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Vladimir Cirkva - One of the best experts on this subject based on the ideXlab platform.

  • microwave photocatalysis iv effects of additional operational parameters on the microwave photocatalytic degradation of mono Chloroacetic Acid using titania coated mercury electrodeless discharge lamps
    Journal of Chemical Technology & Biotechnology, 2013
    Co-Authors: Hana Kmentova, Vladimir Cirkva
    Abstract:

    Background Mercury electrodeless discharge lamps (Hg-EDLs) coated with titania in the form of thin films were used to generate UV/Vis radiation when placed in a microwave field. Effects of additional operational parameters (i.e. initial MCAA concentration, reaction temperature, and the presence of inorganic anions) on the photocatalytic degradation of aqueous mono-Chloroacetic Acid (MCAA) in a microwave field are discussed. Results Studies were carried out in atmospheric or low-pressure batch type microwave photocatalytic reactors. The photocatalytic process was monitored by the change in concentration of Cl− in the solution. Coupled UV/MW irradiation led to effective photodegradation at higher MCAA concentration at an optimum value of 0.15 mol L−1. Photocatalytic reaction of MCAA was favoured at higher temperature mainly owing to thermal dependence of the Hg-EDL light intensity on the 366 nm line. Inhibition of MCAA photodegradation was observed in the presence of CO32− and SO42− anions, whereas the effect of NO3− was negligible. Conclusions It was found that additional operational parameters had important effects on photocatalytic efficiency in a microwave field. The MCAA photodegradation process with titania-coated Hg-EDLs can be enhanced in the TiO2/UV/MW system. © 2012 Society of Chemical Industry

  • microwave photocatalysis iii transition metal ion doped tio2 thin films on mercury electrodeless discharge lamps preparation characterization and their effect on the photocatalytic degradation of mono Chloroacetic Acid and rhodamine b
    Journal of Chemical Technology & Biotechnology, 2009
    Co-Authors: Hana žabova, Vladimir Cirkva
    Abstract:

    BACKGROUND: Mercury electrodeless discharge lamps (Hg-EDLs) were used to generate UV radiation when exposed to a microwave field. EDLs were coated with doped TiO2 in the form of thin films containing transition metal ions Mn+ (M = Fe, Co, Ni, V, Cr, Mn, Zr, Ag). Photocatalytic degradation of mono-Chloroacetic Acid (MCAA) to HCl, CO2, and H2O, and decomposition of Rhodamine B on the thin films were investigated in detail. RESULTS: Polycrystalline thin doped TiO2 films were prepared by dip-coating of EDL via a sol–gel method using titanium n-butoxide, acetylacetone, and a transition metal acetylacetonate. The films were characterized by Raman spectroscopy, UV/Vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), electron microprobe analysis and by atomic force microscopy (AFM). The photocatalytic activity of doped TiO2 films was monitored in the decomposition of Rhodamine B in water. Compared with the pure TiO2 film, the UV/Vis spectra of V, Zr and Ag-doped TiO2 showed significant absorption in the visible region, and hence the photocatalytic degradation of MCAA had increased. The best apparent degradation rate constant (0.0125 min−1), which was higher than that on the pure TiO2 film by a factor of 1.7, was obtained with the Ag(3%)/TiO2 photocatalyst. The effect of doping level of vanadium acetylacetonate on the photocatalytic efficiency of the V-doped TiO2 was determined. CONCLUSIONS: Transition metal ion-doped TiO2 thin films showed significant absorption in the visible region. The metal doped TiO2 photocatalyst (with an appropriate amount of V, Zr and Ag) on the Hg-EDLs increased the degradation efficiency of MCAA in a microwave field. Copyright © 2009 Society of Chemical Industry

  • microwave photochemistry v low pressure batch and continuous flow microwave photoreactors with quartz mercury electrodeless discharge lamps photohydrolysis of mono Chloroacetic Acid
    Journal of Chemical Technology & Biotechnology, 2009
    Co-Authors: Vladimir Cirkva, Stanislav Relich, Milan Hajek
    Abstract:

    BACKGROUND: Low-pressure batch and continuous-flow microwave photoreactors were equipped with microwave powered quartz mercury electrodeless discharge lamps (Hg-EDLs). Photohydrolysis of aqueous mono-Chloroacetic Acid (MCAA) into hydroxyacetic Acid and HCl was chosen as the model reaction to evaluate these photoreactors. The effects of operational parameters on the MCAA photolysis through a UV/MW process were investigated. RESULTS:StudieswerecarriedoutatrelativelyhighMCAAconcentration(0.1 mol L −1 ).Thephotoreactioncoursewasmonitored bythepHchangeinthesolution.TheMCAAconversionwasoptimizedasaresultofatrade-offbetweenthethermaldependence of the photochemical quantum yield (which increases with increasing temperature) and the thermal dependence of the EDL light intensityof 254 nm line(which increases with decreasingtemperature).The microwave photoreactors made itpossible to study the temperature dependence of MCAA photohydrolysis. CONCLUSION: It was found that operational parameters (i.e. reaction temperature, quantum yield) had important effects on photoefficiency. Photohydrolysisof MCAA in themicrowave photoreactors canbe enhancedby theUV/MW system.Theresults of conversions (in 120 min) for the particular photoreactor set-ups show that the best reaction conditions for MCAA photolysis were obtained in the low-pressure batch microwave photoreactor (the conversion was 46% at 80 ◦ C). c � 2009 Society of Chemical Industry

  • microwave photocatalysis of mono Chloroacetic Acid over nanoporous titanium iv oxide thin films using mercury electrodeless discharge lamps
    Journal of Photochemistry and Photobiology A-chemistry, 2008
    Co-Authors: Vladimir Cirkva, Hana žabova, Milan Hajek
    Abstract:

    The degradation of mono-Chloroacetic Acid (MCAA) by microwave-assisted photocatalysis has been examined by a new method. A novel electrodeless discharge lamp (EDL) was employed as UV light source generated by microwave irradiation. Titanium(IV) oxide film was used as the photocatalyst due to its superior characteristics. Several factors influencing the degradation of MCAA, such as number of coating cycles, light intensity, initial pH value, gas bubbling, and H2O2 dosage have been studied in detail. Mono-Chloroacetic Acid was efficiently decomposed to HCl, CO2, and H2O by the UV irradiated titanium dioxide thin film in a microwave field. The decomposition was enhanced in an alkaline solution and in the presence of H2O2, and significantly enhanced by increasing the intensity of UV light. © 2008 Elsevier B.V. All rights reserved.

Milan Hajek - One of the best experts on this subject based on the ideXlab platform.

  • microwave photochemistry v low pressure batch and continuous flow microwave photoreactors with quartz mercury electrodeless discharge lamps photohydrolysis of mono Chloroacetic Acid
    Journal of Chemical Technology & Biotechnology, 2009
    Co-Authors: Vladimir Cirkva, Stanislav Relich, Milan Hajek
    Abstract:

    BACKGROUND: Low-pressure batch and continuous-flow microwave photoreactors were equipped with microwave powered quartz mercury electrodeless discharge lamps (Hg-EDLs). Photohydrolysis of aqueous mono-Chloroacetic Acid (MCAA) into hydroxyacetic Acid and HCl was chosen as the model reaction to evaluate these photoreactors. The effects of operational parameters on the MCAA photolysis through a UV/MW process were investigated. RESULTS:StudieswerecarriedoutatrelativelyhighMCAAconcentration(0.1 mol L −1 ).Thephotoreactioncoursewasmonitored bythepHchangeinthesolution.TheMCAAconversionwasoptimizedasaresultofatrade-offbetweenthethermaldependence of the photochemical quantum yield (which increases with increasing temperature) and the thermal dependence of the EDL light intensityof 254 nm line(which increases with decreasingtemperature).The microwave photoreactors made itpossible to study the temperature dependence of MCAA photohydrolysis. CONCLUSION: It was found that operational parameters (i.e. reaction temperature, quantum yield) had important effects on photoefficiency. Photohydrolysisof MCAA in themicrowave photoreactors canbe enhancedby theUV/MW system.Theresults of conversions (in 120 min) for the particular photoreactor set-ups show that the best reaction conditions for MCAA photolysis were obtained in the low-pressure batch microwave photoreactor (the conversion was 46% at 80 ◦ C). c � 2009 Society of Chemical Industry

  • microwave photocatalysis of mono Chloroacetic Acid over nanoporous titanium iv oxide thin films using mercury electrodeless discharge lamps
    Journal of Photochemistry and Photobiology A-chemistry, 2008
    Co-Authors: Vladimir Cirkva, Hana žabova, Milan Hajek
    Abstract:

    The degradation of mono-Chloroacetic Acid (MCAA) by microwave-assisted photocatalysis has been examined by a new method. A novel electrodeless discharge lamp (EDL) was employed as UV light source generated by microwave irradiation. Titanium(IV) oxide film was used as the photocatalyst due to its superior characteristics. Several factors influencing the degradation of MCAA, such as number of coating cycles, light intensity, initial pH value, gas bubbling, and H2O2 dosage have been studied in detail. Mono-Chloroacetic Acid was efficiently decomposed to HCl, CO2, and H2O by the UV irradiated titanium dioxide thin film in a microwave field. The decomposition was enhanced in an alkaline solution and in the presence of H2O2, and significantly enhanced by increasing the intensity of UV light. © 2008 Elsevier B.V. All rights reserved.

Fengcheng Tang - One of the best experts on this subject based on the ideXlab platform.

  • Chloroacetic Acid triggers apoptosis in neuronal cells via a reactive oxygen species induced endoplasmic reticulum stress signaling pathway
    Chemico-Biological Interactions, 2015
    Co-Authors: Fengcheng Tang, Chunhung Chen, Chengchieh Yen, Kaimin Fang, Kuani Lee, Dongzong Hung, Yawen Chen
    Abstract:

    Chloroacetic Acid (CA), a chlorinated analog of acetic Acid and an environmental toxin that is more toxic than acetic, diChloroacetic, or triChloroacetic Acids, is widely used in chemical industries. Furthermore, CA has been found to be the major disinfection by-products (DBPs) of drinking water. CA has been reported to be highly corrosive and to induce severe tissue injuries (including nervous system) that lead to death in mammals. However, the effects and underlying mechanisms of CA-induced neurotoxicity remain unknown. In the present study, we found that CA (0.5-2.0 mM) significantly increased LDH release, decreased the number of viable cells (cytotoxicity) and induced apoptotic events (including: increases in the numbers of apoptotic cells, the membrane externalization of phosphatidylserine (PS), and caspase-3/-7 activity) in Neuro-2a cells. CA (1.5 mM; the approximate to LD50) also triggered ER stress, which was identified by monitoring several key molecules that are involved in the unfolded protein responses (including the increase in the expressions of p-PERK, p-IRE-1, p-eIF2α, ATF-4, ATF-6, CHOP, XBP-1, GRP 78, GRP 94, and caspase-12) and calpain activity. Transfection of GRP 78- and GRP 94-specific si-RNA effectively abrogated CA-induced cytotoxicity, caspase-3/-7 and caspase-12 activity, and GRP 78 and GRP 94 expression in Neuro-2a cells. Additionally, pretreatment with 2.5 mM N-acetylcysteine (NAC; a glutathione (GSH) precursor) dramatically suppressed the increase in lipid peroxidation, cytotoxicity, apoptotic events, calpain and caspase-12 activity, and ER stress-related molecules in CA-exposed cells. Taken together, these results suggest that the higher concentration of CA exerts its cytotoxic effects in neuronal cells by triggering apoptosis via a ROS-induced ER stress signaling pathway.

  • Chloroacetic Acid induced neuronal cells death through oxidative stress mediated p38 mapk activation pathway regulated mitochondria dependent apoptotic signals
    Toxicology, 2013
    Co-Authors: Chunhung Chen, Fengcheng Tang, Chengchieh Yen, Kuani Lee, Dongzong Hung, Szjie Chen, Tojung Tseng, Tzyyrong Jinn, Kuoliang Chen, Chunfa Huang
    Abstract:

    Chloroacetic Acid (CA), a toxic chlorinated analog of acetic Acid, is widely used in chemical industries as an herbicide, detergent, and disinfectant, and chemical intermediates that are formed during the synthesis of various products. In addition, CA has been found as a by-product of chlorination disinfection of drinking water. However, there is little known about neurotoxic injuries of CA on the mammalian, the toxic effects and molecular mechanisms of CA-induced neuronal cell injury are mostly unknown. In this study, we examined the cytotoxicity of CA on cultured Neuro-2a cells and investigated the possible mechanisms of CA-induced neurotoxicity. Treatment of Neuro-2a cells with CA significantly reduced the number of viable cells (in a dose-dependent manner with a range from 0.1 to 3mM), increased the generation of ROS, and reduced the intracellular levels of glutathione depletion. CA also increased the number of sub-G1 hypodiploid cells; increased mitochondrial dysfunction (loss of MMP, cytochrome c release, and accompanied by Bcl-2 and Mcl-1 down-regulation and Bax up-regulation), and activated the caspase cascades activations, which displayed features of mitochondria-dependent apoptosis pathway. These CA-induced apoptosis-related signals were markedly prevented by the antioxidant N-acetylcysteine (NAC). Moreover, CA activated the JNK and p38-MAPK pathways, but did not that ERK1/2 pathway, in treated Neuro-2a cells. Pretreatment with NAC and specific p38-MAPK inhibitor (SB203580), but not JNK inhibitor (SP600125) effectively abrogated the phosphorylation of p38-MAPK and attenuated the apoptotic signals (including: decrease in cytotoxicity, caspase-3/-7 activation, the cytosolic cytochrome c release, and the reversed alteration of Bcl-2 and Bax mRNA) in CA-treated Neuro-2a cells. Taken together, these data suggest that oxidative stress-induced p38-MAPK activated pathway-regulated mitochondria-dependent apoptosis plays an important role in CA-caused neuronal cell death.

Hana žabova - One of the best experts on this subject based on the ideXlab platform.

  • microwave photocatalysis iii transition metal ion doped tio2 thin films on mercury electrodeless discharge lamps preparation characterization and their effect on the photocatalytic degradation of mono Chloroacetic Acid and rhodamine b
    Journal of Chemical Technology & Biotechnology, 2009
    Co-Authors: Hana žabova, Vladimir Cirkva
    Abstract:

    BACKGROUND: Mercury electrodeless discharge lamps (Hg-EDLs) were used to generate UV radiation when exposed to a microwave field. EDLs were coated with doped TiO2 in the form of thin films containing transition metal ions Mn+ (M = Fe, Co, Ni, V, Cr, Mn, Zr, Ag). Photocatalytic degradation of mono-Chloroacetic Acid (MCAA) to HCl, CO2, and H2O, and decomposition of Rhodamine B on the thin films were investigated in detail. RESULTS: Polycrystalline thin doped TiO2 films were prepared by dip-coating of EDL via a sol–gel method using titanium n-butoxide, acetylacetone, and a transition metal acetylacetonate. The films were characterized by Raman spectroscopy, UV/Vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), electron microprobe analysis and by atomic force microscopy (AFM). The photocatalytic activity of doped TiO2 films was monitored in the decomposition of Rhodamine B in water. Compared with the pure TiO2 film, the UV/Vis spectra of V, Zr and Ag-doped TiO2 showed significant absorption in the visible region, and hence the photocatalytic degradation of MCAA had increased. The best apparent degradation rate constant (0.0125 min−1), which was higher than that on the pure TiO2 film by a factor of 1.7, was obtained with the Ag(3%)/TiO2 photocatalyst. The effect of doping level of vanadium acetylacetonate on the photocatalytic efficiency of the V-doped TiO2 was determined. CONCLUSIONS: Transition metal ion-doped TiO2 thin films showed significant absorption in the visible region. The metal doped TiO2 photocatalyst (with an appropriate amount of V, Zr and Ag) on the Hg-EDLs increased the degradation efficiency of MCAA in a microwave field. Copyright © 2009 Society of Chemical Industry

  • microwave photocatalysis of mono Chloroacetic Acid over nanoporous titanium iv oxide thin films using mercury electrodeless discharge lamps
    Journal of Photochemistry and Photobiology A-chemistry, 2008
    Co-Authors: Vladimir Cirkva, Hana žabova, Milan Hajek
    Abstract:

    The degradation of mono-Chloroacetic Acid (MCAA) by microwave-assisted photocatalysis has been examined by a new method. A novel electrodeless discharge lamp (EDL) was employed as UV light source generated by microwave irradiation. Titanium(IV) oxide film was used as the photocatalyst due to its superior characteristics. Several factors influencing the degradation of MCAA, such as number of coating cycles, light intensity, initial pH value, gas bubbling, and H2O2 dosage have been studied in detail. Mono-Chloroacetic Acid was efficiently decomposed to HCl, CO2, and H2O by the UV irradiated titanium dioxide thin film in a microwave field. The decomposition was enhanced in an alkaline solution and in the presence of H2O2, and significantly enhanced by increasing the intensity of UV light. © 2008 Elsevier B.V. All rights reserved.

Yawen Chen - One of the best experts on this subject based on the ideXlab platform.

  • Chloroacetic Acid triggers apoptosis in neuronal cells via a reactive oxygen species induced endoplasmic reticulum stress signaling pathway
    Chemico-Biological Interactions, 2015
    Co-Authors: Fengcheng Tang, Chunhung Chen, Chengchieh Yen, Kaimin Fang, Kuani Lee, Dongzong Hung, Yawen Chen
    Abstract:

    Chloroacetic Acid (CA), a chlorinated analog of acetic Acid and an environmental toxin that is more toxic than acetic, diChloroacetic, or triChloroacetic Acids, is widely used in chemical industries. Furthermore, CA has been found to be the major disinfection by-products (DBPs) of drinking water. CA has been reported to be highly corrosive and to induce severe tissue injuries (including nervous system) that lead to death in mammals. However, the effects and underlying mechanisms of CA-induced neurotoxicity remain unknown. In the present study, we found that CA (0.5-2.0 mM) significantly increased LDH release, decreased the number of viable cells (cytotoxicity) and induced apoptotic events (including: increases in the numbers of apoptotic cells, the membrane externalization of phosphatidylserine (PS), and caspase-3/-7 activity) in Neuro-2a cells. CA (1.5 mM; the approximate to LD50) also triggered ER stress, which was identified by monitoring several key molecules that are involved in the unfolded protein responses (including the increase in the expressions of p-PERK, p-IRE-1, p-eIF2α, ATF-4, ATF-6, CHOP, XBP-1, GRP 78, GRP 94, and caspase-12) and calpain activity. Transfection of GRP 78- and GRP 94-specific si-RNA effectively abrogated CA-induced cytotoxicity, caspase-3/-7 and caspase-12 activity, and GRP 78 and GRP 94 expression in Neuro-2a cells. Additionally, pretreatment with 2.5 mM N-acetylcysteine (NAC; a glutathione (GSH) precursor) dramatically suppressed the increase in lipid peroxidation, cytotoxicity, apoptotic events, calpain and caspase-12 activity, and ER stress-related molecules in CA-exposed cells. Taken together, these results suggest that the higher concentration of CA exerts its cytotoxic effects in neuronal cells by triggering apoptosis via a ROS-induced ER stress signaling pathway.