Apparent Reaction Rate Constant Research Articles

Ag QDs modified BiOCl/UiO-66-NH2 Z-scheme heterojunction for accelerated visible light-driven photocatalytic degradation of ciprofloxacin

Ag quantum dots (QDs) anchored on the surface of BiOCl/UiO-66-NH2 Z-scheme heterojunctions were synthesized and characterized by various techniques such as X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis DRS), electrochemical impedance spectroscopy (EIS), and photoluminescence (PL). The effects of Ag QDs loading, pH values and co-existing anions on the photocatalytic performance were comprehensively analyzed. The results concluded that the Ag QDs modified catalysts exhibited excellent photocatalytic performance for the degradation of ciprofloxacin (CIP), especially, the catalyst with 5 % Ag QDs loading (referred to as ABU-5) achieved a degradation efficiency of 72 % within 120 min and the apparent reaction rate constant was 0.00538 min−1. The outstanding performance of the ABU-5 catalyst is attributed to the introduction of Ag QDs as electron transfer bridges, improving visible light absorption and enhancing charge transfer between BiOCl and UiO-66-NH2. Free radical trapping experiments and leaching tests were carried out to determine the contribution rates of reactive species to the degradation efficiency and the concentration of Ag+ in solution after the reaction. The possible degradation pathways of CIP by ABU-5 were investigated by gas chromatography-mass spectrometry (GC-MS).

Theoretical evidence for a pH-dependent effect of carbonate on the degradation of sulfonamide antibiotics

Carbonate (CO32−/HCO3−) have a significant impact on advanced oxidation processes (AOPs) by consuming reactive free radicals such as HO• to generate CO3•-. However, research on the mechanisms and kinetics of CO3•- remains limited. This study investigates the degradation mechanism and kinetics of sulfonamide antibiotics (SAs) by CO3•- through theoretical calculations. The calculation results revealed that the effect of CO3•- on SAs degradation is pH-dependent due to the dissociable sulfonamide group (-SO2NH-) of SAs in the common water treatment pH range (3–8). The main reaction type of CO3•- with both neutral and anionic molecules of SAs is single electron transfer reaction. Frontier molecular orbital theory (FMO) illustrated that deprotonation of the sulfonamide group of SAs decreases the charge density on the heterocyclic ring, facilitating the electrophilic addition of CO3•-. The second-order rate constants of the neutral and anionic molecules of SAs with CO3•- were calculated as 7.57 × 101∼1.84 × 108 and 1.81 × 107∼7.94 × 109 M−1 s−1, respectively, resulting in an increase in the apparent reaction rate constants with pH. Stepwise multiple linear regression was employed to predict reactivity with anionic sulfonamide antibiotics (SAs−). Two models with outstanding prediction and stability were developed with coefficients of determination R2 of 0.660 and 0.681, respectively. The degradation kinetics simulation indicated that in the UV/H2O2 process in the presence of carbonate, the degradation rate of SAs increased with pH. Furthermore, the contribution of CO3•- to SMX degradation increased while that of HO• decreased. This study highlights the contribution of carbonates to the micropollutant degradation in the UV/H2O2 process as the model, providing theoretical insights into the development of carbonate-based AOPs.

Mechanism of iron-activated ozone/persulfate coupled oxidation for petroleum-contaminated soil

Soil contamination by petroleum remains a critical environmental challenge. Single oxidation methods, while widely employed for remediation, often exhibit limitations in effectively degrading these contaminants. This hinders their broader application and necessitates the investigation of the complementary effects of commonly employed single oxidation method such as ozone (O3) and persulfate (PS) oxidation to explore their potential for enhanced degradation. In this study, the O3/PS coupling oxidation system activated by iron-loaded activated carbon (Fe@AC) was employed for the remediation of petroleum contaminated soil, and to evaluate the removal efficiency and underlying mechanism for petroleum contaminants. The results demonstrated a significant improvement in the apparent reaction rate constant of the O3/PS/Fe@AC system, recorded at 0.1253 h−1. This rate was approximately twice that of the PS/Fe@AC system (0.0572 h−1) and two orders of magnitude greater than the Fe2+/PS system (0.0014 day−1). Under the conditions of 6 % PS dosage, 0.6 % Fe@AC dosage, a soil-to-water ratio of 1:2, an O3 gas flow rate of 2.5 mg/L, and a pH of 5 at room temperature, the O3/PS/Fe@AC system removed 46.8 % of total petroleum hydrocarbon at an initial concentration of 5000–6000 mg/kg within 3 h. The reaction of the O3/PS/Fe@AC system involved multiple radicals, such as sulfate radicals (SO4•-), hydroxyl radicals (•OH), and superoxide radicals (O2•-), with the reactivity of SO4•- enhanced by O3. This study demonstrates an efficient method for remediating petroleum contaminated soil, providing a theoretical and technical foundation for the application of the O3/PS/Fe@AC system.

Ultrasonication-assisted synthesis of CuO-decorated montmorillonite K30 nanocomposites for photocatalytic removal of emerging contaminants: A response surface methodology approach

Environmental pollution is increasing worldwide due to population and industrialization. Among the various forms of pollution, water pollution poses a significant challenge in contemporary times. In this study, we synthesized CuO-decorated montmorillonite K30 (MK30) nanosheets via a simple ultrasonication technique. The structural, morphological, compositional, and optical properties of the synthesized nanocomposites were evaluated using advanced instrumentation techniques. The morphology of CuO was cubic and cubic CuO evenly designed on the MK30, which was proved by Field Emission Scanning Electron Microscopy (FESEM). The adsorption photocatalytic activity of the synthesized cubic CuO/MK30 composites was examined through the degradation of MB under visible light irradiation. The apparent reaction rate constant of 20% CuO/MK30 was 12.5 folds higher than that of CuO. These conditions included a catalyst dosage ranging from 5 to 15 mg, a pH level ranging from to 3–11, and a pollutant concentration ranging from 5 to 20 mg/L. The optimal conditions for MB dye removal were determined using response surface methodology (RSM). A scavenger study of the composite was conducted and verified that •O2− and •OH radicals play an important role in the degradation process. This investigation addressed the process of adsorption and potential removal pathways, with a particular emphasis on the role of functional groups. The environmentally friendly CuO/MK30 nanocomposites exhibited potential as photocatalysts for efficiently absorbing and degrading MB dye and TC drug pollutants. They represent promising candidates for the treatment of industrial wastewater, aiming to mitigate the environmental threats posed by organic pollutants.

2D–2D g-C3N4/WS2 Z-scheme heterojunction: Comparison of the photocatalytic degradation of tetracycline and sulfamethoxazole

In recent years, 2D–2D layered heterojunctions have emerged as promising photocatalytic platforms for the sustainable destruction of refractory pollutants because of their distinct advantages. Herein, we have rationally synthesized an organic–inorganic g-C3N4/WS2 heterojunction, with intimate interfacial contact, via a facile hydrothermal-driven self-assembling approach. Systematic investigations involving electrochemical impedance spectroscopy measurements and Mott–Schottky analysis reveal that the internal electric field between g-C3N4 and WS2 induces a Z-scheme charge transfer mechanism. Under visible light irradiation, the optimized photocatalyst exhibits a high degradation efficiencytowards two broad-spectrum antibiotics, i.e., tetracycline (TC) (89%) and sulfamethoxazole (SMX) (97%), with the apparent reaction rate constants several folds higher than that of bulk g-C3N4 and pristine WS2 nanosheets. Further, the g-C3N4/WS2 photocatalyst exhibits a favorable reusability of four operation cycles. Additionally, the impacts of different reaction variables are explored and the probable routes of photocatalytic dissociation of TC and SMX by g-C3N4/WS2 are proposed. The present findings not only validate the feasibility of g-C3N4/WS2 to eliminate consumer-derived micropollutants from the aqueous phase without creating secondary pollutants but also provide important insights for designing highly efficient 2D material-based heterojunction photocatalysts for decentralized wastewater treatment.

Modeling and experimental verification for photodegradation in a spinning disk reactor

The spinning disk reactor has been regarded as a process intensification device in photochemical processes, which decreases the light path length by the thin film formation created by centrifugal force. A reliable reactor model was indispensable for the practical application of photoreactors. Our previous studies proposed a spinning disk reactor with elliptic-cylindrical and cylindrical spoilers for photochemical process intensification, and then hydrodynamic parameters of liquid film thickness, photon absorption rate, and residence time distribution were obtained. Based on the obtained parameters, herein, a reactor model was further established for the description of photodegradation reaction in the innovative spinning disk reactor. Different non-ideal flow models were employed during the model development, including the tanks-in-series model and axial dispersion model. The apparent reaction rate constant of a spinning disk reactor with spoilers was determined by the photon absorption rate, which was in the range of 0.088–0.268 s−1. The reactor model was verified by the experiments on photodegradation of Methylene Blue under different disk configurations and operating conditions. The degradation efficiency of Methylene Blue could reach up to 89.8 % in 25 min at N = 200 r/min, Q = 60 L/h, and I0 = 8 mW/cm2. The deviation between predicted and experimental Methylene Blue degradation efficiencies was within ± 20 %, confirming the rationality of the reactor model. The developed model lays the foundation for the scaling-up and commercial applications of the novel spinning disk reactors.

Effect of Gold Nanoparticle Size on Regulated Catalytic Activity of Temperature-Responsive Polymer-Gold Nanoparticle Hybrid Microgels.

Gold nanoparticles (AuNPs) possess attractive electronic, optical, and catalytic properties, enabling many potential applications. Poly(N-isopropyl acrylamide) (PNIPAAm) is a temperature-responsive polymer that changes its hydrophilicity upon a slight temperature change, and combining PNIPAAm with AuNPs allows us to modulate the properties of AuNPs by temperature. In a previous study, we proposed a simpler method for designing PNIPAAm-AuNP hybrid microgels, which used an AuNP monomer with polymerizable groups. The size of AuNPs is the most important factor influencing their catalytic performance, and numerous studies have emphasized the importance of controlling the size of AuNPs by adjusting their stabilizer concentration. This paper focuses on the effect of AuNP size on the catalytic activity of PNIPAAm-AuNP hybrid microgels prepared via the copolymerization of N-isopropyl acrylamide and AuNP monomers with different AuNP sizes. To quantitatively evaluate the catalytic activity of the hybrid microgels, we monitored the reduction of 4-nitrophenol to 4-aminophenol using the hybrid microgels with various AuNP sizes. While the hybrid microgels with an AuNP size of 13.0 nm exhibited the highest reaction rate and the apparent reaction rate constant (kapp) of 24.2 × 10-3 s-1, those of 35.9 nm exhibited a small kapp of 1.3 × 10-3 s-1. Thus, the catalytic activity of the PNIPAAm-AuNP hybrid microgel was strongly influenced by the AuNP size. The hybrid microgels with various AuNP sizes enabled the reversibly temperature-responsive on-off regulation of the reduction reaction.

An intermediary route to CdS/Bi2S3 architectures with high-activity and stability in photocatalytic water splitting and dye degradation

The binary CdS/Bi2S3 heterostructures were fabricated by employing ZnO/Bi2S3 as active intermediates for the first time, which consisted of 0D CdS nanoparticles with sizes of 10–20 nm decorated on 3D Bi2S3 mircoflowers assembled by 1D nanorods. The whole formation mechanism of CdS/Bi2S3 heterostructure was systematically investigated. Specifically, the optimal CdS/Bi2S3 sample (CB-3) achieved the highest photocatalytic hydrogen evolution reaction rate of 3.85 mmol·g−1·h−1, about 16.74 and 25.67 times greater than that of single Bi2S3 and CdS. Besides, the apparent reaction rate constant of CB-3 for photodegradation of Congo red reached up to 0.0412 min−1, being 41.2 and 4.08 folds higher than that of solo Bi2S3 and CdS. The recycled tests over CB-3 were ready to take on the superb photostability. Furthermore, the S-scheme mechanism of photoinduced charges was rationally proposed. This work provides a new insight for the construction of composite photocatalysts for boosted solar-light-driven photocatalytic performance.

Microelectrode investigation of iron and copper surfaces aged in presence of monochloramine.

Ductile iron and copper coupons were aged 137-189 days and 2 days, respectively, with 2 mg Cl2 L-1 monochloramine under four water chemistries (pH 7 or 9 and 0 or 3 mg L-1 orthophosphate). Subsequently, microelectrode profiles of monochloramine concentration, oxygen concentration, and pH were measured from the bulk water to near the coupon reactive surface, allowing estimation of flux and apparent surface reaction rate constants for monochloramine and oxygen. Both metals showed similar trends with orthophosphate where orthophosphate decreased metal reactivity with monochloramine (pH 9) and oxygen (pH 7). Comparing iron and copper coupons, apparent surface reaction rate constants for monochloramine and oxygen were one and two orders of magnitude greater, respectively, for iron coupons under all conditions. Overall, this research provides the first insights into monochloramine concentration, oxygen concentration, and pH by direct measurement near ductile iron and copper reactive surfaces aged in the presence of monochloramine.

Gas-liquid-soild triphasic continuous flow microreactor for improving homogeneous distribution of solid composites in heterogeneous photocatalytic degradation progress

The homogeneous distribution of solid composites in continuous flow photocatalytic progress is difficult due to the settle and clog in capillary. To overcome this challenge, a gas–liquid-soild triphasic continuous flow photoreactor was designed and used for heterogeneous photocatalytic degradation of antibiotics wastewater. In this work, take Bi2WO6 as photocatalyst, photocatalytic degradation of ofloxacin wastewater was studied systematically under different operational parameters and flow characteristics. The photocatalytic degradation performance of flow photoreactor was superior to batch counterpart, especially in later stage of reaction. The apparent reaction rate constants (k) of flow photoreactor was about 1.6 times that of batch counterpart. The gas–liquid mass transfer coefficient of flow photoreactor was more than 25 times that of batch photoreactor. Moreover, the influence mechanism of gas fraction, flow rate and tube diameter on photocatalytic degradation performance was investigated under various continuous flow conditions. Higher gas fraction, faster flow rate and smaller tube diameter were beneficial to improve photocatalytic degradation performance due to the enhancement of irradiation transmission and intensification of mass transfer. Therefore, the results of this work provided a guideline for the application of gas–liquid-soild triphasic continuous flow photocatalytic degradation technology in the future.

Degradation and mineralization of anti-cancer drugs Capecitabine, Bicalutamide and Irinotecan by UV-irradiation and ozone

The degradation of three anti-cancer drugs (ADs), Capecitabine (CAP), Bicalutamide (BIC) and Irinotecan (IRI), in ultrapure water by ozonation and UV-irradiation was tested in a bench-scale reactor and AD concentrations were measured through ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). A low-pressure mercury UV (LP-UV) lamp was used and degradation by UV (λ = 254 nm) followed pseudo-first order kinetics. Incident radiation in the reactor was measured via chemical actinometry using uridine. The quantum yields (φ) for the degradation of CAP, BIC and IRI were 0.012, 0.0020 and 0.0045 mol Einstein−1, respectively. Ozone experiments with CAP and IRI were conducted by adding ozone stock solution to the reactor either with or without addition of tert-butanol (t-BuOH) as radical quencher. Using this experimental arrangement, no degradation of BIC was observed, so a semi-batch setup was employed for the ozone degradation experiments of BIC. Without t-BuOH, apparent second order reaction rate constants for the reaction of the ADs with molecular ozone were determined to be 3.5 ± 0.8 ∙ 103 L mol−1 s−1 (CAP), 7.9 ± 2.1 ∙ 10−1 L mol−1 s−1 (BIC) and 1.0 ± 0.3 ∙ 103 L mol−1 s−1 (IRI). When OH-radicals (∙OH) were quenched, rate constants were virtually the same for CAP and IRI. For BIC, a significantly lower constant of 1.0 ± 0.5 ∙ 10−1 L mol−1 s−1 was determined. Of the tested substances, BIC was the most recalcitrant, with the slowest degradation during both ozonation and UV-irradiation. The extent of mineralization was also determined for both processes. UV irradiation was able to fully degrade up to 80% of DOC, ozonation up to 30%. Toxicity tests with Daphnia magna (D. magna) did not find toxicity for fully degraded solutions of the three ADs at environmentally relevant concentrations.

Synthesis of 1D magnetic Fe3O4@SiO2/TiO2 nanostir bar photocatalyst for the degradation of MB under UV light

Here, a novel one-dimensional (1D) magnetic Fe3O4@SiO2/TiO2 nanostir bar both with high-efficient adsorption and photocatalysis of Methylene blue (MB) has been explored. Firstly, silicon and titanium precursor were loaded on the surface of Fe3O4 through the static magnetic induced self-assembly. Then the TiO2/SiO2 hybrid shell were formed by the hydrothermal treatment process to achieve the 1D magnetic nanostir bar. The 1D magnetic Fe3O4@SiO2/TiO2 photocatalyst exhibited good adsorption capacity and degradation activity of MB. The adsorption capacity of MB by Fe3O4@SiO2/TiO2(60 %) was 40 mg g−1. The apparent reaction rate constant of Fe3O4@SiO2/TiO2 (60 %) was 0.129 min−1. This work will provide a general strategy to explore other useful 1D magnetic nanomaterials for micro-reaction system.

Integrated model of ozone mass transfer and oxidation kinetic: Construction, solving and analysis

Ozone-based advanced oxidation process (O3-AOPs) is rapidly evolving, but the surge of emerging pollutants brings new challenges for ozone oxidation research. Herein, we proposed a state-of-the-art model for simultaneously analyzing both ozone mass transfer and oxidation kinetics during ozone oxidation of emerging organic contaminants. The numerical solution and graphical representations of the integrated model were utilized to analyze the dynamics of ozone and pollutant concentration. An in-depth analysis of the integrated model revealed that the reaction rate constants in this present study were higher than previously reported apparent reaction rate constants, and catalysts were not always necessary. Finally, we developed an installable mobile application (APP) that allowed the simulation of the dynamic process for ozone oxidizing organic pollutants in the laboratory, which offered theoretical support for the selection of experimental conditions. The results of model simulation not only provide scientific explanations for counter-intuitive experimental phenomena, but also optimized experimental conditions to enhance ozone utilization.

Distinguishable photorecycling of PVDF nanocomposites membrane for reactive yellow 145 dye and real industrial wastewater treatment by different photocatalytic processes

This paper investigates the photocatalytic performance and recyclability of PVDF-MWCNTs-TiO2 nanocomposite membranes for the treatment of textile wastewater under sunlight irradiation. The nanocomposites were fabricated by incorporating varying weight ratios of MWCNTs-TiO2 (1 %, 3 %, 6 %, and 9 %) into PVDF matrices using a solvent casting method. Optimal loading of MWCNTs-TiO2 at 9 wt% resulted in nanocomposites with enhanced surface area (94.15 m2/g), reduced band gap (2.38 eV), uniform dispersion of nanoparticles, and abundant surface hydroxyl groups. Under Xenon lamp irradiation, the optimized PVDF-9 %(MWCNTs-9 %TiO2) nanocomposite achieved a high apparent reaction rate constant (kapp) of 9.92 × 10−3 s−1 for photocatalytic degradation of the model dye Reactive Yellow 145. Significantly, when tested on-site at a Saudi Arabian textile facility over 6 months, this nanocomposite effectively reduced the chemical oxygen demand (COD) of real wastewater samples to regulatory limits of 1000 ppm under natural sunlight irradiation. The COD values were lowered from an initial 5050–6200 ppm to a final range of 785–945 ppm using the PVDF-9 %(MWCNTs-9 %TiO2) membrane. Furthermore, the optimized nanocomposite exhibited good recyclability, retaining around 87 % of its initial activity after 8 reuse cycles for industrial wastewater treatment. The excellent photocatalytic efficiency and reusability of the MWCNTs-TiO2 modified PVDF nanocomposite under solar irradiation highlight its promise as a sustainable membrane technology for environmental remediation.

Exfoliated MXene-AuNPs hybrid in sensing and multiple catalytic hydrogenation reactions.

The increasing use of nanomaterials in consumer products is expected to lead to environmental contamination sometime soon. As water pollution is a pressing issue that threatens human survival and impedes the promotion of human health, the search for adsorbents for removing newly identified contaminants from water has become a topic of intensive research. The challenges in the recyclability of contaminated water continue to campaign the development of highly reusable catalysts. Although exfoliated 2D MXene sheets have demonstrated the capability towards water purification, a significant challenge for removing some toxic organic molecules remains a challenge due to a need for metal-based catalytic properties owing to their rapid response. In the present study, we demonstrate the formation of hybrid structure AuNPs@MXene (Mo2CTx) during the sensitive detection of Au nanoparticle through MXene sheets without any surface modification, and subsequently its applications as an efficient catalyst for the degradation of 4-nitrophenol (4-NP), methyl orange (MO), and methylene blue (MB). The hybrid structure (AuNPs@MXene) reveals remarkable reusability for up to eight consecutive cycles, with minimal reduction in catalytic efficiency and comparable apparent reaction rate constant (Kapp) values for 4-NP, MB, and MO, compared to other catalysts reported in the literature.

Applying microelectrodes to investigate aged ductile iron and copper coupon reactivity during free chlorine application

In drinking water distribution systems, including premise plumbing, dissolved oxygen (DO) and free chlorine (FC) are common oxidants and ductile iron (DI) and copper (Cu) are commonly used pipe materials. Microelectrodes as a tool have been applied in previous corrosion research and were used in this study to collect quantifiable data and understand DO and FC reactivity and pH changes at the water-metal interface. Using microelectrodes, pH, DO, and FC profiles from the bulk water to near and at the surface of aged DI (154–190 d) and Cu (2 d and 86–156 d) coupons were investigated during periods of flow and stagnation (30 min). Using the measured microelectrode profiles, oxidant fluxes and apparent surface reaction rate constants were calculated to elucidate differences between DO and FC reactivity with the coupons. Microelectrodes were successfully applied to measure pH, DO, and FC profiles from the bulk water to near aged DI and Cu coupon surfaces; Cu coupons aged quickly and exhibited less reactivity at 2 d with DO and FC than aged DI coupons did after 154–190 d; and for the aged DI coupon experiments, orthophosphate presence stabilized pH profiles where without orthophosphate pH fluctuations of greater than 2 pH units occurred from the bulk water to the DI coupon surface.

Photothermal-assisted S-scheme PDIs/C, N, S-CeO2 derived from MOF-808 (Ce) heterojunction for photocatalytic removal of antibiotics

In this research, an organic supermolecule self-assembly perylene diimides (PDIs) semiconductor was wrapped around the surface of three-dimensional metal oxides frame (C, N, S-CeO2) by oil bath heating method. The photocatalytic ability was determined by the degradation of organic pollutants under visible light. The photodegradation rate of tetracycline (TC) was nearly 80.1% within 30 min, and the apparent reaction rate constant (k) was 15.83 times higher than that of C, N, S-CeO2. Free radical capture experiments and electron spin resonance analysis showed that •O2-, •OH and 1O2 were the main active species. The structure of PDIs/C, N, S-CeO2 maintained stable after four cycles, meanwhile, anti-ion interference experiment illustrated that degradation efficiency was not affected by neutral ionic intensity. Further, the formation pathways of main degradation intermediates during the degradation process and the toxicity prediction of degradation intermediates were proposed. In addition, 10% PDIs/C, N, S-CeO2 could also efficiently degrade other organic pollutants (chlorotetracycline (CTC), ciprofloxacin (CIP), rhodamine B (RhB), methylene blue (MB)). The excellent photocatalytic activity of 10% PDIs/C, N, S-CeO2 was attributed to the matched energy band structure, establishment of multi-dimensional channels, more significant visible light assimilation performance and enhanced photothermal ability. This work provides a new perspective on the construction of n-n S-scheme heterojunction photocatalysts between self-assembled organic supramolecular materials and MOF-derived metal oxides.

Magnetic recoverable Ag3PO4/Fe3O4/γ-Fe2O3 nanocomposite

The use of nanomaterials in water treatment is an alternative for the development of new systems to optimize the purification process. Heterogeneous photocatalysis is used for the treatment of wastewaters contaminated with recalcitrant pollutants that cannot be removed with conventional wastewater treatment techniques. Silver phosphate (Ag3PO4) can be used in visible-light driven photocatalysis. An important challenge of heterogeneous photocatalysis is to find a proper support for the photocatalysts to reduce the expense associated with the separation and reuse of these materials. However, the immobilization of the catalyst leads to lower reaction rates because the exposed surface area decreases and the material used as support can also interfere. In the last years, the use of magnetic materials to support photocatalysts has attracted special attention because it allows high surface areas to be exposed. Only few authors have reported the use of Ag3PO4/magnetic nanocomposites for photocatalysis and these need to be continued to improve their efficiency. In this work we synthesized Ag3PO4 and supported it on ferromagnetite (Fe3O4). In this study, Fe3O4 was synthesis following the Massart’s method. Ag3PO4 was synthesised over Fe3O4 from the reaction between silver nitrate (AgNO3) and disodium hydrogen phosphate (Na2HPO4). For characterization, DRS, SEM, XRD and magnetization studies were carried out. Ag3PO4 was synthesised and satisfactorily supported over magnetite (Fe3O423). The photodegradation of 10 mg·L−1 of methylene blue was achieved, although the apparent reaction rate constant was slightly lower for the magnetic composite than for bare Ag3PO4. This is explained because the composite contained 48% of the active Ag3PO4 material, as depicted form XRD studies.

Investigation of α-Fe2O3 catalyst structure for efficient photocatalytic fenton oxidation removal of antibiotics: preparation, performance, and mechanism.

Currently, the surface structure modification of photocatalysts is one of the effective means of enhancing their photocatalytic efficiency. Therefore, it is critically important to gain a deeper understanding of how the surface of α-Fe2O3 photocatalysts influences catalytic activity at the nanoscale. In this work, α-Fe2O3 catalysts were prepared using the solvothermal method, and four distinct morphologies were investigated: hexagonal bipyramid (THB), cube (CB), hexagonal plate (HS), and spherical (RC). The results indicate that the hexagonal bipyramid (THB) exhibits the highest degradation activity towards tetracycline (TC), with a reaction rate constant of k = 0.0969 min-1. The apparent reaction rate constants for the cube (CB), hexagonal plate (HS), and spherical (RC) morphologies are 0.0824, 0.0726, and 0.0585 min-1, respectively. In addition, it has been observed that the enhancement of photocatalytic activity is closely related to the increase in surface area, which provides more opportunities for interactions between Fe2+ and holes. The quenching experiments and electron paramagnetic resonance (EPR) results indicate that the ˙O2, ˙OH and h+ contribute mainly to the degradation of TC in the system. This research contributes to a more comprehensive understanding of catalyst surface alterations and their impact on catalytic performance.

Exploring the Remarkably High Photocatalytic Efficiency of Ultra-Thin Porous Graphitic Carbon Nitride Nanosheets.

Graphitic carbon nitride (g-C3N4) is a metal-free photocatalyst used for visible-driven hydrogen production, CO2 reduction, and organic pollutant degradation. In addition to the most attractive feature of visible photoactivity, its other benefits include thermal and photochemical stability, cost-effectiveness, and simple and easy-scale-up synthesis. However, its performance is still limited due to its low absorption at longer wavelengths in the visible range, and high charge recombination. In addition, the exfoliated nanosheets easily aggregate, causing the reduction in specific surface area, and thus its photoactivity. Herein, we propose the use of ultra-thin porous g-C3N4 nanosheets to overcome these limitations and improve its photocatalytic performance. Through the optimization of a novel multi-step synthetic protocol, based on an initial thermal treatment, the use of nitric acid (HNO3), and an ultrasonication step, we were able to obtain very thin and well-tuned material that yielded exceptional photodegradation performance of methyl orange (MO) under visible light irradiation, without the need for any co-catalyst. About 96% of MO was degraded in as short as 30 min, achieving a normalized apparent reaction rate constant (k) of 1.1 × 10-2 min-1mg-1. This represents the highest k value ever reported using C3N4-based photocatalysts for MO degradation, based on our thorough literature search. Ultrasonication in acid not only prevents agglomeration of g-C3N4 nanosheets but also tunes pore size distribution and plays a key role in this achievement. We also studied their performance in a photocatalytic hydrogen evolution reaction (HER), achieving a production of 1842 µmol h-1 g-1. Through a profound analysis of all the samples' structure, morphology, and optical properties, we provide physical insight into the improved performance of our optimized porous g-C3N4 sample for both photocatalytic reactions. This research may serve as a guide for improving the photocatalytic activity of porous two-dimensional (2D) semiconductors under visible light irradiation.