A facile approach to build Bi2O2CO3/PCN nanohybrid photocatalysts for gaseous acetaldehyde efficient removal

Food waste anaerobic digestion plants: Underestimated air pollutants and control strategy

Food waste management is an important global issue, and anaerobic digestion (AD) is a sustainable technology for treating food waste and developing a circular economy. Odor and health problems in AD plants have drawn increasing public attention. Therefore, this study investigated the odor characteristics and health risks in different workshops of food waste AD plants. At each site, the treatment capacities for kitchen and restaurant waste were 200 and 200-250 tons per day, respectively. Among the detected odorants, ethanol was the dominant component in terms of concentrations, while methanethiol, propanethiol, H2S, and acetaldehyde were the major odor contributors in different workshops. The odor contribution of propanethiol had been previously overlooked in several workshops. The unloading, pretreatment, and bio-hydrolysis workshops were identified as major areas requiring odor control. Besides odor, carcinogenic and non-carcinogenic risks commonly existed in food waste AD plants. The carcinogenic risk of acetaldehyde had been underestimated previously, and it was identified as the dominant carcinogen. Furthermore, benzene was a potential carcinogen. Non-carcinogenic risks were mainly caused by acetaldehyde, H2S, and ethyl acetate. The health risks were not always consistent with odor nuisance. Based on the odor and health risk assessments, several air pollution control strategies for food waste AD plants were proposed, including food waste source control, in-situ pollution control, and ex-situ pollution control.

Protrudent electron transfer channels on kaolinite modified iron oxide QDs/N vacancy graphitic carbon nitride driving superior catalytic oxidation

Optimizing electron transfer channels and sufficiently exposing active sites to trigger an efficient Fenton-like reaction are vital for manipulating catalytic properties of water treatment. Herein, Fe₂O₃ quantum dots were prepared and integrated with composites of g-C₃N₄ and kaolinite with nitrogen (N) vacancies (FONGK-10) for bisphenol A (BPA) removal in a peroxymonosulfate (PMS)/visible light (Vis) system. X-ray absorption near-edge structures and extended X-ray absorption fine structures demonstrated interface's combined properties. In particular, the tight interfacial contact and introduction of N vacancies resulted in the formation of effective electron channels, which caused more effective separation of electron-hole pairs and an extended response time of 1.5 × 10^-4 s. Furthermore, the introduction of kaolinite reduced the Fe₂O₃ particle size and accelerated PMS consumption. The k value in FONGK-10/PMS/Vis system was 4.5 times that of the FONGK-10/PMS and 27.5 times that of the FONGK-10/Vis system, and the synergetic system exhibited superior consecutive catalytic performance in a fluidized-bed catalytic unit, degrading ~100% of BPA in 200 min. The exposed electron channels significantly maintained the Fe(III)/Fe(II) stable dynamic cycle, thereby enhancing the activation of PMS and photocatalysis performance.

Application of One-Dimensional Nanomaterials in Catalysis at the Single-Molecule and Single-Particle Scale

The morphology of nanomaterials has a great influence on the catalytic performance. One-dimensional (1D) nanomaterials have been widely used in the field of catalysis due to their unique linear morphology with large specific surface area, high electron-hole separation efficiency, strong light absorption capacity, plentiful exposed active sites, and so on. In this review, we summarized the recent progress of 1D nanomaterials by focusing on the applications in photocatalysis and electrocatalysis. We highlighted the advanced characterization techniques, such as scanning tunneling microscopy (STM), atomic force microscopy (AFM), surface photovoltage microscopy (SPVM), single-molecule fluorescence microscopy (SMFM), and a variety of combined characterization methods, which have been used to identify the catalytic action of active sites and reveal the mechanism of 1D nanomaterials. Finally, the challenges and future directions of the research on the catalytic mechanism of single-particle 1D nanomaterials are prospected. To our best knowledge, there is no review on the application of single-molecule or single-particle characterization technology to 1D nanomaterial catalysis at present. This review provides a systematic introduction to the frontier field and opens the way for the 1D nanomaterial catalysis.

Nitrogen and sulfur co-doped CeO2 nanorods for efficient photocatalytic VOCs degradation

Nitrogen and sulfur-co-doped ceria with a regular nanorod morphology was prepared by one-step calcination treatment. N and S dopants can generate new impurity level states and promote the photocatalytic performance of CeO2 for VOCs degradation.

Optimized strategies for (BiO)2CO3 and its application in the environment

Photocatalysis is a new type of technology, which has been developed rapidly for solving environmental problems such as wastewater or air pollutants in recent years. Also, the effective performance and non-secondary pollution of photocatalytic technology attract much attention from researchers. As a "sillén" phase oxide, the (BiO)₂CO₃ (BOC) is a great potential photocatalyst attributing to composed of alternate Bi₂O₂²⁺ and CO₃^2- layers, which is a benefit for transportation of electrons. Besides, BOC has attracted much attention from researchers because of its excellent characters of non-toxic, environmentally friendly, and low-cost. However, BOC has a defect on wide band gap, which is limited for the usage of visible light, so a great number of published papers focus on the modifications of BOC to improve its photocatalytic efficiency. This article mainly summarizes the modifications of BOC and its application in the environment, guiding for designing BOC-based materials with high photocatalytic activity driven by light. Moreover, the research trend and prospect of BOC photocatalyst were briefly summarized, which could lay the foundation for forming a green and efficient BOC-based photocatalytic reaction system. Importantly, this review might provide a theoretical basis and guidance for further research in this field.

Polypyrrole merged zirconium-based metal-organic framework NU-1000 for detection of levodopa

A post-synthetic integration of polypyrrole onto NU-1000 MOF (PPy@NU-1000) was done by pyrrole adsorption, followed by oxidative polymerization. The synthesized materials were characterized by XRD, SEM, BET, and FTIR. The ultra-high specific surface area with high-density catalytic sites of NU-1000 (2223 m² g^-1) was combined with the electrical conductivity of PPy (2-100 S cm^-1). PPy@NU-1000 provides superior electrocatalytic activity and charge transfer properties compared to an individual component. The PPy@NU-1000-modified GCE was applied to detect the biomolecule Levodopa (LD). The DPV oxidation peak of LD was strongest at 272 ± 10 mV vs. Ag/AgCl reference electrode. Under the optimized experimental condition, the fabricated electrochemical sensor exhibited a wide quantification range of 0.005-70 μM with a sub-nanomolar detection limit of 0.0001 μM (S/N 3). The described sensor exhibits high sensitivity (2.08 μA μM^-1 cm^-2) with reasonable stability, reproducibility, and selectivity for the detection LD in the presence of potentially interfering compounds. Furthermore, human serum analysis showed excellent recovery values within the range 99.3-101.6%. Validation of the method was performed against HPLC.Graphical abstract.

Complementary SEM-AFM of Swelling Bi-Fe-O Film on HOPG Substrate

The objective of this work is to study the delamination of bismuth ferrite prepared by atomic layer deposition on highly oriented pyrolytic graphite (HOPG) substrate. The samples' structures and compositions are provided by XPS, secondary ion mass spectrometry (SIMS) and Raman spectroscopy. The resulting films demonstrate buckling and delamination from the substrates. The composition inside the resulting bubbles is in a gaseous state. It contains the reaction products captured on the surface during the deposition of the film. The topography of Bi-Fe-O thin films was studied in vacuum and under atmospheric conditions using simultaneous SEM and atomic force microscopy (AFM). Besides complementary advanced imaging, a correlative SEM-AFM analysis provides the possibility of testing the mechanical properties by using a variation of pressure. In this work, the possibility of studying the surface tension of the thin films using a joint SEM-AFM analysis is shown.

(002) Oriented Bi2O2CO3 Nanosheets with Enhanced Photocatalytic Performance for Toluene Removal in Air

Layer-structured Bi2O2CO3 is a novel photocatalyst for eliminating environmental pollutants. In this work, Bi2O2CO3 nanosheets were synthesized by hydrothermal methods, followed by annealing in nitrogen. (002) oriented Bi2O2CO3 nanosheets were obtained and characterized by XRD, SEM, XPS, BET and UV-Vis diffuse reflectance spectra. Photocatalytic properties were investigated by toluene removal in air, with the assistant of Bi2O2CO3 nanosheets under artificial irradiation. Our results show that Bi2O2CO3 annealed in nitrogen exhibited high full-light-driven photocatalytic activity for toluene photocatalytic decomposition, which may be ascribed to facet orientation evolution during the annealing process and enhanced efficient charge separation. The sample annealed at 150 °C for 8 h (BOC-150-8 h) showed high stability and the highest toluene removal rate, which was up to 99%. The final degradation products were detected by gas chromatography–mass spectrometer (GC-MS) and CO2 was verified to be the primary product. Photocatalytic mineralization of toluene in air over Bi2O2CO3 was proposed. This work may provide a foundation for application of annealed Bi2O2CO3 in indoor air purification.

Band bending of TiO2 induced by O-xylene and acetaldehyde adsorption and its effect on the generation of active radicals

Most studies on the photodegradation of volatile organic compounds (VOCs) have focused on the synthesis of efficient photocatalysts. However, little attention has been paid to the band bending change of semiconductive photocatalysts after the adsorption of VOCs. Herein, we first disclose how the adsorption of two typical VOCs influences the band bending of P-type rutile TiO₂ and consequently changes the amount of reactive radicals. This provides a new way to understand the experimental phenomenon of heterogeneous reactions. Theoretical computations of the adsorption model and zeta potential tests both verified that o-xylene is an acceptor molecule when it adsorbs on the TiO₂ surface, and it tends to attract electrons from TiO₂. In contrast, acetaldehyde is a donor molecule. A distinct electron transfer direction between TiO₂ and adsorbed molecules (o-xylene and acetaldehyde) induces a different band bending degree. O-xylene adsorption alleviates the downward band bending of TiO₂ itself, whereas acetaldehyde adsorption strengthens the downward band bending. The probability of electrons and holes reaching the TiO₂ surface is influenced by this change, which has a considerable influence on the generation of active radicals. Consequently, o-xylene adsorption leads to more hydroxyl radical generation, and acetaldehyde adsorption results in less hydroxyl radical generation. As a result, hydroxyl radicals play the predominant role in the degradation of o-xylene, whereas the photocatalysis of acetaldehyde is dominant for superoxide radicals. In addition, the band bending of a semiconductor induced by gaseous molecule adsorption has the potential for application in gas sensors to improve sensitivity.

Comparison of TiO2 and g-C3N4 2D/2D nanocomposites from three synthesis protocols for visible-light induced hydrogen evolution

Knowledge of the interfacial structure of nanocomposite materials is a prerequisite for rational design of nanostructured photocatalysts.