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Dmitry V. Evtuguin - One of the best experts on this subject based on the ideXlab platform.
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effect of oxygen ozone and hydrogen peroxide bleaching stages on the contents and composition of extractives of eucalyptus globulus kraft Pulps
Bioresource Technology, 2006Co-Authors: Carmen S R Freire, Carlos Pascoal Neto, Armando J D Silvestre, Dmitry V. EvtuguinAbstract:The effects of oxygen (O), ozone (Z) and hydrogen peroxide (P) bleaching stages on the composition and total amount of Eucalyptus globulus kraft Pulp lipophilic extractives was studied. These bleaching stages led to the partial removal and to several oxidative transformations of fatty acids and sterols, the main lipophilic extractives found in the Unbleached Pulp. Unsaturated extractives were found to be partially degraded while saturated ones were, in general, stable. The oxygen and hydrogen peroxide bleaching stages were more effective than ozone in removing fatty acids from Pulp, by dissolution in the liquid phase. On the other hand, the ozone stage was more effective in the oxidative degradation of sterols. Oxygen and hydrogen peroxide bleaching stages were also effective in sterols removal, but led to the formation of sterol oxidation derivatives, previously shown to be involved in the formation of pitch that accumulates in the bleaching filtrates.
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hexenuronic acid contents of eucalyptus globulus kraft Pulps variation with Pulping conditions and effect on ecf bleachability
Tappi Journal, 2003Co-Authors: Ana Dias Daniel, Dmitry V. Evtuguin, Carlos Pascoal Neto, Armando J D SilvestreAbstract:This study investigates the effect of Pulping time and process parameters on the content of hexenuronic acid (HexA) in Eucalyptus globulus kraft Pulps. Under selected standard Pulping conditions, the amount of HexA in Pulps increases during cooking. This behavior, significantly different from that of softwood Pulps, is tentatively attributed to the milder conditions used in the Pulping or to topochemical effects rather than to differences in the chemical structure of the glucuronoxylans from hardwoods and softwoods. We found that, for the same kappa number (14, obtained by adjusting Pulping time), the HexA content decreases when active alkali increases from 17% to 24% and increases with sulfidity in the range 15%-28%. A decrease in the HexA content occurs when the temperature rises from 150°C to 170°C and when liquor-to-wood ratio increases from 4 to 8. The variations observed are determined by two simultaneously occurring processes: HexA formation and degradation or dissolution with xylans. When the Unbleached Pulps with kappa number 14 were fully bleached by a DEDED sequence, we observed a general increase in chlorine dioxide consumption as the HexA of the Unbleached Pulp decreases.
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Effect of Pulping conditions on the ECF bleachability of Eucalyptus globulus kraft Pulps
Industrial & Engineering Chemistry Research, 2002Co-Authors: Carlos Pascoal Neto, Dmitry V. Evtuguin, Fernanda P. Furtado, Antonio P. Mendes SousaAbstract:The effect of Eucalyptus globulus wood kraft Pulping conditions on the chlorine dioxide consumption in elemental chlorine free bleaching of Pulps was investigated. When the Pulping is extended (kappa number decreases), the bleachability [as (OXE/ton)/kappa number] is reduced, suggesting that residual lignin and other oxidizable unsaturated structures in Pulp become less reactive as their content in the Pulp decreases. For the same Unbleached Pulp kappa number, the increase in active alkali and sulfidity used in Pulping improves bleachability, whereas the Pulping temperature (150-170°C) does not affect the bleaching response. The increase in liquor-to-wood ratio has a detrimental effect on the bleachability. No clear correlation could be established between Unbleached Pulp brightness and its bleaching response. Overall, the results obtained show a good correlation between the integral of the relative reaction rate constant (H factor) used in the Pulping and Pulp bleachability, with a low H factor being beneficial to the bleaching response of the Pulp.
Carlos Pascoal Neto - One of the best experts on this subject based on the ideXlab platform.
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effect of oxygen ozone and hydrogen peroxide bleaching stages on the contents and composition of extractives of eucalyptus globulus kraft Pulps
Bioresource Technology, 2006Co-Authors: Carmen S R Freire, Carlos Pascoal Neto, Armando J D Silvestre, Dmitry V. EvtuguinAbstract:The effects of oxygen (O), ozone (Z) and hydrogen peroxide (P) bleaching stages on the composition and total amount of Eucalyptus globulus kraft Pulp lipophilic extractives was studied. These bleaching stages led to the partial removal and to several oxidative transformations of fatty acids and sterols, the main lipophilic extractives found in the Unbleached Pulp. Unsaturated extractives were found to be partially degraded while saturated ones were, in general, stable. The oxygen and hydrogen peroxide bleaching stages were more effective than ozone in removing fatty acids from Pulp, by dissolution in the liquid phase. On the other hand, the ozone stage was more effective in the oxidative degradation of sterols. Oxygen and hydrogen peroxide bleaching stages were also effective in sterols removal, but led to the formation of sterol oxidation derivatives, previously shown to be involved in the formation of pitch that accumulates in the bleaching filtrates.
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hexenuronic acid contents of eucalyptus globulus kraft Pulps variation with Pulping conditions and effect on ecf bleachability
Tappi Journal, 2003Co-Authors: Ana Dias Daniel, Dmitry V. Evtuguin, Carlos Pascoal Neto, Armando J D SilvestreAbstract:This study investigates the effect of Pulping time and process parameters on the content of hexenuronic acid (HexA) in Eucalyptus globulus kraft Pulps. Under selected standard Pulping conditions, the amount of HexA in Pulps increases during cooking. This behavior, significantly different from that of softwood Pulps, is tentatively attributed to the milder conditions used in the Pulping or to topochemical effects rather than to differences in the chemical structure of the glucuronoxylans from hardwoods and softwoods. We found that, for the same kappa number (14, obtained by adjusting Pulping time), the HexA content decreases when active alkali increases from 17% to 24% and increases with sulfidity in the range 15%-28%. A decrease in the HexA content occurs when the temperature rises from 150°C to 170°C and when liquor-to-wood ratio increases from 4 to 8. The variations observed are determined by two simultaneously occurring processes: HexA formation and degradation or dissolution with xylans. When the Unbleached Pulps with kappa number 14 were fully bleached by a DEDED sequence, we observed a general increase in chlorine dioxide consumption as the HexA of the Unbleached Pulp decreases.
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Effect of Pulping conditions on the ECF bleachability of Eucalyptus globulus kraft Pulps
Industrial & Engineering Chemistry Research, 2002Co-Authors: Carlos Pascoal Neto, Dmitry V. Evtuguin, Fernanda P. Furtado, Antonio P. Mendes SousaAbstract:The effect of Eucalyptus globulus wood kraft Pulping conditions on the chlorine dioxide consumption in elemental chlorine free bleaching of Pulps was investigated. When the Pulping is extended (kappa number decreases), the bleachability [as (OXE/ton)/kappa number] is reduced, suggesting that residual lignin and other oxidizable unsaturated structures in Pulp become less reactive as their content in the Pulp decreases. For the same Unbleached Pulp kappa number, the increase in active alkali and sulfidity used in Pulping improves bleachability, whereas the Pulping temperature (150-170°C) does not affect the bleaching response. The increase in liquor-to-wood ratio has a detrimental effect on the bleachability. No clear correlation could be established between Unbleached Pulp brightness and its bleaching response. Overall, the results obtained show a good correlation between the integral of the relative reaction rate constant (H factor) used in the Pulping and Pulp bleachability, with a low H factor being beneficial to the bleaching response of the Pulp.
Antonio P. Mendes Sousa - One of the best experts on this subject based on the ideXlab platform.
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Effect of Pulping conditions on the ECF bleachability of Eucalyptus globulus kraft Pulps
Industrial & Engineering Chemistry Research, 2002Co-Authors: Carlos Pascoal Neto, Dmitry V. Evtuguin, Fernanda P. Furtado, Antonio P. Mendes SousaAbstract:The effect of Eucalyptus globulus wood kraft Pulping conditions on the chlorine dioxide consumption in elemental chlorine free bleaching of Pulps was investigated. When the Pulping is extended (kappa number decreases), the bleachability [as (OXE/ton)/kappa number] is reduced, suggesting that residual lignin and other oxidizable unsaturated structures in Pulp become less reactive as their content in the Pulp decreases. For the same Unbleached Pulp kappa number, the increase in active alkali and sulfidity used in Pulping improves bleachability, whereas the Pulping temperature (150-170°C) does not affect the bleaching response. The increase in liquor-to-wood ratio has a detrimental effect on the bleachability. No clear correlation could be established between Unbleached Pulp brightness and its bleaching response. Overall, the results obtained show a good correlation between the integral of the relative reaction rate constant (H factor) used in the Pulping and Pulp bleachability, with a low H factor being beneficial to the bleaching response of the Pulp.
Peter Axegård - One of the best experts on this subject based on the ideXlab platform.
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the effect of the transition from elemental chlorine bleaching to chlorine dioxide bleaching in the Pulp industry on the formation of pcdd fs
Chemosphere, 2019Co-Authors: Peter AxegårdAbstract:The article reviews the transition from bleaching kraft Pulp with elemental chlorine to bleaching with chlorine dioxide with respect to formation of chlorinated dioxins and furans (PCDD/Fs). New data is also presented for bleaching with 100% chlorine dioxide and the effect of elemental chlorine impurities. The typical fingerprint of PCDD/Fs in Pulp bleached with elemental chlorine was unique compared to all other sources such as incineration and metallurgic processes. 2,3,7,8-TCDD and 2,3,7,8-TCDF were the dominating congeners formed during the period Pulp was bleached with elemental chlorine. Elimination of unchlorinated precursors lowered, but did not eliminate, the formation of 2,3,7,8-TCDD and 2,3,7,8-TCDF. The formation of 2,3,7,8-TCDD and 2,3,7,8-TCDF increases exponentially with the amount of elemental chlorine used. Replacing elemental chlorine with chlorine dioxide (with levels of elemental chlorine contamination of <0.3% in the chlorine dioxide) in Pulp bleaching eliminates the formation of 2,3,7,8-TCDD and 2,3,7,8-TCDF. PCDD/Fs can also be found in background levels in ecosystems, food, soil and air as well as in Unbleached Pulp, bleached Pulp, and paper and fiber products. Thus, the only way to determine if PCDD/Fs are present from bleaching is to make a full congener analysis and compare to known sources and processes as well as to laboratory blanks and Unbleached reference samples.
Jiping Chen - One of the best experts on this subject based on the ideXlab platform.
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mechanistic aspects of polychlorinated dibenzo p dioxins and dibenzofurans pcdd fs formation from chlorine bleaching of non wood Pulp
Journal of Hazardous Materials, 2020Co-Authors: Yuwen Ni, Faqiang Zhan, Boyu Song, Yichi Zhang, Jiping ChenAbstract:Abstract Chlorine bleaching of non-wood Pulp can produce and release polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) into environment. In this study, a series of chlorination experiments were conducted to explore the source, formation pathway and formation kinetics of Cl1−8DD/Fs during the chlorine bleaching of wheat straw Pulp. The 13C isotope-labeling experiment verified that PCDD/Fs could not be formed from the chlorination of phenols in Pulp. Above 80% of the observed PCDFs originated from the direct chlorination of dibenzofuran (DBF) in Unbleached wheat straw Pulp, while approximately 60% of the observed PCDDs came from the chlorination of nonextractable precursors in the Pulp. The yield of total PCDFs was 2 orders of magnitude higher than that of total PCDDs. The kinetic study indicated that DBF was more easily chlorinated than dibenzo-p-dioxin (DBD) in the Pulp solution. Pseudo-first-order reaction kinetic equations fitted the formation and degradation of PCDD/Fs well. The direct chlorination of DBD/F primarily preferred a selective pattern at the 2 position, followed by the 8, 7 and 3 positions. A higher content of DBF in Unbleached Pulp led to a higher yield of 2,3,7,8-Cl4DF. Finally, the practical implication for dioxin formation control was discussed.