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Jihgaw Lin - One of the best experts on this subject based on the ideXlab platform.
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Carbofuran degradation by the application of MW-assisted H2O2 process
Journal of environmental science and health. Part. B Pesticides food contaminants and agricultural wastes, 2011Co-Authors: Neelancherry Remya, Jihgaw LinAbstract:Carbofuran removal performance of a microwave (MW)-assisted H₂O₂ system under different MW-power levels (300-900 W) was investigated. Batch experiments were conducted at 100 mg/L Carbofuran concentration using a modified-MW reactor with 2450 MHz of fixed frequency. As a precursor, control experiments were carried out with H₂O₂ alone, MW alone and conventional heating (CH). A maximum Carbofuran removal of 14 % was observed in both H₂O₂ alone and CH systems. On the other hand, only 2 % removal was observed in the MW alone system irrespective of the operation-mode, i.e. continuous or pulsed. The combination of MW and H₂O₂ produced 100 % Carbofuran removal in all the MW-assisted experiments. The MW-assisted system operated under continuous-mode and at 750 W has showed rapid Carbofuran degradation, i.e. 30 sec, with the highest first-order removal rate constant of 25.82/min. However, 97 % carbon oxygen demand (COD) removal was observed in the same system only after 30 min. On the other hand, 100 % Carbofuran removal and 49 % COD removal were observed in the pulsed-mode MW-assisted H₂O₂ system after 10 and 30 min, respectively. Carbofuran mineralization in the system was evidenced by the formation of ammonium and nitrate, and Carbofuran intermediates.
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microwave assisted Carbofuran degradation in the presence of gac zvi and h2o2 influence of reaction temperature and ph
Separation and Purification Technology, 2011Co-Authors: Neelancherry Remya, Jihgaw LinAbstract:Abstract Carbofuran degradation in microwave (MW)-assisted granular activated carbon (GAC)/zero-valent iron (ZVI)/hydrogen peroxide (H 2 O 2 ) system(s) was investigated under different reaction temperatures, i.e. 30 °C, 50 °C and 80 °C, and at varying pHs, i.e. 2, 4, 6, 8 and 10. Batch experiments were conducted using a modified-MW reactor (750 W power and 2450 MHz frequency) at 100 mg L −1 Carbofuran concentration. The lower MW-reaction temperatures, i.e. 30 °C and 50 °C, have produced poor Carbofuran degradation efficiencies whereas complete Carbofuran degradation (100%) was observed at 80 °C and pH 6 in all the systems, i.e. MW with GAC, ZVI and H 2 O 2 . Under the similar conditions, insignificant Carbofuran removal/degradation (2–24%) was observed in the presence of GAC/ZVI/H 2 O 2 without MW. On the other hand, the Carbofuran degradation rate was accelerated under the alkaline pHs, i.e. pH 8 and 10 (at 80 °C), and 100% Carbofuran degradation was observed within 10 min in all the MW-assisted systems. However, the complete Carbofuran degradation was accomplished rapidly (5 min) in the MW-assisted GAC and ZVI systems under pH 10 and 80 °C. Carbofuran removal in the MW-assisted systems was modeled using the first-order reaction kinetics and a maximum removal rate constant of 4.17 min −1 was obtained in the MW-assisted ZVI system. A maximum of 86% Carbofuran mineralization was achieved in the MW-assisted GAC system via hydrolysis and the removal of carbamate group. The comparison of energy consumption in MW-assisted systems with other processes reveals that the MW-assisted process is highly efficient and cost-effective for Carbofuran degradation and mineralization.
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degradation of Carbofuran in aqueous solution by ultrasound and fenton processes effect of system parameters and kinetic study
Journal of Hazardous Materials, 2010Co-Authors: Ying Shih, Chi Fanga Sung, Jihgaw LinAbstract:To establish an efficient oxidation process for Carbofuran degradation, the effects of some operating parameters such as dosages of H2O2, Fe2+ and initial Carbofuran concentrations were observed during Carbofuran degradation by the ultrasound process, Fenton process and a combined ultrasound/Fenton process. The degradation kinetics of Carbofuran was also examined based on the experimental data. The results show that more than 99% of the Carbofuran was degraded by the ultrasound/Fenton process within short reaction time periods. Increased dosages of H2O2 and Fe2+ enhanced the degradation of Carbofuran in the ultrasound and Fenton oxidation processes, but initial Carbofuran concentrations decreased Carbofuran degradation in both the Fenton and ultrasound/Fenton processes. The degradation kinetics of Carbofuran by the three oxidation processes was found to be in accordance with first-order reaction kinetics. The results provide fundamental information about the treatment of Carbofuran wastewater and/or other pesticides by the ultrasound/Fenton oxidation process.
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Degradation of Carbofuran-contaminated water by the Fenton process
Journal of environmental science and health. Part A Toxic hazardous substances & environmental engineering, 2009Co-Authors: Mathava Kumar, Jihgaw LinAbstract:In this study, the Fenton process was applied for the degradation of Carbofuran from aqueous system. Batch experiments were conducted at two different Carbofuran concentrations i.e., 10 and 50 mg/L, and at pH 3. Batch experiments at each Carbofuran concentration were designed by central composite design (CCD) with two independent variables i.e. Fe2 + and H2O2. Experimental results indicate that more than 90% of Carbofuran removal was observed within 5 mins of Fenton reaction at 5 mg/L of Fe2 + concentration and 100 mg/L of H2O2 concentration. Increases in Fe2 + and/or H2O2 concentrations beyond 5 and 100 mg/L, respectively produced 100% Carbofuran removal. Based on the experimental observations, the optimal Fe2 + and H2O2 dosages required for 10 mg/L of aqueous Carbofuran removal were estimated as 7.4 and 143 mg/L, respectively. During this study, three Carbofuran intermediates such as 7-benzofuranol,2,3,-dihydro-2,2-dimethyl, 7-hydroxy-2,2-dimethyl-benzofuran-3-one and 1,4-Benzene-di-carboxaldehyde were ...
Andrew Ogram - One of the best experts on this subject based on the ideXlab platform.
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Dynamics of Carbofuran-degrading microbial communities in soil during three successive annual applications of Carbofuran
Soil Biology and Biochemistry, 2001Co-Authors: Steven Trabue, Andrew OgramAbstract:The influence of repeated annual field applications of the insecticide‐nematicide Carbofuran on Carbofuran-degrading microbial communities was studied at a site in Florida that exhibited enhanced degradation toward the chemical. Three successive annual applications of Carbofuran at 4.5 kg ha 21 y 21 did not result in an increase in the size of the microbial community capable of mineralizing uniformly ringlabeled 14 C-Carbofuran (Carbofuran-ring degraders) in surface soil (0‐15 cm depth). After the second annual application, however, the community capable of mineralizing carbonyl-labeled 14 C-Carbofuran (Carbofuran hydrolyzers) in the treated surface soil was significantly larger than that after the first annual application. Communities of methylamine utilizers in treated and untreated soils were much larger than the communities of Carbofuran phenol degraders, but not statistically different from the sizes of Carbofuran hydrolyzers. In addition to no increase in the number of Carbofuran ring degraders in the treated site during three consecutive annual applications of Carbofuran, laboratory addition of 10 mg Carbofuran g 21 to treated and untreated soils collected in 1995 did not result in an increase in the number of Carbofuran ring degraders. This suggests that degradation of the ring structure of Carbofuran in soil is a cometabolic process. q 2001 Elsevier Science Ltd. All rights reserved.
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Carbofuran degradation mediated by three related plasmid systems
FEMS microbiology ecology, 2000Co-Authors: Andrew Ogram, Steven Trabue, Y. P. Duan, X. Feng, Hector F. CastroAbstract:Two Carbofuran-metabolizing Sphingomonas strains, TA and CD, were isolated from soils with differing histories of exposure to Carbofuran. These strains were compared with a previously described strain, Sphingomonas sp. CFO6, with regard to growth rate, formation of metabolites, and plasmid content and structure. Extensive regions of similarity were observed between the three different plasmid systems as evidenced by cross hybridization. In addition, all three systems harbor IS1412, an insertion sequence (IS) element involved in heat-induced loss of Carbofuran phenotype in CFO6, and heat-induced Carbofuran deficient mutants of all three strains correlated with loss of IS1412. A Carbofuran deficient mutant of TA generated by induction of IS elements was complemented by reintroduction of the wild-type plasmid, confirming the presence of genes required for Carbofuran metabolism on this plasmid. Carbofuran metabolism in these three strains is clearly linked via plasmids of different numbers and sizes that share extensive common regions, and Carbofuran-degrading genes may be associated with active IS elements.
Jesús Simal-gándara - One of the best experts on this subject based on the ideXlab platform.
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Influence of micelles on the basic degradation of Carbofuran.
Journal of agricultural and food chemistry, 2005Co-Authors: Manuel Arias, Juan C. Mejuto, Luis García-río, P. Rodríguez-dafonte, Jesús Simal-gándaraAbstract:The effect of micellar aggregates upon the stability of Carbofuran in basic media has been studied. The effect of the presence of micelles upon the basic hydrolysis of Carbofuran is a function of the nature of the surfactant monomer. Important catalysis of basic hydrolysis of Carbofuran in the presence of colloid aggregates with positive surface charge has been reported. On the other hand, the presence of anionic and nonionic surfactants implies a large inhibition of the basic hydrolysis of Carbofuran. Both catalysis and inhibition are due to the association of Carbofuran with the micellar core. The kinetic constants for the basic hydrolysis of Carbofuran in these microheterogeneous media have been obtained on the basis of a micellar pseudophase model. No significant changes in the intrinsic reactivity of HO- against Carbofuran have been observed. Keywords: Carbofuran; cationic micelles; anionic micelles; nonionic micelles; basic hydrolysis
Tapan K. Adhya - One of the best experts on this subject based on the ideXlab platform.
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Influence of repeated applications of Carbofuran on nitrogenase activity and nitrogen-fixing bacteria associated with rhizosphere of tropical rice
Chemosphere, 1995Co-Authors: P.k. Kanungo, Tapan K. AdhyaAbstract:Abstract In a greenhouse study, the effect of repeat applications of the insecticide Carbofuran (2,3- dihydro 2,2- dinethyl-7 benzofuranyl-N- methylcarbanate), on nitrogenase activity and nitrogen-fixing bacteria associated with rice rhizosphere was investigated. Repeat applications of Carbofuran effected a significant stimulation of rhizosphere associated nitrogenase activity. Thus the nitrogenase activity, which was stimulated following first application of Carbofuran, was further enhanced after the second addition of Carbofuran. Interestingly, no further enhancement in the nitrogenase activity occurred due to subsequent applications. Populations of nitrogen-fixing Azospirillum sp., Azotobacter sp. and anaerobic nitrogen-fixing bacteria increased progressively upto third application of Carbofuran. Results indicate that repeated applications of Carbofuran stimulated nitrogenase and the populations of nitrogen-fixing bacteria associated with rice rhizosphere.
Steven Trabue - One of the best experts on this subject based on the ideXlab platform.
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Dynamics of Carbofuran-degrading microbial communities in soil during three successive annual applications of Carbofuran
Soil Biology and Biochemistry, 2001Co-Authors: Steven Trabue, Andrew OgramAbstract:The influence of repeated annual field applications of the insecticide‐nematicide Carbofuran on Carbofuran-degrading microbial communities was studied at a site in Florida that exhibited enhanced degradation toward the chemical. Three successive annual applications of Carbofuran at 4.5 kg ha 21 y 21 did not result in an increase in the size of the microbial community capable of mineralizing uniformly ringlabeled 14 C-Carbofuran (Carbofuran-ring degraders) in surface soil (0‐15 cm depth). After the second annual application, however, the community capable of mineralizing carbonyl-labeled 14 C-Carbofuran (Carbofuran hydrolyzers) in the treated surface soil was significantly larger than that after the first annual application. Communities of methylamine utilizers in treated and untreated soils were much larger than the communities of Carbofuran phenol degraders, but not statistically different from the sizes of Carbofuran hydrolyzers. In addition to no increase in the number of Carbofuran ring degraders in the treated site during three consecutive annual applications of Carbofuran, laboratory addition of 10 mg Carbofuran g 21 to treated and untreated soils collected in 1995 did not result in an increase in the number of Carbofuran ring degraders. This suggests that degradation of the ring structure of Carbofuran in soil is a cometabolic process. q 2001 Elsevier Science Ltd. All rights reserved.
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Carbofuran degradation mediated by three related plasmid systems
FEMS microbiology ecology, 2000Co-Authors: Andrew Ogram, Steven Trabue, Y. P. Duan, X. Feng, Hector F. CastroAbstract:Two Carbofuran-metabolizing Sphingomonas strains, TA and CD, were isolated from soils with differing histories of exposure to Carbofuran. These strains were compared with a previously described strain, Sphingomonas sp. CFO6, with regard to growth rate, formation of metabolites, and plasmid content and structure. Extensive regions of similarity were observed between the three different plasmid systems as evidenced by cross hybridization. In addition, all three systems harbor IS1412, an insertion sequence (IS) element involved in heat-induced loss of Carbofuran phenotype in CFO6, and heat-induced Carbofuran deficient mutants of all three strains correlated with loss of IS1412. A Carbofuran deficient mutant of TA generated by induction of IS elements was complemented by reintroduction of the wild-type plasmid, confirming the presence of genes required for Carbofuran metabolism on this plasmid. Carbofuran metabolism in these three strains is clearly linked via plasmids of different numbers and sizes that share extensive common regions, and Carbofuran-degrading genes may be associated with active IS elements.