Photodegradation Rate Research Articles

A novel interpretable machine learning model approach for the prediction of TiO2 photocatalytic degradation of air contaminants

Air contaminants lead to various environmental and health issues. Titanium dioxide (TiO2) features the benefits of autogenous photocatalytic degradation of air contaminants. To evaluate its performance, laboratory experiments are commonly used to determine the kinetics of the photocatalytic-degradation rate, which is labor intensive, time-consuming, and costly. In this study, Machine Learning (ML) models were developed to predict the photo-degradation rate constants of air-borne organic contaminants with TiO2 nanoparticles and ultraviolet irradiation. The hyperparameters of the ML models were optimized, which included Artificial Neural Network (ANN) with Bayesian optimization, gradient booster regressor (GBR) with Bayesian optimization, Extreme Gradient Boosting (XGBoost) with optimization using Hyperopt, and Catboost combined with Adaboost. The organic contaminant was encoded through Molecular fingerprints (MF). Imputation method was applied to deal with the missing data. A generative ML model Vanilla Gan was utilized to create synthetic data to further augment the size of available dataset and the SHapley Additive exPlanations (SHAP) was employed for ML model interpretability. The results indicated that data imputation allowed for the full utilization of the limited dataset, leading to good machine learning prediction performance and preventing common overfitting problems with small-sized data. Additionally, augmenting experimental data with synthetic data significantly improved prediction accuracy and considerably reduced overfitting issues. The results ranked the feature importance and assessed the impacts of different experimental variables on the rate of photo-degradation, which were consistent with physico-chemical laws.

Solution combustion synthesis and exploration of chromium reduction and organic dyes degradation of cobalt tungstate (CoWO4) nanoparticles

Facile preparation route for cobalt tungstate (CoWO4) via cost effective, time saving, easy and solution combustion approach is described in the present paper. The structural, morphological properties of cobalt tungstate characterized by different physiochemical techniques which include X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray absorption (EDS). The optical properties assessed by UV–visible spectroscopy (DRS) and photoluminescence spectroscopy (PL). Using these methods, it was discovered that CoWO4 which has been synthesized displayed a monoclinic phase of Wolframite with great crystallinity and purity. The average crystallite size of prepared CoWO4 was 22 nm and band gap obtained was 2.84 eV due to which it can be used as visible light photocatalyst in aqueous medium. As a result, in this study, the photocatalytic degradation ability of CoWO4 was assessed by observing the aqueous phase degradation of the most widely used dyes, methylene blue (MB) and Rhodamine-B as well as Cr(VI) reduction under visible light. Almost all MB degraded in 90 min whereas 69 % degradation of RhB takes place in 240 min under visible light irradation. The different aspects for low rate of photodegradation of RhB dye than MB dye was also discussed in this report. The present study deals advanced approach that CoWO4 can also be used as capable visible light photocatalyst for degradation of dangerous contaminants and for reduction of carcinogenic Cr(VI) into nontoxic Cr(III) from waste water.

Understanding the role of ZnO nanosheet surface in photocatalytic dye degradation: The key to effective wastewater treatment

The current study proposes an introduction of interfering ions to the reaction medium as a simple way for obtaining efficient visible-light driven photocatalysts with active surface based on ZnO nanosheets. 9 samples with different morphological and structural parameters were obtained via simple and inexpensive precipitation and hydrothermal methods. XRD, SEM, FTIR, SSA, XPS, Raman, absorption spectra and DLS methods were used for ZnO nanosheet characterisation. An original approach was used to determine the amount of defects by processing Raman spectra via software specially designed for this purpose. XPS was used to estimate an overall amount of oxygen vacancies in the samples, and the DFT method was employed to model oxygen vacancies in the crystal structure. The latter were verified via absorption spectra. The most effective sample showed a dye degradation efficiency of 94 % after 60 min of irradiating by a common LED lamp available in a local store. The kinetic studies showed that the rate of adsorption and photodegradation depends on the DFT-calculated “surface-dye” interaction energy. Consequently, by regulating the ratio of ZnO nanosheet surface parameters, adsorption and photodegradation efficiency against a particular dye can be improved.

A polyethylene surrogate for microbial community enrichment and characterization

AbstractPlastic pollution is a vast and increasing problem that has permeated the environment, affecting all aspects of the global food web. Plastics and microplastics have spread to soil, water bodies, and even the atmosphere due to decades of use in a wide range of applications. Plastics include a variety of materials with different properties and chemical characteristics, with polyethylene being a dominant fraction. Polyethylene is also an extremely persistent compound with slow rates of photodegradation or biodegradation. In this study, we developed a method to isolate communities of microbes capable of biodegrading a polyethylene surrogate. This method allows us to study potential polyethylene degradation over much shorter time periods. Using this method, we enriched several communities of microbes that can degrade the polyethylene surrogate within weeks. We also identified specific bacterial strains with a higher propensity to degrade compounds similar to polyethylene. We provide a description of the method, the variability and efficacy of four different communities, and key strains from these communities. This method should serve as a straightforward and adaptable tool for studying polyethylene biodegradation.

A versatile one-stone-two-birds strategy for facile fabrication of molecularly imprinted BiOBr composites: An efficient approach for selective removal of target contaminants from water

In this work, we presented a versatile “one-stone-two-birds” strategy to directly introduce the imprinted cavities into BiOBr/polydopamine composite (BD-MIP) for selective removal of target contaminants from water. BD-MIP exhibited a superior adsorption capacity which is 3.49-times higher than that of the non-imprinted composite, due to the imprinted cavities in polydopamine. BD-MIP showed an improved photogenerated carriers’ behavior, with a superior photodegradation rate of 96.6% in 30 min, excellent selectivity with coefficients above 2.53, and good reusability. All imprinted composites, including BD-MIPs for different templates and MIPs in different BiOBr-based composites, demonstrated greater degradation efficiency than their corresponding non-imprinted composites. This work suggests that the proposed strategy is versatile for selective removal of contaminants, offering flexibility with BiOBr/composites and confirming its potential as an intelligent, eco-friendly, and adjustable method for contaminant removal from water.

Zeolite supported zinc oxide nanoparticles composite: Synthesis, characterization, and photocatalytic activity for methylene blue dye degradation

In the first stage of this study, zinc oxide nanoparticles (ZnO-NPs) were synthesized. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), selected area diffraction (SAED), and X-ray diffraction analyses (XRD). Subsequently, a composite material was obtained by coating ZnO-NPs with zeolite from Rátka, Hungary. The photocatalytic degradation of ZnO-NPs using Hungarian zeolite in the ZnO-Zeolite composite was investigated. The objective was to evaluate the efficacy of the ZnO-Zeolite composite in degrading methylene blue (MB) under ultraviolet-visible spectroscopy (UV). It was observed that the composite materials were influenced by the light source. The degradation rates showed that the ZnO-Zeolite composite with 100 mg L−1 MB achieved the highest photodegradation rate of 96.70 % when exposed to sunlight for 210 min. These findings indicate that the ZnO-Zeolite composite with a 1:5 ratio has the potential to significantly increase the photocatalytic activity, achieving a high yield of 96.70 % compared to raw zeolite. In the last stage of the study, equilibrium, kinetic, and thermodynamic studies were carried out. The photocatalytic maximum adsorption capacity of MB for the ZnO-Zeolite composite was calculated as qm= 41.32 mg g−1. In the adsorption and kinetic studies of the obtained composite, the best results were obtained with the Langmuir adsorption isotherm and pseudo-second-order kinetics. A desorption study has been conducted, and it has been determined that the composite can be reused for up to 7 cycles.

Enhanced Photocatalytic Activity of V2C MXene-Coupled ZnO Porous Nanosheets with Increased Surface Area and Effective Charge Transfer.

Photocatalysis performs excellently when degrading organic pollutants, but the photocatalytic degradation rate is not high for most photocatalysts due to their narrow sunlight adsorption range and high recombination rate of electron hole pairs. Herein, we use V2C-MXene with a wide sunlight adsorption range to couple ZnO porous nanosheets and form ZnO/MXene hybrids using a facile electrostatic self-assembly method. The ZnO/MXene hybrids acquired demonstrated improved photochemical efficiency in breaking down methylene blue (MB) when contrasted with porous ZnO nanosheets. The degradation rate of MB reached 99.8% under UV irradiation for 120 min after the ZnO/MXene hybrid formation, while 38.6% was attained by the ZnO porous nanosheets. Moreover, photodegradation rate constants (k) were calculated as 3.05 × 10-3 and 5.42 × 10-2 min-1 for ZnO porous nanosheets and ZnO/MXene hybrids, respectively, indicating that the photodegradation performance was enhanced by 17.8 times after the modification of V2C. This was probably because the modification of V2C can increase the specific surface area to provide more sites for MB adsorption, widen the sunlight adsorption range to produce good photothermal effect, and facilitate the transfer of photogenerated carriers in ZnO to promote the reaction of more photogenerated carriers with MB. Hence, this work offers a simple approach to creating effective photocatalysts for breaking down organic contaminants.

In-situ growth, and potent photocatalytic performance of gold-decorated reduced graphene oxide (Au/rGO): A soft nanocomposite material

The investigation focuses on the phenomenon of in-situ growth of gold-decorated reduced graphene oxide (Au/rGO) nanocomposites and its applications as a highly efficient photo-catalyst in the realm of mitigating environmental pollutants. In order to explore the degrading impact of rGO, rGO decorated with gold nanoparticles (Au/rGO) was successfully synthesized via a chemical reduction technique. The purity and functional characteristics of as-grown Au/rGO nanostructures were ascertained by structural, morphological, elemental, and optical investigation. Analysis of the acquired XRD pattern, FTIR and Raman spectra, and SEM and TEM images demonstrated the successful preparation of rGO and its decoration with Au nanoparticles. Moreover, under UV–VIS light, the as-prepared nanocomposite (Au/rGO) was employed as a photocatalyst for the degradation of a selected organic pollutant, methyl orange (MO) dye. The ‘Langmuir-Hinshelwood (L-H) model’ has been effectively used to show that the exposure of a surface monolayer to light causes MO dye molecules to adsorb. The mechanism and kinetics of the MO elimination approach suggest that pseudo-second-order kinetics are most accurately followed and described. The maximal photodegradation rates for MO dye using Au/rGo and rGO nanocomposite were determined to be 92% and 64%, respectively, in the same 45-minute time frame. The improved photocatalytic activity of Au/rGO was proposed to be caused by the effective suppression of electron-hole recombination by the rGO on the Au nanoparticles. Hence, the results suggest that graphene decorated with gold yields a more efficient photocatalyst for environmental applications. One of the novel aspects of this study lies in the proficiently managed synthesis of Au/rGO and its prospective applications as a photo- catalyst for environmental pollution such as to remove pollutants from water.

Construction of Azo‐Linked Covalent Organic Frameworks via Monomer Exchange for Enhanced Photocatalytic Performance

AbstractThe structural uniqueness of covalent organic frameworks (COFs) has brought great potential for their applications in photocatalysis. Two novel azo‐linked COFs AZO‐B‐COF and AZO‐T‐COF were successfully constructed by the monomer exchange method. Significantly, two as‐synthesized azo COFs presented a much higher photodegradation rate of 96 % and 51 % for AZO‐T‐COF and AZO‐B‐COF, respectively, which was in sharp contrast to the almost 0 degradation rate of imine COFs. And as expected, AZO‐T‐COF could be cycled at least 5 runs without a significant decrease in catalytic efficiency. Systematical experiments and theoretical calculations showed that comparing with imine COFs, conjugated structure of azo COFs broadened the visible‐light absorption range and improved the transfer efficiency of the photocarriers. The N‐rich azo bonds acted as an electron acceptor and made the materials better planarity. This work not only enriches COFs family but also demonstrated the superiority of azo‐linked COFs.

Earth-abundant quaternary chalcogenide copper zinc tin sulfide-based nanocomposites CZTS-gCN and CZTS-GO (graphene oxide) as photocatalysts for degradation of methylene blue

This study explores the potential of Cu2ZnSnS4 (CZTS) as an environmentally friendly and nontoxic semiconductor photocatalytic material with a narrow band gap. The research focuses on investigating, photocatalytic degradation of Methylene Blue (MB) using CZTS-based nanocomposites prepared through hydrothermal approach. The experiments conducted in this study aim to determine the kinetics of photodegradation and adsorption of MB. Several models are applied to the experimental data to understand the underlying principles governing photocatalysis. The CZTS-gCN and CZTS-GO nanocomposites are thoroughly characterized using various analytical techniques such as X-ray diffraction for phase purity and crystallite size, Scanning Electron Microscopy, and other characterization are also employed to observe the morphology, phase structure, optical band gap, recombination of charge carriers The study discusses a potential method for enhancing the photocatalytic performance of the CZTS nanocomposite under light conditions. The photodegradation rate of MB dye is evaluated, showing a remarkable 64% degradation.

Green route to fabrication of Semal-ZnO nanoparticles for efficient solar-driven catalysis of noxious dyes in diverse aquatic environments.

This work successfully demonstrates a sustainable and environmentally friendly approach for synthesizing Semal-ZnO nanoparticles (NPs) using the aqueous leaf extract of Bombax ceiba L. These NPs exhibit an absorption peak at approximately 390nm in the UV-visible spectrum and an energy gap (Eg) of 3.11eV. Detailed analyses of the morphology and particle size using various spectroscopic and microscopic techniques, XRD, FE-SEM with EDS, and HR-TEM reveal crystallographic peaks attributable to the hexagonal phase, with an average crystal size of 17nm. The Semal-ZnO NPs also exhibit a notable photocatalytic efficiency for degrading methylene blue (MB) and methyl orange (MO) under sunlight in different water samples collected from diverse natural sources, indicating that they are promising photocatalysts for environmental remediation. The photocatalytic efficiency of the biofabricated Semal-ZnO NPs is impressive, exhibiting a photodegradation rate of up to 99% for MB and 79% for MO in different water samples under exposure to sunlight. The novel phytofabricated Semal-ZnO NPs are thus a beacon of hope for the environment, with their desirable photocatalytic efficiency, pseudo-first-order kinetics, and ability to break down noxious dye pollutants in various aquatic environments.

A new Ag‐based photocatalyst for efficient degradation of antibiotic nitrofurantoin

In this paper, a new 0D Ag(I)‐based coordination polymer [Ag2(dib)(H2L)2](1) is proposed as a photocatalyst for the photocatalytic degradation of nitrofurantoin (NFT) under ultraviolet irradiation. The catalytic 1 was analyzed by various methods such as PXRD, SEM, FT‐IR, TGA, UV–vis, DRS, and electrochemical tests. The experimental result shows that 1 is an n‐type semiconductor, which can effectively catalyze the photodegradation of NFT under ultraviolet irradiation. Under the optimal reaction conditions, the photodegradation rate of NFT was 97.95% within 60 min when the concentration of NFT was 30 ppm. The experiment of free radical capture shows that O2˙− is the main active substance for photodecomposition, and the possible mechanism of 1 catalytic degradation of NFT is proposed. This research will lay the foundation for Ag(I)‐based coordination polymers in the field of antibiotic photocatalytic degradation.

Boosting the Photocatalytic Performance of g-C3N4 through MoS2 Nanotubes with the Cavity Enhancement Effect.

The development of catalysts with high photon utilization efficiency is crucial for enhancing the catalytic performance of photocatalysts. Graphitic carbon nitride (g-C3N4) is a prominent material in the field of photocatalysis. However, it still exhibits drawbacks such as low utilization of visible light and severe recombination of photogenerated carriers. To address these issues, this study employs MoS2 nanotubes (NTs) as cocatalysts and constructs MoS2 NTs/g-C3N4. The MoS2 NTs/g-C3N4 exhibits a significant cavity enhancement effect through multiple light reflections. This results in a broad spectral absorption range and high photon utilization efficiency, while also reducing the recombination of photogenerated carriers. The photocatalyst demonstrates outstanding performance in both photocatalytic hydrogen production and photodegradation of organic pollutants. Specifically, the hydrogen production rate is 1921 μmol·g-1·h-1, which is approximately 2.4 times that of g-C3N4. Furthermore, the photodegradation rate of Rhodamine B reaches 98.6% within 30 min, which is approximately three times higher than that of g-C3N4. Free radical capture experiments confirm that holes (h+) are the primary active species in photodegradation. A plausible photocatalytic mechanism for the catalyst is proposed. This study provides valuable insights into the development of heterojunction photocatalysts with high photon utilization efficiency.

Efficient photodegradation of antibiotics by g-C3N4 and 3D flower-like Bi2WO6 perovskite structure: Insights into the preparation, evaluation, and potential mechanism

Antibiotics are emerging organic pollutants that have attracted huge attention owing to their abundant use and associated ecological threats. The aim of this study is to develop and use photocatalysts to degrade antibiotics, including tetracycline (TC), ciprofloxacin (CIP), and amoxicillin (AMOX). Therefore, a novel Z-scheme heterojunction composite of g-C3N4 (gCN) and 3D flower-like Bi2WO6 (BW) perovskite structure was designed and developed, namely Bi2WO6/g-C3N4 (BW/gCN), which can degrade low-concentration of antibiotics in aquatic environments under visible light. According to the Density Functional Theory (DFT) calculation and the characterization results of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FITR), Scanning electron microscopy - energy spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS), this heterojunction was formed in the recombination process. Furthermore, the results of 15 wt%-BW/gCN photocatalytic experiments showed that the photodegradation rates (Rp) of TC, CIP, and AMOX were 92.4%, 90.1% and 82.3%, respectively, with good stability in three-cycle photocatalytic experiments. Finally, the quenching experiment of free radicals showed that the holes (h+) and superoxide radicals (·O2−) play a more important role than the hydroxyl radicals (·OH) in photocatalysis. In addition, a possible antibiotic degradation pathway was hypothesized on the basis of High performance liquid chromatography (HPLC) analysis. In general, we have developed an effective catalyst for photocatalytic degradation of antibiotic pollutants and analyzed its photocatalytic degradation mechanism, which provides new ideas for follow-up research and expands its application in the field of antibiotic composite pollution prevention and control.

SYNTHESIS OF Ag-MODIFIED TiO2 SOL-GEL FILMS AND ITS APPLICATION AS PHOTOCATALYSTS FOR METHYLENE BLUE DEGRADATION

In the study, the photocatalytic activity of TiO2 films that are created by dip-coating from a sol that contained titanium (IV) isopropoxide, monoethanolamine, and 2-methoxyethanol is demonstrated. Through photo-fixation of Ag (I) ions with varied concentration (10-2 - 10-4 M) in the water phase under UV illumination, the films are subsequently surface-modified with Ag co-catalyst layers. Scanning Electron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), Ultraviolet-Visible (UV) Spectroscopy, and Electron Paramagnetic Resonance (EPR) techniques are used to physically characterize the samples. Results reveal that the modification of the co-catalyst had no impact on the thickness and porosity of the films. In addition, the study show that the modified TiO2 films had increased photocatalytic activity. All the characterization methods used have shown the formationof surface - bound Ag (I) species and metallic silver nanoclusters. By measuring the Methylene Blue (MB) dye degradation under UV light illumination, as - prepared and Ag -modified TiO2 films are evaluated for their photocatalytic activity, and the impact of the silver precursor concentration during photo-fixation is investigated.The highest catalytic activity is seen for films that have been modified at a concentration of Ag (I) of 10-2 M. Ordered from highest to lowest, the MB photodegradation rate constants are TiO2 < TiO2 /Ag, 10-4 < TiO2 /Ag, 10-3 < TiO2 / Ag, 10-2.

Photocatalytic self-cleaning and antibacterial activity of modified wood by Ag doped TiO2 nanoparticles

The use of nanoparticles has attracted widespread attention in surface science to improve the characteristics of substrates such as thermal stability, corrosion resistance, self-cleaning, and antibacterial effects. Nonetheless, porous materials like wood have received limited attention due to their inherent absorbency. This study aims to evaluate the antibacterial and photo-activity of modified wood employing Ag-doped TiO2 coating applied on the wood surface. The main characteristics of the modified wood were measured through XRD, SEM, AFM, TGA, and DRS analysis to determine structure and crystallinity, shape of particles, physical modifications of the wood surface, degradation rate, band gap alterations, and light absorbance, respectively. Methylene blue indicator witnessed a photo-degradation rate of 90 percent under UV irradiation after 21 h. This rate was observed at around 38 percent under irradiation of visible light. All in all, the modified wood underwent less color change whereas the parent wood witnessed a major change regarding its color. The antibacterial properties of wood were also measured. Two bacterial infections, S. Aureus and E. Coli, were employed for the following experiments. The results illustrated that the coating was able to reduce the amount of colonization and adhesion of E. Coli by 50 % and S. Aureus to zero.

A developed novel Hal′@MIL-PMA triple composite utilized as a robust photocatalyst for activated removal of antibiotic contaminants: A new chemical mechanism for Tetracycline degradation

In this research, an appreciable Hal′@MIL-PMA photocatalyst was prepared through a hydrothermal approach to photo-oxidize Tetracycline. The as-fabricated composite was diagnosed by multiple catalyst characterization tests, including XRD, FTIR, FESEM, PL, EIS, EDS, TGA, BET, and DRS techniques. Under optimized conditions (i.e.; a 1 g/L dosage of photocatalyst, antibiotic concentration of 40 mg/L, pH = 7 and at ambient temperature), 97.11% of Tetracycline elimination was achieved by the pristine Hal′@MIL-PMA photocatalyst. Kinetics computation revealed that the photo-degradation rate of Tetracycline obeys the pseudo-first-order model. Tests on radical trapping manifested that hydroxyl radical was a predominant oxidating reactive agent during the photocatalysis process. The mechanistic decontamination route of Tetracycline was deduced on the basis of the detected transformation products. The decay rate of TOC (63.23%) displayed that the Tetracycline was transferred to H2O, CO2, and simple degradable substances during the photocatalysis procedure. Additionally, the photocatalytic mechanism of Tetracycline degradation over the Hal′@MIL-PMA heterojunction photocatalyst was presented. The as-fabricated photocatalyst displayed significant oxidation efficiency in degrading multiple antibiotics, such as Rifampicin (90.87%) and Sulfasalazine (95.31%) under the above determined optimized conditions. Besides, the photocatalytic rate of Hal′@MIL-PMA heterostructured composite had no remarkable diminish even after five consecutive cycles. On the whole, this investigation evinces that Hal′@MIL-PMA composite can be regarded as a sustainable and promising photocatalyst for decontaminating non-biodegradable and tenacious substances from aqueous environments.

Constructed of Cd-based organic framework heterostructure material for solar-powered organic dye purification

A novel water-stable Cd-based organic framework material (Cd-MOF) has been synthesized based on the 4,4′-([2,2′-bipyridine]-6,6′-diylbis(oxy))phthalic acid (H4L) ligand and Cadmium nitrate tetrahydrate (Cd(NO3)2·4H2O) with a solvothermal method. We also prove that the rational design and preparation of Cd-MOF\\Ag heterojunctions by depositing Ag nanoparticles on the surface of Cd-MOF is an effective photocatalyst for the degradation of organic dyes in water. The photodegradation rates of RhB and MO were significantly improved under simulated sunlight conditions (AM1.5G), which reaching 0.68 and 1.549 min−1 g−1, respectively. The prominent performance is attributed to the efficient separation of photo-generated electrons and holes caused by the composite heterojunction of Cd-MOF/Ag. The surface plasmonic resonance (SPR) effect of Ag nanoparticles and the Schottky junction between Ag and Cd-MOF play crucial role in the photocatalytic degradation process. This work provides a new strategy for preparing photocatalysts and promoting the development of the degradation of organic dye pollutants in effluent with MOF-based material as photocatalysts.

Copper-Based Two-Dimensional Metal-Organic Frameworks for Fenton-like Photocatalytic Degradation of Methylene Blue under UV and Sunlight Irradiation.

To efficiently degrade organic pollutants, photocatalysts must be effective under both ultraviolet (UV) radiation and sunlight. We synthesized a series of new metal-organic frameworks by using mild hydrothermal conditions. These frameworks incorporate three distinct bipyridyl ligands: pyrazine (pyr), 4,4'-bipyridine (bpy), and 1,2-bis(4-pyridyl)ethane (bpe). The resulting compounds are denoted as [Cu(pyz)(H2O)2MF6], [Cu(bpy)2(H2O)2]·MF6, and [Cu(bpe)2(H2O)2]·MF6·H2O [M = Zr (1, 3, and 5) and Hf (2, 4, and 6)]. All six compounds exhibited a two-dimensional crystal structure comprising infinitely nonintersecting linear chains. Compound 3 achieved 100% degradation of methylene blue (MB) after 8 min under UV irradiation and 100 min under natural sunlight in the presence of H2O2 as the electron acceptor. For compound 5, 100% MB degradation was achieved after 120 min under sunlight and 10 min under UV light. Moreover, reactive radical tests revealed that the dominant species involved in photocatalytic degradation are hydroxyl (•OH), superoxide radicals (•O2-), and photogenerated holes (h+). The photodegradation process followed pseudo-first-order kinetics, with photodegradation rate constants of 0.362 min-1 (0.039 min-1) for 3 and 0.316 min-1 (0.033 min-1) for 5 under UV (sunlight) irradiation. The developed photocatalysts with excellent activity and good recyclability are promising green catalysts for degrading organic pollutants during environmental decontamination.

Metal-free g-C3N5 photocatalysts with defect sites as efficient peroxymonosulfate activators for antibiotic removal in aqueous media

Nitrogen-rich graphitic carbon nitride (g-C3N5) has emerged as a promising and fascinating photocatalyst for tackling problems related to antibiotic pollution. Herein, porous O-doped g-C3N5 with N vacancy (g-C3N5-x-O) was fabricated via a facile two-step pyrolysis technique using 3-amino-1,2,4-triazole and oxalic acid as precursors. The sample modified with 2.0 mol.% oxalic acid (CN-2.0) exhibits a porous structure with a specific surface area of 249.78 m2. g−1, 2.77 times greater than that of pristine g-C3N5 (CN-0). In addition, the existence of O-doping and N vacancies in g-C3N5 framework not only promotes charge transfer properties but also suppresses photogenerated electron-hole recombination according to the results of transient photocurrent responses, photoluminescence and electrochemical impedance spectra. The CN-2.0 sample displays the highest photocatalytic activity, which eliminates 77.3% sulfamethoxazole (SMX, 20 mg. L−1) after 60 min irradiation under UV 365 nm light source. The addition of peroxymonosulfate (PMS, HSO5-) significantly accelerates SMX photodegradation rate as well as reduces the influence of pH solution during treatment process. The reactive oxygen species including •O2−, 1O2, SO4•−, •OH, h+ contribute to SMX removal. The efficient degradation of numerous antibiotic classes highlights the possible applicability of g-C3N5-x-O. Interestingly, the catalyst retains its high activity and stability even after four consecutive reuse cycles. The intermediates of SMX degradation were determined and plausible SMX degradation pathways were proposed. Toxicity assessments demonstrated that the overall toxicity of the solution decreased after treatment. This work provides a feasible strategy to design and modulate g-C3N5 photocatalyst activated by PMS for antibiotic removal in wastewater.