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Kelvin R. O'halloran - One of the best experts on this subject based on the ideXlab platform.
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Acid yellow 17 as a spectrophotometric reagent for the determination of low concentrations of residual free chlorine
Analytica Chimica Acta, 1991Co-Authors: Barry Chiswell, Kelvin R. O'halloranAbstract:Abstract Recommended spectrophotometric procedures for chlorine are investigated and are found to have significant disadvantages, thus a new method for the spectrophotometric determination of free chlorine in the presence of other chlorine species, viz. chlorine dioxide, Chlorite, chlorate and combined chlorine, based on Acid Yellow 17, has been developed. Only chlorine dioxide interferes. The detection limit is 50 ng ml−1 for free chlorine, and the calibration graph is linear up to at least 1.0 μg ml−1. Cyclic voltammetry has been used to explain the findings of the spectrophotometric work.
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Use of Lissamine Green B as a spectrophotometric reagent for the determination of low residuals of chlorine dioxide
Analyst, 1991Co-Authors: Barry Chiswell, Kelvin R. O'halloranAbstract:A method for the spectrophotometric determination of chlorine dioxide in the presence of other chlorine species, viz., free chlorine, Chlorite, chloramine and chlorate, has been developed. The method overcomes the major problem found with the commonly used N,N′-diethyl-p-phenylenediamine method for determining chlorine dioxide, namely interference from free and combined chlorine. The detection limit of the proposed method is 0.03 ± 0.01 ppm of chlorine dioxide; the calibration graph is linear over the range 0–0.5 ppm of chlorine dioxide. Cyclic voltammetric studies of the chlorine species were used to verify the findings of the spectrophotometric work.
Barry Chiswell - One of the best experts on this subject based on the ideXlab platform.
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Spectrophotometric method for the determination of Chlorite and chlorate
The Analyst, 1993Co-Authors: Barry Chiswell, Beatrice Keller-lehmannAbstract:The concentrations of aqueous Chlorite and chlorate in mixtures can be determined by the decolorization of Indigo Carmine at 610 nm in the presence of FeII. The reactions are stoichiometric and therefore a good correlation between the absorbance and the concentration is found. The linear range for measurements of Chlorite is 0–0.51 mg l–1 and that of chlorate is 0–0.78 mg l–1. The detection limits for Chlorite and chlorate are 0.036 and 0.008 mg l–1, respectively. The presence of chlorine interferes with the determinations.
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Acid yellow 17 as a spectrophotometric reagent for the determination of low concentrations of residual free chlorine
Analytica Chimica Acta, 1991Co-Authors: Barry Chiswell, Kelvin R. O'halloranAbstract:Abstract Recommended spectrophotometric procedures for chlorine are investigated and are found to have significant disadvantages, thus a new method for the spectrophotometric determination of free chlorine in the presence of other chlorine species, viz. chlorine dioxide, Chlorite, chlorate and combined chlorine, based on Acid Yellow 17, has been developed. Only chlorine dioxide interferes. The detection limit is 50 ng ml−1 for free chlorine, and the calibration graph is linear up to at least 1.0 μg ml−1. Cyclic voltammetry has been used to explain the findings of the spectrophotometric work.
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Use of Lissamine Green B as a spectrophotometric reagent for the determination of low residuals of chlorine dioxide
Analyst, 1991Co-Authors: Barry Chiswell, Kelvin R. O'halloranAbstract:A method for the spectrophotometric determination of chlorine dioxide in the presence of other chlorine species, viz., free chlorine, Chlorite, chloramine and chlorate, has been developed. The method overcomes the major problem found with the commonly used N,N′-diethyl-p-phenylenediamine method for determining chlorine dioxide, namely interference from free and combined chlorine. The detection limit of the proposed method is 0.03 ± 0.01 ppm of chlorine dioxide; the calibration graph is linear over the range 0–0.5 ppm of chlorine dioxide. Cyclic voltammetric studies of the chlorine species were used to verify the findings of the spectrophotometric work.
Hasan Jameel - One of the best experts on this subject based on the ideXlab platform.
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inorganic reactions in chlorine dioxide bleaching of softwood kraft pulp
Journal of Wood Chemistry and Technology, 2006Co-Authors: Douglas R Svenson, Hasan Jameel, Houmin Chang, John F KadlaAbstract:Abstract A softwood kraft pulp (27 kappa) was bleached with chlorine dioxide to various end pH values. The formation of Chlorite, chlorate, and chloride was measured to quantify the amount of chlorine dioxide wasted as a function of pH during a Do (pre‐bleaching) stage. Chlorate formation increased with a decrease in final pH. Conversely, residual Chlorite increased with an increase in the final pH. After 120 min of bleaching the total residual Chlorite and chlorate showed that no substantial increase in residual oxidant occurs when bleaching to an end pH below 3.4. As a result, the brightness and permanganate numbers for low pH chlorine dioxide bleached pulps did not differ when bleaching to an end pH between 3.4 and 1.8. However, decreasing the pH below 3.4 did result in increased organic chloride formation. The results are contrary to previous studies where the maximum bleaching efficiency for a D1 stage was reported to occur when the end pH was between 3 and 4.
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The role of non-phenolic lignin in chlorate-forming reactions during chlorine dioxide bleaching of softwood kraft pulp
Holzforschung, 2005Co-Authors: Douglas R Svenson, Hasan Jameel, Houmin Chang, John F KadlaAbstract:The affect of phenolic hydroxyl groups on the reaction efficiency during chlorine dioxide pre-bleaching of a softwood kraft pulp was investigated. The removal of phenolic hydroxyl groups via pulp methylation did not adversely affect the chlorine dioxide bleaching efficiency or the amount of chlorate formed during exposure to chlorine dioxide. Ion analysis of the reaction systems revealed that the formation of chloride and Chlorite ions during the bleaching process were very similar between the kraft and methylated kraft pulps. These results indicate that the kinetic rates of lignin oxidation by chlorine dioxide and its reduction products, Chlorite and hypochlorous acid, are much faster than the rate of inorganic reactions leading to chlorate formation.
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effect of ph on the inorganic species involved in a chlorine dioxide reaction system
Industrial & Engineering Chemistry Research, 2002Co-Authors: Douglas R Svenson, Houmin Chang, John F Kadla, Hasan JameelAbstract:The effects of pH on the inorganic products formed during the reaction of chlorine dioxide with an etherified lignin model compound have been studied. Analyses of the inorganic species produced during the reaction at pH 8 revealed that 2 mol of Chlorite are liberated for every 1 mol of oxidized nonphenolic lignin model compound formed, consistent with two consecutive one-electron-transfer processes. In contrast, the low-pH reactions produced mostly ring oxidation products and chlorinated organic material, accompanied by increased levels of hypochlorous acid. The transient hypochlorous acid rapidly reacted with Chlorite to generate chloride ions, with a maximum chloride formation at pH 4. Chlorate formation was shown to increase with increasing reaction pH. These results are in contrast to those previously reported for reactions with wood pulps and are explained on the basis of the slow reaction kinetics of nonphenolic lignin moieties as compared to phenolic ones, thereby enabling hypochlorous acid to reac...
Douglas R Svenson - One of the best experts on this subject based on the ideXlab platform.
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inorganic reactions in chlorine dioxide bleaching of softwood kraft pulp
Journal of Wood Chemistry and Technology, 2006Co-Authors: Douglas R Svenson, Hasan Jameel, Houmin Chang, John F KadlaAbstract:Abstract A softwood kraft pulp (27 kappa) was bleached with chlorine dioxide to various end pH values. The formation of Chlorite, chlorate, and chloride was measured to quantify the amount of chlorine dioxide wasted as a function of pH during a Do (pre‐bleaching) stage. Chlorate formation increased with a decrease in final pH. Conversely, residual Chlorite increased with an increase in the final pH. After 120 min of bleaching the total residual Chlorite and chlorate showed that no substantial increase in residual oxidant occurs when bleaching to an end pH below 3.4. As a result, the brightness and permanganate numbers for low pH chlorine dioxide bleached pulps did not differ when bleaching to an end pH between 3.4 and 1.8. However, decreasing the pH below 3.4 did result in increased organic chloride formation. The results are contrary to previous studies where the maximum bleaching efficiency for a D1 stage was reported to occur when the end pH was between 3 and 4.
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The role of non-phenolic lignin in chlorate-forming reactions during chlorine dioxide bleaching of softwood kraft pulp
Holzforschung, 2005Co-Authors: Douglas R Svenson, Hasan Jameel, Houmin Chang, John F KadlaAbstract:The affect of phenolic hydroxyl groups on the reaction efficiency during chlorine dioxide pre-bleaching of a softwood kraft pulp was investigated. The removal of phenolic hydroxyl groups via pulp methylation did not adversely affect the chlorine dioxide bleaching efficiency or the amount of chlorate formed during exposure to chlorine dioxide. Ion analysis of the reaction systems revealed that the formation of chloride and Chlorite ions during the bleaching process were very similar between the kraft and methylated kraft pulps. These results indicate that the kinetic rates of lignin oxidation by chlorine dioxide and its reduction products, Chlorite and hypochlorous acid, are much faster than the rate of inorganic reactions leading to chlorate formation.
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effect of ph on the inorganic species involved in a chlorine dioxide reaction system
Industrial & Engineering Chemistry Research, 2002Co-Authors: Douglas R Svenson, Houmin Chang, John F Kadla, Hasan JameelAbstract:The effects of pH on the inorganic products formed during the reaction of chlorine dioxide with an etherified lignin model compound have been studied. Analyses of the inorganic species produced during the reaction at pH 8 revealed that 2 mol of Chlorite are liberated for every 1 mol of oxidized nonphenolic lignin model compound formed, consistent with two consecutive one-electron-transfer processes. In contrast, the low-pH reactions produced mostly ring oxidation products and chlorinated organic material, accompanied by increased levels of hypochlorous acid. The transient hypochlorous acid rapidly reacted with Chlorite to generate chloride ions, with a maximum chloride formation at pH 4. Chlorate formation was shown to increase with increasing reaction pH. These results are in contrast to those previously reported for reactions with wood pulps and are explained on the basis of the slow reaction kinetics of nonphenolic lignin moieties as compared to phenolic ones, thereby enabling hypochlorous acid to reac...
John F Kadla - One of the best experts on this subject based on the ideXlab platform.
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inorganic reactions in chlorine dioxide bleaching of softwood kraft pulp
Journal of Wood Chemistry and Technology, 2006Co-Authors: Douglas R Svenson, Hasan Jameel, Houmin Chang, John F KadlaAbstract:Abstract A softwood kraft pulp (27 kappa) was bleached with chlorine dioxide to various end pH values. The formation of Chlorite, chlorate, and chloride was measured to quantify the amount of chlorine dioxide wasted as a function of pH during a Do (pre‐bleaching) stage. Chlorate formation increased with a decrease in final pH. Conversely, residual Chlorite increased with an increase in the final pH. After 120 min of bleaching the total residual Chlorite and chlorate showed that no substantial increase in residual oxidant occurs when bleaching to an end pH below 3.4. As a result, the brightness and permanganate numbers for low pH chlorine dioxide bleached pulps did not differ when bleaching to an end pH between 3.4 and 1.8. However, decreasing the pH below 3.4 did result in increased organic chloride formation. The results are contrary to previous studies where the maximum bleaching efficiency for a D1 stage was reported to occur when the end pH was between 3 and 4.
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The role of non-phenolic lignin in chlorate-forming reactions during chlorine dioxide bleaching of softwood kraft pulp
Holzforschung, 2005Co-Authors: Douglas R Svenson, Hasan Jameel, Houmin Chang, John F KadlaAbstract:The affect of phenolic hydroxyl groups on the reaction efficiency during chlorine dioxide pre-bleaching of a softwood kraft pulp was investigated. The removal of phenolic hydroxyl groups via pulp methylation did not adversely affect the chlorine dioxide bleaching efficiency or the amount of chlorate formed during exposure to chlorine dioxide. Ion analysis of the reaction systems revealed that the formation of chloride and Chlorite ions during the bleaching process were very similar between the kraft and methylated kraft pulps. These results indicate that the kinetic rates of lignin oxidation by chlorine dioxide and its reduction products, Chlorite and hypochlorous acid, are much faster than the rate of inorganic reactions leading to chlorate formation.
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effect of ph on the inorganic species involved in a chlorine dioxide reaction system
Industrial & Engineering Chemistry Research, 2002Co-Authors: Douglas R Svenson, Houmin Chang, John F Kadla, Hasan JameelAbstract:The effects of pH on the inorganic products formed during the reaction of chlorine dioxide with an etherified lignin model compound have been studied. Analyses of the inorganic species produced during the reaction at pH 8 revealed that 2 mol of Chlorite are liberated for every 1 mol of oxidized nonphenolic lignin model compound formed, consistent with two consecutive one-electron-transfer processes. In contrast, the low-pH reactions produced mostly ring oxidation products and chlorinated organic material, accompanied by increased levels of hypochlorous acid. The transient hypochlorous acid rapidly reacted with Chlorite to generate chloride ions, with a maximum chloride formation at pH 4. Chlorate formation was shown to increase with increasing reaction pH. These results are in contrast to those previously reported for reactions with wood pulps and are explained on the basis of the slow reaction kinetics of nonphenolic lignin moieties as compared to phenolic ones, thereby enabling hypochlorous acid to reac...