The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
James N. Jensen - One of the best experts on this subject based on the ideXlab platform.
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sequential chemical biological oxidation of Chlorendic Acid
Water Research, 1996Co-Authors: Joseph H. Sebastian, Scott A Weber, James N. JensenAbstract:Chlorendic Acid, a fire retardant, was subjected to sequential chemical/biological oxidation. Degradation of Chlorendic Acid was achieved by ozonation with chlorinated and non-chlorinated by-product production. The destruction of Chlorendic Acid and by-product distribution was a function of ozone contact time. After 450 min of ozonation, Chlorendic Acid and TOC removal percentages equaled 98% and 62.5%, respectively. When subject to 210 min of UV oxidation, Chlorendic Acid and TOC removal equaled 70 and 31%, respectively. With combined ozone/UV, near complete removal of Chlorendic Acid and TOC was achieved in 90 and 120 min, respectively. In biodegradation testing, Chlorendic Acid was not degradable. Biodegradation efficiency (DOC removal) of Chlorendic Acid ozonation by-products was a function of ozone contact time and approached 80%. Chlorendic Acid UV oxidation products (210 min contact time) were poorly biodegraded. Ozone/UV oxidation products (40 min contact time) from Chlorendic Acid achieved 89% biodegradation. Biodegradation rates of Chlorendic Acid chemical oxidation by-products also were assessed. Based on the computed biokinetic values of biodegradation rates for the chemical oxidation products of Chlorendic Acid are sufficiently high to enable use of existing biological process infrastructure for treatment of chemical oxidation products.
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Sequential chemical/biological oxidation of Chlorendic Acid
Water Research, 1996Co-Authors: Joseph H. Sebastian, A. Scott Weber, James N. JensenAbstract:Chlorendic Acid, a fire retardant, was subjected to sequential chemical/biological oxidation. Degradation of Chlorendic Acid was achieved by ozonation with chlorinated and non-chlorinated by-product production. The destruction of Chlorendic Acid and by-product distribution was a function of ozone contact time. After 450 min of ozonation, Chlorendic Acid and TOC removal percentages equaled 98% and 62.5%, respectively. When subject to 210 min of UV oxidation, Chlorendic Acid and TOC removal equaled 70 and 31%, respectively. With combined ozone/UV, near complete removal of Chlorendic Acid and TOC was achieved in 90 and 120 min, respectively. In biodegradation testing, Chlorendic Acid was not degradable. Biodegradation efficiency (DOC removal) of Chlorendic Acid ozonation by-products was a function of ozone contact time and approached 80%. Chlorendic Acid UV oxidation products (210 min contact time) were poorly biodegraded. Ozone/UV oxidation products (40 min contact time) from Chlorendic Acid achieved 89% biodegradation. Biodegradation rates of Chlorendic Acid chemical oxidation by-products also were assessed. Based on the computed biokinetic values of biodegradation rates for the chemical oxidation products of Chlorendic Acid are sufficiently high to enable use of existing biological process infrastructure for treatment of chemical oxidation products.
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DECHLORINATION OF Chlorendic Acid WITH OZONE
Water Research, 1991Co-Authors: Janice P. Stowell, James N. JensenAbstract:Abstract An experimental study was conducted to investigate the use of ozone to dechlorinate Chlorendic Acid [1,4,5,6,7,7-hexachlorobicyclo-(2,2,1)-hept-5-ene-2,3-dicarboxylic Acid; CAS Number 115-28-6]. The dechlorination and subsequent degradation of Chlorendic Acid by ozonation is influenced by the pH, applied ozone dose and bicarbonate concentration. A change in the initial Chlorendic Acid concentration to 50, 100 and 200 mg/l did not influence the rate of degradation of Chlorendic Acid. Ultraviolet radiation alone also dechlorinated Chlorendic Acid. Ultraviolet radiation (u.v.) was also shown to greatly enhance the oxidation of Chlorendic Acid in the presence of ozone. In a typical case, 80% dechlorination of Chlorendic Acid was obtained in 60 min when using an ozone dose of 125 mg/min ozone at pH 7.4. In addition to the experimental results, a model describing the dechlorination of Chlorendic Acid is presented. The pseudo-first order rate constants for a two-step model were calculated and ranged from 0.002 to 0.295 min−1 for the first step and 0.008 to 6 × 1012 min−1 (calculated) for the second step. The magnitude of the rate constants and corresponding rates of dechlorination of Chlorendic Acid were shown to be dependent upon the production and/or scavenging of hydroxyl radicals in solution. Conditions favoring radicals in solution, such as high pH and the addition of u.v., resulted in much faster dechlorination. The conditions which did not favor radicals, such as low pH and the addition of bicarbonate, resulted in slower dechlorination.
Jaco Vangronsveld - One of the best experts on this subject based on the ideXlab platform.
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Fenton-Mediated Biodegradation of Chlorendic Acid – A Highly Chlorinated Organic Pollutant – By Fungi Isolated From a Polluted Site
Frontiers in microbiology, 2019Co-Authors: Inge Jambon, Sofie Thijs, Giselle Torres-farradá, Francois Rineau, Nele Weyens, Robert Carleer, Pieter Samyn, Jaco VangronsveldAbstract:Chlorendic Acid is a recalcitrant, highly chlorinated organic pollutant for which no microbial degrader has yet been identified. To address this knowledge gap, fungi were isolated from bulk soil, rhizosphere, and roots of the common bent (Agrostis capillaris) and the hybrid poplar (Populus deltoides x (Populus trichocarpa x Populus deltoides) cv. Grimminge), both of which grow on a Chlorendic Acid polluted site in Belgium. Isolates were taxonomically identified and phenotypically screened for Chlorendic Acid degradation. Several fungal isolates could degrade Chlorendic Acid in liquid media up to 45%. The Chlorendic Acid degrading fungal isolates produced higher levels of hydroxyl radicals when exposed to the pollutant when compared to non-exposed controls, suggesting that the oxidative degradation of Chlorendic Acid occurs through production of Fenton-mediated hydroxyl radicals. In addition, the isolated Ascomycete Penicillium sp. 1D-2a degraded 58% of the original Chlorendic Acid concentration in the soil after 28 days. This study demonstrates that the presence of fungi in a Chlorendic Acid polluted soil can degrade this highly chlorinated organic pollutant. These results indicate that recalcitrant, seemingly non-biologically degradable organic pollutants, such as Chlorendic Acid, can be remediated by using bioremediation, which opens new perspectives for in-situ bioremediation.
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fenton mediated biodegradation of Chlorendic Acid a highly chlorinated organic pollutant by fungi isolated from a polluted site
Frontiers in Microbiology, 2019Co-Authors: Inge Jambon, Sofie Thijs, Francois Rineau, Nele Weyens, Robert Carleer, Pieter Samyn, Jaco Vangronsveld, Giselle TorresfarradaAbstract:Chlorendic Acid is a recalcitrant, highly chlorinated organic pollutant for which no microbial degrader has yet been identified. To address this knowledge gap, fungi were isolated from bulk soil, rhizosphere, and roots of the common bent (Agrostis capillaris) and the hybrid poplar (Populus deltoides x (Populus trichocarpa x Populus deltoides) cv. Grimminge), both of which grow on a Chlorendic Acid polluted site in Belgium. Isolates were taxonomically identified and phenotypically screened for Chlorendic Acid degradation. Several fungal isolates could degrade Chlorendic Acid in liquid media up to 45%. The Chlorendic Acid degrading fungal isolates produced higher levels of hydroxyl radicals when exposed to the pollutant when compared to non-exposed controls, suggesting that the oxidative degradation of Chlorendic Acid occurs through production of Fenton-mediated hydroxyl radicals. In addition, the isolated Ascomycete Penicillium sp. 1D-2a degraded 58% of the original Chlorendic Acid concentration in the soil after 28 days. This study demonstrates that the presence of fungi in a Chlorendic Acid polluted soil can degrade this highly chlorinated organic pollutant. These results indicate that recalcitrant, seemingly non-biologically degradable organic pollutants, such as Chlorendic Acid, can be remediated by using bioremediation, which opens new perspectives for in-situ bioremediation.
Joseph H. Sebastian - One of the best experts on this subject based on the ideXlab platform.
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sequential chemical biological oxidation of Chlorendic Acid
Water Research, 1996Co-Authors: Joseph H. Sebastian, Scott A Weber, James N. JensenAbstract:Chlorendic Acid, a fire retardant, was subjected to sequential chemical/biological oxidation. Degradation of Chlorendic Acid was achieved by ozonation with chlorinated and non-chlorinated by-product production. The destruction of Chlorendic Acid and by-product distribution was a function of ozone contact time. After 450 min of ozonation, Chlorendic Acid and TOC removal percentages equaled 98% and 62.5%, respectively. When subject to 210 min of UV oxidation, Chlorendic Acid and TOC removal equaled 70 and 31%, respectively. With combined ozone/UV, near complete removal of Chlorendic Acid and TOC was achieved in 90 and 120 min, respectively. In biodegradation testing, Chlorendic Acid was not degradable. Biodegradation efficiency (DOC removal) of Chlorendic Acid ozonation by-products was a function of ozone contact time and approached 80%. Chlorendic Acid UV oxidation products (210 min contact time) were poorly biodegraded. Ozone/UV oxidation products (40 min contact time) from Chlorendic Acid achieved 89% biodegradation. Biodegradation rates of Chlorendic Acid chemical oxidation by-products also were assessed. Based on the computed biokinetic values of biodegradation rates for the chemical oxidation products of Chlorendic Acid are sufficiently high to enable use of existing biological process infrastructure for treatment of chemical oxidation products.
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Sequential chemical/biological oxidation of Chlorendic Acid
Water Research, 1996Co-Authors: Joseph H. Sebastian, A. Scott Weber, James N. JensenAbstract:Chlorendic Acid, a fire retardant, was subjected to sequential chemical/biological oxidation. Degradation of Chlorendic Acid was achieved by ozonation with chlorinated and non-chlorinated by-product production. The destruction of Chlorendic Acid and by-product distribution was a function of ozone contact time. After 450 min of ozonation, Chlorendic Acid and TOC removal percentages equaled 98% and 62.5%, respectively. When subject to 210 min of UV oxidation, Chlorendic Acid and TOC removal equaled 70 and 31%, respectively. With combined ozone/UV, near complete removal of Chlorendic Acid and TOC was achieved in 90 and 120 min, respectively. In biodegradation testing, Chlorendic Acid was not degradable. Biodegradation efficiency (DOC removal) of Chlorendic Acid ozonation by-products was a function of ozone contact time and approached 80%. Chlorendic Acid UV oxidation products (210 min contact time) were poorly biodegraded. Ozone/UV oxidation products (40 min contact time) from Chlorendic Acid achieved 89% biodegradation. Biodegradation rates of Chlorendic Acid chemical oxidation by-products also were assessed. Based on the computed biokinetic values of biodegradation rates for the chemical oxidation products of Chlorendic Acid are sufficiently high to enable use of existing biological process infrastructure for treatment of chemical oxidation products.
Anh Le-tuan Pham - One of the best experts on this subject based on the ideXlab platform.
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Reduction of Chlorendic Acid by zero-valent iron: Kinetics, products, and pathways.
Journal of hazardous materials, 2019Co-Authors: Min-sik Kim, Emily Piggott, Nick Zrinyi, Chang-ha Lee, Anh Le-tuan PhamAbstract:Abstract Chlorendic Acid (CA) is a recalcitrant groundwater contaminant for which an effective treatment technology does not currently exist. In this study, a series of batch experiments were conducted to investigate the treatment of CA by zero-valent iron (ZVI) under various water chemistry conditions. It was observed that CA was removed by ZVI via both adsorption and degradation, with the degradation rate being proportional to the fraction of CA adsorbed onto ZVI. The rate of CA degradation decreased as pH increased, presumably due to the passivation of ZVI and diminishing CA adsorption. Chloride (Cl−) did not appreciably affect CA adsorption and degradation, while sulfate (SO42−) significantly inhibited both processes because SO42− competed with CA for ZVI adsorptive sites. The rate of CA degradation was significantly accelerated by ZVI-associated Fe(II). Nine byproducts of CA transformation were identified by high-resolution mass spectrometry. The formation and subsequent degradation of these products revealed that the transformation of CA by ZVI occurred via a step-wise reductive dechlorination pathway. Overall, this study suggests that ZVI may be effective at remediating CA-contaminated sites.
John Ashby - One of the best experts on this subject based on the ideXlab platform.
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Articles Prediction of Rodent Nongenotoxic Carcinogenesis: Evaluation of Biochemical and Tissue Changes in Rodents Following Exposure to Nine Nongenotoxic
2013Co-Authors: Ntp Carcinogens, Jenny Odum, Susan C Hasmall, Anthony R. Soames, Clifford R. Elcombe, Susan Stone, Ian Kimber, John R. Foster, John AshbyAbstract:We studied nine presumed nongenotoxic rodent carcinogens, as defined by the U.S. National Toxicology Program (NTP), to determine their ability to induce acute or subacute biochemical and tissue changes that may act as useful predictors of nongenotoxic rodent carcinogenesis. The chemicals selected included six liver carcinogens (two of which are peroxisome proliferators), three thyroid gland carcinogens, and four kidney carcinogens. We administered the chemicals (diethylhexyl phthalate, cinnamyl anthranilate, Chlorendic Acid, 1,4-dichlorobenzene, monuron, ethylene thiourea, diethyl thiourea, trimethyl thiourea, and d-limonene) to the same strains of mice and rats used in the original NTP bioassays (nine chemicals to rats and seven to mice). Selected tissues (liver, thyroid gland, and kidney) were collected from groups of animals at 7, 28, and 90 days for evaluation. Tissue changes selected for study were monitored for all of the test groups, irrespective of the specificity of the carcinogenic responses observed in those tissues. This allowed us to assess both the carcinogen specificity and the carcinogen sensitivity of the events being monitored. We studied relative weight, cell labeling indices, and pathologic changes such as hypertrophy in all tissues; a range of cytochrome P450 enzymes and palmitoyl coenzyme A oxidase in the liver; changes in the levels of plasma total triiodothyronine, total thyroxine, and thyroid-stimulatin
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prediction of rodent nongenotoxic carcinogenesis evaluation of biochemical and tissue changes in rodents following exposure to nine nongenotoxic ntp carcinogens
Environmental Health Perspectives, 2002Co-Authors: Clifford R. Elcombe, Jenny Odum, Susan C Hasmall, Anthony R. Soames, Susan Stone, John L R Foster, Ian Kimber, John AshbyAbstract:We studied nine presumed nongenotoxic rodent carcinogens, as defined by the U.S. National Toxicology Program (NTP), to determine their ability to induce acute or subacute biochemical and tissue changes that may act as useful predictors of nongenotoxic rodent carcinogenesis. The chemicals selected included six liver carcinogens (two of which are peroxisome proliferators), three thyroid gland carcinogens, and four kidney carcinogens. We administered the chemicals (diethylhexyl phthalate, cinnamyl anthranilate, Chlorendic Acid, 1,4-dichlorobenzene, monuron, ethylene thiourea, diethyl thiourea, trimethyl thiourea, and d-limonene to the same strains of mice and rats used in the original NTP bioassays (nine chemicals to rats and seven to mice). Selected tissues (liver, thyroid gland, and kidney) were collected from groups of animals at 7, 28, and 90 days for evaluation. Tissue changes selected for study were monitored for all of the test groups, irrespective of the specificity of the carcinogenic responses observed in those tissues. This allowed us to assess both the carcinogen specificity and the carcinogen sensitivity of the events being monitored. We studied relative weight, cell labeling indices, and pathologic changes such as hypertrophy in all tissues; a range of cytochrome P450 enzymes and palmitoyl coenzyme A oxidase in the liver; changes in the levels of plasma total triiodothyronine, total thyroxine, and thyroid-stimulating hormone (TSH) as markers of thyroid gland function; and hyaline droplet formation, tubular basophilia, and the formation of granular casts in the kidney. There were no single measurements that alerted specifically to the carcinogenicity of the agents to the rodent liver, thyroid gland, or kidney. However, in the majority of cases, the chemical induction of cancer in a tissue was preceded by a range of biochemical/morphologic changes, most of which were moderately specific for a carcinogenic outcome, and some of which were highly specific for it (e.g., increases in TSH in the thyroid gland and increases in relative liver weight in the mouse). The only measurements that failed to correlate usefully with carcinogenicity were the induction of liver enzymes (with the exception of the enzymes associated with peroxisome proliferation). Most of the useful markers were evident at the early times studied (7 days and 28 days), but no overall best time for the measurement of all markers was identified. The judicious choice of markers and evaluation times can aid the detection of potential nongenotoxic rodent carcinogens.