Apparent Reaction Rate Research Articles

Accelerated Zymonic Acid Formation from Pyruvic Acid at the Interface of Aqueous Nanodroplets.

To explore the role of the liquid interface in mediating reactivity in small compartments, the formation kinetics of zymonic acid (ZA) is measured in submicron aerosols (average radius = 240 nm) using mass spectrometry. The formation of ZA, from a condensation reaction of two pyruvic acid (PA) molecules, proceeds over days in bulk solutions, while in submicron aerosols, it occurs in minutes. The experimental results are replicated in a kinetic model using an apparent interfacial reaction rate coefficient of krxn = (0.9 ± 0.2) × 10-3 M-1 s-1. The simulation reveals that surface activity of PA coupled with an enhanced interfacial reaction rate drives accelerated ZA formation in aerosols. Experimental and simulated results provide compelling evidence that the condensation reaction of PA occurs exclusively at the aerosol interface with a reaction rate coefficient that is enhanced by 4 orders of magnitude (∼104) relative to what is estimated for macroscale solutions.

Energy Recovery from Municipal Sewage Sludge: Combustion Kinetics in a Varied Oxygen–Carbon Dioxide Atmosphere

Energy from municipal sewage sludge can be obtained by applying a thermal conversion method. In this study, the combustion kinetics of municipal sewage sludge were analyzed in an O2/CO2 atmosphere. Studies were conducted in different gaseous atmospheres consisting of varying proportions of oxygen and carbon dioxide. The participation of oxygen was as follows: 20, 40, 60, 80 and 100% vol. The experimental temperatures varied from 873 to 1273 K. The experimentally obtained results helped establish the basic kinetic parameters, such as the reaction order n, factor Ko and activation energy Ea of sludge grains. The values of the activation energy Ea and Ko were, respectively, 46 kJ/mol and 0.0127 mg/m2sPa. They show that the limiting factor of combustion is the diffusion of oxygen and that combustion reactions take place in the outer layer of the unreacted core. Therefore, sludge is promising for energy recovery because it has quite a high net calorific value (NCV) and a high gross calorific value (GCV). The GCV was 14.1 MJ/kg and the NCV was 12.8 MJ/kg. The experimental studies with a wide range of process parameters helped to create an array of apparent reaction rates as a function of the temperature and oxygen concentration, showing the significant effect of oxygen on the apparent reaction rate, in contrast to the effect of temperature.

An S-scheme TiO2/g-C3N4 nanocomposite effectively degrades phenanthrene under visible light

It is a challenge to effectively degrade phenanthrene (PHE) pollutants, which are widely present in aquatic environments, in order to reduce harm to humans and ecosystems. In this study, an S-scheme TiO2/g-C3N4 photocatalytic system is constructed using 0D TiO2 nanospheres and 2D g-C3N4 nanosheets for the removal of PHE from water under sunlight irradiation. The effects of irradiation time, quality ratio of TiO2 to g-C3N4, and cycle time on the performance of the TiO2/CN photocatalyst are investigated. The experimental results show that the ratio of TiO2 to g-C3N4 significantly affects the photocatalytic activity of the photocatalyst. Under the optimal ratio of TiO2 to g-C3N4 (50 % TiO2/CN), the apparent reaction rate constant for phenanthrene reached 0.00796 min−1, which is 11.5 times higher than that of pure TiO2 (0.00069 min−1). The tests of optical performance and photoelectrochemical properties further confirmed that the construction of the TiO2/g-C3N4 S-type photocatalyst successfully enhanced the spatial separation efficiency of photogenerated carriers and ensured a continuous supply of energy during the redox reaction process. Converting highly toxic phenanthrene into a non-toxic green degradation product provides an practical strategy for the safe treatment of PHE in aqueous environments through the use of visible-light-driven heterojunction photocatalysts. Additionally, the data collected on phenanthrene degradation in this study will provide valuable references for developing degradation methods for other PAHs, such as naphthalene, anthracene, and pyrene.

UV-enhanced Fe2+/PDS system for degradation of acid orange 7: Kinetics, degradation mechanism and toxicity assessment

Based on the deficiency of the Fe2+ catalyzed persulfate (PDS) process, ultraviolet (UV) synergistic Fe2+ activated PDS system was introduced in this study for the degradation of acid orange 7 (AO7) dye. The effects of different initial pH, PDS dosage, Fe2+ dosage, and different UV intensities on the degradation rate of AO7 were investigated, and a kinetic model for the apparent reaction rate was determined. The results showed that the UV/ Fe2+/ PDS system was effective in degrading AO7 in a wide pH range. Under optimal conditions, 96 % removal of AO7 was achieved in 10 min. The effects of different inorganic anions on AO7 were discussed; Cl− had little effect on the degradation effect, and SO42−, NO3− and HCO3− inhibited the degradation of AO7 by the system to varying degrees. The presence of reactive radicals (SO4·− and·OH) in the reaction was determined by quenching experiments and EPR capture and their degradation contribution was further investigated. Nine intermediates of AO7 were detected by LC- MS/ MS, and the degradation pathway of AO7 was inferred by combining with UV– Vis spectra. Finally, the ecotoxicity and tritogenic effects of AO7 intermediates were assessed by Toxtree and T.E.S.T toxicity prediction models, which showed that the final degradation product toxicity was non-mutagenic, non-teratogenic, and devoid of hereditary and non-hereditary carcinogenicity.

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).

Polydopamine modification on dendritic porous silica surface for efficient adhesion of functional nanoparticles

The uniform and high-density immobilization of functional nanoparticles (NPs) on porous carriers is crucial to enhance various physicochemical properties and performances in diverse applications. However, there is a limited control towards the size and distribution of functional nanoparticles loaded on the carriers. In this work, the dendritic porous silica nanoparticles (DPSNs) featuring a three-dimensional center-radial porous structure were utilized as a nanocarrier, coated with a thin layer of polydopamine (PDA) to form DPSNs@PDA. The modified PDA exhibits strong adhesion and photothermal conversion properties. The pre-synthesized gold or platinum NPs (Au or Pt NPs) with tunable sizes were uniformly and densely loaded on the DPSNs@PDA, taking advantage of the strong adhesion properties of PDA. The resulting functional NPs-loaded DPSNs@PDA composites demonstrated excellent catalytic activity and recycling stability in heterogeneous catalysis, achieving over 95 % catalytic conversion efficiency of methylene blue (MB) after six cycles. Furthermore, due to the excellent photothermal effects of PDA and Au NPs, the apparent reaction rate increased by nearly threefold under 808 nm near-infrared (NIR) laser irradiation. The developed strategy of loading pre-synthesized NPs with tunable sizes by strong PDA adhesion force shows great potential for achieving efficient integration of various functional NPs, thereby facilitating the construction of advanced multifunctional materials.

Interfacial engineering for the construction of iron sulfide/boride nanosheets heterostructure bifunctional electrocatalysts for high-efficiency overall water splitting

Iron-based materials have been extensively studied and applied as electrocatalysts. However, the electronic structure of iron itself is not conducive to effectively activating adsorbed intermediates, leading to slower kinetic steps. In this study, a heterogeneous composite catalyst with a nano-sheet array structure consisting of iron boron/sulfide (FeS@Fe2B/IP) was successfully prepared through a two-step process involving boriding and sulfidation of iron plates. The nanosheet array structure provides numerous catalytic active sites, promotes effective contact between electrolytes and catalytic sites, and enhances the apparent reaction rate of the catalyst. Additionally, the heterogeneous interface of FeS/Fe2B plays a crucial role in regulating the electronic structure of the metal Fe site, improving charge transfer rates, and accelerating electrocatalytic reaction kinetics. Ultimately, FeS@Fe2B/IP demonstrates outstanding water splitting performance, with only 177 and 191 mV overpotential providing 10 mA cm−2 toward HER and OER, respectively. Furthermore, it achieves a high current density of 500 mA cm−2 at 473 and 520 mV overpotentials for HER and OER, respectively. In addition to its excellent performance in water splitting applications, a bipolar alkaline cell was constructed using the FeS@Fe2B/IP bifunctional catalyst. This achieved current densities of 10 and 100 mA cm−2 at potentials of 1.63 and 1.75 V. Moreover, the catalytic stability of the FeS@Fe2B/IP system remained consistent for nearly 50 hours at current densities of 10 and 100 mA cm−2. These results confirm that FeS@Fe2B/IP is indeed a high-performance bifunctional electrocatalytic material which can significantly improve energy utilization efficiency in various applications.

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.

Immobilization of silver-loaded graphene oxide (Ag-GO) on canvas fabric support for catalytic conversion of 4 nitrophenol.

Due to the rising human population and industrialization, harmful chemical compounds such as 4-nitrophenol (4-NP) and various dyes are increasingly released into the environment, resulting in water pollution. It is essential to convert these harmful chemicals into harmless compounds to mitigate this pollution. This research focuses on synthesizing a novel heterogeneous catalyst using modified canvas fabric (CF) decorated with silver metal nanoparticles on graphene oxide nanosheets (Ag-GO/CF). The process involves coating the fabrics (CF) with graphene oxide (GO) nanosheets through sonication. Subsequently, silver nanoparticles are deposited in situ and reduced on the GO surface, resulting in the formation of the Ag-GO/CF composite. Various physicochemical characterizations were conducted to examine the interfacial interactions between CF, GO, and Ag nanoparticles. The catalytic activity of the nanocomposite was assessed by hydrogenating 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride (NaBH4). The results showed that the 10%Ag-5%GO/CF with a surface of 6 cm2 (3 × 2 cm) exhibited the highest catalytic activity, achieving a reduction efficiency of over 96% in 5 min. The 4-NP reduction reaction rate was well-fitted with a pseudo-first-order kinetics model with an apparent reaction rate constant (Kapp) of 0.676min-1. Furthermore, the Ag-GO/CF composite demonstrated remarkable stability over successive cycles, with no noticeable decrease in its catalytic activity, suggesting its promising application for long-term chemical catalytic processes. This synthesized composite can be easily added to and removed from the reaction solution while maintaining high catalytic performance in the reduction of 4-NP, and it could be beneficial in avoiding problems related to powder separation.

Photocatalytic activities of Fe2O3 coated ZnO nanowires grown by electrochemical anodization method

In this study, the visible light photocatalytic activities of the ZnO and ZnO/Fe2O3 structures were investigated. Anodization of Zn plates to obtain ZnO nanowires was carried out by applying 35 V between 1 and 30 min durations. Fe2O3 layers were coated on initially obtained ZnO nanowires through a sol-gel spin-coating process. All samples were examined for morphological, structural, optical, and photocatalytic activities in detail. The results showed that the conducted anodization process was successful where up to micrometer-length nanowires were obtained. SEM images confirmed the presence of Fe2O3 deposits surrounding the nanowires, while UV and visible absorption spectra indicated increased absorption due to Fe2O3, leading to enhanced photocatalytic performance. The best-performing ZnO nanowire anodized for 5 min almost doubled its photocatalytic activity after Fe2O3 coating, in which an apparent reaction rate of 12.24 × 10−3 min−1 and degrading 90.32 % of the initial MB concentration was recorded.

Highly efficient CoFe LDO/α-Bi2O3/g-C3N4 heterojunction for photocatalytic elimination of antibiotic pollutants

Efficiently enhancing the photocatalytic activity of graphite carbon nitride (g-C3N4), a promising candidate for pollutants degradation, is of great importance but remains a challenge. Herein, bismuth oxide (Bi2O3) and layered double oxides (i.e. LDO) were applied to improve the photocatalytic performance of g-C3N4 by constructing a ternary CoFe LDO/α-Bi2O3/g-C3N4 heterostructure. Physicochemical characterization results indicate that CoFe LDO/α-Bi2O3/g-C3N4 exhibits large surface area, competitive visible-light harvesting ability and effective separation and transfer efficiency of the photogenerated carriers. Thus, CoFe LDO/α-Bi2O3/g-C3N4 demonstrates the excellent photocatalytic activity for Tetracycline (TC) degradation, achieving approximately 90% degradation within 60 min, and its apparent reaction rate (about 0.03919 min−1) is 1.78, 1.84 and 9.9 times higher than that of CoFe LDO/g-C3N4, α-Bi2O3/g-C3N4 and g-C3N4, respectively. The major active free radicals, namely •O2− and photogenerated h+, are largely responsible for the photocatalytic degradation of TC, as demonstrated by the radical trapping tests and electron spin resource (ESR) measurements. The feasible photocatalytic mechanism for degrading TC by the CoFe LDO/α-Bi2O3/g-C3N4 heterostructure is tentatively proposed.

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.

2D/2D SnOx/TiO2 Z-scheme heterojunction with oxygen vacancies for boosted photocatalytic performance and mechanistic insight

A Z-Scheme heterojunction two-dimensional/two-dimensional (2D/2D) SnOx/TiO2 photocatalyst modified with oxygen vacancies (OVs) was successfully prepared using a hydrothermal method. Compared with SnOx and TiO2, the optimized SnOx/TiO2 heterojunction exhibited significantly higher photocatalytic activity for degrading methyl orange (MO). The apparent reaction rate of the SnOx/TiO2 heterostructure under visible light illumination reached 1.8355 min−1, approximately 15.74 times higher than that of SnOx alone. The results confirmed the presence of abundant oxygen vacancies on SnOx/TiO2, which acted as electron traps accelerating electron transfer. Furthermore, analyses including UPS, ESR, and reactive active species trapping experiments indicating a Z-scheme heterojunction were presented between SnOx and TiO2. According to density functional theory (DFT) calculations, the energy bands’ alignment enabled the Z-scheme heterojunction formation, while the inherent electric field drove the reaction. The experimental and computational findings demonstrated that the combined influence of the Z-Scheme heterojunction and OVs enhanced the photocatalytic reaction mechanism, facilitating efficient electron transport and preserving charge carriers with excellent redox capability. And a possible mechanism degradation pathway of MO dye is proposed. This study serves as a source of inspiration for future endeavors in the design and development of Z-Scheme heterojunction photocatalysts incorporating oxygen vacancies, with the aim of achieving enhanced efficiency in environmental remediation processes.

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.