In situfabrication of S-type BiOIxBryheterojunction with metallic Bi for boosting photocatalytic activity for CO2reduction.

Heterojunction construction and morphology control have always been considered effective ways to promote the capability of photocatalysts. In this work, BiOIxBry, S-type heterojunction photocatalysts with metallic Bi nanoparticles, were synthesizedin situusing a solvothermal method, and the influence of reaction temperature (180 °C-220 °C) and dopant doping amount on the catalysts' microscopic morphology, structure, and catalytic properties were researched. Study results revealed the 1:1 BiOIxBrysynthesized at 200 °C exhibited the optimum behavior in CO2reduction. Its catalytic CO2reduction to CH3OH was 932.88µmol gcat-1and C2H5OH was 324.46µmol gcat-1under the analog light source for 8 h, which was approximately 1.92 and 1.49 times higher than that of BiOI-200 °C, respectively. The reinforced catalytic properties are probably attributed to the synergistic effect between metallic Bi nanoparticles and BiOIxBryheterojunction. Thanks to the SPR effect ofin situmetallic Bi, the catalysts' photocarrier separation efficiency is facilitated. Additionally, the heterojunction formation contributes to that trend and more importantly, preserves the charge carriers with strong redox capacity in BiOIxBry, proving product selectivity. We also present a potential electron transfer mechanism involved in the BiOIxBryphotocatalytic CO2reduction based on the characterization analysis and experimental results.

Distribution and sources of PM2.5-bound free silica in the atmosphere of hyper-arid regions in Hotan, North-West China.

The composition of atmospheric fine particulate matter (PM2.5) is complex and exhibits strong regional differences. Free silica (α-SiO2) in atmospheric particulate matter is carcinogenic and is an important component of respirable particulate matter in urban areas. Measurements determined that the concentration of silicon dioxide (α-SiO2) in PM2.5 in the urban area of Hotan City, China, was 8.02 µg·m-3 during the dust period and exceeded 1.77 µg·m-3 during the non-dust period. The proportion of α-SiO2 in PM2.5 was 8.07% during the dust period and 2.25% during the non-dust period. Atmospheric visibility during the dust period was mainly influenced by the content of atmospheric floating dust. Analysis of α-SiO2 pollution sources during the dust period showed that the air masses containing sand and dust originated from the desert hinterland. Following passage through oasis areas, the air mass was effectively reduced in the concentration of α-SiO2 in PM2.5. During the dusty period, α-SiO2 and PM2.5 originated from the same source in Hotan City. Moreover, wind speed was the main influencing factor for the α-SiO2 concentration. During the non-dust period, α-SiO2 and PM2.5 were not from the same source of pollution.

In situ ultrasound-assisted ion exchange synthesis of sphere-like AgClxBr1-x composites with enhanced photocatalytic activity and stability.

AgClxBr1-x composites with different halogen molar ratios (Cl/Br) were prepared by a facile ultrasound-assisted ion-exchange method. The formation of close contact between AgCl and AgBr facilitated the transportation of photoexcited charge carriers and contributed to the enhanced visible-light-driven photocatalytic degradation of different kinds of antibiotics. The AgClxBr1-x composites had a sphere-like morphology and tunable band gaps from 2.95 to 2.57 eV depending on Cl/Br mole ratios. Besides, the AgClxBr1-x composite was optimized by varying halogen mole ratios (Cl/Br) to achieve the highest photocatalytic activity. Results indicated that AgCl0.75Br0.25 showed the best photocatalytic degradation performance, which was about 2.36 and 2.78 times that of the single AgCl towards ciprofloxacin (CIP) and metronidazole (MNZ) degradation, respectively. Meanwhile, a possible photocatalytic degradation mechanism was discussed, and results indicated that the holes (h+) and •OH were the dominant active species in the AgCl0.75Br0.25 system.

Distribution, sources, risks, and vitro DNA oxidative damage of PM2.5-bound atmospheric polycyclic aromatic hydrocarbons in Urumqi, NW China.

Research has focused on the impacts of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere due to their potential carcinogenicity. In this study, we investigated the seasonal variation, sources, incremental lifetime cancer risks (ILCRS), and vitro DNA oxidative damage of PAHs in Urumqi in NW China. A total of 72 atmospheric samples from Urumqi were collected over a year (September 2017-September 2018) and were analyzed for 16 PAHs that are specifically prioritized by the U.S Environmental Protection Agency (U·S EPA). The highest PAHs concentrations were in winter (1032.66 ng m-3) and lowest in spring (146.00 ng m-3). Middle molecular weight PAHs with four rings were the most abundant species (45.28-61.19% of the total). The results of the diagnostic ratio and positive matrix factorization inferred that the major sources of atmospheric PAHs in Urumqi were biomass burning, coking, and petrogenic sources (52.9%), traffic (30.1%), coal combustion (8.9%), and the plastics recycling industry (8.1%). ILCRS assessment and Monte Carlo simulations suggested that for all age groups PAHs cancer risks were mainly associated with ingestion and dermal contact and inhalation was negligible. The plasmid scission assay results showed a positive dose-response relationship between PAHs concentrations and DNA damage rates, demonstrating that toxic PAHs was the primary cause for PM2.5-induced DNA damage in the air of Urumqi.

One-pot sonochemical synthesis of 3D flower-like hierarchical AgCl microsphere with enhanced photocatalytic activity.

A highly uniform 3D flower-like hierarchical AgCl microsphere was prepared by sonochemical method with the existence of ß-dextrin. The 3D flower-like hierarchical structure can be ascribed to the existence of ß-dextrin, which provides nucleation sites for the growth of nanosheets because of the strong interaction between ß-dextrin and Ag+. The 3D flower-like hierarchical AgCl microspheres were assembled by numerous interleaving nanosheet petals with small thickness. Benefiting from the unique structural features, the as-prepared 3D flower-like hierarchical AgCl microsphere exhibited higher degradation efficiency with degrading 98.17% of methylene blue (MB) and 88.50% of tetracycline (TC) within 40 min, which were both remarkably higher than those of irregular AgCl under visible light irradiation. Besides, the photocatalytic degradation rate constant of 3D flower-like hierarchical AgCl microsphere (0.063 min-1) for MB was 3.94 times higher than that of irregular AgCl (0.016 min-1). Moreover, a possible mechanism for the formation and excellent photocatalytic performance of 3D flower-like hierarchical AgCl microsphere was also proposed.

Facile photo-ultrasonic assisted reduction for preparation of rGO/Ag2CO3 nanocomposites with enhanced photocatalytic oxidation activity for tetracycline.

Various antibiotics in the aquatic systems have threat the aquatic ecosystem balance and the human health. In this study, a degradation treatment method for tetracycline (TC), one of the commonly used antibiotics, was explored by using novel photocatalysts of rGO/Ag2CO3 under simulated sunlight, because conventional treatment methods are not efficient on the removal of TC. rGO/Ag2CO3 nanocomposites were synthesized via a facile photo-ultrasonic assisted reduction method. More than 90% of TC was removed by 1% (weightrGO/weightcomposites) rGO/Ag2CO3 within 60 min at pH = 4, which was about 1.3 times higher than that of pure Ag2CO3. The cycling experiments indicated that 1% rGO/Ag2CO3 was highly stable and could be reused for at least 5 cycles without significant deactivation to its photocatalytic activity. In addition, the effects of pH, temperature, and dosage amount of 1% rGO/Ag2CO3 on photocatalytic degradation were investigated. Meanwhile, the effect of ultrasonic on the degradation of TC was also investigated. This study can provide a new method for the preparation of smaller nanosized materials and photocatalysts with high activity and stability for its environmental or other applications.

Biomass gasification for hydrogen rich gas in a decoupled triple bed gasifier with olivine and NiO/olivine.

Catalytic steam gasification of biomass has been carried out in decoupled triple bed gasification (DTBG) system which consists of pyrolyzer, reformer and combustor. Olivine and NiO/olivine used as in-situ tar destruction catalyst. The result shows the gasification system with catalytic bed materials allows an option to improve tar removal that enhances H2 production. A gas yield of 1.59 Nm3/kg daf with H2 concentration of 56.1 vol% and tar content as low as 0.6 g/Nm3 has been achieved with the presence of NiO/olivine. Olivine and NiO/olivine reduced tar yield by 55% and 94% respectively compared to quartz. Gas yield, tar removal efficiency and water conversion enhanced by higher reformer temperature. The longer residences time of catalyst in reformer leads in-situ reduction of olivine and NiO/olivine that adds up in-situ tar reforming. Particularly, in-situ reduction of NiO to metallic Ni enhances tar and CH4 reforming reaction.

Concentration characteristics, source apportionment, and oxidative damage of PM2.5-bound PAHs in petrochemical region in Xinjiang, NW China.

Polycyclic aromatic hydrocarbons (PAHs) are of considerable concern due to their potential as human carcinogens. Thus, determining the characteristics, potential source, and examining the oxidative capacity of PAHs to protect human health is essential. This study investigated the PM2.5-bound PAHs at Dushanzi, a large petrochemical region in Xinjiang as well as northwest China. A total of 33 PM2.5 samples with 13 PAHs, together with molecular tracers (levoglucosan, and element carbon), were analyzed during the non-heating and heating periods. The results showed that the PM2.5 concentrations were 70.22 ± 22.30 and 95.47 ± 61.73 µg/m3, while that of total PAHs were 4.07 ± 2.03 and 60.33 ± 30.80 ng/m3 in sampling period, respectively. The fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, and benzo[k]fluoranthene were the most abundant (top five) PAHs, accounting for 71.74 and 72.80% of total PAH mass during non-heating and heating periods. The BaP equivalent (BaPeq) concentration exceeded 1 ng/m3 as recommended by National Ambient Air Quality Standards during heating period. The diagnostic ratios and positive matrix factorization indicated that oil industry, biomass burning, coal combustion, and vehicle emissions are the primary sources. The coal combustion remarkably increased during heating period. The plasmid scission assay (PSA) results showed that higher DNA damage rate was observed during heating period. PAHs in PM2.5 such as Chr, BaP, and IcdP were found to have significantly positive correlations with the plasmid DNA damage rates. Additionally, the relationship among BaPeq and DNA damage rate suggested that synergistic reaction may modify the toxicity of PAHs.

Facile One-Step Sonochemical Synthesis and Photocatalytic Properties of Graphene/Ag3PO4 Quantum Dots Composites.

In this study, a novel graphene/Ag3PO4 quantum dot (rGO/Ag3PO4 QD) composite was successfully synthesized via a facile one-step photo-ultrasonic-assisted reduction method for the first time. The composites were analyzed by various techniques. According to the obtained results, Ag3PO4 QDs with a size of 1-4 nm were uniformly dispersed on rGO nanosheets to form rGO/Ag3PO4 QD composites. The photocatalytic activity of rGO/Ag3PO4 QD composites was evaluated by the decomposition of methylene blue (MB). Meanwhile, effects of the surfactant dosage and the amount of rGO on the photocatalytic activity were also investigated. It was found that rGO/Ag3PO4 QDs (WrGO:Wcomposite = 2.3%) composite exhibited better photocatalytic activity and stability with degrading 97.5% of MB within 5 min. The improved photocatalytic activities and stabilities were majorly related to the synergistic effect between Ag3PO4 QDs and rGO with high specific surface area, which gave rise to efficient interfacial transfer of photogenerated electrons and holes on both materials. Moreover, possible formation and photocatalytic mechanisms of rGO/Ag3PO4 QDs were proposed. The obtained rGO/Ag3PO4 QDs photocatalysts would have great potentials in sewage treatment and water splitting.

Preparation and sonophotocatalytic performance of hierarchical Bi2WO6 structures and effects of various factors on the rate of Rhodamine B degradation.

Hierarchical Bi2WO6 structures with high surface area were prepared in the presence of polyvinylpyrrolidone by using an optimized hydrothermal method. The samples prepared were characterized by X-ray diffraction, field-emission scanning electron microscopy and N2 adsorption-desorption technique. The results of these characterizations showed the formation of the hierarchical Bi2WO6 structures with high surface area (51m2/g). The degradation of Rhodamine B (RhB) with or without visible light was investigated under various experimental conditions to evaluate the sonophotocatalytic activity of the hierarchical Bi2WO6 structures. The result showed that the degradation efficiency was found to be in the following order: sonocatalysis