First-order Reaction Rate Research Articles

Highly effective catalytic degradation of bisphenol a through activation of peroxymonosulfate by an Fe-Nx structure anchored on novel lignin-based graphitic biochar: Electron transfer mechanism

A lignin-based Fe/N co-doped carbonaceous catalyst was synthesized via freeze-drying followed by pyrolysis to activate peroxymonosulfate (PMS) for efficient degradation of bisphenol A (BPA). The Fe/N co-doped biochar exhibited a high specific surface area (364.84 m2/g), hierarchical porous structures, and abundant oxygen-containing functional groups (hydroxyl and carboxyl groups), which enhancing the dispersion of Fe3O4 nanoparticle and exposure of catalytic site. The Fe8-N10-C/PMS system achieved 100 % BPA degradation within 20 min with a corresponding first-order reaction rate constant (kobs) of 0.4056 min−1, which outperformed most reported catalysts in efficiency. Quenching and EPR analyses revealed that both free radicals (•OH, SO4•−, and O2•−) and non-radical (1O2) were rate-limiting steps, while graphitic N and Fe-Nx structures facilitated direct electron transfer from BPA to PMS in electrochemical tests. XPS results confirmed that pyrrolic N, rather than pyridinic N, played a crucial role in forming the Fe-Nx structure. Moreover, the catalyst showed excellent stability, regeneration capability, and adaptability under diverse conditions, highlighting the potential of the Fe-N-C/PMS system for practical wastewater treatment applications.

TiO2 Catalysts Co-Modified with Bi, F, SnO2, and SiO2 for Photocatalytic Degradation of Rhodamine B Under Simulated Sunlight

The organic pollutants discharged from industrial wastewater have caused serious harm to human health. The efficient photocatalytic degradation of organic pollutants under sunlight shows promise for industrial applications and energy utilization. In this study, a modified TiO2 photocatalyst doped with bismuth (Bi) and fluorine (F) and composited with SnO2 and SiO2 was prepared, and its performance for the degradation of Rhodamine B (RhB) under simulated sunlight was evaluated. Through the optimization of the doping levels of Bi and F, as well as the ratio of SnO2 and SiO2 to TiO2, the optimal catalyst reached degradation efficiency of 100% for RhB within 20 min under simulated sunlight, with a first-order reaction rate constant of 0.291 min−1. This value was 15, 41, 6.5, and 3.3 times higher than those of TiO2/SnO2, Bi/TiO2, Bi-TiO2/SnO2, and F/Bi-TiO2/SnO2, respectively. The active species detection showed that h+ was the most crucial active species in the process. The role of Bi and F addition and SnO2-SiO2 compositing was investigated by characterization. Bi formed a chemical bonding with TiO2 by doping into TiO2. The absorbance intensity in the UV and visible light regions was improved by SnO2 and F modification. Composite with SiO2 led to a larger surface area that allowed for more RhB adsorption sites. These beneficial modifications greatly enhanced the photocatalytic activity of the catalyst.

Evaluating a hybrid process of anaerobic digestion, aerobic degradation, and electrochemical separation for swine wastewater treatment with methane and nutrient recovery

A hybrid process of anaerobic digestion (AD), aerobic degradation, and electrochemical separation was evaluated for treating real swine wastewater that is rich in organic and nutrient to achieve methane and nutrient recovery and industry standard discharge quality. Fe anode electrocoagulation and Mg anode struvite electrochemical precipitation (SEP) were evaluated as AD pretreatments. Both removed partial chemical oxygen demand (COD) from raw swine wastewater, but only SEP slightly enhanced the methane yield of pretreated swine wastewater. The SEP efficiency of the AD effluent was significantly better than raw swine wastewater. A further coupled micro/ultra-filtration produced high-purity (96%) struvite. SEP and struvite chemical precipitation (SCP) were evaluated for AD effluent treatment. This showed that compared with SCP following first-order reaction kinetics (reaction rate constant of 0.791 and 0.854 h−1 for NH4+-N and PO43--P), SEP not only achieved better removal of COD, NH4+-N and PO43--P, but was also shown to follow zero-order reaction kinetics (reaction rate constant of 5.72 and 5.78 mmol L−1 h−1 for NH4+-N and PO43--P). The SEP and SCP treated AD effluent was evaluated by conventional activated sludge (CAS), showing faster COD removal (first-order reaction rate constant of 0. 213 and 0.163 h−1) and lower residual COD (150 and 248 mg L−1) from SEP than SCP treated AD effluent, making the final effluent well below Chinese livestock wastewater discharge standards. Therefore, an emerging hybrid anaerobic membrane bioreactor (AnMBR)-SEP-CAS is proposed for swine wastewater treatment and proved to be more economically viable than the conventional hybrid AD-SCP-CAS process via cost-benefit analysis.

Characterization of wind effect on environmental dispersion for a shallow wetland flow

The present work focuses on the dispersion of pollutants under the influence of wind and ecological degradation in a fully developed steady flow for a shallow wetland. The dispersion coefficient is determined by Aris’ method of moments and Meis’ multi-scale analysis. Based on the comparison study, the concentration profiles obtained using multi-scale analysis converge with Aris’ method of moments, indicating that both analytical approaches provide reliable and consistent descriptions of pollutant dispersion in the system. In first-order degradation reaction rates, high degradation rates lead to lower mean concentrations and potentially more pronounced concentration gradients, while low degradation rates result in higher mean concentrations. The critical length of the region influenced by the contaminated cloud is computed analytically. It shows that for the common contaminant constituent lead (Pb), initially, it increases gradually to reach the maximum; after that as time increases, it decreases to zero under wind conditions.

Insights into the degradation of sulfamethoxazole in UV/nitrite system: Mechanism, transformation process and disinfection by-products formation

Antibiotics removal from wastewater by conventional methods is limited, and their lingering presence in the environment can be hazardous to both human health and the ecosystem. Sulfamethoxazole (SMX) is one of the primary study subjects for antibiotic contamination, the degradation behavior, mechanism, transformation pathway, disinfection byproducts (DBPs) formation and variations about toxicity in UV/nitrite (NO2−) system were examined in this study. Compared with UV irradiation, the first-order reaction rate of SMX in UV/NO2− system rose from 0.0397 to 0.0528 min−1. This enhancement was linked to the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), which promoted the degradation. SMX removal was more favorable under high dissolved oxygen (DO) levels and acidic conditions. When NO2− concentrations ranged from 0.1 to 1.0 mM, the higher concentration was more favorable to the degradation. The addition of 10 mM of HA and HCO3− hindered the oxidation of SMX by 48.46 % and 26.85 %, respectively, while the addition of Cl− slightly accelerated the decay of SMX at certain concentrations (5, 10 mM). The results of HPLC-ESI-MS and DFT computation suggested three possible SMX degradation pathways, including nitrification, hydroxylation, and bond breaking (such as sulfonamide cleavage). The primary DBPs produced by the post-chlorination of SMX in UV/NO2− system were TCM (87.02 % of the total detected DBPs) with a minor quantity of DBPs containing nitrogen. The presence of bromide ions (Br−) can lead to the production of highly toxic bromine containing disinfection by-products (Br-DBPs). After adding Br− in UV/NO2− system, 100 % of N-DBPs (TCNM, DCAN) and 93.43 % of C-DBPs (TCM, DCAA, TCAA) were converted to Br-DBPs (TBM, DBAA, TBAA, BDCM, DBCM), with the production of Br-DBPs accounting for 82.63 % of the detected DBPs.

Synergistic Elimination of Chlorophenols Using a Single-Atom Nickel with Single-Walled Carbon Nanotubes: The Roles of Adsorption, Hydrodechlorination, and the Electro-Fenton Process.

Electrocatalytic degradation enables the efficient treatment of chlorinated pollutants (COPs); however, its application has been significantly hindered by the large amounts of unsafe intermediate products. In this study, we present a single-atom nickel with single-walled carbon nanotubes (SWCNTs) as an electrochemical reactor for the complete elimination of chlorophenols. Distinct products and reductive mechanisms were observed for Ni-N-C compared to Cu-N-C. Ni-N-C incorporation has a novel degradation pathway for efficient chlorophenol degradation involving hydrodechlorination and the electro-Fenton process. Most importantly, the weak adsorption between the chlorophenols and the SWCNTs promoted their dechlorination by the attached active atomic hydrogen (H*) formed on the Ni-N-C. Meanwhile, the SWCNTs improved the reduction of O2 to H2O2, which was subsequently decomposed by Ni-N-C to form hydroxyl radicals (·OH) for phenol oxidation. As a result, the degradation rate of 4-chlorophenol was increased by 5 and 10 times compared with those of the Ni-N-C and SWCNTs alone, respectively. The first-order reaction rate constant was 2.7 h-1, and the metal mass kinetics constant was 1956.5 min-1g-1. Aromatic COPs containing benzene rings could be degraded, but chloroacetic acids could not. This study demonstrates a new design for multifunctional electrochemical degradation that functions via dechlorination and the ·OH activation mechanism.

Efficient hydrolytic dehydrogenation of ammonia borane catalyzed by ultrafine Pt clusters confined in Ni–Ti layered double hydroxides with closo-dodecaborate

Ammonia borane (NH3BH3, AB) is a highly promising candidate for hydrogen storage. Nevertheless, there is an urgent need to develop an efficient and stable catalyst that can control hydrogen generation under mild conditions. The use of catalysts with numerous surface atoms anchored to a carrier to achieve a synergistic effect is an appealing approach in catalysis. In this work, a series of highly dispersed metal clusters NiTi-LDH@B12H12@M (M = Au, Pd, Pt, Ag) catalysts were successfully synthesized at room temperature by leveraging the reductivity of [closo-B12H12]2- immobilized in the layered double hydroxide (LDH) laminate, along with the spatial confinement and anion exchange capabilities of LDH. Specifically, utilizing the optimal catalyst NiTi-LDH@B12H12@Pt 2.4% (wt. Pt), the AB hydrolysis reaction exhibited extraordinary catalytic activity. It exhibited a first-order reaction rate with respect to Pt and a near zero-order reaction rate with respect to AB concentration. The AB hydrolysis can be achieved in a mere 29 s at 25 °C with a conversion rate of 100%. The corresponding turnover frequency (TOF) attains a value of 454.06 molH2molPtmin−1, and the apparent activation energy (Ea) is 41.8 kJ mol−1, surpassing numerous previously reported Pt-based catalysts. The outstanding catalytic performance can be ascribed to the uniform distribution of ultrafine Pt clusters, along with the synergistic effect conferred by NiTi-LDH and intercalated anions ([closo-B12H12]2-).

Fabrication of a reusable carbon quantum dots (CQDs) modified nanocomposite with enhanced visible light photocatalytic activity

In awareness of industrial dye wastewater, carbon quantum dots (CQDs) and cobalt zinc ferrite (CZF) nanocomposites were synthesised for the making of carbon quantum dots coated cobalt zinc ferrite (CZF@CQDs) nanophotocatalyst using oxidative polymerization reaction. The results of TEM, zeta potential value, and FTIR confirm highly dispersed 1–4 nm particles with the − 45.7 mV carboxylic functionalized surface of CQDs. The results of the synthesised CZF@CQDs photocatalyst showed an average particle size of ~ 15 nm according to TEM, SEM, and XRD. The photocatalyst showed a 1.20 eV band gap, which followed the perfect visible light irradiation. TGA and DTA revealed the good thermal stability of the nanophotocatalyst. VSM was carried out, and the saturation magnetisations for CZF and CZF@CQDs were 42.44 and 36.14 emu/g, respectively. A multipoint study determined the BET-specific surface area of the CZF@CQDs photocatalyst to be 149.87 m2/g. Under visible light irradiation, the final CZF@CQDs nanophotocatalyst demonstrated remarkable efficiency (~ 95% within 25 min) in the photocatalytic destruction of Reactive Blue 222 (RB 222) and Reactive Yellow 145 (RY 145) dyes, as well as mechanical stability and recyclability. Even after the recycling of the degradation study, the nanophotocatalyst efficiency (~ 82%, 7th cycles) was predominantly maintained. The effects of several parameters were also investigated, including initial dye concentration, nanophotocatalyst concentration, CQD content, initial pH of the dye solution, and reaction kinetics. Degradation study data follow the first-order reaction rate (R2 > 0.93). Finally, a simple and low-cost synthesis approach, rapid degradation, and outstanding stability of the CQD-coated CZF nanophotocatalyst should make it a potential photocatalyst for dye wastewater treatment.

Causal prior-embedded physics-informed neural networks and a case study on metformin transport in porous media

This study introduces a novel approach to transport modelling by integrating experimentally derived causal priors into neural networks. We illustrate this paradigm using a case study of metformin, a ubiquitous pharmaceutical emerging pollutant, and its transport behaviour in sandy media. Specifically, data from metformin's sandy column transport experiment was used to estimate unobservable parameters through a physics-based model Hydrus-1D, followed by a data augmentation to produce a more comprehensive dataset. A causal graph incorporating key variables was constructed, aiding in identifying impactful variables and estimating their causal dynamics or “causal prior.” The causal priors extracted from the augmented dataset included underexplored system parameters such as the type-1 sorption fraction F, first-order reaction rate coefficient α, and transport system scale. Their moderate impact on the transport process has been quantitatively evaluated (normalized causal effect 0.0423, -0.1447 and -0.0351, respectively) with adequate confounders considered for the first time. The prior was later embedded into multilayer neural networks via two methods: causal weight initialization and causal prior regularization. Based on the results from AutoML hyperparameter tuning experiments, using two embedding methods simultaneously emerged as a more advantageous practice since our proposed causal weight initialization technique can enhance model stability, particularly when used in conjunction with causal prior regularization. amongst those experiments utilizing both techniques, the R-squared values peaked at 0.881. This study demonstrates a balanced approach between expert knowledge and data-driven methods, providing enhanced interpretability in black-box models such as neural networks for environmental modelling.

Sulfur autotrophic electrodialysis ion exchange membrane bioreactor (SEDIMB) for nitrate removal in water: Synergism and adaptability of electrodialysis and sulfur autotrophy

In this study, the novel sulfur autotrophic electrodialysis ion-exchange membrane bioreactor (SEDIMB) with high denitrification performance was developed without the addition of carbon source. Sulfur autotrophic denitrification occurs at the same time of nitrate enrichment by electric field to achieve harmless nitrate transformation in water. The final nitrate concentration in water chamber was 2.16 mg-N/L (removal efficiency of 94.49 %) at an initial nitrate concentration of 40 mg-N/L, with the maximum nitrate concentration in biological chamber of 4.09 mg-N/L. Nitrate removal in water chamber of the SEDIMB conformed to the first-order kinetic model (R2 = 0.98) and reaction rate constant K1 = 0.0030 (1/min). The effect of environmental variables (i.e., voltage, initial nitrate concentration and water body) on the SEDIMB denitrification performance was investigated. Increasing voltage could promote nitrate migration in water chamber, and when the voltage was 7 V, initial nitrate concentrations of 20 ∼ 60 mg-N/L was effectively removed (all > 93.54 %). Moreover, the change of water body (i.e., tap water, lake water and deionized water) did not affect denitrification performance of SEDIMB. Microbial community structure analysis indicated that Betaproteobacteria were dominant in the SEDIMB. Membrane characterizations (ATR-IR, SEM and CLSM) confirmed that the bacteria in biological chamber tended to accumulate and grow on one side of the anion exchange membrane (AEM), while could not affect the selective permeability of AEM.

Development of novel API-based deep eutectic solvents for esterification of high free fatty acid

Low-value feedstocks containing high free fatty acid (FFA) content are incompatible with direct alkali-catalysed transesterification, and require a deacidification step through esterification to reduce its FFA level. Herein, innovative acid catalysts were developed based on deep eutectic solvents (DESs) to pretreat low-quality palm oil (12.43 % FFA). DESs were formed using Brønsted acids (5-sulfosalicylic acid and benzenesulfonic acid) and an active pharmaceutical ingredient (paracetamol) at a 3:1 molar ratio. The DESs were characterized using ATR-FTIR and Hammett acidity function (H0). DES catalyst dosage, methanol requirement, reaction time and temperature parameters were optimized, and its recyclability was evaluated. The FFA contents were reduced to below the limit of < 2 % using acidic DESs at optimized conditions. Reaction kinetics revealed that DES-catalysed reactions followed the pseudo first order rate of reaction and required the lowest activation energy of 40.91 kJ/mol. Through the Eyring-Polanyi thermodynamic study, the DES-catalysed esterification reactions were endothermic (ΔH° > 0), non-spontaneous (ΔS° < 0 and ΔG° > 0) and endergonic. COSMO-RS computational calculations reveal the viable formation of the DESs based on its moieties, and supports the good solubility of the DESs in methanol. This study demonstrates the feasible valorisation of low-value feedstocks using innovative catalysts in enabling biodiesel production.

Synthesis of Ag2ZnGeO4/g-C3N4 binary heterostructure: A Z-scheme heterojunction photocatalyst for enhanced tetracycline degradation under visible light

Accumulation of tetracycline was hazardous to human health and ecosystems. Ag2ZnGeO4/g-C3N4 heterojunction photocatalysts were successfully prepared by the wet impregnation method. The morphological structure and optical properties of the photocatalysts were measured by a series of characterization methods. Moreover, Ag2ZnGeO4/g-C3N4 with a loading ratio of 20 % exhibited excellent photocatalytic activity by exploring the Ag2ZnGeO4 loading, catalyst dosage, initial concentration, and initial pH of tetracycline. The degradation efficiency of 20 % Ag2ZnGeO4/g-C3N4 for 10 mg/L TC was 94.29 % at 0.2 g/L catalyst dosage, and the corresponding first-order reaction rate constant reached a maximum of 0.0199 min−1. In addition, according to the results of the trapping experiments, superoxide anion radical was the major active species. Eventually, a possible Z-scheme of the photocatalytic degradation mechanism was proposed. The heterojunction formed between Ag2ZnGeO4 and g-C3N4 could accelerate the transfer and separation of photogenerated carriers, enhancing the photocatalytic activity.

Fabrication of porous and defect-rich BiOI/MWCNTs photocatalyst by Ar plasma-etching for emerging pollutants degradation

Carbon material modification and defect engineering are indispensable for bolstering the photocatalytic effectiveness of bismuth halide oxide (BiOX). In this study, a novel porous and defect-rich Ar-CB-2 photocatalyst was synthesized for emerging pollutants degradation. Leveraging the interfacial coupling effect of multi-walled carbon nanotubes (MWCNTs), we expanded the absorption spectrum of BiOI nanosheets and significantly suppressed the recombination of charge carriers. Introducing defects via Argon (Ar) plasma-etching further bolstered the adsorption efficacy and electron transfer properties of photocatalyst. In comparison to the pristine BiOI and CB-2, the Ar-CB-2 photocatalyst demonstrated superior photodegradation efficiency, with the first-order reaction rates for the photodegradation of tetracycline (TC) and bisphenol A (BPA) increasing by 2.83 and 4.53 times, respectively. Further probe experiments revealed that the steady-state concentrations of ·O2− and 1O2 in the Ar-CB-2/light system were enhanced by a factor of 1.67 and 1.28 compared to CB-2/light system. This result confirmed that the porous and defect-rich structure of Ar-CB-2 inhibited electron-hole recombination and boosted photocatalyst-oxygen interaction, swiftly transforming O2 into active oxygen species, thus accelerating their production. Furthermore, the possible degradation pathways for TC and BPA in the Ar-CB-2/light system were predicted. Overall, these findings offered a groundbreaking approach to the development of highly effective photocatalysts, capable of swiftly breaking down emerging pollutants.

Application of environmentally friendly technologies for the management of nanofiltration concentrate from landfill leachate

In this study, the treatability of leachate nanofiltration (NF) concentrate using the modified Fenton process was investigated. The modified Fenton process employs an environmentally friendly oxidant (sodium percarbonate, SPC), an environmentally friendly catalyst (Fe2+), and environmentally friendly activators (electrooxidation-ultraviolet, EO-UV). The study aimed at enhancing the biological degradability of leachate NF concentrate and was conducted in two stages. In the first stage, the process variables of the SPC/Fe2+ process were optimized. In the second stage, combined processes were applied under optimum conditions. With the SPC/Fe2+ process under optimum conditions (pH: 5, SPC dose: 10 mM, Fe2+ concentration: 50 mM, reaction time: 60 min, pre-catalyst dosing), removal efficiencies of 53.5%, 47.1%, and 61.6% were obtained for chemical oxygen demand (COD), UV254, and color, respectively. After optimizing the operational parameters of the SPC/Fe2+ process, combined processes of EO/SPC/Fe2+ and UV/SPC/Fe2+ were applied, and higher pollutant removal efficiencies were achieved with the EO/SPC/Fe2+ process. Under optimum conditions, removal efficiencies of 75.3%, 80.5%, and 85.6% were achieved for COD, UV254, and color, respectively. The first-order reaction rate constant was 0.022 1/min for the EO/SPC/Fe2+ process. The biochemical oxygen demand (BOD)/COD, which increased from 0.040 to 0.080 with the SPC/Fe2+ process, reached 0.455 with the EO/SPC/Fe2+ process. Additionally, with the EO/SPC/Fe2+ process, the biologically degradable COD ratio of leachate NF concentrate increased from 16.7% to 83.5%, and the soluble COD fraction increased from 72.7% to 89.5%.

Preparation and photocatalytic performance of Sn-doped and BiOI-coupled dual modified Bi2WO6 composite

Sn doped and BiOI coupled dual modified Bi2WO6 photocatalytic material was prepared using hydrothermal route. The phase composition, morphology, surface area, elemental composition and oxidation state, as well as optical properties, were comprehensively characterized. Take the methylene blue (MB) as the model pollutant for photodegradation to estimate the photocatalytic property of the synthesized material. The prepared Bi2WO6- based composite material shows a flower-like structure assembled from nanosheets, with a surface area of 45.3 m2 /g and a bandgap width of 2.41 eV, enabling visible light responsiveness. The synergistic effect of Sn doping and BiOI coupling modification enhances the photocatalytic performance. The Sn-BiOI/Bi2WO6 photocatalytic composite material shows excellent photocatalytic activity, with complete degradation of MB after 40 minutes of illumination, and a first-order reaction rate constant (k) of 0.102 min–1 . Experimental evidence suggests that photoinduced holes are the main active species.

Prediction of atrazine degradation in soil based on XGBoost model.

We established the optimal model by using the automatic machine learning method to predict the degradation efficiency of herbicide atrazine in soil, which could be used to assess the residual risk of atrazine in soil. We collected 494 pairs of data from 49 published articles, and selected seven factors as input features, including soil pH, organic matter content, saturated hydraulic conductivity, soil moisture, initial concentration of atrazine, incubation time, and inoculation dose. Using the first-order reaction rate constant of atrazine in soil as the output feature, we established six models to predict the degradation efficiency of atrazine in soil, and conducted comprehensive analysis of model performance through linear regression and related evaluation indicators. The results showed that the XGBoost model had the best performance in predicting the first-order reaction rate constant (k). Based on the prediction model, the feature importance ranking of each factor was in an order of soil moisture > incubation time > pH > organic matter > initial concentration of atrazine > saturated hydraulic conductivity > inoculation dose. We used SHAP to explain the potential relationship between each feature and the degradation ability of atrazine in soil, as well as the relative contribution of each feature. Results of SHAP showed that time had a negative contribution and saturated hydraulic conductivity had a positive contribution. High values of soil moisture, initial concentration of atrazine, pH, inoculation dose and organic matter content were generally distributed on both sides of SHAP=0, indicating their complex contributions to the degradation of atrazine in soil. The XGBoost model method combined with the SHAP method had high accuracy in predicting the performance and interpretability of the k model. By using machine learning method to fully explore the value of historical experimental data and predict the degradation efficiency of atrazine using environmental parameters, it is of great significance to set the threshold for atrazine application, reduce the residual and diffusion risks of atrazine in soil, and ensure the safety of soil environment.

Facile synthesis method of C self-doped g-C3N4 and its performance in photodegradation of sulfamethoxazole

A simple method for preparing C self-doped g-C3N4 (CCN) was proposed by calcining urea and barbituric acid to effectively degrade sulfamethoxazole (SMX). X-ray photoelectron spectroscopy and element content analysis implied C atom replaced the original position of the bridging N atom to form CCN. Compared to g-C3N4, the absorption edge of CCN was red-shifted. As a result, the band gap of CCN was reduced, which improved the light absorption capacity of CCN and the separation efficiency of photogenerated electron-hole. Ultimately, the photocatalytic activity of CCN was finally boosted. CCN can effectively degrade SMX under visible light. Among CCN with various C dosage, when 0.05 g of barbituric acid was added in the preparation process, the obtained sample (CCN-0.05) exhibited uppermost degradation efficiency on SMX, which can reach 99.0 % after irradiation for 60 min. Additionally, the first-order kinetic reaction rate constant (0.086 min−1) was 8.9 times higher than that of g-C3N4 (0.0097 min−1). Electron paramagnetic resonance and trapping experiments showed that the dominant reactive species on SMX degradation were surface ·O2− and photogenerated holes by CCN-0.05 under visible light. Moreover, CCN-0.05 can still achieve effective removal of SMX under actual water backgrounds and showed selective degradation on sulfonamides.

Microstructure and photocatalytic performance study of visible-light-responsive two-dimensional Bi2MoO6 nanosheets

The synthesis of Bi2MoO6 photocatalytic material was carried out at different hydrothermal temperatures (140 °C, 160 °C, 180 °C), and the influence of hydrothermal temperature on its microstructure and photocatalytic performance was investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that Bi2MoO6 exhibited a sheet-like morphology. At a hydrothermal temperature of 160 °C, it had a specific surface area of 17.4 m2/g and an absorption edge at 470 nm, demonstrating the optimal photocatalytic performance. The first-order reaction rate constant for the photodegradation of methylene blue (MB) reached 0.046 min−1.

Insights into the electron transfer mechanisms of peroxydisulfate activation by modified metal-free acetylene black for degradation of sulfisoxazole

Herein, a modified metal-free acetylene black (MMF-AB) catalyst was synthesized by a simple solvothermal-calcination method and designed successfully to activate peroxodisulfate (PDS) for the degradation of sulfisoxazole (SIZ). Due to the doping of N, S and O metal-free elements, the modified catalyst showed excellent catalytic performance with 100% SIZ removal within 30 min. Pseudo first-order reaction rate constants (evaluating catalytic efficiencies and activity) of MMF-AB (kobs = 0.105 min−1) was 3 times higher than pure-AB (kobs = 0.029 min−1). Interestingly, it was demonstrated that the reaction system is based on the transfer of electrons from SIZ to PDS to realize an electron-transfer-based mechanism by the evidence of premixing, electron paramagnetic resonance (EPR) spectroscopy, salt-bridge experiments and electrochemical analyses. The introduction of recyclable filtration device solved the secondary pollution caused by the dispersion of the powdered catalyst in the treated water, which further proved the practicality and superiority of the MMF-AB catalyst.

A Fresh Perspective on the Impact of ZnTiO3 Coupling on the Microstructure and Photocatalytic Properties of TiO2 Fabricated at Varied Temperatures.

ZnTiO3/TiO2 composite photocatalysts were synthesized via the sol-gel technique, and the impact of varying heat treatment temperatures (470, 570, 670 °C) on their crystalline arrangement, surface morphology, elemental composition, chemical state, specific surface area, optical characteristics, and photocatalytic efficacy was systematically investigated. The outcomes revealed that, as the temperature ascends, pure TiO2 undergoes a transition from anatase to rutile, ultimately forming a hybrid crystal structure at 670 °C. The incorporation of ZnTiO3 engenders a reduction in the TiO2 grain dimensions and retards the anatase-to-rutile phase transition. Consequently, the specimens manifest a composite constitution of anatase and ZnTiO3. In contrast, for pure TiO2, the specimen subjected to 670 °C annealing demonstrates superior photocatalytic performance due to its amalgamated crystal arrangement. The degradation efficacy of methylene blue (MB) aqueous solution attains 91% within a 60-min interval, with a calculated first-order reaction rate constant of 0.039 min-1. Interestingly, the ZnTiO3/TiO2 composite photocatalysts exhibit diminished photocatalytic activity in comparison to pristine TiO2 across all three temperature variations. Elucidation of the photocatalytic mechanism underscores that ZnTiO3 coupling augments the generation of photogenerated charge carriers. Nonetheless, concurrently, it undermines the crystalline integrity of the composite, yielding an excess of amorphous constituents that impede the mobility of photoinduced carriers. This dual effect also fosters escalated recombination of photogenerated charges, culminating in diminished quantum efficiency and reduced photocatalytic performance.