Degradation Rate Constants Research Articles

CAZ Composite Photocatalysts for H2 Production and Degradation under Visible Light.

g-C3N4/Ag-ZnO (CAZ) composite photocatalysts were synthesized successfully by the hydrothermal method. The photocatalytic performance of photocatalysts was assessed through experiments measuring both hydrogen (H2) production and the degradation of methylene blue (MB). The H2 production rate of 60% CAZ reached 2.450 mmol·g-1·h-1, which was 8.5 times that of g-C3N4. 25% CAZ degraded 99.14% of MB dye within 40 min, and its degradation rate constant was 12.4 times that of g-C3N4. CAZ composite photocatalysts have good synergistic properties in degradation and hydrogen production and exhibit better photocatalytic performance. A Z-scheme photocatalytic system mechanism of CAZ has been proposed for the enhanced H2 production and photocatalytic degradation rate.

FeOCl/MOF-derived In2S3 photocatalysts with high H2O2 adsorption: Degradation mechanism, H2O2 activation process

The FeOCl-based photo-Fenton heterojunction catalyst holds great promise for effective water pollution treatment. A novel heterojunction FeOCl/MOF-In2S3 (F/M-I) was fabricated by coating hollow MOF-In2S3 nanoflowers onto the surface of FeOCl. Under the optimal conditions, the maximum photo-Fenton degradation rate constants of FeOCl/MOF-In2S3 for oxytetracycline (OTC) within 20 min is 0.88192 L mg−1·min−1, which are 3.2 and 2.5 times that of pure FeOCl (0.27357 L mg−1·min−1) and MOF-In2S3 (0.35222 L mg−1·min−1). Density functional theory (DFT) results confirm that the electron-rich nature of MOF-In2S3 accelerates the cycle between Fe (III)/Fe (II)of FeOCl, promoting H2O2 adsorption by FeOCl/MOF-In2S3 and generating more hydroxyl radicals (·OH) for pollutant degradation. Based on the results of DFT, combined with the results of the reactive oxidation species scavenger (ROSs), electron paramagnetic resonance (EPR) and Mott-Schottky curves, the separation and transfer behavior of photoexcited charges in FeOCl/MOF-In2S3 heterojunction and the possible photocatalytic degradation mechanism were investigated. Finally, a Z-scheme heterostructure is proposed to elucidate the catalytic mechanism. This study provides a new perspective on designing and synthesizing semiconductor materials for water treatment by photo-Fenton catalysis.

Oxygen vacancy and Ce ion co-synergize to enhance the photocatalytic degradation performance of FeTiO3: An experimental and DFT study

Doping the iron titanate (FeTiO3) with rare earth element is considered as an effective method of enhancing its photocatalytic performance. In this work, the novel FeTiO3 doped with cerium (Ce) (Ce/FeTiO3) photocatalysts were designed and synthesized using the sol–gel method. The 10 mol% Ce/FeTiO3 photocatalyst displays excellent photocatalytic performance for degrading the tetracycline hydrochloride (TCH), methylene blue (MB) and brilliant blue (BB). The degradation efficiencies are 97.50 % (TCH), 95.40 % (MB), and 84.60 % (BB), respectively, and the degradation rate constants (k) are 3.68, 2.91, and 7.12 times that of pure FeTiO3. Density functional theory (DFT) calculations were used to study the photocatalytic degradation mechanism in depth. The results show that the content of oxygen vacancy is increased and the oxygen vacancy formation energy is significantly increased from 2.25 eV to 6.97 eV after doping the Ce ion, which can provide more active sites to degrade pollutants and enhance the photocatalytic performance of the FeTiO3. Furthermore, the Ce 4f orbital can narrow the bandgap and form the impurity level to capture the photoexcited electron, inhibiting the recombination rate of photocarriers in FeTiO3. This work is expected to provide a valuable insight into the Ce doped FeTiO3 photocatalyst, which is conductive to expanding the practical applications of FeTiO3-based photocatalyst.

SiO2 surface decorated TiO2 with tunable OVs and enhanced photocatalytic performance

In this study, silicon dioxide (SiO2) surface decorated TiO2 photocatalysts (SiO2/TiO2) were prepared by a hydrothermal method. The experimental results show that decoration of TiO2 by SiO2 can induce abundant OVs and improve the separation rate of photogenerated carriers. The light response range can be expanded from 320–390 nm to 320–420 nm, which improves the effective utilization of light and accelerates the formation of O2−. The existence of SiO2 induces surface effect, and promotes specific surface area of SiO2/TiO2. The photocatalytic activity test confirms that when the mass ratio of SiO2/TiO2 is 6 % (6 % SiO2), the photocatalyst has the strongest degradation ability for rhodamine B (RhB) and ciprofloxacin (CIP). The degradation rate constant of RhB and CIP on 6 % SiO2 is both 2.0 times of that on the reference TiO2. In light of the findings, photocatalytic mechanism of SiO2/TiO2 was reasonably interpreted.

Accelerated mineralization of textile wastewater under 222 nm irradiation from Kr/Cl2 excilamp: an environmentally friendly and energy efficient approach

The textile dyeing and manufacturing industry is the major producer of significant amounts of wastewater that contain persistent substances such as azo dyes that require adequate remediation measures. Far ultraviolet at 222 nm light may provide an advantage for contaminants degradation as compared to conventional UV sources (254 nm). In this paper, the degradation of reactive black 5 (RB5) in artificial wastewater has been performed using a 222 nm Kr/Cl2 excimer source under direct photolysis and an advanced oxidation process using TiO2/H2O2. The solution pH, catalyst concentration, 222 nm intensity, initial concentration of dye, and addition of H2O2 influence the degradation rate constant. The molar absorption coefficient, quantum yield of RB5 at 222 nm and the electrical energy per order (EEO) from different treatment methods have been reported. RB5 shows 1.26 times higher molar absorption at 222 nm than at 254 nm. The EEO for excimer-222/H2O2 (∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document} 13 kWh/m3) is five times lower than that of the excimer-222/TiO2 process, which makes the process energy efficient. The degradation of wastewater has been carried out at three distinct pH values (2, 6, and 10), and the pH level of 10 exhibited the highest degree of degradation. The degradation rate in the alkaline medium is 8.27 and 2.05 times higher than in the acidic or ambient medium. Since textile effluent is highly alkaline, this result is significant, as no neutralization of the wastewater is required, and direct treatment is possible. A possible degradation pathway has been established based on Fourier transform infrared spectroscopy (FTIR) and high resolution mass spectroscopy (HRMS) analysis. The phytotoxicity of the treated wastewater has also been evaluated for its suitability for reuse in agriculture. The study reveals that the excimer-222/H2O2 treated wastewater significantly enhanced the germination percentage of Raphanus sativus seed (97%) compared to dye wastewater-grown seeds (75%). This work offers crucial information for future studies on the direct and indirect photolysis of azo dyes, as well as insight into the process of RB5 degradation under Kr/Cl2 excimer radiation.

Visible light irradiation enhanced sulfidated zero-valent iron/peroxymonosulfate process for organic pollutant degradation

This study developed a novel process named sulfidated zero-valent iron/peroxymonosulfate/visible light irradiation (S-mZVI/PMS/vis) for enhanced organic pollutant degradation. The S-mZVI/PMS/vis process exhibited remarkable catalytic activity, achieving a 99.6% rhodamine B (RhB) removal within 10 min. The degradation rate constant of RhB by the S-mZVI/PMS/vis process was found to be 6.49 and 79.84 times higher than that by the S-mZVI/PMS and PMS/vis processes, respectively. Furthermore, the S-mZVI/PMS/vis process worked efficiently across a wide pH range (3.0−9.0), and the result of five-cycle experiments demonstrated the excellent reusability and stability of S-mZVI. Radical quenching tests and electron paramagnetic resonance analysis indicated that ·O2−, 1O2, and h+ significantly contributed to the degradation of RhB through the S-mZVI/PMS/vis process. The visible light irradiation increased the Fe2+ concentration, improved the Fe3+/Fe2+ cycle, and consequently enhanced the PMS decomposition, reactive species production, and RhB degradation. This work offers a promising strategy to highly efficiently activate PMS for organic pollutants elimination from aqueous solutions.

Mn- or Zn-substituted goethite enhancing tetracycline degradation by increasing oxygen vacancies and promoting electron transfer

The metal-substituted goethite with addition of oxidants can effectively promote the degradation of antibiotics, but the usage of external agents restricts its application in in-situ remediation of antibiotic pollution. In this study, the metal-substituted goethites were prepared through co-precipitation method to investigate the effects of using manganese (Mn) or zinc (Zn) substitution alone on tetracycline (TC) degradation, combining with microscopic characterization and electrochemical methods. The results showed that the degradation rate constants of the first stage on Mn or Zn-substituted goethite were 0.299 h-1 and 0.498 h-1, respectively, which were about 2 and 4 times of the pristine goethite (0.117 h-1). In the pH range of 4.0–9.0, Mn or Zn substitution significantly promoted TC degradation. Free and non-free radical pathways existed in the process of TC degradation by Mn or Zn-substituted goethite. The active site change and enhanced electron transfer ability were the main reasons for promoting degradation. Mn or Zn substitution increased oxygen vacancy (OV) content and promoted the electron transfer between TC and goethite. In Zn-substituted goethite, the coupling of OV and electron transfer produced free radicals, and in Mn-substituted goethite, the redox reaction induced mainly by electron transfer produces free radicals. This study reveals a new mechanism of efficient degradation of TC by iron minerals without the need for external oxidants, and the materials studied can be used for in-situ remediation of antibiotic contaminated groundwater.

Radiolytic degradation of 4-hydroxybenzoate in aerated and deoxygenated aqueous solutions.

The radiolytic degradation of 4-hydroxybenzoate (4-HBA-) in aerated, oxygen-free and N2O-saturated aqueous solutions at concentrations of 0.10 and 0.25 mmol/dm3 were gamma irradiated at different doses in a source of Co-60. The results show that ·OH adds predominantly to the 3 position of the aromatic ring, and elimination of the acid group leads to the degradation of 4-HBA-. With an N2O-saturated 0.10 mmol/dm3 4-HBA- solution, total degradation occurred at 1.6 kGy, and with a 0.25 mmol/dm3 solution, total degradation occurred at 3.5 kGy. In the aerated and oxygen-free 0.25 mmol/dm3 4-HBA- solutions, the behavior was similar, degradation occurring at a dose of 13.1 kGy. At the concentration of 0.10 mmol/dm3, total degradation occurred at 7.0 kGy, with small amounts of radiolytic products and byproducts. We propose a mechanism for the degradation of 4-HBA- caused by water radicals produced in the three environments, leading to formation of the identified stable products. Oxidation was followed by chemical oxygen demand (COD), which decreased as the 4-HBA- concentration increased. The kinetics showed a pseudo-first-order behavior. The rate constant of degradation was similar for the solutions with and without oxygen.

Visible light driven mesoporous ag/Ag2CrO4/g-C3N4 degrades multiple organic pollutants efficiently: Synthesis, mechanism, and degradation pathway

With the development of economy, overuse of antibiotics has been seen as a huge threat to human health. Photocatalytic degradation is an effective method for resolving this problem at present. The method of combining plasmon resonance effect and Z-scheme heterojunction can effectively improve the separation efficiency of photogenerated carrier, which is of great significance for the treatment of antibiotic wastewater. Herein, the Ag/Ag2CrO4/g-C3N4 catalyst was prepared by in-situ loading and photo-reduction method for the degradation of antibiotic wastewater containing tetracycline and quinolone antibiotics. The research results showed that mesoporous graphitized carbon nitride (denoted as g-C3N4) provided good support for Ag and Ag2CrO4 nanoparticles, and mesoporous composite Ag/Ag2CrO4/g-C3N4 (denoted as ACO/CN) provided more reaction sites for organic pollutants degradation. Under visible light irradiation, 5%ACO/CN catalyst showed the best degradation activity and stability for tetracycline (TC), levofloxacin (LVFX), oxytetracycline hydrochloride (OTC) and norfloxacin (NFLX), and their degradation rate constants were respectively 5.66, 8.26, 11.72 and 15.97 times of Ag2CrO4 which indicated it had good potential application value in the treatment of wastewater containing various organic pollutants. This benefits from the plasmon resonance effect of silver effectively improves the utilization efficiency of visible light and the Z-scheme heterojunction between Ag2CrO4 and g-C3N4 promotes the rapid transmission of photogenerated carriers. Based on the experimental results, the possible TC degradation pathway and photocatalytic mechanism were proposed. This study provides a simple way for the successful design and preparation of plasmon resonance effect synergistic Z-scheme heterojunction with promising applications in the treatment of antibiotic wastewater.

LCQDs modified Bi2MoO6 hydrangea composite photocatalyst for tetracycline degradation from wastewater: Performance, efficiency, and adsorption synergistic photocatalytic mechanism

This study used alkaline lignin as the carbon source for preparing alkaline lignin carbon quantum dots (LCQDs) based on the solvothermal method. To achieve efficient photocatalytic degradation of tetracyclic hydrochloride antibiotics (TCH), hydrangea-shaped LCQDs/Bi2MoO6 composites were prepared in situ by the solvothermal method exploiting the optical properties of LCQDs. The composite material was systematically characterized using XRD, FTIR, XPS, SEM, TEM, EIS, nitrogen adsorption-desorption testing, and UV–vis DRS to determine its crystal structure, microstructure, and optoelectronic properties. The results show that the sample has high purity and good crystallinity. The experiment on photocatalytic degradation further demonstrated that the LCQDs/Bi2MoO6 composite material modified with LCQDs exhibited superior photocatalytic activity compared to a single Bi2MoO6. Among them, BMO/LCQDs-7 showed the best effect. After 120 min of illumination, the rate of TCH removal through photocatalysis was 98.76%, with a degradation rate constant: K= 0.026 min−1. After five cycles, the removal rate of TCH can still be maintained at 79.35%. The photocatalytic degradation of TCH has been demonstrated through EPR and LC-MS experiments primarily caused by h+ and ·O2-.

Dissolved Organic Matter-Mediated Photosensitized Activation of Monochloramine for Micropollutant Abatement in Wastewater Effluent.

Utilizing solar light and water matrix components in situ to reduce the chemical and energy demands would make treatment technologies more sustainable for micropollutant abatement in wastewater effluents. We herein propose a new strategy for micropollutant abatement through dissolved organic matter (DOM)-mediated photosensitized activation of monochloramine (NH2Cl). Exposing the chlorinated wastewater effluent with residual NH2Cl to solar irradiation (solar/DOM/NH2Cl process) degrades six structurally diverse micropollutants at rate constants 1.26-34.2 times of those by the solar photolysis of the dechlorinated effluent (solar/DOM process). Notably, among the six micropollutants, the degradation rate constants of estradiol, acetaminophen, bisphenol A, and atenolol by the solar/DOM/NH2Cl process are 1.13-4.32 times the summation of those by the solar/DOM and solar/NH2Cl processes. The synergism in micropollutant degradation is attributed to the generation of reactive nitrogen species (RNS) and hydroxyl radicals (HO·) from the photosensitized activation of NH2Cl. Triplet state-excited DOM (3DOM*) dominates the activation of NH2Cl, leading to the generation of RNS, while HO· is produced from the interactions between RNS and other photochemically produced reactive intermediates (e.g., O2·- and DOM·+/·-). The findings advance the knowledge of DOM-mediated photosensitization and offer a sustainable method for micropollutant abatement in wastewater effluents containing residual NH2Cl.

Enhancing starch functionality through synergistic modification via sequential treatments with cold plasma and electron beam irradiation

The impact of dual sequential modifications using radio-frequency (RF) plasma and electron beam irradiation (EBI) on starch properties was investigated and compared with single treatments within an irradiation dose range of 5–20 kGy. Regardless of sequence, dual treatments synergistically affected starch properties, increasing acidity, solubility, and paste clarity, while decreasing rheological features with increasing irradiation dose. The molecular weight distribution was also synergistically influenced. Amylopectin distribution broadened particularly below 10 kGy. Amylose narrowed its distribution across all irradiation doses. This was due to dominating EBI-induced degradation and molecular rearrangements from RF plasma. With the highest average radiation-chemical yield (G) and degradation rate constant (k) of (2.12 ± 0.14) × 10−6 mol·J−1 and (3.43 ± 0.23) × 10−4 kGy−1, respectively, upon RF plasma pre-treatment, amylose underwent random chain scission. In comparison to single treatments, dual modification caused minor alterations in spectral characteristics and crystal short-range order structure, along with increased granule aggregation and surface irregularities. The synergistic effect was dose-dependent, significant up to 10 kGy, irrespective of treatment sequence. The highest synergistic ratio was observed when RF plasma preceded irradiation, demonstrating the superior efficiency of plasma pre-treatment in combination with EBI. This synergy has the potential to lower costs and extend starch's technological uses by enhancing radiation sensitivity and reducing the irradiation dose.

Integration of hydrogen evolution and dye removal in flexocatalysis by centrosymmetric semiconductor nanorods

In this work, coupling of the hydrogen (H2) production and dye degradation was first realized in a single flexocatalytic process using cerium oxide nanorods (CeO2 NRs). The flexoelectric polarization in a bending nanorod created an internal electric field, which promoted the separation of the thermal-excited electrons and holes. As a consequence, the H2 evolution rate of the flexocatalysis in dark was twice higher than that of the photocatalysis by the same CeO2 NRs. Moreover, simultaneous dye degradation was realized without reducing the H2 evolution rate, with the degradation constant rate of 0.065 min−1, dye removal efficiency of 89.3%, and H2 generation at 486.4 μmol g−1 h−1. The dual-functional catalytic performance of the CeO2 NRs was benefited from the unique periodic flexoelectric field induced by the ultrasound vibration, which could not be achieved by photocatalysis. This work revealed the important role of flexoelectric effect in overcoming the limitation in photocatalysis, which could be extended to a wide range of semiconductor nanomaterials for designing novel kinds of advanced flexocatalysts.

Precise Modulation of the Coordination Environment of Single Cu Site Catalysts to Regulate the Peroxymonosulfate Activation Pathway for Water Remediation.

Single atom site catalysts (SACs) with atomically dispersed active sites can be expected to be potential ideal catalysts for accurately modulating the persulfate activation pathway during the water remediation process because of their well-defined structure and the maximum metallic atom utilization. In this paper, a series of Cu SACs with different coordination environments were synthesized to elaborately regulate the peroxymonosulfate activation pathway in AOPs to clarify active species generation and transformation in water remediation. The degradation rate constants (kobs) of Cu-N2, Cu-N3, and Cu-N4 were 0.028, 0.021, and 0.015 min-1, respectively. Cu-N2 SACs exhibited a noticeable enhanced performance for bisphenol A (BPA) removal from water compared to that of the Cu-Nx SACs (x = 3, 4), accompanied by peroxymonosulfate (PMS) activation pathway variation. As shown by experimental and theoretical results, the PMS activation pathway was transformed from ROS to electron transfer with nitrogen coordination numbers decreasing from 4 to 2, which can be ascribed to the uneven charge distribution of Cu sites as well as upshifts in the d-band center, and thereby optimized electron transfer for PMS activation. Furthermore, the increasing nitrogen vacancies of single Cu site catalysts can also result in more unoccupied 3d orbitals of Cu atoms in SACs, thereby improving the intermediates' (PMS and BPA) adsorption-desorption process and BPA removal performance. These findings provided a beneficial approach for the coordination number regulation of SACs in water remediation.

Continuously Adjustable Thickness of Bi2MoO6 Nanosheets Enhances Photocatalytic Oxidation.

In this study, two-dimensional (2D) nanosheet photocatalysts of Bi2MoO6 with varying thicknesses were synthesized by adjusting the temperature during the hydrothermal reaction. The thinnest Bi2MoO6 nanosheet reached an approximate thickness of ∼4 nm, while the thickest nanosheet measured only ∼16 nm. The photocatalytic performance for Rhodamine B (RhB) degradation was found to be the most effective for the thinnest Bi2MoO6 nanosheet, displaying a degradation rate constant of 0.11 min-1. This rate was 2.5 times higher than that observed for the ∼16 nm thick Bi2MoO6 photocatalyst. The enhanced performance of the thinner two-dimensional nanostructure can be attributed to improved separation and migration of photogenerated charges. Additionally, the study identified hydroxyl radicals (•OH) and superoxide radicals (•O2-) as crucial oxidative species, contributing to the efficient mineralization of RhB dye. This work highlights the controllable synthesis of 2D materials with varying thicknesses and their specific applications in photocatalytic oxidation.

Biochar-Supported FeCo-MOF derivative catalyzes PDS-Mediated degradation of tetracycline

Bimetallic metal–organic framework (MOF) has gained wide attention in the field of advanced oxidative processes (AOPs), however, the agglomeration problem severely limits its active sites and its activation mechanism still needs to be further explored. This study developed the BC@CoFe composite material, utilizing biochar (BC) to support FeCo-MOF derivatives, effectively alleviating their agglomeration and structural collapse. The results of the BC@CoFe activated peroxydisulfate (PDS) system for the degradation of tetracycline (TC) revealed an excellent degradation efficiency up to 97.7 % in 2 h for TC solution (20 mg/L, degradation rate constants k = 7.066 mM-1min−1). Furthermore, the BC@CoFe/PDS system exhibits exceptionally high cyclic stability (73.23 % degradation efficiency after 12 h continuous degradation), a wide range of pH (3–11) and temperature tolerance (20-60℃), resistance to background ion interference (SO42-, H2PO4-, NO3– and HA), and reduced toxicity of the degradation products. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analyses show that the exceptional catalytic performance of BC@CoFe primarily stems from the synergistic effect between Fe(II)/Co(III) and Fe(III)/Co(II). Regarding the reactive active species involved in TC degradation, the contribution rates of 1O2, SO4•- and ·OH were measured and calculated to be 73.6 %, 14.9 %, and 11.5 %, respectively. Thus, the BC@CoFe/PDS system exhibits outstanding catalytic activity and has broad practical applications in water treatment.

Boosting persulfate activation through efficient π → π* transition activated by Cu ion anchored porphyrin-based metal–organic framework

Photocatalytic persulfate activation provides a promising approach for the elimination of persistent organic pollutants from water. This has been exemplified in porphyrin-based metal organic frameworks (PMOFs), which however come with ineffective electron transition within the porphyrin ligand. Herein, we present a Cu ion modification strategy capable of boosting electron transition by inducing electron delocalization under visible light. The introduction of Cu ions increased the degradation rate constant of ciprofloxacin (CIP) by nearly 44 times, surpassing most state-of-the-art photocatalysts. The in-situ characterizations and theoretical calculations suggest that π-electron localization constitutes the origin of ineffective electron transition in PMOFs. The introduction of Cu ions induces π-electron delocalization to intensify the π → π* transition, forming electron-rich centers of Cu to lower the energy barrier for O-O bond cleavage. This work offers fundamental insights into the electron transition within PMOFs, upon which the universal strategy is proposed for improved water decontamination performance via persulfate activation.

Nano-architected titania/gold@GO nanosheets for sonocatalytic degradation of azo dyes in textile wastewater

Environmental pollution is creating serious risks to both human health and the atmosphere which has been a major threat on a global scale. Therefore, it is necessary to focus on the evolution of the environment and trace contaminants for effective and reliable detection and degradation methods. Photochemical methods such as Surface-Enhanced Raman Scattering (SERS) and sono-catalytic degradation can be used to accelerate the detection and degradation of toxic dyes. In the present work, a Gold/Titania/Graphene oxide nanocomposite (ATG) was investigated as a capable dual substrate for SERS sensing and sono-catalytic degradation of pollutants. The nanosize distribution (6–12 nm) of ATG was synthesized by a solvothermal route. X-ray diffraction pattern illustrates the anatase phase of the titanium dioxide. Sonocatalytic degradation was aided using Raman spectroscopy. The effectiveness of ATG as a sono-catalytic substrate and SERS sensor was first evaluated using commercial dyes, such as malachite green and Bismarck brown. Furthermore, research has been conducted on the harmful elements in textile effluents (TE). The NN and C-N bands found in the SERS spectra of TE indicates the presence of carcinogenic azo-dye impurities. The enhancement factor was observed to be 5.77×1012 with the limit of detection (LOD) as 6.0×10−12M. Additionally, the sono-catalysis of ATG was evaluated for the elimination of these dye pollutants in TE. Following sono-catalysis by ATG, a high degradation rate constant of approximately 8.44 ×10−3/min was noted in TE with 89 % of degradation efficiency. The enhanced SERS detection, sono-catalytic degradation of synthetic dyes and effluent stem from the combined action of’ plasmonic characteristics of Au NPs, anatase TiO2, and the π-π stacking characteristic of GO.

Enhanced PMS activation and NSAID degradation selectivity by hydrophobic microenvironment regulation on Fe3+@Cu-MOF

In this study, the activation of peroxymonosulfate (PMS) and selective degradation of nonsteroidal anti-inflammatory drugs were investigated using hydrophobically modified Fe3+@Cu-MOF. The Fe3+@Cu-MOF-CTAB/PMS system demonstrated high-efficiency, achieving near-complete degradation of diclofenac within 120 min. The degradation rate constants for diclofenac, ibuprofen, and naproxen were 0.0048, 0.00103, and 0.00046 min−1, respectively, positively correlated with their hydrophobicity. Longer hydrophobic surfactant chains in Fe3+@Cu-MOFs lead to greater initial adsorption of diclofenac, enhancing degradation efficiency upon the introduction of PMS. The Fe3+@Cu-MOF-CTAB/PMS system removes over 80 % of diclofenac in various water matrices, showing optimal efficiency in acidic environments but reduced effectiveness with competing anions. Post-degradation changes in the oxidation states of copper and iron in the MOF structure indicated a synergistic redox mechanism essential for PMS activation. The hydroxylation and C-N bond cleavage in diclofenac were key degradation pathways. This study highlights the potential of hydrophobically modified Fe3+@Cu-MOFs in water treatment, providing insights into the interplay between material design, hydrophobic interactions, and catalytic performance.

Development of 2D/2D h-MoO3/Ag/g-C3N4 heterojunction photocatalyst with enhanced photocatalytic performance for the detoxification of methylene blue and tetracycline under solar light illumination

In this study, direct thermal polycondensation, hydrothermal, and ultrasonic techniques were used to fabricate photocatalysts consisting of bare g-C3N4 (GCN), h-MoO3 (MoO3), MoO3/g-C3N4 (MGCN), and MoO3/Ag/g-C3N4 (MAGCN) composites. These methods were used to improve the photocatalytic effect, especially for environmental applications. The surface and chemical properties of the fabricated samples were investigated by XRD, FT-IR, FE-SEM, HR-TEM, UV-DRS, XPS, and PL analysis. Bare and composite photocatalysts were tested for photodegradation of the methylene blue (MB) dye and tetracycline (TC) antibiotic under solar irradiation. The MAGCN composite material exhibits remarkable efficiency in degrading 99% of MB dye and 90% of TC antibiotic within a time frame of 60 min when exposed to sunlight irradiation. The degradation rate constants (k) of MB and TC in the most active MAGCN photocatalyst were 11.02 and 7.03 times higher than those of pristine GCN, respectively. The scavenger reaction shows that the most important reactive species in the photocatalytic process are superoxide and photogenerated holes. The outstanding photocatalytic efficiency of the MAGCN catalyst was demonstrated by the fact that Ag nanoparticles act as mediators of fast charge transfer, resulting in higher absorption of sunlight, enhanced charge separation/transfer, and regeneration by MoO3 and GCN. The MAGCN photocatalyst exhibits remarkable activity, maintains its performance over six consecutive reaction cycles, and exhibits excellent stability and reusability. Intermediates were analyzed by GC-MS, and suitable degradation pathways were proposed. These results enable the development of an effective Z-scheme heterojunction photocatalyst and facilitate its wide application in the degradation of organic pollutants in wastewater.