Highly Dispersed Ni Atoms and O3 Promote Room-Temperature Catalytic Oxidation.

Transition metal oxides are promising catalysts for catalytic oxidation reactions but are hampered by low room-temperature activities. Such low activities are normally caused by sparse reactive sites and insufficient capacity for molecular oxygen (O2) activation. Here, we present a dual-stimulation strategy to tackle these two issues. Specifically, we import highly dispersed nickel (Ni) atoms onto MnO2 to enrich its oxygen vacancies (reactive sites). Then, we use molecular ozone (O3) with a lower activation energy as an oxidant instead of molecular O2. With such dual stimulations, the constructed O3-Ni/MnO2 catalytic system shows boosted room-temperature activity for toluene oxidation with a toluene conversion of up to 98%, compared with the O3-MnO2 (Ni-free) system with only 50% conversion and the inactive O2-Ni/MnO2 (O3-free) system. This leap realizes efficient room-temperature catalytic oxidation of transition metal oxides, which is constantly pursued but has always been difficult to truly achieve.

Highly efficient visible-light driven dye degradation via 0D BiVO4 nanoparticles/2D BiOCl nanosheets p-n heterojunctions.

The construction of hybrid heterojunction photocatalysts is an effective strategy to improve the utilization of photogenerated carriers and photocatalytic activity. To enhance the separation distance of photogenerated carriers and accelerate the effective separation at the heterojunction of the interface, a unique 0D-2D hierarchical nanostructured p-n heterojunction was successfully fabricated in this work. BiOCl (BOC) nanosheets (p-type) were in situ grown on BiVO4 (BVO) nanoparticles (n-type) using the microemulsion-calcination method for highly efficient visible-light-driven organic dye degradation. Compared with pure BVO (the degradation rate of rhodamine B (RhB): about 32.0% in 55 min, the mineralization rate: 24.9% in 120 min), the RhB degradation rate can reach about 99.5% in 55 min and the mineralization rate of 62.1% in 120 min by utilizing BVO/25%BOC heterojunction photocatalyst under visible light irradiation. Various characterizations demonstrate that the formation of BVO/BOC p-n heterojunction greatly facilitates photogenerated carriers separation efficiency. Meanwhile, the results of the scavenging experiments and electron spin resonance tests indicate that ·O2- and h+ are the prominent active species for Rh B degradation. In addition, possible degradation pathways for Rh B were proposed using LC-MS tests. This work proves that building low dimensional p-n heterojunction photocatalysts is a promising strategy for developing photocatalysts with high efficiency.

Screening of pesticides in serum, urine and cerebrospinal fluid collected from an urban population in China.

Human exposure to pesticides is a topic of public health concern for decades. Pesticide exposures have been assessed through the analysis of urine or blood matrices, but little is known on the accumulation of these chemicals in cerebrospinal fluid (CSF). CSF plays an important role in maintaining physical and chemical balance of the brain and central nervous system and any perturbation can have adverse effects on health. In this study, we investigated the occurrence of 222 pesticides in CSF from 91 individuals using gas chromatography-tandem mass spectrometry (GC-MS/MS). Measured pesticide concentrations in CSF were compared with those in 100 serum and urine specimens from individuals living in the same urban location. Twenty pesticides were found in CSF, serum and urine, at levels above the limit of detection. Three most frequently detected pesticides in CSF were biphenyl (100%), diphenylamine (75%), and hexachlorobenzene (63%). Median concentrations of biphenyl in CSF, serum and urine were 1.11, 10.6, and 1.10 ng/mL, respectively. Six triazole fungicides were found only in CSF, but not in other matrices. To our knowledge, this is the first study to report pesticide concentrations in CSF in a general urban population.

2D Transition Metal Dichalcogenides for Photocatalysis.

Two-dimensional (2D) transition metal dichalcogenides (TMDs), a rising star in the post-graphene era, are fundamentally and technologically intriguing for photocatalysis. Their extraordinary electronic, optical, and chemical properties endow them as promising materials for effectively harvesting light and catalyzing the redox reaction in photocatalysis. Here, we present a tutorial-style review of the field of 2D TMDs for photocatalysis to educate researchers (especially the new-comers), which begins with a brief introduction of the fundamentals of 2D TMDs and photocatalysis along with the synthesis of this type of material, then look deeply into the merits of 2D TMDs as co-catalysts and active photocatalysts, followed by an overview of the challenges and corresponding strategies of 2D TMDs for photocatalysis, and finally look ahead this topic.

Current Progress on Methods and Technologies for Catalytic Methane Activation at Low Temperatures.

Methane (CH4 ) is an attractive energy source and important greenhouse gas. Therefore, from the economic and environmental point of view, scientists are working hard to activate and convert CH4 into various products or less harmful gas at low-temperature. Although the inert nature of CH bonds requires high dissociation energy at high temperatures, the efforts of researchers have demonstrated the feasibility of catalysts to activate CH4 at low temperatures. In this review, the efficient catalysts designed to reduce the CH4 oxidation temperature and improve conversion efficiencies are described. First, noble metals and transition metal-based catalysts are summarized for activating CH4 in temperatures ranging from 50 to 500 °C. After that, the partial oxidation of CH4 at relatively low temperatures, including thermocatalysis in the liquid phase, photocatalysis, electrocatalysis, and nonthermal plasma technologies, is briefly discussed. Finally, the challenges and perspectives are presented to provide a systematic guideline for designing and synthesizing the highly efficient catalysts in the complete/partial oxidation of CH4 at low temperatures.

Recent advances in sterilization and disinfection technology: A review.

Sterilization and disinfection of pollutants and microorganisms have been extensively studied in order to address the problem of environmental contamination, which is a crucial issue for public health and economics. Various form of hazardous materials/pollutants including microorganisms and harmful gases are released into the environment that enter into the human body either through inhalation, adsorption or ingestion. The human death rate rises due to various respiratory ailments, strokes, lung cancer, and heart disorders related with these pollutants. Hence, it is essential to control the environmental pollution by applying economical and effective sterilization and disinfections techniques to save life. In general, numerous forms of traditional physical and chemical sterilization and disinfection treatments, such as dry and moist heat, radiation, filtration, ethylene oxide, ozone, hydrogen peroxide, etc. are known along with advanced techniques. In this review we summarized both advanced and conventional techniques of sterilization and disinfection along with their uses and mode of action. This review gives the knowledge about the advantages, disadvantages of both the methods comparatively. Despite, the effective solution given by the advanced sterilization and disinfection technology, joint technologies of sterilization and disinfection has proven to be more effective innovation to protect the indoor and outdoor environments.

Insights into the superior resistance of In-Co3O4-Ga2O3/H-Beta to SO2 and H2O in the selective catalytic reduction of NOx by CH4.

The existence of sulfur dioxide and water vapor in the flue gas generated from waste-to-energy stations could lead to catalyst deactivation, which has adverse effects on NOx removal. It is thus particularly important to study the reaction mechanism of catalyst resistance to poisoning. Herein, we report the mechanism of In-Co3O4-Ga2O3/H-Beta catalyst to SO2 and H2O resistance in the selective catalytic reduction (SCR) of NOx by CH4. The catalyst could achieve 74.6% NOx removal efficiency in the presence of 100 ppm SO2 and 5% H2O. In this catalyst, Co3O4 is attributed to enhancing the reversible poisoning of SO2 and CH4 activation and increasing the number of Brønsted acid sites by decomposing H2O. However, the InO+ active center was still eroded by a small amount of water vapor, leading to a reduction in NOx removal efficiency. The addition of Ga2O3 primarily provided an important intermediate NO2 for CH4-SCR reaction and reduced the aggregates of Co3O4 to increase the exposure of indium sites, and could reduce a part of SO2 to S2-. This study provides a good candidate for preparing catalysts with superior resistance towards SO2 and H2O for CH4-SCR.

Amino-acid modulated hierarchical In/H-Beta zeolites for selective catalytic reduction of NO with CH4 in the presence of H2O and SO2.

Selective catalytic reduction of NO with CH4 (CH4-SCR) has been studied over a series of amino-acid mediated hierarchical beta zeolites with indium exchange. Amino acid mesoporogens greatly affect the NO reduction (DeNOx) efficiency of In/H-Beta catalysts. Mesoporous In/H-Beta-P synthesized using proline exhibits the highest NOx removal efficiency of 40% in excess oxygen and poisonous SO2 and H2O, 10% higher than our previously optimized In/H-Beta catalyst using commercial beta zeolites with a similar Si/Al ratio. Analyses using XRD, N2 adsorption-desorption, EPR, SEM, TEM, EDX, ICP, 27Al and 29Si MAS NMR, XPS, H2-TPR, NH3-TPD, and Py-IR reveal that amino acids promote beta crystallization, modulate zeolite acid sites and surface oxygen species, and generate hierarchical pore architectures without affecting the Si/Al ratio, indium content, and percentage of the active InO+ species. The mosaic-structured In/H-Beta-P exhibits the strongest Brønsted acidity and surface labile oxygen which enhance the oxyindium interaction with the zeolite framework, promoting CH4-SCR activity. The strong acidity, surface active oxygen species, and mesopores lead to excellent stability of the In/H-Beta-P catalyst in the presence of SO2 and H2O, withstanding several catalytic DeNOx cycles under harsh reaction conditions.

CdS-based artificial leaf for photocatalytic hydrogen evolution and simultaneous degradation of biological wastewater.

Rational design of all-solid-state Z-scheme heterojunction with advanced structure is essential for boosting photocatalytic efficiency. Herein, we design and fabricate a novel Z-scheme photocatalyst with leaf architecture (named artificial leaf) via a simple dipping-calcination (DC) process followed by a successive ionic layer adsorption and reaction (SILAR) strategy. The prepared artificial leaf, composing of CdS, InVO4, and BiVO4, holds advanced leaf-like structure and Z-scheme electron transfer pathway. As a result, this novel artificial leaf exhibits outstanding capability for the harvesting of visible light and superior efficiency for the separation of photogenerated electron-hole pairs, as well as remarkably enhanced photocatalytic performance and stability for H2 evolution (with the rate of 5033 µm g-1∙h-1) and pollution degradation (46% pollution can be degraded within 3 h).

Coexisting oxidation and reduction of chloroacetaldehydes in water by UV/VUV irradiation.

Haloacetaldehydes (HALs) are the third largest disinfection by-product (DBP) ubiquitously detected in finished drinking water and have relatively higher toxicity than currently regulated DBPs. To efficiently alleviate them, this study investigated a green, chemical-free technology by using ultraviolet/vacuum ultraviolet (UV/VUV) on degrading three refractory chlorinated HALs (Cl-HALs). The results indicate that the rates of Cl-HALs decomposition in tap water irradiated by UV/VUV were 23-70 times higher than those irradiated by UV, proving that VUV instead of UV played the key role in degrading Cl-HALs. Increasing Cl-HALs dosage, pH, and dissolved oxygen (DO) all decreased the Cl-HALs degradations significantly, and the rates in tap water were apparently lower than those in ultrapure water. Unlike previous studies, this study proved that both oxidation and reduction were present during the VUV process. Photooxidation via oxidative radicals like •OH mineralized Cl-HALs, leading to substantial drops of total organic carbon; photoreduction via reductive radicals like •H dehalogenated Cl-HALs, resulting in formation of considerable intermediate organics (e.g., formic acid and acetic acid). No matter what pathway, the mass balances of chlorine were always maintained, meaning that dehalogenation occurred instantaneously rather than sequentially. Although the overall photodegradation rates dropped with rising pH and DO, photoreduction was increased with rising pH while photooxidation was elevated with rising DO. The results hence provide insights to better understand the VUV technology in controlling micropollutants in water.

ZnIn2 S4 -Based Photocatalysts for Energy and Environmental Applications.

As a fascinating visible-light-responsive photocatalyst, zinc indium sulfide (ZnIn2 S4 ) has attracted extensive interdisciplinary interest and is expected to become a new research hotspot in the near future, due to its nontoxicity, suitable band gap, high physicochemical stability and durability, ease of synthesis, and appealing catalytic activity. This review provides an overview on the recent advances in ZnIn2 S4 -based photocatalysts. First, the crystal structures and band structures of ZnIn2 S4 are briefly introduced. Then, various modulation strategies of ZnIn2 S4 are outlined for better photocatalytic performance, which includes morphology and structure engineering, vacancy engineering, doping engineering, hydrogenation engineering, and the construction of ZnIn2 S4 -based composites. Thereafter, the potential applications in the energy and environmental area of ZnIn2 S4 -based photocatalysts are summarized. Finally, some personal perspectives about the promises and prospects of this emerging material are provided.

Investigation into the Phase-Activity Relationship of MnO2 Nanomaterials toward Ozone-Assisted Catalytic Oxidation of Toluene.

Manganese dioxide (MnO2 ), with naturally abundant crystal phases, is one of the most active candidates for toluene degradation. However, it remains ambiguous and controversial of the phase-activity relationship and the origin of the catalytic activity of these multiphase MnO2 . In this study, six types of MnO2 with crystal phases corresponding to α-, ß-, γ-, ε-, λ-, and δ-MnO2 are prepared, and their catalytic activity toward ozone-assisted catalytic oxidation of toluene at room temperature are studied, which follow the order of δ-MnO2  > α-MnO2  > ε-MnO2  > γ-MnO2  > λ-MnO2  > ß-MnO2 . Further investigation of the specific oxygen species with the toluene oxidation activity indicates that high catalytic activity of MnO2 is originated from the rich oxygen vacancy and the strong mobility of oxygen species. This work illustrates the important role of crystal phase in determining the oxygen vacancies' density and the mobility of oxygen species, thus influencing the catalytic activity of MnO2 catalysts, which sheds light on strategies of rational design and synthesis of multiphase MnO2 catalysts for volatile organic pollutants' (VOCs) degradation.

2D MXene Nanomaterials for Versatile Biomedical Applications: Current Trends and Future Prospects.

Research on 2D nanomaterials is still in its early stages. Most studies have focused on elucidating the unique properties of the materials, whereas only few reports have described the biomedical applications of 2D nanomaterials. Recently, important questions about the interaction of 2D MXene nanomaterials with biological components have been raised. 2D MXenes are monolayer atomic nanosheets derived from MAX phase ceramics. As a new type of inorganic nanosystems, they are being widely used in biology and biomedicine. This review introduces the latest developments in 2D MXenes for the most advanced biomedical applications, including preparation and surface modification strategies, treatment modes, drug delivery, antibacterial activity, bioimaging, sensing, and biocompatibility. Besides, this review also discusses the current development trends and prospects of 2D inorganic nanosheets for further clinical applications. These emerging 2D inorganic MXenes will play an important role in next-generation cancer treatments.

Hydrogen peroxide formation in water during the VUV/UV irradiation process: Impacts and mechanisms of selected anions.

Understanding the formation and transformation of radicals generated by a low pressure mercury lamp emitting both 254 nm ultraviolet (UV254) and 185 nm vacuum UV (VUV185) is currently challenging due to the complexity of concurrent redox reactions occurring in this complex system. Because hydrogen peroxide (H2O2) is a common product of both oxidizing and reducing radicals generated during the VUV irradiation process, monitoring the variations in H2O2 levels can help us better understand the presence and relative dominance of different radicals. In this study, we systematically evaluated the effects of several selected anions on the formation of H2O2 under a variety of pH and dissolved oxygen (DO) conditions. Results show that although addition of these anions inhibited the formation of H2O2, their H2O2-inhibition mechanisms are markedly different. At low concentrations (≤1.0 mg/L), chloride reduced the generation of H2O2 primarily by consuming hydroxyl radicals (•OH); however, in high concentrations (11.0 mg/L), its light-screening effect was dominant. In comparison, the presence of bromide (≤1.0 mg/L) inhibited H2O2 formation mainly by reacting rapidly with both •OH and H2O2. Carbonate and phosphorous species exerted influence mainly by consuming •OH. Along with irradiation, increasing pH significantly decreased H2O2 levels, confirming that H2O2 was formed mainly by •OH. In contrast, raising DO did not raise H2O2 maximum yields, confirming that reducing radicals like aqueous electrons (e-aq) and hydrogen atoms (•H) are not the key precursors of H2O2 in this process. Mathematically, the evolutions of H2O2 can be reliably modeled (R2 ≥ 0.80) using a kinetics model incorporating H2O2 formation and decomposition kinetics. The results of this study may contribute to better understanding the use of VUV technology in water/wastewater treatment.

Adsorption of Cr(VI) from aqueous solution by a litchi shell-based adsorbent.

Cr(VI) is a toxic metal pollutant existing in industrial effluents. In this study, Fe3O4 and layered double hydroxide (LDH) were inserted into the litchi shell (LS) successively by the co-precipitation method to synthesize the modified magnetic litchi shell adsorbent (MMLS) for removing Cr(VI). The advantageous structure characteristics of MMLS were confirmed by XRD, FT-IR, SEM and the hysteresis loop characterization. The batch experiments of optimizing the conditions (pH, adsorbent dosage, initial concentration, coexisting ions) for removing Cr(VI) were accomplished to in simulated wastewater at room temperature. And the optimal pH of 3 and initial concentration of 100 mg/L in simulated wastewater were similar to that in the actual chrome-plated rinse water with the stable MMLS. The effect of coexisting ions indicated anions and Cr(VI) competed with each other for the adsorption site, but the interactions were negligible in actual chrome-plated rinse water. Chemisorption as a rate-limiting step was confirmed with a good fit of pseudo-second-order kinetics. And the adsorption behavior of MMLS can not be explained by a single theory according to Sips model. The desorption and recycle experiments demonstrated MMLS was reusable in actual chrome-plated rinse water.

Effect of preparation and reaction conditions on the performance of In/H-Beta for selective catalytic reduction of NOx with CH4.

In/H-Beta catalyst was prepared by optimizing the support, concentration of ion exchange liquid and calcination temperature to investigate the effects of synthesis conditions on catalytic activity of selective catalytic reduction of NOx with CH4. The results showed that the In/H-Beta catalyst exhibited the superior activity when concentration of exchange liquid was 0.033 M and calcination temperature was 500 °C, the NOx removal ratio could reach 97.6%. In addition, reaction conditions could affect the catalytic performance. When O2 concentration was 10%, CH4:NO ratio was no less than one, space velocity was lower than 23600 h-1 and NO initial concentration was no more than 700 ppm, In/H-Beta could exhibit superior catalytic activity. Moreover, the catalytic performances of In/H-Beta catalysts were discussed after enduring H2O or/and SO2. This novel strategy could open the door for selective catalytic reduction of NOx with CH4.

Some issues limiting photo(cata)lysis application in water pollutant control: A critical review from chemistry perspectives.

For decades, photolysis and photocatalysis have been touted as promising environment-benign and robust technologies to degrade refractory pollutants from water. However, extensive, large-scale engineering applications remain limited now. To facilitate the technology transfer process, earlier reviews have advocated to developing more cost-effective and innocuous materials, maximizing efficiency of photon usage, and optimizing photoreactor systems, mostly from material and reactor improvement perspectives. However, there are also some fundamental yet critical chemistry issues in photo(cata)lysis processes demanding more in-depth understanding and more careful consideration. Hence, this review summarizes some of these challenges. Of them, the first and paramount issue is the interference of coexisting compounds, including dissolved organic matter, anions, cations, and spiked additives. Secondly, considerable concerns are pointed to the formation of undesirable reaction by-products, such as halogenated, nitrogenous, and sulfur-containing compounds, which might increase instead of reduce toxicity of water if inadequate fluence and catalyst/additive are supplied due to time and cost constraints. Lastly, a critical issue lies in the uncertainty of current approaches used for identifying and quantifying radicals, especially when multiple radicals coexist together under changing and interconvertible conditions. The review hence highlights the needs to better understand these fundamental chemistry issues and meanwhile calls for more delicate design of experiments in future studies to overcome these barriers.

The performance and reaction pathway of δ-MnO2/USY for catalytic oxidation of toluene in the presence of ozone at room temperature.

In this work, a series of δ-MnO2/USY with different contents of δ-MnO2 (0.3 wt%, 1.5 wt%, 3.0 wt%, 10.0 wt%, and 15.0 wt%) were prepared. In addition, their performances of the adsorption of toluene, degradation and mineralization of toluene, and removal of ozone (O3) were investigated. The results showed that, among all the samples, 3.0 wt% δ-MnO2/USY displayed the best performance of toluene adsorption, degradation and mineralization. Furthermore, according to the in situ DRIFTS and GC-MS analysis, the intermediate by-products during the toluene degradation progress were ascertained and the possible pathway of catalytic oxidation toluene by δ-MnO2/USY in the presence of O3 was proposed.

Photocatalytic Hydrogen Production by RGO/ZnIn2S4 under Visible Light with Simultaneous Organic Amine Degradation.

In this work, the study of photocatalytic hydrogen production by RGO/ZnIn2S4 with simultaneous degradation of organic amines was carried out in the presence of organic amines in wastewater as the sacrificial agents. The effects of several factors, such as organic amine types, pH value, catalyst concentration, organic amine concentration, and sunlight source, on the photocatalytic activity of RGO/ZnIn2S4 for H2 production were investigated. At the same time, its performance of degrading organic amines during H2 production was also examined. The results showed that the order of H2 production activity of RGO/ZnIn2S4 in six organic amine solutions was N(CH2CH3)3 > N(HOCH2CH2)3 > N(CH3)3 > HO(CH2)2NH2 > C6H5-N2> CO(NH2)2, and the highest H2 production was in N(CH2CH3)3 (triethylamine) solution, being 1597 µmol·g-1·h-1, which is 2.6 times as high as that using the aqueous solution mixture of Na2S and Na2SO3 as the sacrificial agent. In addition, when the pH was 13, the catalyst concentration was 1.0 g·L-1, and the triethylamine concentration was 1.0 mol·L-1, the photocatalytic activity was the highest. Furthermore, the relationship between triethylamine concentration and H2 production was analyzed according to the theory of dynamics.

[Heterogeneous Oxidation of Secondary Organic Tracers of Isoprene and Toluene by Ozone].

For this paper, chamber experiments were carried out to investigate the oxidation of secondary organic tracers of toluene and isoprene by ozone under different conditions (relative humidity, mixing state, etc.) using a relative rate constants approach. The uncertainty of the tracer-based method due to the ozone oxidation of secondary organic tracers was also addressed. The results showed that the effective rate constants of analogue of 2-methyl erythritol (AME) and 2,3-dihydroxy-4-oxopentanoic acid (DHOPA) were (4.60±0.66)×10-19 cm3·(molecule·s)-1and (6.57±0.51)×10-19 cm3·(molecule·s)-1, respectively. Given the instability of the secondary organic tracers caused by the oxidation, the contributions of toluene and isoprene to secondary organic aerosols could be underestimated by 16.5%-44.8% and 18.3%-47.3%, respectively.