Latest ArticlesThe increasing occurrence of pesticide micropollutants highlights the need for innovative water treatment technologies, particularly for small-community and household applications. Electro-oxidation is being widely studied in this area, unfortunately, safe, stable and efficient electrocatalytic anodes without released heavy metal ions are still highly required. In this study, we fabricated a Pt/Ti anode by high energy pulse magnetron sputtering (HiPIMS-PtTi) which was used to decompose dichlorvos (DDVP) and azoxystrobin (AZX) in water. The results show that the reaction rate constant (kENR) on HIPIMS was 35.7 min–1 (DDVP) and 41.3 min–1 (AZX), respectively, superior to electroplating Pt/Ti anode (EP-PtTi). The identification of radicals (•OH, 1O2, •O2−) and micro-area analyses evidenced that Pt atoms were embedded into the TiO2 lattice on the surface of Ti plate by high-energy ions, which resulted in more adsorbed hydroxyls, and higher production of •OH under polarization conditions. Besides, the electro-oxidation intermediates of DDVP and AZX were identified and the degradation pathways were speculated: (1) indirect oxidation dominated by •OH attack, and (2) direct electron transfer reaction of pesticides on the anode surface. The cooperated reactions achieve the complete degradation and highly efficient mineralization of DDVP and AZX.
The matched energy band structure and efficient carrier separation efficiency are the keys to heterogeneous photocatalytic reactions. A novel organic/inorganic step scheme (S-scheme) heterojunction PDI-Urea/BiOBr composite photocatalyst was constructed by simple solvothermal reaction combined with in-situ growth strategy. The composite photocatalyst not only has high chemical stability, but also can generate and accumulate a large number of active species (h+, •O2−, •OH, H2O2). PDI-Urea/BiOBr showed higher photocatalytic activity for the degradation of antibiotic such as ofloxacin (OFLO), tetracycline (TC) and the production of H2O2 in the spectral range of 400–800 nm. The apparent rate constant of 15% PDI-Urea/BiOBr for photocatalytic degradation of TC (or OFLO) was 2.7 (or 2.5) times that of pure BiOBr and 1.7 (or 1.8) times that of pure PDI-Urea. The H2O2 evolution rate of 15% PDI-Urea/BiOBr was 2.5 times that of PDI-Urea and 1.5 times that of BiOBr, respectively. This work has formed a mature S-scheme heterojunction design thought and method, which offers new visions for the development of heterogeneous photocatalysts.
Advanced oxidation processes (AOPs) are promising technology to remove organic pollutant in water. However, the main problem in the AOPs is the low generation of hydroxyl radical (•OH) owing to the low decomposition efficiency of hydrogen peroxide (H2O2). Herein, the spinel type cobalt acid manganese (MnCo2O4) with flower morphology was fabricated through a co-precipitation method. In situ Fourier transform infrared spectroscopy confirms that the MnCo2O4 with the optimal molar ratio of Co and Mn precursors (CM3, Co: Mn = 3) has more Lewis acid sites compared with single metal oxide catalysts (Co3O4 and Mn2O3), leading to the excellent performances for H2O2 decomposition rate constant on CM3, which is about 15.03 and 4.21 times higher than those of Co3O4 and Mn2O3, respectively. As a result, the obtained CM3 shows a higher ciprofloxacin degradation ratio than that of Co3O4 and Mn2O3. Furthermore, CM3 shows an excellent stability during several cycles. This work proposes effective catalysts for ciprofloxacin decomposition and provides feasible route for treating practical environmental problems.
Once inevitably released into the aquatic environment, polystyrene nanoplastics (PS-NPs) will present complicated environmental behaviors, of which the aggregation is a key process determining their environmental fate and impact. In this study, the aggregation kinetics of different sizes (30 nm and 100 nm) of PS-NPs with metal cations (Na+, K+, Ca2+, Mg2+ and Pb2+) at different solution pH (3, 6 and 8) were investigated. The results showed that the aggregation of PS-NPs increased with cation concentration. Taking Pb2+ as an example, the adsorption behavior of cations onto PS-NPs was determined by transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) spectroscopy, which demonstrated Pb2+ could be adhered onto the surface of PS-NPs with the effect of charge neutralization. The critical coagulation concentrations (CCC) of smaller PS-NPs were higher than that of larger PS-NPs for monovalent cations, whereas a different pattern is observed for divalent cations. It was suggested that there were other factors that DLVO theory does not consider affect the stability of NPs with different particle sizes. In addition, it should be noted that PS-NPs had the capacity of adsorbing large amounts of heavy metal cations and carried them transport to a long distance, and the corresponding ecological risks need to further elucidate.
Treatment of antibiotics contaminated water remains a global environmental challenge. In this study, tetracycline (TC) was found to effectively sensitize pure TiO2 for visible light photocatalytic degradation via a ligand-to-metal charge transfer mechanism. The sensitization was attributed to the formation of TC-TiO2 complex and the overlap of the molecular orbitals of TC and the conduction band of TiO2. The intermediate degradation products of TC, however, did not sensitize TiO2, which was the reason for the low mineralization rate. Nevertheless, our results showed that the intermediate degradation products of TC had significantly reduced bactericidal effects and less induction of antibiotic-resistance genes (ARGs). This study showcases an effective treatment of antibiotics-containing wastewater using the most common photocatalyst TiO2 with reduced risk in the spread of ARGs.
A novel Mo-doped CuO catalyst is developed and used for low-temperature NH3-SCR reaction. Compared with the undoped CuO sample, the Mo doped CuO catalyst shows an increased SCR performance with above 80% NOx conversion at 175 ℃. The XRD and Raman results have confirmed the incorporation of Mo metal ions into CuO lattice to form Mo-O-Cu species which may be related to the enhanced SCR activity. The XPS and UV–vis results reveal the creation of electron interaction between Cu and Mo in this Mo-O-Cu system which provides an increased amount of Lewis and Brønsted acid sites, thereby promoting the adsorption capacity of NH3 and NOx as verified by NH3-TPD and NOx-TPD characterization. Besides, it also promotes the formation of oxygen vacancies, leading to the increasing of chemisorbed oxygen species, which improves the NO oxidation to NO2 activity. Furthermore, in situ DRIFTS technology was also used to study the reaction mechanism of this Mo doped CuO catalyst. The formed NO2 could react with NHx (x = 3, 2) species to enhance the low-temperature NH3-SCR activity via the "fast-SCR" reaction pathway. The nitrate and nitrite ad-species may react with NH3 and NH4+ ad-species through the L-H pathway.
Wastewater treatment and reclamation from wastewater are essential for the sustainable use of water resource. Zeolite-based heterogeneous catalysis shows great potential in circumventing the current limitations on pollutant removal and transformation to useful chemicals, inspiring advancements towards practical water treatment. This paper summarizes the methods for synthesizing zeolite-based catalyst, and the corresponding advantages and disadvantages. In comparison with traditional Fenton-like reaction, the superiority of zeolite-based catalysis lies in less sludge, wide pH range and easy recyclability. Accordingly, applications of zeolite-based Fenton-like catalysis (ZFCs) in pollutant removal and reclamation of wastewater were reviewed. Emphasis was placed on the methodological strategies in improving ZFCs, including the combination of external driving force (e.g., photocatalysis or electrochemistry), as well as the introduction of various transition metals into zeolite-based catalyst. Possible challenges and future perspectives for ZFCs were proposed.
In recent years, the direct introduction of sulfonyl and sulfenyl groups into unsaturated substrates by using thiosulfonates as unique dual functional reagents has inarguably provided chemists a new platform for the diverse synthesis of important S-containing derivatives. These 1,n-thiosulfonylation reactions usually feature simple procedures, 100% atom economy, and high regioselectivity. This review focuses on the recent advancements in the transformations of thiosulfonates through 1,n-thiosulfonylation involving the formation of two distinct C-S bonds under transition-metal-catalyzed or metal-free conditions, where thiosulfonates act as both a sulfonyl and a sulfenyl component.
The flow-through electro-Fenton (EF-T) reactor with WBC cathode was designed to remove florfenicol (FF). The activated WBC cathode was prepared by facile carbonization and activation methods, and featured high specific surface area, natural multi-channel structure, abundant oxygen-containing groups, good hydrophilicity, and excellent O2 reducing capacity. WBC cathode was located above Ti/Ru-IrO2 mesh anode. O2 evolved at the anode was carried to the inner wall of channel of WBC by the force of buoyancy and water flow, which increases oxygen source of H2O2 generation at the cathode. The flow-through system by using WBC electrode promote the mass transfer of O2 and FF. The production amount of H2O2 at activated WBC was 32.2 mg/L, which was almost twice as much as that at non-activated WBC (15.0 mg/L). FF removal ratio in EF-T system was 98%, which was much higher than that of traditional flow-by electro-Fenton (EF-B, 33%) or single electrooxidation system (EO, 16%). EF-T system has the lowest energy consumption (4.367 kWh/kg) among the three electrochemical systems. The cathodic adsorption, anodic electrooxidation, and EF reaction are responsible for the degradation of FF. After five consecutive cycle experiments, FF removal ratio was still 98%, indicating WBC has the good stability.
As the connecting part of diet and host physiology, intestinal microbes can convert the ingested diet into a huge number of physiologically active small molecules. Indole metabolites of tryptophan are precursors or signal molecules for many biologically active substances, which are involved in serotonin and microbial catabolism pathways. To understand the influence of tryptophan metabolism in the intestinal environment on the neurological and immune systems at the molecular level, it is important to establish a high-coverage analytical method to comprehensively analyze the metabolites involved in tryptophan metabolism. However, due to a small molecular weight and poor response during mass spectrometry analysis, as well as weak retention on the reversed-phase chromatography, determination of indole metabolites of tryptophan is challenging. Here, we proposed a method for the simultaneous determination of 20 indole metabolites of tryptophan in a single run on reversed-phase chromatography by chemical labeling coupled to liquid chromatography-tandem mass spectrometry analysis. 4-(Dimethylamino)benzaldehyde (DMAB) was used for the labeling of indole metabolites of tryptophan, which could significantly improve the detection sensitivities and retention of these metabolites on reversed-phase chromatography. With the developed method, we realized the sensitive detection and comprehensive analysis of 15 endogenous indole metabolites of tryptophan in rat feces samples with functional dyspepsia intervention by acupuncture. The developed method offers a useful tool for studying tryptophan metabolism-related diseases.
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