The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Bruno Delvaux - One of the best experts on this subject based on the ideXlab platform.
-
Sulphate sorption at high Equilibrium Concentration in Andosols
Geoderma, 2006Co-Authors: Thomas Delfosse, Pierre Delmelle, Bruno DelvauxAbstract:The main process by which inorganic SO42- inputs are retained in soils is through adsorption on soil colloids. However, in soils subject to intense SO42- addition, precipitation of Al-x(SO4)(y)(OH)(z) minerals also may contribute to SO42- sorption. While direct observation of Al-x (SO4)(y)(OH)(z) precipitate in soil has been reported only recently, sorption isotherms experiments have been rarely performed to distinguish between adsorption and precipitation processes. Traditionally, SO42- sorption experiments have involved relatively low SO42- Concentrations in the range 0-5 mM. However, for SO42- precipitation to occur, higher Concentrations may be needed. Here, we evaluated SO42- sorption in four contrasting Andosols samples by measuring sorption isotherms with SO42- Concentrations ranging from 0.1 to 15 mM and under low pH conditions (pH 4). A 1 h sorption lowest equilibration time was precipitation at high dissolvedallowed. A sorption isotherms showed a distinct biphasic shape. In the lowest SO42- Concentration range ( 6 mM), SO42- sorption could be described by a linear isotherm. The transition between a Langmuir-type and a linear-type isotherm also corresponded to the transition point where the solution was oversaturated with respect to Al-x(OH)(y)(SO4)(z) minerals, according to thermodynamic calculations. We interpreted these results in terms of initial SO42- adsorption onto the surface of soil constituents at lower dissolved SO42- Concentrations followed by SO42- precipitation at high dissolved SO42- Concentrations. (c) 2006 Elsevier B.V. All rights reserved.
-
Sulphate sorption at high Equilibrium Concentration in Andosols
Geoderma, 2006Co-Authors: Thomas Delfosse, Pierre Delmelle, Bruno DelvauxAbstract:The main process by which inorganic SO42- inputs are retained in soils is through adsorption on soil colloids. However, in soils subject to intense SO42- addition, precipitation of Al-x(SO4)(y)(OH)(z) minerals also may contribute to SO42- sorption. While direct observation of Al-x (SO4)(y)(OH)(z) precipitate in soil has been reported only recently, sorption isotherms experiments have been rarely performed to distinguish between adsorption and precipitation processes. Traditionally, SO42- sorption experiments have involved relatively low SO42- Concentrations in the range 0-5 mM. However, for SO42- precipitation to occur, higher Concentrations may be needed. Here, we evaluated SO42- sorption in four contrasting Andosols samples by measuring sorption isotherms with SO42- Concentrations ranging from 0.1 to 15 mM and under low pH conditions (pH 4). A 1 h sorption lowest equilibration time was precipitation at high dissolvedallowed. A sorption isotherms showed a distinct biphasic shape. In the lowest SO42- Concentration range (< 5 mM), SO42- sorption obeyed a Langumir isotherm, whereas at higher SO42- Concentrations (> 6 mM), SO42- sorption could be described by a linear isotherm. The transition between a Langmuir-type and a linear-type isotherm also corresponded to the transition point where the solution was oversaturated with respect to Al-x(OH)(y)(SO4)(z) minerals, according to thermodynamic calculations. We interpreted these results in terms of initial SO42- adsorption onto the surface of soil constituents at lower dissolved SO42- Concentrations followed by SO42- precipitation at high dissolved SO42- Concentrations. (c) 2006 Elsevier B.V. All rights reserved
Suresh V. Garimella - One of the best experts on this subject based on the ideXlab platform.
-
measurement and prediction of the heat of adsorption and Equilibrium Concentration of co2 on zeolite 13x
Journal of Chemical & Engineering Data, 2018Co-Authors: Karen N Son, Gregory E. Cmarik, James C. Knox, Justin A. Weibel, Suresh V. GarimellaAbstract:Adsorption isotherms are reported for pure carbon dioxide on zeolite 13X (also called zeolite NaX) pellets over a temperature range of 0 to 200 °C and a pressure range of 0.001 to 100 kPa. These pure-component equilibria are fit with Langmuir, Toth, two-site Langmuir, and three-site Langmuir models, both with and without temperature dependence being included in the saturation capacity. The agreement between fitted and measured isotherms is shown to increase with increasing number of available fitting parameters in the model, with the constant-saturation, two-site Langmuir isotherm providing the best balance between agreement with the measurements and model complexity. The isosteric heats of adsorption are measured across a temperature range from 10 to 200 °C using differential scanning calorimetry. The measured heats of adsorption decrease with increasing CO2 loading but show little variation with temperature. The measurements are shown to agree with predicted heats of adsorption derived from the fitted L...
-
Measurement and Prediction of the Heat of Adsorption and Equilibrium Concentration of CO2 on Zeolite 13X
2018Co-Authors: Karen N. Son, Gregory E. Cmarik, James C. Knox, Justin A. Weibel, Suresh V. GarimellaAbstract:Adsorption isotherms are reported for pure carbon dioxide on zeolite 13X (also called zeolite NaX) pellets over a temperature range of 0 to 200 °C and a pressure range of 0.001 to 100 kPa. These pure-component equilibria are fit with Langmuir, Toth, two-site Langmuir, and three-site Langmuir models, both with and without temperature dependence being included in the saturation capacity. The agreement between fitted and measured isotherms is shown to increase with increasing number of available fitting parameters in the model, with the constant-saturation, two-site Langmuir isotherm providing the best balance between agreement with the measurements and model complexity. The isosteric heats of adsorption are measured across a temperature range from 10 to 200 °C using differential scanning calorimetry. The measured heats of adsorption decrease with increasing CO2 loading but show little variation with temperature. The measurements are shown to agree with predicted heats of adsorption derived from the fitted Langmuir and Toth isotherms (via the Clausius–Clapeyron equation); the heats of adsorption predicted using the more complex multisite Langmuir models suffer from nonphysical artifacts
Bernard Legube - One of the best experts on this subject based on the ideXlab platform.
-
Effect of the adsorbate (Bromacil) Equilibrium Concentration in water on its adsorption on powdered activated carbon. Part 3: Competition with natural organic matter.
Journal of Hazardous Materials, 2010Co-Authors: Fadi Al Mardini, Bernard LegubeAbstract:This study (part 3) was carried out to investigate the effect of the natural organic matter (NOM) Concentration on Bromacil (pesticide) adsorption on powdered activated carbon (PAC) in the same experimental conditions as in our previous studies (parts 1 and 2). Our previous findings showed that Bromacil adsorption in buffered pure water (pH 7.8) occurred at two types of site. In the presence of NOM (three kinds), we noted a significant reduction in Bromacil adsorption capacities due to the competitive effects exerted by NOM. Highly reactive sites (or pores) in PAC appeared to be blocked by NOM adsorption, as demonstrated by the application of a pseudo-single solute isotherm and of the simplified ideal adsorbed solution theory (IAST), regardless of the initial Bromacil and NOM Concentrations. The competing effect of low-molecular weight NOM was found to be greater than the competing effect of high-molecular weight NOM. The pseudo-second order surface-reaction model fitted Bromacil adsorption particularly well, even in the presence of NOM. However, the adsorption-kinetic constant values were found to be independent of the aqueous Equilibrium Concentration of the target compound, contrary to that observed in pure water. The kinetic data thus confirmed that high reactivity PAC sites were blocked by NOM adsorption. A practical approach concluded this work.
-
Effect of the adsorbate (Bromacil) Equilibrium Concentration in water on its adsorption on powdered activated carbon. Part 2: Kinetic parameters.
Journal of hazardous materials, 2009Co-Authors: Fadi Al Mardini, Bernard LegubeAbstract:The application of several monosolute Equilibrium models has previously shown that Bromacil adsorption on SA-UF (Norit) powdered activated carbon (PAC) is probably effective on two types of sites. High reactivity sites were found to be 10-20 less present in a carbon surface than lower reactivity sites, according to the q(m) values calculated by isotherm models. The aims of this work were trying, primarily, to identify the kinetic-determinant stage of the sorption of Bromacil at a wide range of initial pesticide Concentrations (approximately 5 to approximately 500 microg L(-1) at pH 7.8), and secondly, to specify the rate constants and other useful design parameters for the application in water treatment. It was therefore not possible to specify a priori whether the diffusion or surface reaction is the key step. It shows that many of the tested models which describe the stage of distribution or the surface reaction are correctly applied. However, the diffusivity values (D and D(0)) were found to be constant only constants for some specific experimental Concentrations. The HSDM model of surface diffusion in pores was also applied but the values of the diffusion coefficient of surface (D(s)) were widely scattered and reduce significantly with the initial Concentration or the Equilibrium Concentration in Bromacil. The model of surface reaction of pseudo-second order fitted particularly well and led to constant values which are independent of the Equilibrium Concentration, except for the low Concentrations where the constants become significantly more important. This last observation confirms perfectly the hypothesis based on two types of sites as concluded by the Equilibrium data (part 1).
-
Effect of the adsorbate (Bromacil) Equilibrium Concentration in water on its adsorption on powdered activated carbon. Part 1. Equilibrium parameters
Journal of Hazardous Materials, 2009Co-Authors: Fadi Al Mardini, Bernard LegubeAbstract:Abstract The application of several monosolute Equilibrium models has previously shown that Bromacil adsorption on SA-UF (Norit) powdered activated carbon (PAC) is probably effective on two types of sites. High reactivity sites were found to be 10–20 less present in a carbon surface than lower reactivity sites, according to the q m values calculated by isotherm models. The aims of this work were trying, primarily, to identify the kinetic-determinant stage of the sorption of Bromacil at a wide range of initial pesticide Concentrations (∼5 to ∼500 μg L −1 at pH 7.8), and secondly, to specify the rate constants and other useful design parameters for the application in water treatment. It was therefore not possible to specify a priori whether the diffusion or surface reaction is the key step. It shows that many of the tested models which describe the stage of distribution or the surface reaction are correctly applied. However, the diffusivity values ( D and D 0 ) were found to be constant only constants for some specific experimental Concentrations. The HSDM model of surface diffusion in pores was also applied but the values of the diffusion coefficient of surface ( D s ) were widely scattered and reduce significantly with the initial Concentration or the Equilibrium Concentration in Bromacil. The model of surface reaction of pseudo-second order fitted particularly well and led to constant values which are independent of the Equilibrium Concentration, except for the low Concentrations where the constants become significantly more important. This last observation confirms perfectly the hypothesis based on two types of sites as concluded by the Equilibrium data (part 1).
Thomas Delfosse - One of the best experts on this subject based on the ideXlab platform.
-
Sulphate sorption at high Equilibrium Concentration in Andosols
Geoderma, 2006Co-Authors: Thomas Delfosse, Pierre Delmelle, Bruno DelvauxAbstract:The main process by which inorganic SO42- inputs are retained in soils is through adsorption on soil colloids. However, in soils subject to intense SO42- addition, precipitation of Al-x(SO4)(y)(OH)(z) minerals also may contribute to SO42- sorption. While direct observation of Al-x (SO4)(y)(OH)(z) precipitate in soil has been reported only recently, sorption isotherms experiments have been rarely performed to distinguish between adsorption and precipitation processes. Traditionally, SO42- sorption experiments have involved relatively low SO42- Concentrations in the range 0-5 mM. However, for SO42- precipitation to occur, higher Concentrations may be needed. Here, we evaluated SO42- sorption in four contrasting Andosols samples by measuring sorption isotherms with SO42- Concentrations ranging from 0.1 to 15 mM and under low pH conditions (pH 4). A 1 h sorption lowest equilibration time was precipitation at high dissolvedallowed. A sorption isotherms showed a distinct biphasic shape. In the lowest SO42- Concentration range ( 6 mM), SO42- sorption could be described by a linear isotherm. The transition between a Langmuir-type and a linear-type isotherm also corresponded to the transition point where the solution was oversaturated with respect to Al-x(OH)(y)(SO4)(z) minerals, according to thermodynamic calculations. We interpreted these results in terms of initial SO42- adsorption onto the surface of soil constituents at lower dissolved SO42- Concentrations followed by SO42- precipitation at high dissolved SO42- Concentrations. (c) 2006 Elsevier B.V. All rights reserved.
-
Sulphate sorption at high Equilibrium Concentration in Andosols
Geoderma, 2006Co-Authors: Thomas Delfosse, Pierre Delmelle, Bruno DelvauxAbstract:The main process by which inorganic SO42- inputs are retained in soils is through adsorption on soil colloids. However, in soils subject to intense SO42- addition, precipitation of Al-x(SO4)(y)(OH)(z) minerals also may contribute to SO42- sorption. While direct observation of Al-x (SO4)(y)(OH)(z) precipitate in soil has been reported only recently, sorption isotherms experiments have been rarely performed to distinguish between adsorption and precipitation processes. Traditionally, SO42- sorption experiments have involved relatively low SO42- Concentrations in the range 0-5 mM. However, for SO42- precipitation to occur, higher Concentrations may be needed. Here, we evaluated SO42- sorption in four contrasting Andosols samples by measuring sorption isotherms with SO42- Concentrations ranging from 0.1 to 15 mM and under low pH conditions (pH 4). A 1 h sorption lowest equilibration time was precipitation at high dissolvedallowed. A sorption isotherms showed a distinct biphasic shape. In the lowest SO42- Concentration range (< 5 mM), SO42- sorption obeyed a Langumir isotherm, whereas at higher SO42- Concentrations (> 6 mM), SO42- sorption could be described by a linear isotherm. The transition between a Langmuir-type and a linear-type isotherm also corresponded to the transition point where the solution was oversaturated with respect to Al-x(OH)(y)(SO4)(z) minerals, according to thermodynamic calculations. We interpreted these results in terms of initial SO42- adsorption onto the surface of soil constituents at lower dissolved SO42- Concentrations followed by SO42- precipitation at high dissolved SO42- Concentrations. (c) 2006 Elsevier B.V. All rights reserved
M. N. Hansen - One of the best experts on this subject based on the ideXlab platform.
-
Field evaluation of the Equilibrium Concentration technique (JTI method) for measuring ammonia emission from land spread manure or fertiliser
Atmospheric Environment, 2001Co-Authors: Tom Misselbrook, M. N. HansenAbstract:Abstract Three experiments were conducted in which intercomparisons were made between the Equilibrium Concentration technique, developed at JTI, Sweden, and the integrated horizontal flux technique for measuring ammonia emissions following applications of urea fertiliser, cattle slurry and solid pig manure to land. Mean square prediction error analysis was used to compare the emission rates measured by the two techniques. There were no significant differences between the measurement techniques, although there was some evidence that emission rates were overestimated by the Equilibrium Concentration method relative to the integrated horizontal flux technique at higher emission rates (>400 g.N ha−1 h−1). The Equilibrium Concentration method provides a practical and relatively inexpensive technique for measuring emissions under ambient conditions from small plots but good sampler preparation, adequate replication of emission measurements and appropriate choice of duration of sampling periods are necessities for obtaining reliable results.