Jing Shang

The use of vacuum ultraviolet irradiation to oxidize SO2 and NOx for simultaneous desulfurization and denitrification

A simple and efficient method for simultaneous desulfurization and denitrification via vacuum ultraviolet (VUV) irradiation and with no additional chemicals is presented. The simultaneous removal of 90% SO2 and 96% NOx (NO+NO2) was achieved from the simulated flue gas under the irradiation from a low-pressure mercury lamp with main wavelengths of 185 and 254 nm, respectively. The composition, flow rate, and temperature of the simulated flue gas, as well as the VUV light intensity, were evaluated as the factors impacting on the efficiency of SO2 and NOx removal. The OH, HO2, O, and O3 produced from the photolysis of H2O and O2 were concluded as the major reactive oxygen species that oxidized SO2 and NOx. The additional OH and HO2 generated through the reactions of NO+HO2 and SO2+OH/HO2 improved treatment efficiency, while the oxidation products of NOx, e.g., NO2, HNO2, HNO3, and HNO4, consumed massive reactive oxygen species (such as O, OH, and HO2) and thereby reducing the removal efficiencies. The main reaction products were characterized as H2SO4 and HNO3 by ion chromatography, which could be used as chemical or fertilizer raw materials.

Photocatalytic degradation of bisphenol A using Ti-substituted hydroxyapatite

Ti-substituted hydroxyapatite (TiHAP) is a new photocatalyst with high adsorption capacity and photocatalytic activity. The morphology and structure of TiHAP were characterized using transmission electron microscopy, X-ray diffraction, ultraviolet-visible spectrophotometry, and the zeta potential. The adsorption and photocatalytic degradation of bisphenol A (BPA, an environmental endocrine disrupting chemical) over TiHAP and P25 TiO2 photocatalysts were studied using liquid chromatography-mass spectrometry. The influences of fulvic acid and Fe3+ ions on the BPA degradtion rate were analyzed. The adsorption of BPA on TiHAP and TiO2 obeyed the Langmuir adsorption equation. TiHAP exhibited much higher adsorption capacity and photocatalytic degradation activity of BPA than TiO2. Fulvic acid and Fe3+ showed different effects on the photocatalytic activity of TiHAP and TiO2 films. These were explained by band structure theory, the electron transfer path, and optical absorption capacity. The results are useful for the application of TiHAP in the photocatalytic degradation of environmental endocrine disrupting chemicals.

Heterogeneous reaction of NO2 on the surface of montmorillonite particles

The studies on heterogeneous reactions over montmorillonite, which is a typical 2:1 layered aluminosilicate, will benefit to the understanding of heterogeneous reactions on clay minerals. Montmorillonite can be classified as sodium montmorillonite or calcium montmorillonite depending on the cation presented between the different layers. Using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the heterogeneous reaction mechanism of NO2 on the surface of montmorillonite was firstly investigated. Results showed that the reaction of NO2 on the surface of sodium and calcium montmorillonite fit a first-order kinetics, and the reaction duration of calcium montmorillonite was longer than that of sodium montmorillonite under the dry condition. For either sodium or calcium montmorillonite, the uptake coefficient decreased as humidify increased.

Ozonized carbon black induces mitochondrial dysfunction and DNA damage.

Black carbon and tropospheric ozone (O3), which are major air pollutants in China, are hazardous to humans following inhalation. Black carbon can be oxidized by O3 forming secondary particles of which the health effects are unknown. The present study utilized carbon black as a representative of black carbon to characterize the cytotoxicity induced by secondary particles in bronchial epithelial cells (16HBE) and C57BL/6J mice, and to investigate the implicated molecular pathways. Two types of carbon black including untreated carbon black (UCB) and ozonized carbon black (OCB) were presented. The effects of carbon black on cell viability, intracellular reactive oxygen species (ROS), oxidized/reduced glutathione ratio, mitochondrial membrane potential (MMP), intracellular ATP, and mitochondrial cytochrome c to cytoplasmic cytochrome c ratio were assessed in 16HBE. In addition, an alkaline comet assay and a cytokinesis‐block micronucleus (CBMN) test with 16HBE cells in vitro and ELISA method for serum 8‐hydroxy‐2′‐deoxyguanosine (8‐OHdG) and a bone marrow micronucleus (BMN) test with C57BL/6J mice in vivo were performed to detect the genotoxicity. When compared with UCB exposed cells, OCB exposed cells had decreased cell viability, increased cell death rate, increased comet length and decreased MMP at 24 h exposure. UCB induced higher level of intracellular ROS than OCB from 4 to 23 h. No changes were observed for both OCB and UCB in serum 8‐OHdG, intracellular ATP and mitochondrial cytochrome c to cytoplasmic cytochrome c ratio. The results of CBMN and BMN tests are negative. Intracellular ROS induced by OCB was lower than that of UCB. In summary, ozonization enhances the mitochondrial toxicity and genotoxicity of carbon black. Oxidative stress may not dominate in toxic effects of OCB.

Comparison of lung damage in mice exposed to black carbon particles and ozone-oxidized black carbon particles

Black carbon (BC) is a key component of atmospheric particles and has a significant effect on human health. Oxidation could change the characteristics of BC and increase its toxicity. The comparison of lung damage in mice exposed to BC and ozone-oxidized BC (oBC) particles is investigated in this study. Mice which were intratracheally instilled with particles have a higher expression of IL-1β, IL-6 and IL-33 in bronchoalveolar lavage fluid (BALF). Also, the IL-6, IL-33 mRNA expression in the lung tissue of mice instilled with oBC was higher than that of mice instilled with BC. The expression of CD3 in the lung tissue of mice intratracheally instilled with oBC was higher than the mice distilled with BC. The pathology results showed that the lung tissue of mice instilled with oBC particles have much more inflammatory cells infiltration than that of mice treated with BC. It is believed that the PI3K-AKT pathway might be involved in the oBC particles caused lung damage. Results indicated that oBC particles in the atmosphere may cause more damage to health.

Heterogeneous oxidation of SO2 by O3-aged black carbon and its dithiothreitol oxidative potential

Ozone (O3) is an important atmospheric oxidant. Black carbon (BC) particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace reducing gases such as SO2 in the atmosphere, leading to different environmental and health effects. In this paper, the heterogeneous reaction process between O3-aged BC and SO2 was explored via in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Combined with ion chromatography (IC), DRIFTS was used to qualitatively and quantitatively analyze the sulfate product. The results showed that O3-aged BC had stronger SO2 oxidation ability than fresh BC, and the reactive species/sites generated on the surface had an important role in the oxidation of SO2. Relative humidity or 254nm UV (ultraviolet) light illumination enhanced the oxidation uptake of SO2 on O3-aged BC. The oxidation potentials of the BC particles were detected via dithiothreitol (DTT) assay. The DTT activity over BC was decreased in the process of SO2 reduction, with the consumption of oxidative active sites.

Synergistic effect of nitrate-doped TiO 2 aerosols on the fast photochemical oxidation of formaldehyde

The uptake of formaldehyde (HCHO) on mineral dust affects its budget as well as particle properties, yet the process has not yet been fully investigate. Here, TiO2 and nitrate-doped TiO2 aerosols were used as proxies for mineral dust, and the uptake of HCHO was explored in a chamber under both dark and illuminated conditions. The uptake loss of HCHO on UV-illuminated aerosols is 2–9 times faster than its gaseous photolysis in our experimental system. The uptake coefficient in the range of 0.43–1.68 × 10−7 is 1–2 orders of magnitude higher than previous reports on model mineral dust particles. The reaction rate exhibits a Langmuir-Hinshelwood-type dependence on nitrate content and relative humidity, suggesting the competitive role of nitrate salts, water vapor and HCHO on the TiO2 surface. The reaction produces carbon dioxide as the main product and gaseous formic acid as an important intermediate. The hydroxyl radical produced on illuminated TiO2 primarily drives the fast oxidation of HCHO. The nitrate radical arising from the TiO2-catalyzed photoreaction of nitrate synergistically promotes the oxidation process. This study suggests a novel oxidation route for HCHO in the atmosphere, taking into account high abundance of both mineral dust and anthropogenic TiO2 aerosols.

Effects of 1,4-naphthoquinone Aged Carbon Black Particles on the Cell Membrane of Human Bronchial Epithelium

Black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs), which are major atmospheric pollutants in China, are hazardous to humans following inhalation. BC can be oxidized by PAHs forming secondary particles of which the health effects are unknown. In this study, carbon black (CB) was used to simulate BC to reveal the adverse effects of 1,4-naphthoquinone aged carbon black (CB/1,4-NQ) particles on the membrane of human bronchial epithelial (16HBE) cells. It was showed that, the cell viability, cell membrane fluidity, membrane potential and mitochondrial membrane potential were significantly decreased after 16HBE cells were treated with CB, 1,4-NQ or CB/1,4-NQ. Meanwhile, the cell membrane permeability and intracellular Ca2+ concentration were increased. CB/1,4-NQ could induce more adverse effects on cell membrane than single CB treated, while less than 1,4-NQ. The results indicated that CB/1,4-NQ particles in the atmosphere may cause more damage to health, and the effects on cell membrane can be used to evaluate the early health effects of the particulate matter exposure.

Black carbon particles and ozone-oxidized black carbon particles induced lung damage in mice through an interleukin-33 dependent pathway

Black carbon (BC) is a key component of atmospheric particles which has adverse effects on human health. Oxidation could lead to chemical property and toxicity potency changes of BC. The key cytokines participating in lung damage in mice induced by BC and ozone-oxidized BC (oBC) particles have been investigated in this study. It was concluded that oBC has stronger potency of inducing lung damage in mice comparing to BC. IL-6 and IL-33 were hypothesized to play important roles in this damage. Accordingly, IL-6 and IL-33 neutralizing antibodies were used to explore which cytokine might play a key role in lung inflammation induced by BC and oBC. As a result, IL-6 neutralizing antibody did not alleviate the lung damage induced by BC and oBC. However, IL-33 neutralizing antibody prevented BC and oBC induced lung damage. Furthermore, IL-33 neutralizing antibody treatment reduced IL-6 mRNA expression. It is hypothesized that MAPK and PI3K-AKT pathways might be involved in the oBC particles caused lung damage. It was concluded that IL-33 plays a key role in BC and oBC induced lung damage in mice.

Using X-ray computed tomography and micro-Raman spectrometry to measure individual particle surface area, volume, and morphology towards investigating atmospheric heterogeneous reactions

Heterogeneous reactions on the aerosol particle surface in the atmosphere play important roles in air pollution, climate change, and global biogeochemical cycles. However, the reported uptake coefficients of heterogeneous reactions usually have large variations and may not be relevant to real atmospheric conditions. One of the major reasons for this is the use of bulk samples in laboratory experiments, while particles in the atmosphere are suspended individually. A number of technologies have been developed recently to study heterogeneous reactions on the surfaces of individual particles. Precise measurements on the reactive surface area, volume, and morphology of individual particles are necessary for calculating the uptake coefficient, quantifying reactants and products, and understanding the reaction mechanism better. In this study, for the first time we used synchrotron radiation X-ray computed tomography (XCT) and micro-Raman spectrometry to measure individual CaCO3 particle morphology, with sizes ranging from 3.5-6.5μm. Particle surface area and volume were calculated using a reconstruction method based on software three-dimensional (3-D) rendering. The XCT was first validated with high-resolution field-emission scanning electron microscopy (FE-SEM) to acquire accurate CaCO3 particle surface area and volume estimates. Our results showed an average difference of only 6.1% in surface area and 3.2% in volume measured either by micro-Raman spectrometry or X-ray tomography. X-ray tomography and FE-SEM can provide more morphological details of individual CaCO3 particles than micro-Raman spectrometry. This study demonstrated that X-ray computed tomography and micro-Raman spectrometry can precisely measure the surface area, volume, and morphology of an individual particle.