic degradation of pharmaceutical under visible light: Insights into mechanism, antimicrobial and cytotoxicity studies

Global concerns include water scarcity and shortage, which are escalated by organic pollutants such as naproxen (NPX) that deteriorate drinking water and taint access to safe drinking water by humans. Moreover, NPX may cause gastrointestinal difficulties, cardiovascular risks, kidney damage, allergic reactions, liver toxicity, bleeding issues and pregnancy risks, hence it is essential to remove it in water. Ag-TiO2 was synthesized by hydrothermal method for NPX degradation. Ag on TiO2 reduced the band gap and surface area of TiO2 and resulted in a plasmonic Ag-TiO2 composite of 0.2 % Ag. The photocatalytic degradation of 0.2 % Ag-TiO2 was 80 % in 180 minutes using a solar simulator during NPX degradation with a first order reaction rate that was 3.6 times faster than that of pure TiO2 and the catalyst showed good stability for four cycles. The dual activity of Ag0 surface plasmon resonance improved light absorption capability and enhanced charge transfer for increased photodegradation rate and stability. The antibacterial studies demonstrated that 0.2 % Ag-TiO2 posted strong antibacterial properties under light irradiation and less in the dark, with a greater effect on gram-negative than gram-positive bacteria. The minimum inhibitory concentration (MIC) values of 620, 1250, 2500, 2500 µg/mL were attained against B. subtilis, S. aureus, E. coli and S. typhimurium bacteria, respectively. The low cell toxicity of 0.2 % Ag-TiO2 was determined using human embryonic kidney (HEK293) cells with an inhibitory concentration (IC50) of 61.09 ± 0.24 µg/mL under light irradiation. Radical trapping experiments demonstrated that hydroxyl radicals (OH•) played a vital role during the degradation and bactericidal activity of NPX under light irradiation. This work advances new insights on the synthesis of less toxic nanoparticles with high photocatalytic and bactericidal activity for possible applications at industrial scale.

Z-Scheme Ag2S-Ag-In2O3 Heterostructure with Efficient Antibiotics Removal under Natural Sunlight.

The widespread distribution of antibiotics in natural waters is a great threat to human health. Photocatalytic degradation is an environmentally friendly technology to remediate antibiotic-polluted waters, driven by endless solar energy. Herein, a Z-scheme Ag2S-Ag-In2O3 heterostructure photocatalyst is prepared to remove antibiotics under environmental conditions. Under natural sunlight (light intensity: ∼78 mW/cm2) irradiation, the optimal Ag2S-Ag-In2O3 (10-ASAIO) exhibits considerable performance for decomposing diverse antibiotics, including norfloxacin (NOR), tetracycline hydrochloride, sulfisoxazole, ciprofloxacin, chlortetracycline hydrochloride, and ofloxacin. The NOR photodegradation rate constant of 10-ASAIO reaches 0.025 min-1, which is 12.50, 5.00, and 6.25 times higher than that of In2O3 (0.002 min-1), Ag-In2O3 (0.005 min-1), and Ag2S-In2O3 (0.004 min-1), respectively. This performance of the 10-ASAIO photocatalyst for decomposing NOR under natural sunlight exceeds most of the previously reported photocatalysts under a xenon lamp. Particularly, due to the intermittency of natural sunlight, a light-emitting diode (LED) lamp (light intensity: 5.1 mW/cm2) is also used as a light source, and 72.20% of NOR can be degraded with irradiation for 12 h. The effects of many water characteristics (water bodies, coexisting inorganic anions, pH, and humic acid) on the degradation performance of 10-ASAIO have been investigated, which exhibits stable degradation efficiency in variable aquatic environments. A 10-ASAIO catalyst-coated frosted glass sheet is fabricated to settle the problem of recovery of powder photocatalysts, and the immobilized catalyst shows outstanding activity and stability to decompose NOR. The photocatalytic mechanism and pathway of degrading NOR over 10-ASAIO have also been systemically investigated and proposed. The ecotoxicity (phytotoxicity and biotoxicity) of the 10-ASAIO photocatalyst and treated NOR solution have been tested by their toxic effects on cabbage seeds and Staphylococcus aureus (S. aureus). This work provides a feasible photocatalytic system for environmental pollutant remediation under natural sunlight or an LED lamp.

Optical characteristic of dissolved organic matter polar fractions by spectrum technologies and the relationship with indirect photodegradation of ofloxacin

Ofloxacin (OFL) is a commonly used antibiotic and is widely present in various water bodies. Indirect photodegradation is crucial for the transformation and fate of antibiotics in surface water, which largely depends on the structure and composition of dissolved organic matter (DOM). Nevertheless, knowledge about the optical characteristics of diverse DOM polar fractions as well as the relationship with indirect photodegradation of antibiotics is still scarce. In this study, XAD-8 in combination with anion and cation exchange resins was used to separate DOM into six polar fractions: hydrophilic acid (HIA), hydrophilic basic (HIB), hydrophilic neutral (HIN), hydrophobic acid (HOA), hydrophobic basic (HOB) and hydrophobic neutral (HON). UV–vis and fluorescence spectroscopy were applied to analyze DOM polar fractions and explore their impact on OFL indirect photodegradation. The results showed that indirect photodegradation was the primary photodegradation route of OFL when the irradiation wavelength was greater than 320 nm, triple-state excited DOM (3DOM*) was the main reactive intermediates (RIs) that affected the indirect photodegradation of OFL. Excitation-emission matrix spectroscopy combined with parallel factor analysis (EEMs-PARAFAC) and correlation analysis demonstrated that terrestrial humic-like substances could yield generous RIs to facilitate OFL indirect photodegradation. The HIB and HOA fractions of SRNOM contained large aromaticity and humification degree and more terrestrial humic-like substances, thus exhibiting greater OFL indirect photodegradation rates. The HOA and HOB fractions of FA had abundant terrestrial humic-like substances and contributed more to OFL indirect photodegradation. This study helped us understand the effect of DOM structural characteristics on the OFL indirect photodegradation.

Effect of 1,4-Napthaquinone (NQ) and benzophenone (BPH)on the photodegradation and biodegradation of methyl cellulose film

The induced photodegradation of methyl cellulose (MC) films in air was investigated in the absence and presence of aromatic carbonyl compounds(photosenssitizers): 1,4-naphthaquinone (NQ) and benzophenone (BPH) by accelerated weathering tester. The addition of (0.01 wt %) of low molecular weight aromatic carbonyl compounds to cellulose derivatives films(25µm in thickness) enhanced the photodegradation of the polymer films.The photodegradation rate was measured by the increase in carbonyl absorbance. Decreases in solution viscosity and reduction of molecular weight were also observed in the irradiated samples. Changes in the number-average chain scission, the degree of deterioration and in the quantum yield of chain scission values are also observed, and it was concluded that branching or cross-linking has occurred for cellulose derivative with NQ and BPH. Findings from all analytical techniques indicated that the 1,4-naphthaquinone (NQ) photosensitizer enhance the photodegradation of methyl cellulose more than benzophenone (BPH). The effect of the photosensitizer concentration, (ranging from 0.01 to 0.1 %), on the rate of photodegradation was also monitored for MC films. The rates are increased with increasing the photosensitizer concentration. The effect of film thickness is also studied at fixed sensitizer concentration (0.05%), and results show that the rate of cellulose derivative photodegradation decreases with increasing film thickness. The rate constants of the photodegradation of the photosensitizers deduced in cellulose derivatives films, [at concentration of (0.1%)by weight and thickness (25µm)]. Biodegradation of irradiated cellulose derivatives films was conclusively established with bacteria type Pseudomonas aeuroginosa Rb-19 isolated from crude oil. The amount of bacteria growth on MC after 30 days was lower, while there was no growth observed in MC with BPH

A novel 0D/3D Z-Scheme heterojunction ZnS/MIL-88(A) with significantly boosted photocatalytic activity toward tetracycline

Coupling two different photocatalytic materials to construct a heterojunction is a preferable strategy for obtaining the composite photocatalyst with high activity. Herein, a novel 0D/3D Z-scheme heterostructure ZnS/MIL-88(A) was constructed by anchoring 0D ZnS nanoparticles on the surface of the 3D MIL-88(A). The prepared ZnS/MIL-88(A) was characterized by using FT-IR, XRD, SEM, UV–vis and XPS. The photodegradation of tetracycline (TC) was conducted under the irradiation of visible light to evaluate the photocatalytic performance of ZnS/MIL-88(A). The creation of the Z-scheme heterostructure between ZnS and MIL-88(A) enables ZnS/MIL-88(A) to exhibit excellent visible-light absorption ability and dramatically boost separation and transfer of the photo-induced charge carriers. Compared with MIL-88(A), ZnS/MIL-88(A) shows prominently enhanced photocatalytic activity toward tetracycline, achieving a TC degradation rate of 94 %. The highest photodegradation rate constant (0.02083 min−1) of TC by ZnS/MIL-88(A) is 7.77 and 12.33 folds as large as those by MIL-88(A) and ZnS, respectively. After five cycles of reuse, ZnS/MIL-88(A) shows only a slightly decreased TC removal rate, presenting excellent photo-stability. Furthermore, the Z-scheme interfacial charge migration mode and the photocatalytic mechanism of ZnS/MIL-88(A) were discussed according to the band position as well as the identification result of the active species. The radicals ·O2− and ·OH generated in photocatalysis serve as major reactive species to decompose TC. This work provides a new way for designing efficient composite photocatalysts.

A Comparative Study of Congo Red Textile Dye Photodegradation Using ZnO Al and ZnO Al+Mn Nanoparticles

Photodegradation of Congo Red textile dye was successfully carried out using ZnO Al and ZnO Al+Mn nanoparticles synthesized using the bottom-up coprecipitation method. Powder X-ray diffraction provides information that Al and Mn doping successfully inserted in the host crystal structure while maintaining the Hexagonal Wurtzite crystal structure. However, a shift in the diffraction peak caused by the lattice distance changes with the addition of doping. FE-SEM EDS provides information that both nanoparticles are nonuniform sphere-like due to the addition of dopping, and each dopping is detected through EDS spectra. There is a decrease in the gap energy in each sample. ZnO Al nanoparticles have a gap energy of 3.29 eV, and ZnO Al+Mn nanoparticles have a gap energy of 3.28 eV. However, the decrease in the gap energy is not directly related to the percentage and kinetic rate of Congo Red photodegradation. Adding 5 mg of ZnO Al Nanoparticles powder could degrade Congo Red up to 97.9 % within 120 min using UV A radiation or 0.03504/min. At the same time, adding ZnO Al+Mn Nanoparticles powder with the same parameters could only degrade 67.6 % or 0.00759/min. HIGHLIGHTS Energy Bandgap Modification of ZnO Nanoparticles The incorporation of Al single dopants and Al, Mn co-dopants into ZnO nanoparticles synthesized via a bottom-up coprecipitation method significantly alters the energy bandgap. Al single doping resulted in a bandgap of 3.29 eV, while Al, Mn double doping yielded a bandgap of 3.28 eV. Enhanced Photocatalytic Activity of Al-Doped ZnO Al-doped ZnO nanoparticles exhibited superior photocatalytic activity toward the degradation of Congo Red textile dye. With a photodegradation rate constant of 0.03504 min⁻¹, these nanoparticles achieved 97.9 % degradation of Congo Red within 120 minutes. Comparative Photocatalytic Performance of Al, Mn Co-Doped ZnO While Al, Mn co-doped ZnO nanoparticles were synthesized using the same method, their photocatalytic performance for Congo Red degradation was notably lower than that of Al-doped ZnO. The calculated photodegradation rate constant was 0.00759 min⁻¹, resulting in 67.6 % degradation within the same timeframe. GRAPHICAL ABSTRACT

Effects of coexisting nanomaterials on the photodegradation behavior and ecotoxicity of antibiotics in the aqueous

Nanomaterials (NPs) and antibiotics, as two emergent pollutants, forms a complex contamination through their interaction, potentially causing adverse effects on the organism. This study systematically examined the influence of two NPs (CuO NPs and carbon nanotubes, CNTs) on the photodegradation behavior of tetracycline (TC) and their combined toxic effects on Chlorella vulgaris. The results showed that CuO NPs significantly accelerated TC photodegradation compared to CNTs, increasing the TC photodegradation rate constant by187.6%. Electron spin resonance (ESR) indicated that under the coexistence of CuO NPs or CNTs, 1O2、O2•- and •OH were the main active species promoting TC photodegradation. Probe and quenching experiments confirmed the predominant role of O2•- and 1O2 in the presence of CuO NPs and CNTs. Additionally, three possible TC photodegradation pathways were proposed for the coexistence of CuO NPs and CNTs. In the Chlorella vulgaris growth inhibition experiment, the combined toxicity of CuO NPs or CNTs and TC was higher than that of individual substance, indicating significant synergistic effects, especially with the combination of CNTs and TC. This study provides a new perspective on accurately assessing the environmental behaviors and risks when NPs and antibiotics coexist.

2D porous hexaniobate-bismuth vanadate hybrid photocatalyst for photodegradation of aquatic refractory pollutants

Metal oxide semiconductors are highly promising due to their excellent photocatalytic performance in the photodegradation of industrial waste containing refractory chemical compounds. A hybrid structure with other semiconductors provides improved photocatalytic performance. In this work, porous and two-dimensional (2D) hexaniobate-bismuth vanadate (Nb6-BiVO4) Z-scheme hybrid photocatalysts are synthesized by chemical solution growth (CSG) of BiVO4 over electrophoretically deposited Nb6 thin films. The structural and morphological analysis of Nb6-BiVO4 hybrid thin films evidenced the well-crystalline uniform growth of monoclinic scheelite BiVO4 over lamellar Nb6 nanosheets. The Nb6-BiVO4 hybrid thin films exhibit a highly porous randomly aggregated nanosheet network, creating the house-of-cards type morphology. The Nb6-BiVO4 hybrid thin films display a strong visible light absorption with band gap energy of 2.29 eV and highly quenched photoluminescence signal, indicating their visible light harvesting nature and intimate electronic coupling between hybridized species beneficial for photocatalytic applications. The visible-light-driven photodegradation performance of methylene blue (MB), rhodamine-B (Rh-B) dyes, and tetracycline hydrochloride (TC) antibiotic over Nb6-BiVO4 hybrid are studied. The best optimized Nb6-BiVO4 thin film shows superior photocatalytic activity for photodegradation of MB, Rh-B dyes, and TC antibiotic with photodegradation rates of 87.3, 92.8, and 64.7 %, respectively, exceptionally higher than that of pristine BiVO4. Furthermore, the mineralization study of Nb6-BiVO4 thin film is conducted using chemical oxygen demand (COD) analysis. The optimized Nb6-BiVO4 thin film shows superior percentage COD removal of 83.33, 85.42, and 61.36 % for MB, Rh-B dyes and TC antibiotic, respectively. The present results highlight the expediency of hybridization in enhancing the photocatalytic activity of pristine BiVO4 by minimizing its charge recombination rate and improving chemical stability.

The synthesis of Bi2MoO6 with metallic and nonmetallic vacancies for degradation of LVF in visible light

Defect engineering advantages include regulating the band structure of photocatalytic materials, inhibiting the recombination of photoelectron-hole pairs, and promoting the conversion of photogenerated electrons into active radicals. In this paper, bismuth molybdate (Bi2MoO6) photocatalysts with double vacancies (VBi-O-BMO) were prepared by solvothermal and ionic eutectic solvent methods. EPR, TEM, and XPS results confirmed the successful construction of oxygen and bismuth vacancies on Bi2MoO6. The photocatalytic performance of the prepared catalysts was investigated by photodegradation of levofloxacin hydrochloride (LVF) under visible light. The double vacancies markedly enhanced the photocatalytic properties of Bi2MoO6, with the photodegradation rate of VBi-O-BMO reaching 88.36 % for 40 mg/L LVF within 60 min. Kinetic studies have demonstrated that the reaction rate constant of VBi-O-BMO can reach 0.0351 min−1, which is 3.2 times higher than that of bulk-BMO. This can be attributed to the favorable synergistic effect of oxygen and bismuth double vacancies. VO not only captures oxygen and electrons, facilitating the generation of superoxide radicals (O2−), but also elevates the conduction band position and boosts the reduction capability of Bi2MoO6. VBi not only captures photogenerated holes (h+) to directly impact LVF degradation, but also promotes interfacial charge transfer and inhibits the recombination of electron-hole pairs. Furthermore, the intermediates and degradation pathways of LVF photodegradation were surmised based on the LC-MS analysis. The reaction mechanism of LVF photodegradation by VBi-O-BMO was elucidated through the application of the free radical pathway. This study demonstrates a methodology for the creation of double vacancies in catalysts and the significant potential of VBi-O-BMO for the remediation of antibiotic residues in water under visible light.