The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Daniel K Cha - One of the best experts on this subject based on the ideXlab platform.
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enhanced reduction of perchlorate by Elemental Iron at elevated temperatures
Journal of Hazardous Materials, 2006Co-Authors: Pei C Chiu, Byung J Kim, Daniel K ChaAbstract:Abstract Kinetics of perchlorate reduction by Elemental Iron was examined at elevated temperatures using microwave heating and conventional block heating. It was hypothesized that increasing the solution temperature may accelerate the reduction of perchlorate by overcoming the high activation energy barrier. Results from microwave heating study showed that 98% of aqueous perchlorate was removed in 1 h at 200 °C. Similar results observed in control experiments with a block heater indicated that the enhancement in the extent and rate of perchlorate removal by Elemental Iron was mostly due to heat energy at high temperature. The rapid and complete reduction of perchlorate by Elemental Iron at elevated temperatures suggests that Iron reduction process at elevated temperature may be an option to consider for complete removal of perchlorate from industrial discharges.
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enhanced biodegradation of azo dyes using an integrated Elemental Iron activated sludge system i evaluation of system performance
Water Environment Research, 2006Co-Authors: Jennie Perey Saxe, Pei C Chiu, Brian L Lubenow, C P Huang, Daniel K ChaAbstract:The objective of this research is to evaluate an integrated system coupling zero-valent Iron (Fe(0)) and aerobic biological oxidation for the treatment of azo dye wastewater. Zero-valent (Elemental) Iron can reduce the azo bond, cleaving dye molecules into products that are more amenable to aerobic biological treatment processes. Azo dye reduction products, including aniline and sulfanilic acid, were shown to be readily biodegradable at concentrations up to approximately 25 mg/L. Batch reduction and biodegradation data support the proposed integrated Iron pretreatment and activated sludge process for the degradation of the azo dyes orange G and orange I. The integrated system was able to decolorize dye solutions and yield effluents with lower total organic carbon concentrations than control systems without Iron pretreatment. The success of the bench-scale integrated system suggests that Iron pretreatment may be a feasible approach to treat azo dye containing wastewaters.
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enhanced biodegradation of azo dyes using an integrated Elemental Iron activated sludge system ii effects of physical chemical parameters
Water Environment Research, 2006Co-Authors: Jennie Perey Saxe, Pei C Chiu, Brian L Lubenow, C P Huang, Daniel K ChaAbstract:As part of a study to evaluate an integrated zero-valent Iron (Fe(0))-biological oxidation process for treating azo dye wastewaters, we conducted batch and column experiments with the azo dye orange G to assess the effects of solution conditions on the performance of Iron pretreatment. The influence of Iron type and surface area, solution pH, dissolved inorganic salts, and phosphate ion on the reduction (decolorization) of orange G solution were examined. In batch experiments, increased Iron surface area, decreased pH, and chloride and sulfate salts enhanced dye decolorization, whereas high pH (9.9) and phosphate concentrations (> 3 mg/L PO4-P) inhibited dye reduction. Results from batch experiments were confirmed in column experiments. An increase in temperature from 22 to 35 degrees C resulted in a near doubling of the reduction rate constant in a column study. The abiotic reduction results illustrate the feasibility and potential limitations of an integrated Iron column, activated sludge treatment process for wastewaters containing azo dyes.
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reductive transformation of hexahydro 1 3 5 trinitro 1 3 5 triazine octahydro 1 3 5 7 tetranitro 1 3 5 7 tetrazocine and methylenedinitramine with Elemental Iron
Environmental Toxicology and Chemistry, 2005Co-Authors: Daniel K Cha, Byung J Kim, Pei C ChiuAbstract:Reductive (pre)treatment with Elemental Iron is a potentiallyuseful method for degrading nitramine explosives in water and soil. In the present study, we examined the kinetics, products, and mechanisms of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) degradation with Elemental Iron. Both RDX and HMX were transformed with Iron to formaldehyde, NH, N2O, and soluble products. The yields of formaldehyde were relatively constant (71% ± 5%), whereas the yields of NH and N2O varied, depending on the nitramine and the mechanism. The reactions most likely were controlled by a surface process rather than by external mass transfer. Methylenedinitramine (MDNA) was an intermediate of both RDX and HMX and was transformed quantitatively to formaldehyde with Iron. However, product distributions and kinetic modeling results suggest that MDNA represented a minor reaction path and accounted for only 30% of the RDX reacted and 14% of the formaldehyde produced. Additional experiments showed that RDX reduction with Elemental Iron could be mediated by graphite and Fe2+ sorbed to magnetite, as demonstrated previously for nitroaromatics and nitrate esters. Methylenedinitramine was degraded primarily through reduction in the presence of Elemental Iron, because its hydrolysis was slow compared to its reactions with Elemental Iron and surface-bound Fe2+. Our results show that in a cast Iron-water system, RDX may be transformed via multiple mechanisms involving different reaction paths and reaction sites.
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reduction of nitroglycerin with Elemental Iron pathway kinetics and mechanisms
Environmental Science & Technology, 2004Co-Authors: Daniel K Cha, Byung J Kim, Pei C ChiuAbstract:Nitroglycerin (NG) is a nitrate ester used in dynamites, propellants, and medicines and is therefore a common constituent in propellant-manufacturing and pharmaceutical wastewaters. In this study w...
Pei C Chiu - One of the best experts on this subject based on the ideXlab platform.
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enhanced reduction of perchlorate by Elemental Iron at elevated temperatures
Journal of Hazardous Materials, 2006Co-Authors: Pei C Chiu, Byung J Kim, Daniel K ChaAbstract:Abstract Kinetics of perchlorate reduction by Elemental Iron was examined at elevated temperatures using microwave heating and conventional block heating. It was hypothesized that increasing the solution temperature may accelerate the reduction of perchlorate by overcoming the high activation energy barrier. Results from microwave heating study showed that 98% of aqueous perchlorate was removed in 1 h at 200 °C. Similar results observed in control experiments with a block heater indicated that the enhancement in the extent and rate of perchlorate removal by Elemental Iron was mostly due to heat energy at high temperature. The rapid and complete reduction of perchlorate by Elemental Iron at elevated temperatures suggests that Iron reduction process at elevated temperature may be an option to consider for complete removal of perchlorate from industrial discharges.
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enhanced biodegradation of azo dyes using an integrated Elemental Iron activated sludge system i evaluation of system performance
Water Environment Research, 2006Co-Authors: Jennie Perey Saxe, Pei C Chiu, Brian L Lubenow, C P Huang, Daniel K ChaAbstract:The objective of this research is to evaluate an integrated system coupling zero-valent Iron (Fe(0)) and aerobic biological oxidation for the treatment of azo dye wastewater. Zero-valent (Elemental) Iron can reduce the azo bond, cleaving dye molecules into products that are more amenable to aerobic biological treatment processes. Azo dye reduction products, including aniline and sulfanilic acid, were shown to be readily biodegradable at concentrations up to approximately 25 mg/L. Batch reduction and biodegradation data support the proposed integrated Iron pretreatment and activated sludge process for the degradation of the azo dyes orange G and orange I. The integrated system was able to decolorize dye solutions and yield effluents with lower total organic carbon concentrations than control systems without Iron pretreatment. The success of the bench-scale integrated system suggests that Iron pretreatment may be a feasible approach to treat azo dye containing wastewaters.
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enhanced biodegradation of azo dyes using an integrated Elemental Iron activated sludge system ii effects of physical chemical parameters
Water Environment Research, 2006Co-Authors: Jennie Perey Saxe, Pei C Chiu, Brian L Lubenow, C P Huang, Daniel K ChaAbstract:As part of a study to evaluate an integrated zero-valent Iron (Fe(0))-biological oxidation process for treating azo dye wastewaters, we conducted batch and column experiments with the azo dye orange G to assess the effects of solution conditions on the performance of Iron pretreatment. The influence of Iron type and surface area, solution pH, dissolved inorganic salts, and phosphate ion on the reduction (decolorization) of orange G solution were examined. In batch experiments, increased Iron surface area, decreased pH, and chloride and sulfate salts enhanced dye decolorization, whereas high pH (9.9) and phosphate concentrations (> 3 mg/L PO4-P) inhibited dye reduction. Results from batch experiments were confirmed in column experiments. An increase in temperature from 22 to 35 degrees C resulted in a near doubling of the reduction rate constant in a column study. The abiotic reduction results illustrate the feasibility and potential limitations of an integrated Iron column, activated sludge treatment process for wastewaters containing azo dyes.
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reductive transformation of hexahydro 1 3 5 trinitro 1 3 5 triazine octahydro 1 3 5 7 tetranitro 1 3 5 7 tetrazocine and methylenedinitramine with Elemental Iron
Environmental Toxicology and Chemistry, 2005Co-Authors: Daniel K Cha, Byung J Kim, Pei C ChiuAbstract:Reductive (pre)treatment with Elemental Iron is a potentiallyuseful method for degrading nitramine explosives in water and soil. In the present study, we examined the kinetics, products, and mechanisms of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) degradation with Elemental Iron. Both RDX and HMX were transformed with Iron to formaldehyde, NH, N2O, and soluble products. The yields of formaldehyde were relatively constant (71% ± 5%), whereas the yields of NH and N2O varied, depending on the nitramine and the mechanism. The reactions most likely were controlled by a surface process rather than by external mass transfer. Methylenedinitramine (MDNA) was an intermediate of both RDX and HMX and was transformed quantitatively to formaldehyde with Iron. However, product distributions and kinetic modeling results suggest that MDNA represented a minor reaction path and accounted for only 30% of the RDX reacted and 14% of the formaldehyde produced. Additional experiments showed that RDX reduction with Elemental Iron could be mediated by graphite and Fe2+ sorbed to magnetite, as demonstrated previously for nitroaromatics and nitrate esters. Methylenedinitramine was degraded primarily through reduction in the presence of Elemental Iron, because its hydrolysis was slow compared to its reactions with Elemental Iron and surface-bound Fe2+. Our results show that in a cast Iron-water system, RDX may be transformed via multiple mechanisms involving different reaction paths and reaction sites.
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reduction of nitroglycerin with Elemental Iron pathway kinetics and mechanisms
Environmental Science & Technology, 2004Co-Authors: Daniel K Cha, Byung J Kim, Pei C ChiuAbstract:Nitroglycerin (NG) is a nitrate ester used in dynamites, propellants, and medicines and is therefore a common constituent in propellant-manufacturing and pharmaceutical wastewaters. In this study w...
Richard F Hurrell - One of the best experts on this subject based on the ideXlab platform.
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comparison of the efficacy of wheat based snacks fortified with ferrous sulfate electrolytic Iron or hydrogen reduced Elemental Iron randomized double blind controlled trial in thai women
The American Journal of Clinical Nutrition, 2005Co-Authors: Michael B Zimmermann, Visith Chavasit, Pattanee Winichagoon, Sueppong Gowachirapant, Sonja Y Hess, Mary Harrington, Sean R Lynch, Richard F HurrellAbstract:BACKGROUND Although Elemental Iron powders are widely used to fortify cereal products, little data exist on their efficacy in humans. OBJECTIVE We compared the efficacy of wheat-based snacks fortified with ferrous sulfate, electrolytic Iron, or hydrogen-reduced Iron in Thai women with low Iron stores. DESIGN A double-blind intervention was conducted in 18-50-y-old women (n = 330) randomly assigned into 4 groups to receive either no fortification Iron or 12 mg Fe/d for 6 d/wk for 35 wk as ferrous sulfate, electrolytic Iron, or hydrogen-reduced Iron in a baked, wheat-flour-based snack. Snacks were not consumed with meals, and consumption was monitored. At baseline, 20 wk, and 35 wk, hemoglobin status and Iron were measured and the groups were compared. RESULTS Between baseline and 35 wk, geometric mean serum ferritin (SF) increased significantly in all 3 groups receiving Iron (P < 0.01), and geometric mean serum transferrin receptor (TfR) decreased significantly in the groups receiving ferrous sulfate and electrolytic Iron (P < 0.05). Calculated mean (+/-SD) body Iron stores increased from 1.5 +/- 2.8 to 5.4 +/- 2.9 mg/kg in the ferrous sulfate group, from 1.5 +/- 3.5 to 4.4 +/- 3.6 mg/kg in the electrolytic Iron group, and from 1.3 +/- 3.2 to 3.2 +/- 4.3 mg/kg in the hydrogen-reduced Iron group (P < 0.01 for all 3 groups) but did not change significantly in the control group. CONCLUSIONS Ferrous sulfate, electrolytic Iron, and hydrogen-reduced Iron, fortified into wheat-based snacks, significantly improved Iron status. On the basis of the change in body Iron stores during the 35-wk study, the relative efficacy of the electrolytic and hydrogen-reduced Iron compared with ferrous sulfate was 77% and 49%, respectively.
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the usefulness of Elemental Iron for cereal flour fortification a sustain task force report
Nutrition Reviews, 2002Co-Authors: Richard F Hurrell, Leif Hallberg, Susan J Fairweathertait, Thomas Bothwell, James D Cook, Omar Dary, Lena Davidsson, Sean Lynch, Jorge L Rosado, Tomas WalterAbstract:Fortification of cereal flours may be a useful public health strategy to combat Iron deficiency. Cereal flours that are used shortly after production (e.g., baking flour) can be fortified with soluble Iron compounds, such as ferrous sulfate, whereas the majority of flours stored for longer periods is usually fortified with Elemental Iron powders to avoid unacceptable sensory changes. Elemental Iron powders are less well absorbed than soluble Iron compounds and they vary widely in their absorption depending on manufacturing method and physicochemical characteristics. Costs vary with powder type, but Elemental Iron powders are generally less expensive than ferrous sulfate. This review evaluates the usefulness of the different Elemental Iron powders based on results from in vitro studies, rat assays, human bioavailability studies, and efficacy studies monitoring Iron status in human subjects. It concludes that, at the present time, only electrolytic Iron powder can be recommended as an Iron fortificant. Because it is only approximately half as well absorbed as ferrous sulfate, it should be added to provide double the amount of Iron.
Trent Stellingwerff - One of the best experts on this subject based on the ideXlab platform.
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single versus split dose of Iron optimizes hemoglobin mass gains at 2106 m altitude
Medicine and Science in Sports and Exercise, 2019Co-Authors: Rebecca Hall, Peter Peeling, Elizabeta Nemeth, Dan Bergland, Walter T P Mccluskey, Trent StellingwerffAbstract:PURPOSE To determine if a single versus a split equivalent daily dose of Elemental Iron was superior for hemoglobin mass (Hbmass) gains at altitude while minimizing gastrointestinal (GI) discomfort. METHODS Twenty-four elite runners attended a 3.1 ± 0.3 wk training camp (Flagstaff, AZ; 2106 m). A two-group design, randomized and stratified to baseline Hbmass, sex, and ferritin (>30 μ·L), was implemented daily as: 1) single dose of 1 × 200 mg (PM only, SINGLE) versus 2) split dose of 2 × 100 mg (AM and PM; SPLIT) Elemental Iron (ferrous fumarate). The Hbmass and venipuncture assessments were completed upon arrival and departure (±2 d) from camp for ferritin, hepcidin, and erythroferrone (ERFE) concentrations. Validated food frequency, GI distress, menstrual blood loss (MBL) and training questionnaires were implemented throughout. Univariate analysis was used to compare Hbmass, with baseline ferritin, dietary Iron intake, MBL, and training volume used as covariates. RESULTS Both conditions increased Hbmass from baseline (P 0.05). CONCLUSIONS A single nightly 200-mg dose of Elemental Iron was superior to a split dose for optimizing Hbmass changes at altitude in runners over an approximately 3-wk training camp.
Tomas Walter - One of the best experts on this subject based on the ideXlab platform.
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bioavailability of Elemental Iron powder in white wheat bread
European Journal of Clinical Nutrition, 2004Co-Authors: Tomas Walter, Fernando Pizarro, Steven A Abrams, Erick BoyAbstract:Objective: Iron fortification of wheat flour is widely used. In most cases, Elemental Iron powders are utilized as fortificants due to their lower cost and few, if any, sensory problems. However, their bioavailability is unknown. We aimed to measure the bioavailability of H2-reduced Elemental Iron powder in white wheat bread made from 72% extraction flour. Design: A stable isotope of H2-reduced Iron powder (mean particle size 15 μm) was used as fortificant in bread prepared from unfortified wheat flour. In all, 12 5- to 7-y-old children were fed bread with 4 mg of H2-reduced 58Fe /100 g of flour. The next day 57Fe ascorbate was given as reference dose. After 14 days, erythrocytes were analyzed for isotopic enrichment using mass spectrometry. Results: When normalized to 40% absorption of the reference dose, the geometric mean (±range of 1 s.d.) bioavailability of reduced 58Fe in wheat bread rolls was 6.5% (3.7–11.8). Conclusions: When compared to previous radioIron studies of ferrous sulfate showing 10% absorption from an identical meal in adult women, the relative bioavailability can be estimated at about 65%. However, the bioavailability of this smaller particle size 58Fe (15 μm) is likely to be higher than that of commercial Iron powder (45 μm) although the precise difference cannot be ascertained with current methods. Thus, the bioavailability of commercial Elemental Iron powders currently used in fortification programs is likely to be substantially lower than that of ferrous sulfate. Sponsorship: This work was funded in part by Grant No 910313 by Micronutrient Initiative, IDRC, Ottawa, Canada.
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the usefulness of Elemental Iron for cereal flour fortification a sustain task force report
Nutrition Reviews, 2002Co-Authors: Richard F Hurrell, Leif Hallberg, Susan J Fairweathertait, Thomas Bothwell, James D Cook, Omar Dary, Lena Davidsson, Sean Lynch, Jorge L Rosado, Tomas WalterAbstract:Fortification of cereal flours may be a useful public health strategy to combat Iron deficiency. Cereal flours that are used shortly after production (e.g., baking flour) can be fortified with soluble Iron compounds, such as ferrous sulfate, whereas the majority of flours stored for longer periods is usually fortified with Elemental Iron powders to avoid unacceptable sensory changes. Elemental Iron powders are less well absorbed than soluble Iron compounds and they vary widely in their absorption depending on manufacturing method and physicochemical characteristics. Costs vary with powder type, but Elemental Iron powders are generally less expensive than ferrous sulfate. This review evaluates the usefulness of the different Elemental Iron powders based on results from in vitro studies, rat assays, human bioavailability studies, and efficacy studies monitoring Iron status in human subjects. It concludes that, at the present time, only electrolytic Iron powder can be recommended as an Iron fortificant. Because it is only approximately half as well absorbed as ferrous sulfate, it should be added to provide double the amount of Iron.