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Degradation of pesticide residues by ultrasonic-assisted photocatalytic technology with a semiconductor catalyst is an effective method to reduce environmental wastewater pollutant. At present, researchers devote enormous time and energy to exploit new-type semiconductor catalysts which have larger specific surface area and suitable bandgap energy. While, there are few researches to explore the effect on the semiconductors composites with different dimensional material. Herein, we successfully immobilized spherical-like AgCl0.75Br0.25 particles on skeleton surface of reduced graphene oxide (RGO) with different dimensions (0D, 2D, 3D) via the photo-ultrasonic method for the first time. The results indicated that AgCl0.75Br0.25 demonstrated distinctly different specific surface areas, light harvesting ability and charge carrier separation efficiency after coupling with different dimensional RGO. Particularly, the 3D RGO/AgCl0.75Br0.25 composite revealed the optimal ultrasound-assisted photocatalytic activity for removal of chloridazon (Chl), and its degradation efficiency had reached at 75.2%, which was about 1.83, 1.27, and 1.19 times higher than that of pristine AgCl0.75Br0.25 (41%), 2D RGO/AgCl0.75Br0.25 (59.2%) and 0D RGO/AgCl0.75Br0.25 (63.4%), respectively. Moreover, the cyclic degradation experiments suggested that the 3D RGO/AgCl0.75Br0.25 composite had excellent sono-photocatalytic stability and repeatability. The radicals trapping experiments revealed that ·OH and h+ were the main reactive species in the ultrasound-assisted photocatalytic degradation process, and the possible mechanism was further proposed based on above results. Overall, this work could provide an effective strategy to construct the heterojunction semiconductors with excellent ultrasound-assisted photocatalytic activity to alleviate environmental wastewater pollution.

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.

The composition of atmospheric fine particulate matter (PM

Daily fine particulate matter samples were collected in Dushanzi district within four months from September 2015 to August 2016 and represent the four seasons. The samples were determined for major chemical components in PM2.5, including elements, water-soluble ions (WSIs) and the organic/elemental carbon (OC/EC). The results indicated that the annual mean PM2.5 concentration was 62.85 ± 43.5 μg m−3 in the Dushanzi district, with the highest seasonal average in winter (95.47 ± 61.7 μg m−3) and the lowest in summer (33.22 ± 17.7 μg m−3). The crustal elements were the most abundant elements and accounted for 96.51% of the total analyzed elements. Carcinogenic metals, such as Cr, Pb, As and Cd, originated from human activity, especially during winter. The highest total WSI concentration was 68.99 μg m−3 in winter, followed by autumn (16.32 μg m−3), spring (10.23 μg m−3) and summer (7.06 μg m−3). SO42−, NO3− and NH4+ were the most abundant WSIs in Dushanzi. Ion balance calculations showed that PM2.5 in winter was acidic; in autumn and spring alkaline; and in summer nearly neutral. Total carbonaceous aerosol (TCA) accounted for 34% of the PM2.5. The chemical mass closure (CMC) indicated that minerals and WSIs were the major fraction, accounting for 33.58% and 23.17% of PM2.5 mass concentration, respectively. Dushanzi was controlled by four major air masses, and the relative contributions of these air masses differ by season. Positive matrix factorization (PMF) analysis identified six sources including vehicle emission, biomass burning, coal combustion, industrial pollution, secondary aerosols and soil dust, with annual mean contributions of 9.43%, 10.86%, 18.45%, 12.15%, 18.26% and 30.85%, respectively. Moreover, the relative contributions of these identified sources varied significantly with the changing seasons.

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.

Here we prepared sphere-like AgCl by stirring in the presence of sodium oleate, and loaded it on the surface of reduced graphene oxide (rGO) to form sphere-like AgCl/ rGO composite. Sphere-like AgCl exhibited enhanced degradation efficiency after the inserting of rGO with degrading 80.6% of tetracycline (TC) within 90 min, which was about 15.4% higher than pristine spherical AgCl (65.2%) under simulated sunlight irradiation. Moreover, five times cycling test of the obtained samples had revealed the improved stability of AgCl/ rGO. The remarkable photocatalytic activity was mainly due to the better interaction between AgCl and rGO, where charge separation and transfer as well as the utilization of sunlight were boosted. Improved photocatalytic stability was majorly ascribed to the fast electrons transfer from AgCl to rGO before the reduction of Ag+ to Ag. Besides, a possible photocatalytic reaction mechanism under simulated sunlight was proposed. Meanwhile, AgCl/ rGO also exhibited better photocatalytic efficiency for the degradation of TC under natural sunlight irradiation (73.2%), which is hopeful for practical application of photocatalysts.

Urumqi, the administrative center of Xinjiang, suffers from severe atmospheric aerosol pollution; however, no study has comprehensively analyzed the local constituents and sources of fine particulate matter (PM2.5). The characteristics of PM2.5 in Urumqi were observed the first winter (2012–2013) after natural gas replaced coal as an energy source. Enrichment factors, backward trajectories, the potential source contribution function (PSCF) model, and positive matrix factorization (PMF) were used to identify the source area and categories. The results showed a mean concentration of 197.40 µg m–3 for the PM2.5, which significantly decreased after the conversion from coal to natural gas. Although the concentration of NO3– increased post-conversion, the SO42– and Cl– decreased by 42.54% and 32.93%, respectively. The water-soluble ions (WSIs) mainly consisted of NH4HSO4, CaSO4, MgSO4, Ca(NO3)2, Mg(NO3)2, and KCl. Elements such as Pb, Cr, and As decreased following the fuel switch. The organic carbon and elemental carbon were strongly correlated, and the mean concentration of the secondary organic carbon was 18.90 µg m–3. Pyr, Chr, BbF, BkF, IcdP, and BghiP were the most prevalent individual polycyclic aromatic hydrocarbons, and BaP exceeded health-based guidelines. The results from trajectory clustering and PSCF modeling suggested that emissions from both the city and its surroundings, as well as the valley-and-basin topography, may be responsible for the heavy PM2.5 pollution in southern Urumqi. PMF identified five primary sources: secondary formation, biomass and waste burning, vehicle emissions, crustal minerals, and industrial pollution and coal combustion.

AgCl

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 (ILCR

Visible-light-active reduced graphene oxide/ Ag2CrO4 (RGO/ Ag2CrO4) composites were prepared by a novel photo-ultrasonic assisted reduction process. Compared to single Ag2CrO4 photocatalyst, as-prepared RGO/ Ag2CrO4 composites had displayed dramatically enhanced photocatalytic activity toward the degradation of methylene blue (MB) and tetracycline (TC) under visible light illumination (λ > 420 nm). And when the mass ratio of RGO to Ag2CrO4 was 0.5%, sample showed the most superior photocatalytic activity,with degrading 97.68% and 80.03% of MB and TC in 60 min, respectively, which was about 0.9 times and 2 times higher than that of pure Ag2CrO4. The excellent photocatalytic activity was majorly due to the coupling of nano-sized Ag2CrO4 (6–9 nm) with high electron-conductive RGO, which had boosted charge separation and transfer. Improved photocatalytic stability was mainly ascribed to the fast transferring of photogenerated electrons from Ag2CrO4 to RGO before the reduction of Ag ions to metallic Ag. This work can provide a more economical and effective method for the exploration of efficient RGO-based photocatalysts.

β-Ag2MoO4/AgBr heterojunctions were successfully prepared by a facile ultrasonic-assisted in-situ anion-exchange method, anchoring sphere-like AgBr particles on the surface of octahedral β-Ag2MoO4. Photocatalytic performances of the obtained samples were studied by the degradation of Rhodamine B (RhB), tetracycline hydrochloride (TC) and 4-Chlorophenol (4-CP) under visible-light irradiation. Results proved that the introduction of β-Ag2MoO4 had improved the photocatalytic activity of AgBr, and 5% β-Ag2MoO4/AgBr composites exhibited the highest degradation efficiency with degrading 98.4% RhB during 5 min, which was about 1.05 times and 13 times higher than that of pure AgBr and Ag2MoO4, respectively. Meanwhile, cycling test of as-prepared samples had indicated the excellent cycling stability of as-prepared samples. The obviously enhanced photocatalytic activity and stability could be attributed to the well-matched binding energies and heterostructure between AgBr and β-Ag2MoO4, where the utilization efficiency of solar light was improved, and charge separation at the heterojunction interfaces was accelerated. Besides, trapping experiments implied that holes and ·O2− were the predominant active species during the degradation process of RhB. Meanwhile, a possible mechanism for the degradation of organic pollutants by β-Ag2MoO4/AgBr photocatalysts was proposed.

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.

This paper presents a comprehensive study on characteristics and kinetics of the gas component (H2, CH4, CO, CO2) releasing during oil shale (OS) pyrolysis. Firstly, the thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA-FTIR) was used to determine the decomposition regions of OS. The results showed that the OS undergoes two pyrolysis regions: first stage (400∼600 °C) and second stage (600∼800 °C). The isothermal pyrolysis of OS was carried out in a micro-fluidized bed reaction analyzer (MFBRA). The evolved temperature and time span of each gas product are different in both sections. Reaction kinetics were investigated with respect to the formation of individual gas component and gas mixture. The kinetics of gas components and gas mixture were calculated by model fitting method. The activation energy (Ea) calculated by the three models for H2, CH4 and CO2 were in the range of 51.05∼60.15, 6.84∼9.65 and 13.21∼14.10 kJ/mol, respectively, while the values varied significantly in high temperature zone. In particular, the resulting Ea values for H2 decreased to 38.88∼40.57 kJ/mol, while that for CH4 and CO2 increased to 25.16∼27.61and 26.12∼35.12 kJ/mol, respectively. However, compared with other three gases, CO only appears in the high temperature zone, and the activation energy of CO is in the range of 32.98∼34.82 kJ/mol. The Ea of the stage 2 is higher than that of the stage 1. The result indicated that the control step gradually transits from the surface chemical reaction control to the joint control of reaction and diffusion with increasing temperature.

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

Catalytic steam gasification of an Inner Mongolia lignite for hydrogen-rich gas production was investigated in a decoupled triple bed reaction system with olivine and Ni/olivine as both solid heat carrier and in-situ tar cracking/reforming catalyst. In the system, tar cracking/reforming, pyrolysis/gasification, and char combustion reactions are decoupled into three separated reactors, i.e. a reformer, a fuel reactor and a combustor, which are connected in series by solid heat carrier. The system configuration provides an option to strengthen tar cracking/reforming reaction to improve hydrogen-rich gas production and tar removal. Specifically, using olivine and Ni/olivine in a mass ratio of 1:1 as circulating bed material and in-situ tar cracking/reforming catalyst, a product gas with the H 2 concentration of 51.7 vol.% and the tar content of 2.2 g/Nm 3 has been obtained at the pyrolyzer temperature of 700 °C, reformer temperature 850 °C, steam to carbon mass ratio (S/C) 1.2, and ratio of bed material circulating rate to coal feeding rate (C/F) 8.0. Nevertheless, the gasification performance suffered from the limited char steam gasification.

The methanation process based on the Sabatier reaction is becoming a key instrument in solving CO2 emissions and surplus electricity. A Sabatier fixed-bed reactor model with randomly stacked cylindrical particles was established by discrete element method (DEM), and the variation of the substances distribution, reaction characteristics and carbon deposition in the micro-scale catalyst was simulated by computational fluid dynamics (CFD). The effects of catalyst hole number and operating conditions on CO2 conversion and CH4 yield were also discussed. The result shows that as the reaction proceeds, the concentration distribution of the substances in the catalyst changes from a ring to a uniform, and the distribution of the reaction rate values in the catalyst changes from a V-shape to a U-shape. In the steady state, the catalyst is only effectively used in about 10% of the outer layer. The carbon deposition in the outer layer of the catalyst and the inlet of the reactor is more serious. And the average porosity value in the catalyst decreased by 0.012 as the reaction progressed to 1000 s. In the steady state, CH4 yield from high to low catalyst bed arrangement is 4 holes, 7 holes, 1 hole and solid. The CH4 yield can be increased by increasing the heat transfer coefficient and decreasing the inlet flow rate, and the reaction can reach a steady state faster by increasing the inlet temperature and pressure.

Steam co-gasification of pine sawdust and bituminous coal was conducted in a lab-scale external circulating radial-flow moving bed (ECRMB) gasification system. The system is composed of three decoupled reactors, i.e., a gas–solid countercurrent moving bed pyrolyzer, a radial-flow moving bed gasifier and a riser-type combustor. Calcined olivine was used as circulating heat carrier and in-situ tar destruction catalyst as well. The influences of biomass blending ratio (BR), pyrolyzer temperature, gasifier temperature and steam to carbon mass ratio (S/C) on the gasification performance were investigated. The results indicated that the gas and tar yields increased with the increase of BR. Synergetic effect based on gas composition was found during co-gasification. At the S/C range of 0 to 1.3, the gas yield and H 2 content in product gas increased but CO 2 decreased with the increase of S/C. Higher gasifier temperature promoted the gas yield, H 2 + CO in product gas, carbon conversion and chemical efficiency of the process. A gas yield of 0.60 Nm 3 /kg daf and a tar yield of 5.8 g/Nm 3 in the gas were obtained at the gasifier temperature of 850 °C, BR of 50% and S/C of 1.3. Pyrolyzer temperature at the range of 500 to 700 °C had no remarkable influence on the product gas composition.

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.

In this work, a facile ultrasonic method for the fabrication of AgCl quantum dots (AgCl QDs) with an average diameter of about 2.5[Formula: see text]nm was reported for the first time. The material was analyzed by various techniques. In addition, effects of material’s size on its photocatalytic activities were studied. Results suggested that the AgCl QDs exhibited excellent photocatalytic activity to degrade Rhodamine B (RhB) and tetracycline (TC) under visible light illumination, and the degradation rate of RhB (TC) had reached up to 96.6% (72.2%) in 20 min, which was higher than that of AgCl nanoparticles (23[Formula: see text]nm) and AgCl nanospheres (114[Formula: see text]nm), respectively. Besides, the band gap of the material was increased when the size of material decreased from 23[Formula: see text]nm to 2.5[Formula: see text]nm. The significantly improved photocatalytic performance and increased band gap of AgCl QDs were mainly related to the quantum size effects of AgCl, which results in the more electron fluctuation in quantized energy levels and the lower recombination of electrons and holes.

A photocatalyst of high-performance hierarchical nitrogen-doped MoS2 (N-MoS2) microsphere was fabricated by an in situ hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB). The as-prepared N-MoS2 microsphere was self-assembled by extremely thin interleaving petals, where CTAB acts as a nucleation site for the formation of the interleaving petals due to the strong interaction between CTA+ and [Formula: see text]. N-MoS2 showed higher N2 fixation ability (101.2 [Formula: see text] mol/g(cat)h) than the non-doped MoS2 under the visible light irradiation, and the improved photocatalytic activity could be ascribed to that the doped N narrows the band gap, and the surface reflecting and scattering effect caused by the hierarchical structure enhance the light adsorption. The trapping experiment of active species was also investigated to evaluate the role of photogenerated electrons in the photocatalytic reaction process. Meanwhile, the possible mechanism for the formation and excellent photocatalytic performance of N-MoS2 microsphere were also presented.

Development of efficient photocatalyst via a simple method is critical for environmental remediation and energy conversion. Herein, a highly efficient N and Pt co-doped hollow hierarchical BiOCl microsphere (HHBs) photocatalyst was prepared by an in situ hydrothermal method. HHBs was assembled by numerous interleaving nanosheets petals with small thickness. The synthesized photocatalyst exhibited excellent photocatalytic performance for photoreduction of CO2 into hydrocarbons and photodegradation of organic contaminant (ciprofloxacin (CIP) and rhodamine B (RhB)), which can be attributed to the scattering effect and surface reflecting caused by the hierarchical architecture, the N doping that narrows the band gap, and the Schottky barrier due to the existence of Pt that improves the charge transfer and carrier separation. The Pt1/N0.25-HHBs with optimal content of Pt and N exhibited the fastest degradation rate for CIP (0.011 min−1) and RhB (0.144 min−1). Besides, the yields of methanol and ethanol over Pt1/N0.25-HHBs were 328.7 and 113.2 µmol/gcat in 8 h of simulated sunlight irradiation, respectively, which were 3.4 and 5.7 times higher than that over single HHBs. Moreover, possible mechanism of excellent photocatalytic performance of Pt1/N0.25-HHBs was also investigated. This work represented a promising candidate photocatalyst for environmental remediation and energy conversion using cost efficient materials.

A highly uniform 3D flower-like hierarchical AgCl microsphere was prepared by sonochemical method with the existence of β-dextrin. The 3D flower-like hierarchical structure can be ascribed to the existence of β-dextrin, which provides nucleation sites for the growth of nanosheets because of the strong interaction between β-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.

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.

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/Ag

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. Electronic supplementary material The online version of this article (10.1186/s11671-018-2466-9) contains supplementary material, which is available to authorized users.

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 PM

The micro-morphological characteristics of PM_(2.5), collected in the Kuitun-Dushanzi petrochemical area of the Xinjiang Uygur Autonomous Region, China, were studied using a high-resolution field emission scanning electron microscope with energy dispersive X-ray spectroscopy (FESEM-EDX). The individual particle types of PM_(2.5) were identified, including mineral particles (regular minerals and irregular minerals), spherical particles (coal-fired fly ash and some secondary particles), soot aggregates, and other particles (some particles remained unclassified). Factories, power plants, vehicle emissions, and road dust were major sources of PM_(2.5) in the Kuitun-Dushanzi petrochemical area. Vehicle exhaust and waste gas from a power plant were defined as primary sources of mineral particles. Wind speed in September which was higher than July during the sampling time leads to the lower concentration of regular mineral particles since high wind speeds would reduce the chance of secondary particle generation. As a high wind speed would also easily diffuse the fine particles, the coarse-grained mineral particles had the highest percentages in September; the chain-like soot aggregates and the compact soot aggregates were the majority of all kinds of particles. The sizes of various particles in July and September primarily ranged from 0.1 to 0.5 μm.

Steam co-gasification of pine sawdust and bituminous coal blend was performed in a pyrolysis-reforming-combustion decoupled triple bed gasification (DTBG) system with Fe2O3/olivine as both solid heat carrier and in-situ tar cracking/reforming catalyst. The effects of reformer temperature (RT) and circulation rate (CR) of catalyst on gasification performance were investigated. Besides, X-ray diffraction (XRD) and temperature programmed reduction (TPR) are employed to reveal the properties of Fe2O3/olivine catalyst during the continuous redox cycle between those decoupled reactors. The results indicated that, the configuration of the DTBG system favor tar cracking/reforming reaction to enhance H2 yield. Higher RT promotes the gas yield, H2 content in product gas, carbon conversion and cold gas efficiency of the process. Specifically, a gas yield of 0.66 Nm3/kg, tar content as low as 4.87 g/Nm3 with the H2 content of 42.2 vol% has been obtained at the RT of 850 °C. Lower CR of catalyst leads further reduction of Fe2O3 that allows increment on the gas yield and H2 content. The H2 content reduced from 44.5 vol% to 40.8 vol% and CO2 increased from 37.3 vol% to 41.4 vol% with increasing catalyst CR from 1.9 kg/h to 4.5 kg/h. Reduction level of Fe2O3/olivine increased with decreasing catalyst CR. Fe2O3/olivine not only has catalytic effect on tar cracking/reforming but also acts as an oxygen carrier transports oxygen from the combustor to the reformer.

Biomass gasification was carried out in an External Circulating Countercurrent Moving Bed (ECCMB) gasification system. The system is composed of three reactors, a solid–solid co-current moving bed pyrolyzer, a gas–solid countercurrent moving bed gasifier and a riser-type combustor. A series of experiments were conducted with pine sawdust as feedstock and calcined olivine as solid heat carrier as well as catalyst. The operation conditions including the temperature of pyrolyzer, the steam/biomass ( S/B ) ratio, the particle size of feedstock, and the height of catalyst bed in the gasifier were investigated. The results show that the pyrolyzer temperature and S / B ratio are important factors for the product distribution. Gas yield and chemical efficiency are greatly increased with increased pyrolyzer temperature. The hydrogen content follows the same tendency. The introduction of steam improves gas quality and tar content of as low as 2 g/Nm 3 in the gas has been obtained. Both smaller particle size and higher catalyst bed height favor tar destruction, but impact no significant influence on the product gas composition.

Catalytic coal gasification was carried on a lab-scale external circulating co-current moving-bed (ECCMB) gasification system with steam as gasification agent and olivine as catalytic solid heat carrier. The system is composed of a moving-bed gasifier and a riser combustor. The effects of gasifier temperature, steam/coal mass ratio (S/C), bed materials and bed height on the product gas compositions, carbon conversion, and chemical efficiency were investigated. The result show that the gas yield and carbon conversion increase with the increase of the gasifier temperature. The highest H 2 concentration of 60.4 vol.% is produced from Dayan lignite at the gasifier temperature of 800 °C and S/C ratio of 1.0. The carbon conversion increases remarkably at the S/C range from 0 to 0.4. Olivine as the bed material has a satisfying catalytic tar cracking efficiency. Appropriate bed height favors tar destruction because of the increase in the contact time of the tar and steam with the catalytic bed material.