Journal articles: 'Desorption kinetic'

1

Li, Zhe, Suwei Xu, Ying Li, and Yuji Arai. "Novel Application of Hybrid Anion Exchange Resin for Phosphate Desorption Kinetics in Soils: Minimizing Re-Adsorption of Desorbed Ions." Soil Systems 4, no. 2 (June 17, 2020): 36. http://dx.doi.org/10.3390/soilsystems4020036.

Full text

Abstract:

The process of phosphate desorption from soils is difficult to measure using stirred batch techniques because of the accumulation of desorbed ions in a bathing solution. To accurately measure the apparent rate coefficient of phosphate desorption from soils, it is necessary to remove the desorbed ions. In this study, a novel hybrid (i.e., iron oxide coated) anion exchange resin was used as a sink to study long-term (seven days) P desorption kinetics in intensively managed agricultural soils in the Midwestern U.S. (total phosphorus (TP): 196–419 mg/kg). The phosphate desorption kinetics in the hybrid anion exchange resin method were compared with those in the other conventional batch desorption method with pure anion exchange resins or without any sink. The extent of P desorption in the hybrid resin methods was >50% of total desorbed phosphate in the other methods. The initial kinetic rate estimated in the pseudo-second-order kinetic model was also highest (3.03–31.35 mg/(g·hr)) in the hybrid resin method when the same soil system was compared. This is because adsorbed P in the hybrid resins was nearly irreversible. The hybrid anion exchange resin might be a new and ideal sink in measuring the P desorption process in soils and sediments.

APA, Harvard, Vancouver, ISO, and other styles

2

Rojas, Raquel, Guillermo Repetto, José Morillo, and José Usero. "Sorption/Desorption and Kinetics of Atrazine, Chlorfenvinphos, Endosulfan Sulfate and Trifluralin on Agro-Industrial and Composted Organic Wastes." Toxics 10, no. 2 (February 14, 2022): 85. http://dx.doi.org/10.3390/toxics10020085.

Full text

Abstract:

The use of pesticides presents a risk to terrestrial and aquatic ecosystems. For this reason, the development of strategies to prevent and restore pollution is of the greatest interest, including the adsorption to organic matter. The aim of the present study was to investigate the sorption/desorption and kinetics of atrazine, chlorfenvinphos, endosulfan sulfate, and trifluralin onto several raw organic wastes by batch experiments. Three kinetic models were used to fit the obtained sorption kinetics data and two to fit the obtained adsorption isotherm data; both the Freundlich and pseudo-second-order kinetic models described the sorption isotherms well. The desorption study revealed hysteresis in all cases, showing strong, and not completely reversible, adsorption in most cases, with the exception of atrazine-sawdust and chlorfenvinphos-sawdust and chicken manure combinations, for which responses were weak and irreversible. The best kinetic, adsorption and desorption constants were achieved for the hydrophobic pesticides. With respect to sorption-desorption rates, orujillo was found to be the best adsorbent for atrazine, while composted urban solid waste was more suitable for trifluralin and endosulfan sulfate. Sorption constants and simple correlations indicated that, not only the organic matter content, but also the nature of the organic matter itself, and the pesticide and adsorbent properties, determine pesticide sorption-desorption. The use of wastes as efficient and cheap adsorbents for reducing the risk of pesticide pollution is proposed.

APA, Harvard, Vancouver, ISO, and other styles

3

Bozbag, Selmi Erim, Deniz Şanlı, Barkın Özener, Gökhan Hisar, and Can Erkey. "An Aging Model of NH3 Storage Sites for Predicting Kinetics of NH3 Adsorption, Desorption and Oxidation over Hydrothermally Aged Cu-Chabazite." Catalysts 10, no. 4 (April 8, 2020): 411. http://dx.doi.org/10.3390/catal10040411.

Full text

Abstract:

A unified transient kinetic model which can predict the adsorption, desorption and oxidation kinetics of NH3 over hydrothermally aged Cu-chabazite was developed. The model takes into account the variation of fractional coverages of NH3 storage sites due to hydrothermal aging. In order to determine the fractional coverage of these sites, the catalyst was aged for various times at a certain temperature followed by NH3 adsorption, desorption and temperature-programmed desorption (TPD) experiments. TPD profiles were deconvoluted mainly into three peaks with centres at 317, 456 and 526 °C, respectively. Hydrothermal aging resulted in the progressive increase in the intensity of the peak at 317 °C and decrease in the intensity of the peaks at 456 and 526 °C, along with decreased NH3 oxidation at high temperatures. A model for hydrothermal aging kinetics of the fractional coverage of storage sites was developed using three reactions with appropriate rate expressions with parameters regressed from experimental data. The model was then incorporated into a multi-site kinetic model for the degreened Cu-Chabazite by the addition of aging reactions on each storage site. The effects of both aging time and temperature on the kinetics NH3 adsorption, desorption and oxidation were successfully predicted in the 155-540 °C range. This study is the first step towards the development of a hydrothermal aging-unified kinetic model of NH3-Selective Catalytic Reduction over Cu-chabazite.

APA, Harvard, Vancouver, ISO, and other styles

4

Ugrina, Marin, Nediljka Vukojević Medvidović, Jelena Perić, and Marina Trgo. "A study of kinetics and successive sorption/desorption of Zn and Cd uptake onto iron-modified zeolite." Clay Minerals 50, no. 1 (March 2015): 117–32. http://dx.doi.org/10.1180/claymin.2015.050.1.11.

Full text

Abstract:

AbstractThe sorption properties of iron-modified zeolite (IMZ) and the kinetics of zinc and cadmium uptake by the IMZ were investigated by the batch method. Two kinetic stages were observed, fast uptake up to 240 min, followed by slow uptake up to equilibrium. Kinetic results were fitted to the reaction and diffusion kinetic models, which indicated that intra-particle diffusion was the rate-limiting step. The Vermeulen’s approximation model was used to predict the quantity of Zn and Cd ions removed per gram of IMZ. The results of the successive sorption and desorption of Zn and Cd ions, with different electrolyte solutions, showed the best desorption efficiency with sodium salt solutions. Four successive repetitions of the sorption/desorption cycles showed a small difference between the amount of sorbed and desorbed Zn and Cd ions from the second to the fourth cycle. This indicates excellent sorption/regeneration properties of the IMZ.

APA, Harvard, Vancouver, ISO, and other styles

5

Nurul Aini, Olyvia Putri Wardhani, and Iriany. "DESORPSI β-KAROTEN MINYAK KELAPA SAWIT (CRUDE PALM OIL) DARI KARBON AKTIF MENGGUNAKAN ISOPROPANOL." Jurnal Teknik Kimia USU 5, no. 4 (January 24, 2017): 1–7. http://dx.doi.org/10.32734/jtk.v5i4.1547.

Full text

Abstract:

The aim of the research is to study the ability of isopropyl alcohol in the desorption of β-carotene and to obtain kinetic model and desorption isoterm which is suitable in β-carotene desorption. The main material used were isopropyl alcohol and activated carbon containing β-carotene. The variabels used in this research are desorption temperature, activated carbon concentration and parameter observed is concentration of β-carotene in isopropyl alcohol. In the desorption process, activated carbon which adsorp β-carotene was soaked in isopropyl alcohol. To review the desorption kinetics, this research was carried out in various temperature such as 40 oC, 50 oC, and 60 oC. In desorption isoterm process is, various mass of activated carbon was used. Desorption process will be analyzed at spesified time. This research used the first order of desorption kinetics model. The desorption constant rate obtained for 40 oC, 50 oC, and 60 oC are 0,013, 0,014, and 0,036 minute-1 with activation energy is 0,226 kkal/mol. The maximum desorption percentage obtain is 41,94 %. The desorption isoterm model which fit with the β-carotene desorption was Langmuir isoterm model with constanta value 1,2077 L/mg and -0,2218.

APA, Harvard, Vancouver, ISO, and other styles

6

Elbana, Tamer A., and H. Magdi Selim. "Multireaction Modeling of Lead (Pb) and Copper (Cu) Sorption/Desorption Kinetics in Different Soils." Soil Systems 3, no. 2 (May 31, 2019): 38. http://dx.doi.org/10.3390/soilsystems3020038.

Full text

Abstract:

Batch kinetic experiments were carried out to quantify and describe the sorption/desorption of Cu and Pb in ten soils that exhibited a wide range of properties. Sorption isotherms were quantified using the Langmuir equation, whereas modeling of sorption/desorption kinetics was described using multireaction model (MRM). Results revealed the nonlinear sorption behavior of Cu and Pb in all soils. The ten soils exhibited higher affinity to Pb (6.4 to 36.5 mmol kg−1) in comparison to Cu (3.6 to 22.4 mmol kg−1). Simulation of Cu and Pb kinetic data indicated that the rate of sorption reaction was two orders of magnitude higher than the rate of release. Considering one irreversible site in addition to one-reversible kinetic site improved the estimation of rates of reaction for both Cu and Pb in acidic and alkaline soils. All soils exhibited sorption/desorption hysteresis where Pb-releases ranged between <0.2% and 14.4% of the total sorbed. The respective Cu releases ranged from <0.85% and 23.4%. The multireaction model, which was successful in describing Cu and Pb for all ten soils, provided insight into the processes of sorption/desorption of Cu and Pb in all soils.

APA, Harvard, Vancouver, ISO, and other styles

7

Berez, A., F. Ayari, N. Abidi, G. Schäfer, and M. Trabelsi-Ayadi. "Adsorption-desorption processes of azo dye on natural bentonite: batch experiments and modelling." Clay Minerals 49, no. 5 (December 2014): 747–63. http://dx.doi.org/10.1180/claymin.2014.049.5.10.

Full text

Abstract:

AbstractThe purpose of this study was to determine whether a bentonite from the Gafsa deposit (western Tunisia) could be used to remove the Foron Blue 291 (FB) azo dye from wastewater. Batch adsorption and desorption experiments were conducted using untreated and purified bentonite and the influence of contact time, pH, adsorbent mass and temperature of the dye solution on the adsorption of FB was evaluated. Kinetic and isotherm data were fitted using two non-linear kinetic and two non-linear isotherm equations. In addition, the fits were evaluated using the coefficient of determination (R2) and the RMSE. The percentage of dye removal increased with increasing amount of adsorbent until total discolouration was achieved. The adsorption isotherms followed the Langmuir model, with the purified bentonite having a higher adsorption capacity than the raw material due to its higher specific surface area. In addition, the FB molecules were removed from the liquid medium by physical adsorption. Batch desorption experiments were conducted to study the desorption kinetics and the characteristics of the desorption isotherms as well as to quantify the portion of the FB (by mass) that was irreversibly fixed on the solid. Overall, the desorption kinetics were similar to the adsorption kinetics, which indicated that the adsorption-desorption process of azo dye is non-singular; irreversibility occurred that was underlined by an observed thermodynamic index of irreversibility (TII) of 0.69–0.94. The desorption isotherms of the FB depended on the mass of the FB that was initially adsorbed on the bentonite sample, suggesting hysteresis. The amount of irreversibly retained FB was between 46 and 68% of the initial adsorbed mass.

APA, Harvard, Vancouver, ISO, and other styles

8

Korovin, Vadym, Oleksandr Valiaiev, Oleksandr Zontov, Larysa Zontova, Volodymyr Pilchyk, and Borys Pysmennyi. "Uranium (VI) sorption from sulphuric solutions by AM-p-2 anionite." E3S Web of Conferences 109 (2019): 00039. http://dx.doi.org/10.1051/e3sconf/201910900039.

Full text

Abstract:

Research results were presented for equilibrium and kinetics of uranium sorption by AM-p-2 strong-base anionite from model sulphuric solution. Kinetic experimental data agreed with the pseudo second-order model while equilibrium ones – with the modified Langmuir-Freundlich equation. Testing of the anionite including sorption-desorption process operations used at uranium-mining industrial facilities showed that the resin had high sorption-desorption characteristics.

APA, Harvard, Vancouver, ISO, and other styles

9

Al-Ameri, Baydaa H. A. "Boron Desorption Kinetic in Calcareous Soils." Journal of Agricultural Science 11, no. 5 (April 15, 2019): 525. http://dx.doi.org/10.5539/jas.v11n5p525.

Full text

Abstract:

Boron release (desorption) is one of the important factors use in estimating fertilizers use efficiency and management of boron in agricultural soils and correlation soil properties with it availability to plant. Chemical kinetics for boron desorption experiment was carried out of boric acid (source for boron fertilizer) under controlled conditions in three calcareous soils (clay, loamy and sandy loam) from central Iraq at three temperatures (278, 298 and 308 Kelvin), by using six mathematical and empirical equations viz. Zero order, First order, Second order, Parabolic diffusion, Power function and Elovich equation were used to study kinetic behavior of boron in calcareous soils. Elovich equation was the best for predication and describing boron released with highest correlation r = 0.942 and t value (9.004), and lowest SE.e (0.530) where boron release rate constant (K) was positively correlated with temperature (r = 0.978). Released rate constant (K) was increased from 0.329 to 0.561 hrs-1 as increasing incubation temperature from 278 to 308 K. Soils texture effect in boron release activation energy (Ea) in three soils under study. The overall average of boron release activation energy of three soils was 15.284 and the highest was 20.923 in clay soil and the lowest amount was 4.596 in sandy loam while loamy soil gave 20.332 KJ mol-1.

APA, Harvard, Vancouver, ISO, and other styles

10

Cruz-Tirado, JP, Arnold Cabanillas, Raúl Siche, J. Espina, Leonardo Díaz-Sánchez, and Albert Ibarz. "Bleaching of sugar cane juice using a food-grade adsorber resin and explained by a kinetic model describing the variation in time of the content of adsorbate." Food Science and Technology International 24, no. 3 (December 14, 2017): 264–74. http://dx.doi.org/10.1177/1082013217747711.

Full text

Abstract:

This work studies the adsorption of colored compounds in cane juice using a food-grade macroporous adsorber resin without functional groups. The adsorption equilibrium was studied through the adsorption isotherms at 30, 40, and 50 ℃. The absorbance at 420 nm was used to measure the concentration of colored compounds, which enables correlation of the residual concentration with the adsorbed concentration. Furthermore, the efficiency of the adsorption process was studied, from which it was observed that there was an improvement in efficiency with increasing resin content, while the increase in temperature was less important in the process. The kinetic study was performed using the Ibarz model and intraparticle diffusion model, which correctly account for the kinetics of the adsorption process. The adsorption kinetic constant was always greater than the desorption kinetic constant, indicating that the adsorption step predominates over the desorption step.

APA, Harvard, Vancouver, ISO, and other styles

11

Spinicci, R. "Desorption kinetic parameters as deduced from temperature programmed desorption curves." Journal of Thermal Analysis 30, no. 1 (January 1985): 293. http://dx.doi.org/10.1007/bf02128137.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

SMITH, R. SCOTT, and BRUCE D. KAY. "MOLECULAR BEAM STUDIES OF KINETIC PROCESSES IN NANOSCALE WATER FILMS." Surface Review and Letters 04, no. 04 (August 1997): 781–97. http://dx.doi.org/10.1142/s0218625x97000766.

Full text

Abstract:

Studies of the properties of crystalline ice and amorphous solid water are the focus of considerable diverse and interdisciplinary research. The reasons include understanding heterogeneous atmospheric processes, interstellar and cometary astrophysics, cryobiology, and the physics and chemistry of liquids. In this review we summarize our recent work using nanoscale ice films to characterize the kinetic behavior of crystalline ice and amorphous solid water. The adsorption, desorption, crystallization and diffusion kinetics of the nanoscale films are studies using molecular beam and programmed desorption techniques. The results of these experiments and their implications for the physical properties of nanoscale ice films are presented.

APA, Harvard, Vancouver, ISO, and other styles

13

Reddy, Krishna N., and Martin A. Locke. "Sulfentrazone sorption, desorption, and mineralization in soils from two tillage systems." Weed Science 46, no. 4 (August 1998): 494–500. http://dx.doi.org/10.1017/s0043174500090950.

Full text

Abstract:

Sulfentrazone sorption kinetics, desorption, and mineralization were evaluated in surface 7.5 cm of soils collected from long-term conventional-till (CT) and no-till (NT) plots. The soils used were Miami silt loam and Drummer silty clay loam from Illinois and Dundee silt loam from Mississippi. Sulfentrazone sorption kinetics in Dundee silt loam CT and NT soils were adequately described by a simple two-site equilibrium/kinetic model. Rapid initial sorption (within 1 h) was followed by a slower sorption and equilibrium, largely achieved by 72 h of shaking, with a negligible increase in sorption thereafter. The sorptionKfranged from 1.02 to 3.44 among the six CT and NT soils. TheKfvalues were greater for NT compared to their respective CT soils. Overall,Kfvalues were higher in Drummer silty clay loam followed by Dundee silt loam and Miami silt loam soil. TheNvalues were less than unity in all soils indicating nonlinear sorption. Sulfentrazone desorption was hysteretic with a very low rate of desorption. The total amount desorbed in four desorptions ranged from 58 to 72% of that sorbed. Less than 2.1% of applied14C-sulfentrazone was mineralized to14CO2 in Dundee silt loam CT and NT soils during a 77–d incubation. Relatively low mineralization of sulfentrazone suggests poor adaptability of native microbial populations that have not been exposed to this herbicide. Higher sorption and lower desorption of sulfentrazone in NT soils compared to CT soils suggest that NT systems (which tend to increase plant residues) may prolong sulfentrazone residence time in soil.

APA, Harvard, Vancouver, ISO, and other styles

14

Filippova, Nadezhda L. "Kinetic-Diffusion-Controlled Adsorption and Desorption Kinetics on Planar Surfaces." Journal of Colloid and Interface Science 206, no. 2 (October 1998): 592–602. http://dx.doi.org/10.1006/jcis.1998.5771.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

M.F. Ledoh, Sherlly, Hermania Em Wogo, and Siti Arianti S.A. "LAJU ADSORPSI DAN DESORPSI PARAQUAT PADA TANAH PERTANIAN DESA OESAO KECAMATAN KUPANG TIMUR." Molekul 5, no. 1 (May 1, 2010): 1. http://dx.doi.org/10.20884/1.jm.2010.5.1.70.

Full text

Abstract:

The research about determination of kinetic adsorption and desorption rate of paraquat on agriculture area Oesao-east Kupang has been done. The aim of this research was to determine the kinetic of paraquat adsorption before and after saturated and to model the desorption. The research consisted of evaluation of the analitycal procedure for paraquat, pattern of soil kinetic adsorption and paraquat desorption. The result of procedure evaluation showed that reduced paraquat absorbed at λ maximum 606 nm and relative stability at 0-150 minutes. Constant of paraquat kinetic adsorption at natural state bigger than saturated state. k1 value at natural state was 0,011 per minute whereas k1 value at saturated state was 0,003 per minute. Desorption model of paraquat by using three desorbents were ammonium chloride, 29,2% of sea water salinity and aquadest showed the best desorbent was ammonium chloride, followed by sea water and aquadest.

APA, Harvard, Vancouver, ISO, and other styles

16

Liu, Yongfeng, Jianjiang Hu, Zhitao Xiong, Guotao Wu, and Ping Chen. "Improvement of the hydrogen-storage performances of Li–Mg–N–H system." Journal of Materials Research 22, no. 5 (May 2007): 1339–45. http://dx.doi.org/10.1557/jmr.2007.0165.

Full text

Abstract:

Li2MgN2H2 can reversibly store more than 5.5 wt% hydrogen. However, the high activation energy of hydrogen desorption poses a kinetic barrier for low-temperature operation. In this work, the composition of the Li–Mg–N–H system has been modified by the partial substitution of Mg or Li by Na. The changes in structure and hydrogen absorption/desorption kinetics have been investigated. It was found that the peak temperature for hydrogen desorption was decreased by ∼10 °C, and that the hydrogen absorption/desorption isotherms were also significantly changed. Furthermore, the activation energy calculated by the Kissinger’s approach was reduced after the substitution of Mg or Li by Na. In addition, the different dehydrogenation structures were detected at different molar ratios of Mg, Li, and Na.

APA, Harvard, Vancouver, ISO, and other styles

17

Carotenuto, Gianfranco. "How 'Hydrophilic Sites' Work in Water Adsorption/Desorption by Natural Clinoptilolite." European Journal of Engineering Research and Science 4, no. 3 (March 28, 2019): 183–89. http://dx.doi.org/10.24018/ejers.2019.4.3.1197.

Full text

Abstract:

The kinetic mechanism of water adsorption/desorption on samples of natural clinoptilolite-K has been investigated by using an electrical method based on measurements of variation of AC current intensity during the time. In particular, a high-frequency sinusoidal voltage (5kHz) was applied to the sample (high frequency was required to avoid sample/electrode interface polarization phenomena) and the resulting AC micro-current intensity was monitored during the time. The sample was hydrated by exposition to a 75% humidity atmosphere, while dehydration was achieved by exposing the sample to activated silica gel in a close container or simply taking it in air. The hydration reaction followed a pseudo-zero-order kinetics, while the dehydration reaction followed a first-order kinetics both in air or dry atmosphere. The observed kinetic behaviors can be explained on the basis of a 'catalytic effect' of cations in both water adsorption and desorption from the 3D-framework walls.

APA, Harvard, Vancouver, ISO, and other styles

18

Carotenuto, Gianfranco. "How 'Hydrophilic Sites' Work in Water Adsorption/Desorption by Natural Clinoptilolite." European Journal of Engineering and Technology Research 4, no. 3 (March 28, 2019): 183–89. http://dx.doi.org/10.24018/ejeng.2019.4.3.1197.

Full text

Abstract:

The kinetic mechanism of water adsorption/desorption on samples of natural clinoptilolite-K has been investigated by using an electrical method based on measurements of variation of AC current intensity during the time. In particular, a high-frequency sinusoidal voltage (5kHz) was applied to the sample (high frequency was required to avoid sample/electrode interface polarization phenomena) and the resulting AC micro-current intensity was monitored during the time. The sample was hydrated by exposition to a 75% humidity atmosphere, while dehydration was achieved by exposing the sample to activated silica gel in a close container or simply taking it in air. The hydration reaction followed a pseudo-zero-order kinetics, while the dehydration reaction followed a first-order kinetics both in air or dry atmosphere. The observed kinetic behaviors can be explained on the basis of a 'catalytic effect' of cations in both water adsorption and desorption from the 3D-framework walls.

APA, Harvard, Vancouver, ISO, and other styles

19

Jansson, Mats, Mats Jonsson, and Joel Mohlén. "Kinetic evaluation of sorption and desorption." Adsorption 16, no. 3 (February 12, 2010): 155–59. http://dx.doi.org/10.1007/s10450-010-9208-3.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Kanervo, J. M., K. M. Reinikainen, and A. O. I. Krause. "Kinetic analysis of temperature-programmed desorption." Applied Catalysis A: General 258, no. 2 (February 2004): 135–44. http://dx.doi.org/10.1016/j.apcata.2003.08.019.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Seyedvakili, Farnaz, and Mohammad Samipoorgiri. "Thermo-kinetic investigation of heavy metal ions adsorption onto lignin considering coupled adsorption–desorption mechanisms: Modeling and experimental validation." International Journal of Modeling, Simulation, and Scientific Computing 09, no. 02 (March 20, 2018): 1850014. http://dx.doi.org/10.1142/s1793962318500149.

Full text

Abstract:

A coupled adsorption–desorption thermo-kinetic model is developed incorporating both adsorption and desorption reactions. A local pseudo-equilibrium condition at the interface of adsorbent and adsorbate bulk phases was used as isotherm equation which can even be applied for multi-pollutants scenarios. The developed model is then validated using collected experimental data of heavy metal ions (Pb, Cu, Cd, Zn, and Ni). Comparisons were made for a number of isotherm and kinetic models to examine the performance of the proposed model. The developed model revealed desirable accuracy and superiority over other models in predicting the adsorption behavior and can be used for other systems of concern. The model correlates the adsorption kinetic with an [Formula: see text] value of 0.9391 and desorption kinetic with an [Formula: see text] value of 0.9383. By application of the proposed model to any available adsorption datasets, the individual characteristics of adsorption and desorption can be determined.

APA, Harvard, Vancouver, ISO, and other styles

22

Yu, Caoming, Fang Wang, Yunlei Zhang, Leihong Zhao, Botao Teng, Maohong Fan, and Xiaona Liu. "H2 Thermal Desorption Spectra on Pt(111): A Density Functional Theory and Kinetic Monte Carlo Simulation Study." Catalysts 8, no. 10 (October 12, 2018): 450. http://dx.doi.org/10.3390/catal8100450.

Full text

Abstract:

Theoretical investigation of the static and kinetic behaviors of H and H2 on metal surface plays a key role in the development of hydrogenation catalysts and new materials with high H2 storage capacity. Based on the density functional theory (DFT) calculation of H and H2 adsorption on Pt(111), H(a) adatom strongly interacts with surface Pt; while H2 weakly adsorbs on Pt(111). H(a) adatoms stably occupy the face-centered cubic sites on Pt(111) which agrees with the experimental LERS observations. By using kinetic Monte Carlo (kMC) simulation, the qualitative effects of the kinetic parameters on the H2 TDS spectra indicate that the H2 desorption peaks shift to the low temperature with increasing pre-exponential factor and decreasing desorption barrier. Simultaneously, the desorption peaks shift downwards and broaden to two peaks with the increase of the lateral interaction energy among H(a) adatoms. Using the kMC simulation based on DFT calculation, the predicted H2 TDS spectra are well consistent with the experimental ones. It unanimously proves that the two peaks of TDS spectra are derived from the lateral interactions among H(a). This work provides the intrinsic kinetics of H(a) and H2 on Pt(111) at an atomic level, and gives insight into the development of hydrogenation catalysts.

APA, Harvard, Vancouver, ISO, and other styles

23

Zhang, Zhen Yu, Jun Meng, Shu Dang, Ming Chao Gao, and Wen Fu Che. "Research on Cadmium Adsorption-Desorption Dynamics of Biochar." Advanced Materials Research 726-731 (August 2013): 179–83. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.179.

Full text

Abstract:

This research studies the effect of cadmium adsorption-desorption kinetics with different pyrolysis temperature biochar. The biochar which derived from rice husk at 300°C, 400°C, 500°C temperature for 30 minutes were added into Cd2+ solutions of 0.5 mg/L, 2.5 mg/L and 5 mg/L respectively. The optimal model of cadmium adsorption desorption kinetic behavior is the Level 1 dynamic equation. Indicates the increasing Cd2+ adsorption ability of biochar with pyrolysis temperature rising. Biochar also shortens adsorption process at relatively low Cd2+ initical concentrations.

APA, Harvard, Vancouver, ISO, and other styles

24

Barbero, Giovanni, Antonio M. Scarfone, and Luiz R. Evangelista. "The Kinetics of Sorption–Desorption Phenomena: Local and Non-Local Kinetic Equations." Molecules 27, no. 21 (November 5, 2022): 7601. http://dx.doi.org/10.3390/molecules27217601.

Full text

Abstract:

The kinetics of adsorption phenomena are investigated in terms of local and non-local kinetic equations of the Langmuir type. The sample is assumed in the shape of a slab, limited by two homogeneous planar-parallel surfaces, in such a manner that the problem can be considered one-dimensional. The local kinetic equations in time are analyzed when both saturation and non-saturation regimes are considered. These effects result from an extra dependence of the adsorption coefficient on the density of adsorbed particles, which implies the consideration of nonlinear balance equations. Non-local kinetic equations, arising from the existence of a time delay characterizing a type of reaction occurring between a bulk particle and the surface, are analyzed and show the existence of adsorption effects accompanied by temporal oscillations.

APA, Harvard, Vancouver, ISO, and other styles

25

Brar, B. S., and A. C. Vig. "Kinetics of phosphate release from soil and its uptake by wheat." Journal of Agricultural Science 110, no. 3 (June 1988): 505–13. http://dx.doi.org/10.1017/s0021859600082071.

Full text

Abstract:

SummaryLaboratory and glasshouse experiments were conducted to study P release kinetics and uptake of P by wheat (Trilicum, aestivum L.) in ten benchmark soils of Punjab (India). Phosphorus desorption, determined by successive extraction with 0·01 m-CaCl2 solution, was lower in calcareous soils (group I) than in non-calcareous soils (group II). Desorption of surface P in soils followed pseudo-first-order kinetics. The values of the kinetic constant of desorption and the radial diffusion coefficient of P increased with the amount of added P in soils.A significant linear relationship between cumulative desorbed P and both dry-matter yield and P uptake indicated that the rate of release of P from the solid matrix is important in determining P uptake by wheat crop. Phosphate uptake was less dependent on the initial solution P concentration than on the rate of phosphate release.

APA, Harvard, Vancouver, ISO, and other styles

26

Ермоченков and Mihail Ermochenkov. "Kinetics of drying and moistering of wood." Forestry Engineering Journal 6, no. 4 (May 3, 2017): 161–67. http://dx.doi.org/10.12737/23451.

Full text

Abstract:

The article presents the results of experimental and computational studies of the kinetics of drying of different types of wood in a helium environment. Wood is considered as a multi-component composite, one component of which is free and bound moisture. A model describing the removal of bound moisture, as a set of direct (desorption) and reverse (sorption) processes is described. The experimental-computational method for determining the kinetic parameters of sorption is suggested. They are determined from the condition that the rate of sorption and desorption is equal with equilibrium moisture content of wood.

APA, Harvard, Vancouver, ISO, and other styles

27

Ren, Jie, Yin Shan Lou, Hai Kuan Yuan, and Lian Shen. "Relationships Between Acidity and Catalytic Performance of Solid Acid in Synthesis of Linear Alkyl Benzene (LAB)." Advanced Materials Research 233-235 (May 2011): 1447–50. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.1447.

Full text

Abstract:

Through the benzene alkylation experiments with long chain olefin over solid acid catalysts activated at different temperature in the fixed-bed reactor, the kinetics of alkylation reaction and the deactivation kinetics of catalyst were established. The results showed that the activity and stability of catalyst decreased with increasing the activation temperature of catalysts. The reaction rate constant (k) and the deactivation rate constant (kd) of catalyst in kinetic models were also estimated through the optimization method, respectively. The acidity of catalyst was characterized by ammonia (NH3)-temperature programmed desorption (TPD), and the desorption kinetics of NH3was obtained. The characterization results showed that the acid amount or the acid density gradually decreased, while the desorption activation energy or the acid strength increased, as the activation temperature of catalyst increased. In addition, the relationships between the acidity and catalytic performance of catalysts were correlated. It was found that the catalyst with higher acid amount and the lower acid strength on the surface exhibited the better catalytic performance and stability.

APA, Harvard, Vancouver, ISO, and other styles

28

Luo, Li Jun, Ping Bao Ban, Xue Jiao Huang, and Jun Hong Li. "Functionalized Mesporous Silica with Ethylenediamine for Removal of Pb(II)." Applied Mechanics and Materials 395-396 (September 2013): 610–14. http://dx.doi.org/10.4028/www.scientific.net/amm.395-396.610.

Full text

Abstract:

Amine-functionalized mesporous silicas ((referred as NH2MS)) were synthesized by grafting with ethylenediamine. The obtained materials have been characterized by N2 adsorption desorption measurement (BET). Adsorption behaviors of the adsorbent for lead (containing effects factors, kinetics, isotherms, thermodynamics) were investigated. The result indicated that the obtained particles possessed mesoporous structrure. The Pb (II) adsorption isotherm and kinetic data fit Freundlich model and the pseudo second-order kinetic model respectively. the adsorption of Pb (II) onto NH2-MS was an enothermic nature.

APA, Harvard, Vancouver, ISO, and other styles

29

Elkhatib, E. A., A. M. Mahdy, and N. H. Barakat. "Thermodynamics of copper desorption from soils as affected by citrate and succinate." Soil and Water Research 2, No. 4 (January 7, 2008): 135–40. http://dx.doi.org/10.17221/2110-swr.

Full text

Abstract:

Desorption of Cu and low molecular weight dissolved organics are the primary factors that impact fate and transport of Cu in soils. To improve predictions of the toxicity and threat from Cu contaminated soil, it is critical that time-dependent desorption behaviour be understood. In this paper, the effect of organic ligands citrate and succinate on the kinetics of Cu desorption from contaminated soils varying widely in soil characteristics was investigated at three different temperatures. The results showed that the first order equation adequately described the kinetics of Cu desorption from clay and sandy soils under isothermal conditions. The reaction rate constant (k<sub>d</sub>) values of the first order kinetic equation for Cu desorption increased consistently with temperature, indicating faster release of Cu at higher temperatures. The Cu desorption rate from the studied soils at all three temperatures was as follows: citric > succinic. The E<sub>a</sub>values indicates that Cu desorption from the studied soils in the presence of two organic ligands is a diffusion controlled reaction. The negative values of ΔH* suggest that the desorption reactions are not energy consuming process. The higher negative values of (ΔH*) for Cu desorption from the studied soils in the presence of succinic ligand indicate that the heat energy required to overcome the Cu desorption barrier was greater than that for Cu desorption in the presence of citric ligand. Computation of the free energy of activation (ΔG*) yielded values ranging for 87 to 87.9 kJ/mol. The largest value represents ΔG* for Cu desorption for clay soil in the presence of succinic acid while the lowest value represents ΔG* for Cu desorption for sandy soil in the presence of citric acid. The information in this study is quite necessary to construct full functioning models that will help scientists to better understand mobility and bioavailability of metals in soils.

APA, Harvard, Vancouver, ISO, and other styles

30

Mejías, Carmen, Juan Luis Santos, Julia Martín, Irene Aparicio, and Esteban Alonso. "Thermodynamic and Kinetic Investigation of the Adsorption and Desorption of Trimethoprim and Its Main Metabolites in Mediterranean Crop Soils." Molecules 28, no. 1 (January 3, 2023): 437. http://dx.doi.org/10.3390/molecules28010437.

Full text

Abstract:

The adsorption–desorption processes of organic pollutants into the soil are one of the main factors influencing their potential environmental risks and distribution in the environment. In the present work, the adsorption–desorption behavior of an antibiotic, trimethoprim (TMP), and two of its main metabolites, 3-desmethyltrimethoprim (DM-TMP) and 4-hydroxytrimethoprim (OH-TMP), were assessed in three Mediterranean agricultural soils with different physicochemical characteristics. Results showed that the adsorption kinetic is performed in two steps: external sorption and intraparticle diffusion. The adsorptions of the studied compounds in soils were similar and fitted to the three models but were better fitted to a linear model. In the case of DM-TMP and OH-TMP, their adsorptions were positively correlated with the soil organic matter. In addition, desorption was higher in less organic matter soil (from 1.3 to 30.9%). Furthermore, the desorptions measured for the TMP metabolites were lower than those measured in the case of TMP (from 2.0 and 4.0% for OH-TMP and DM-TMP, respectively, to 9.0% for TMP).

APA, Harvard, Vancouver, ISO, and other styles

31

Kim, Yanghwa, Ocktaeck Lim, and Hongsuk Kim. "Determination of Chemical Kinetic Parameters for Adsorption and Desorption of NH3 in Cu-Zeolite Used as a DeNOx SCR Catalyst of Diesel Engines." Catalysts 12, no. 8 (August 19, 2022): 917. http://dx.doi.org/10.3390/catal12080917.

Full text

Abstract:

Ammonia-based selective catalytic reduction is one of the most effective NOx reduction technologies for diesel engines, but its low NOx reduction efficiency under low-temperature conditions needs further improvement. Previous studies have broadened our understanding of the NH3 adsorption and desorption that occurs in an SCR catalyst of Cu ion-exchanged zeolite. However, many studies conducted to data on the control of the NH3 adsorption and desorption in SCR catalysts have considered a simple chemical reaction related to a single acid site. This study demonstrates a detailed process for determining the chemical kinetic parameters of the adsorption and desorption of NH3 for different types of acid sites of a zeolite catalyst. The determined chemical kinetics parameters will be used for more effective control of the SCR system in future studies.

APA, Harvard, Vancouver, ISO, and other styles

32

Haug, C. "Generalized kinetic theory of sticking and desorption." Zeitschrift f�r Physik B Condensed Matter 94, no. 3 (September 1994): 319–30. http://dx.doi.org/10.1007/bf01320685.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

García, V. J., J. M. Briceño-Valero, and L. Martinez. "Kinetic parameters from complex thermal desorption spectrum." Vacuum 48, no. 11 (November 1997): 941–45. http://dx.doi.org/10.1016/s0042-207x(97)00101-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Ibarz, A., S. Garza, A. Garvín, and J. Pagan. "Kinetics of Peach Clarified Juice Discoloration Process with an Adsorbent Resin." Food Science and Technology International 14, no. 5_suppl (October 2008): 57–62. http://dx.doi.org/10.1177/1082013208095327.

Full text

Abstract:

This paper deals with the effects of adsorbent resin upon kinetic process of peach juice adsorption de-coloration at different temperatures ranged from 10 °C to 50 °C. The adsorption equilibrium was quantified by means of adsorption isotherms in the range from 10 °C to 50 °C. Absorbance data at 420 nm were used to plot all the isotherms, which correlated reasonable well with the Freundlich and Langmuir isotherms. Also, the efficiency of the adsorption process was studied for different resin/juice ratios at different temperatures, from which it was observed that there was a notable improvement in efficiency as the resin content increased, while the increase in temperature was not so important in the process. The adsorption kinetics was also studied at 30 °C, for relationships of 1, 2, and 3 g resin/100g juice. A kinetic adsorption— desorption model in two simultaneous steps was proposed, where the adsorption step is considered as zero order and the desorption step as first order. This allows a global expression to be obtained that fits the experimental data appropriately to this kinetic type equation. The initial adsorption rate depended on the resin/juice relationship in such a way that the higher its value, the lower this relationship was. It was also shown that the equilibrium constant showed a similar tendency, its value being superior to the unit, which indicates that the retention stage over the resin prevails over the colored product desorption stage.

APA, Harvard, Vancouver, ISO, and other styles

35

Liu, Ting Yue, Su Shuang Nie, Tiao Yin, Xiao Ling Xu, and Chao Ying Shao. "Studies on Dynamic Adsorption and Desorption of Total Flavonoids with Ion-Exchange Fiber." Advanced Materials Research 415-417 (December 2011): 2016–23. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.2016.

Full text

Abstract:

The adsorption and desorption property of total flavonoids with ion-exchange fiber were studied. The kinetic study on dynamic adsorption and desorption indicates that the adsorption and desorption property of fiber is function of the concentration、pH value and flow velocity of column liquid. Flavonoids can be effectively desorbed by ethanol.

APA, Harvard, Vancouver, ISO, and other styles

36

Hu, Qili, Nan Chen, Chuanping Feng, Jing Zhang, Weiwu Hu, and Long Lv. "Kinetic studies of nitrate removal from aqueous solution using granular chitosan-Fe(III) complex." Water Science and Technology 73, no. 5 (November 24, 2015): 1211–20. http://dx.doi.org/10.2166/wst.2015.596.

Full text

Abstract:

In the present study, a granular chitosan-Fe(III) complex was prepared as a feasible adsorbent for the removal of nitrate from an aqueous solution. There was no significant change in terms of nitrate removal efficiency over a wide pH range of 3–11. Nitrate adsorption on the chitosan-Fe(III) complex followed the Langmuir–Freundlich isotherm model. In order to more accurately reflect adsorption and desorption behaviors at the solid/solution interface, kinetic model I and kinetic model II were proposed to simulate the interfacial process in a batch system. Nitrate adsorption on the chitosan-Fe(III) complex followed the pseudo-first-order kinetic model and kinetic model I. The proposed half-time could provide useful information for optimizing process design. Adsorption and desorption rate constants obtained from kinetic model I and kinetic model II were beneficial to understanding the interfacial process and the extent of adsorption reaction. Kinetic model I and kinetic model II implied that nitrate uptake exponentially approaches a limiting value.

APA, Harvard, Vancouver, ISO, and other styles

37

Moshfegh, A. Z., and K. H. Zakeri. "The Kinetic Study of H2S Formation and Desorption on the S/Pt(111) Surface by Computer Simulation." Surface Review and Letters 10, no. 05 (October 2003): 745–50. http://dx.doi.org/10.1142/s0218625x03005542.

Full text

Abstract:

In this investigation, we have studied the kinetics and mechanism of formation and desorption of H 2 S on the Pt (111) surface using a kinetic random walk model. The effect of temperature on the H 2 S formation was studied in the range of 85–150 K. It was observed that a maximum amount of H 2 S is formed at 90 K and the amount is reduced at higher temperatures. H 2 S production yield as a function of time at different initial sulfur coverage ranging from 0.02 to 0.33 ML (1 ML ≃ 1 × 1015 atoms/cm 2) was also examined. It was obvious that as the initial S coverage increases, the rate of H 2 S formation rapidly increases and reaches a maximum value and then declines gradually. Furthermore, according to our simulated TPD spectra, for β = 1 K/s the maximum desorption rate occurs at Tp = 107.2 K . In addition, analysis of simulated TPD spectra of H 2 S desorption showed in an activation energy of H 2 S desorption Ed = 27.2 kcal/mol . Finally, the obtained simulated results were compared with the experimental data reported very recently, showing excellent agreement.

APA, Harvard, Vancouver, ISO, and other styles

38

Wang, Zhihong, Zhigang She, Mijun Peng, Qiuling Yang, and Tao Huang. "Determining the adsorption and desorption properties of flavonoids found in Eucommia ulmoides Oliv. leaves using macroporous resin and acetylcholinesterase inhibitor screening." BioResources 16, no. 1 (November 24, 2020): 470–91. http://dx.doi.org/10.15376/biores.16.1.470-491.

Full text

Abstract:

The adsorption and desorption properties of 12 resins containing flavonoid compounds found in Eucommia ulmoides Oliv. leaves (EUOL) extracts were investigated. The static adsorption and desorption, kinetic, adsorption, and thermodynamic properties of the adsorption of the flavonoids onto macroporous resins were determined. The HPD-300, NKA-9, and AB-8 resins exhibited a greater adsorption capacity and desorption characteristics. A pseudo-second-order kinetic model was suitable to characterize the kinetics of the adsorption of flavonoids onto the resins selected, and the diffusion of flavonoids was divided into three stages, with the boundary layer diffusion and intra-particle diffusion being the rate-controlling factors. The Langmuir model was found to be the best description of the adsorption behavior of flavonoids. Thermodynamic studies indicated that the adsorption of flavonoids was a physical, exothermic, and spontaneous process. The 60% ethanol eluted fraction from the NKA-9 resin column not only had the highest flavonoid content, but also possessed the strongest inhibitory effect on acetylcholinesterase. In addition, the degree of binding of the main flavonoid compounds found in the EUOL to acetylcholinesterase compounds was investigated via molecular docking technology. The results showed that the docking total score of isoquercetin and enzyme proteins were the highest, followed by kaempferol-3-O-rutinoside.

APA, Harvard, Vancouver, ISO, and other styles

39

Dickbreder, Tobias, Ralf Bechstein, and Angelika Kühnle. "Crucial impact of exchange between layers on temperature programmed desorption." Physical Chemistry Chemical Physics 23, no. 34 (2021): 18314–21. http://dx.doi.org/10.1039/d1cp01924d.

Full text

Abstract:

Kinetic modelling shows that layer exchange between the 1st and 2nd adsorbate layer on a surface alters the appearance of desorption spectra considerably. Especially, a rapid layer exchange causes a broader desorption peak and a flatter leading edge.

APA, Harvard, Vancouver, ISO, and other styles

40

Li, Zhongmin, Wanwan Wu, Wenyan Jiang, Guangtao Wei, Yunshang Li, and Linye Zhang. "Adsorption of Ni(II) by a thermo-sensitive colloid: methylcellulose/calcium alginate beads." Journal of Water Supply: Research and Technology-Aqua 68, no. 7 (August 16, 2019): 495–508. http://dx.doi.org/10.2166/aqua.2019.141.

Full text

Abstract:

Abstract The adsorption of Ni(II) by a thermo-sensitive adsorbent of methylcellulose/calcium alginate beads (CAMCBs) was studied using batch adsorption tests to determine the adsorption process and properties, the effects of adsorbent dosage, initial concentration, adsorption time and temperature. The adsorption process was further investigated using kinetics, isotherms and thermodynamic methods. The kinetics and isotherms studies showed the adsorption of Ni(II) on CAMCBs was fitted by the pseudo-second-order kinetic model and Langmuir isothermal adsorption model, respectively. The thermodynamic parameters indicated that the adsorption process was spontaneous and exothermic at lower temperature, and the entropy of the adsorption process was negative. In the study of regeneration, it was confirmed that under the temperature of 60 °C, the desorption agent of CaCl2 with concentration of 3 g·L−1 was more conducive to the desorption of Ni(II) from CAMCBs. Both adsorption capacity and mechanical strength of the used CAMCBs could be basically recovered to the level of fresh CAMCBs after desorption. The prepared CAMCBs had a good property of adsorption of Ni(II) and an excellent regeneration performance.

APA, Harvard, Vancouver, ISO, and other styles

41

Lívanský, Karel. "Kinetics of pH equilibration in solutions of hydrogen carbonate during bubbling with a gas containing carbon dioxide." Collection of Czechoslovak Chemical Communications 50, no. 3 (1985): 553–58. http://dx.doi.org/10.1135/cccc19850553.

Full text

Abstract:

The kinetics of the title process is approximated by differential equations based on kinetic and equilibrium data for carbon dioxide. The course of pH after a sudden change of the concentration of CO2 in the gas is calculated by numerical integration. The course of pH during absorption of CO2 is different from that during desorption. The course of pH during desorption calculated on the assumption that the rate of the noncatalysed hydration of CO2 is sufficient to ensure chemical equilibrium is in good agreement with experimental data from the literature. During absorption of CO2 in a solution of hydrogen carbonate, the chemical reaction rate is sometimes insufficient to ensure chemical equilibrium prior to pH measurement.

APA, Harvard, Vancouver, ISO, and other styles

42

Cheng, CY, JF Atkinson, and JV DePinto. "Desorption during resuspension events: Kinetic v. equilibrium model." Marine and Freshwater Research 46, no. 1 (1995): 251. http://dx.doi.org/10.1071/mf9950251.

Full text

Abstract:

The spills and release of hydrophobic organic chemicals (HOCs) into waterbodies have resulted in the contamination of bottom sediments. When these sediments are resuspended by runoff events or by dredging, particulate-phase contaminants desorb to the water phase. Equilibrium between the particulate phase and the dissolved phase is usually assumed for most modelling applications regardless of time scale. For well mixed systems in which chemical transport is not limited by mass transfer between the bulk water phase and sediment aggregates, an intraparticle diffusion model can be applied to estimate the time required for various HOCs to reach an equilibrium state between dissolved and particulate-phase concentrations. Calculations from this model show that total equilibrium time scales cover a wide range, from less than a day to a few hundred days. This study compares predicted suspension times for sediments of various sizes with expected equilibration times for desorption. This comparison indicates that the equilibrium assumption is not valid for a wide range of parameter values typical of natural systems. In particular, compounds with high partition coefficients, greater than about 104 mL g-1, will have minimum equilibration times of at least one to ten days. This is likely to be greater than the expected resuspension time.

APA, Harvard, Vancouver, ISO, and other styles

43

Geldart, D. J. W., H. J. Kreuzer, and Franz S. Rys. "Kinetic ising model for desorption from a chain." Surface Science Letters 176, no. 1-2 (October 1986): A552. http://dx.doi.org/10.1016/0167-2584(86)91053-4.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Geldart, D. J. W., H. J. Kreuzer, and Franz S. Rys. "Kinetic Ising model for desorption from a chain." Surface Science 176, no. 1-2 (October 1986): 284–94. http://dx.doi.org/10.1016/0039-6028(86)90176-7.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

García, V. J., J. M. Briceño-Valero, and L. Martinez. "Kinetic parameters from a single thermal desorption spectrum." Surface Science 339, no. 1-2 (September 1995): 189–93. http://dx.doi.org/10.1016/0039-6028(95)00608-7.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Sibold, D., and H. M. Urbassek. "Kinetic study of pulsed desorption flows into vacuum." Physical Review A 43, no. 12 (June 1, 1991): 6722–34. http://dx.doi.org/10.1103/physreva.43.6722.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Skryabina, N. E., Vladimir M. Pinyugzhanin, and Daniel Fruchart. "Relationship between Micro-/Nano-Structure and Stress Development in TM-Doped Mg-Based Alloys Absorbing Hydrogen." Solid State Phenomena 194 (November 2012): 237–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.194.237.

Full text

Abstract:

In the most recent years, MgH2has attracted considerable attention for reversible hydrogen storage purposes because of a large 7.6 w% H-uptake, single plateau reaction at low pressure and abundance of metal. If the Mg ↔ H reactions take place at rather high temperature (> 300°C), the kinetic remains very low. However, early transition metal based additives (Ti, V, Nb...) improve dramatically the kinetics of hydrogen absorption/desorption, while having no essential impact on the reversible sorption capacity. Systematic analysis of many experimental data led to question chemical, physical, mechanical... parameters contributing significantly to improve the kinetics of absorption/desorption. Besides, results of theoretical and numerical computation enlighten the impact of structural and mechanical parameters owing to the local bonds of Mg/MgH2with of TM elements, in terms of total energy and electronic structure. More specifically, we found highly relevant to consider 1 - the impact of the crystallite sizes of Mg and the TM-phase, 2 - the role of internal and external stresses, as well as 3 - the role of texture on the kinetics of hydrogen absorption/desorption. Apart the previous considerations, we like to underline the role of specific TM in trapping intermediately hydrogen thus forming TMHxprior initiating the Mg ↔ MgH2nucleation process.

APA, Harvard, Vancouver, ISO, and other styles

48

Ouyang, Qiu Lin, Gui Qing Gao, Su Su Liu, Xiao Ling Shi, and Hai Yan Ju. "Study on Adsorption and Desorption of Suspended Sediments to Phosphorus in Ganjiang River." Advanced Materials Research 599 (November 2012): 669–72. http://dx.doi.org/10.4028/www.scientific.net/amr.599.669.

Full text

Abstract:

Based on isothermal adsorption experiment and adsorption/desorption kinetic experiment,the adsorption and desorption characteristics of suspended sediments in Ganjiang River to phophorus was studied.The results show the phosphorus adsorption of sediment reaches balance basically in 2~4h; the adsorption capacity is increased with the increment of the initial concentration of phosphorus,and decreased with the increment of sediment conentration. The isothermal adsorption of phosphorus by sediment can be fitted preferably by Langmuir and Freundlic model. The adsorption and desorption process can be fitted by Langmuir equation.The phosphorus desorption of sediment reaches balance basically in about 14h. The phosphorus desorption capacity of sediment is decreased with the increment of sediment concentration.

APA, Harvard, Vancouver, ISO, and other styles

49

Pan, Feng, Zai Yuan Li, and Chun Ji Li. "Study on Kinetics of Nano-Ni(OH)₂Powder Ethanol Desorption Process." Advanced Materials Research 1015 (August 2014): 509–12. http://dx.doi.org/10.4028/www.scientific.net/amr.1015.509.

Full text

Abstract:

This paper studies on the thermal analysis kinetics of nanometer powders ethanol desorption process.The DTA-TG-DTG curves obtain by SDT 2960 Simultaneous DSC-TGA analysis apparatus. Under the condition of N2atmosphere operation and rise temperature velocity was 10°C·min-1. The mechanism functionis used to calculate the kinetics factors. Reaction progressionnwas obtained by calculation of the kissinger peak shape factor method. The results showed that the apparent activation energy of nano-Ni(OH)2was 73.210 kJ·mol-1, the pre-exponential factor was 2.349×1012, the reaction progression was obtained as 1.2767, the kinetic equation is

APA, Harvard, Vancouver, ISO, and other styles

50

Safarzadeh, Sedigheh, Sadegh Kasmaei, and Abadi Ahmad. "Effect of organic substances on iron-release kinetics in a calcareous soil after basil harvesting." Journal of the Serbian Chemical Society 83, no. 7-8 (2018): 941–52. http://dx.doi.org/10.2298/jsc171115019s.

Full text

Abstract:

Desorption of iron from soil is important for evaluating the availability and toxicity of soil Fe in agriculture. The aim of this investigation was to study the effect of organic substances (cow and sheep manures and vermicompost) on Fe release from a calcareous soil and determine the best models for the description of the Fe desorption kinetics. Organic substances were added to soils at the rate of 3 %. Basil (Ocimum basilicum L.) seeds were sown in each pot and pots were kept at 24?25?C at about field capacity for 90 days. After 90 days, plants were harvested and soil samples were used for Fe desorption analysis. Seven kinetic models were evaluated to describe the rate of Fe desorption in soil extracted with diethylenetriaminepentaacetic acid (DTPA). Results showed that Fe release from soil samples increased with time. Release of Fe was rapid at first and then became slower. Iron release in the organic substances treatments was higher than in the unamended soil and the two-constant rate, parabolic diffusion and simple Elovich models were the best equations for the description of Fe release from soils.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Desorption kinetic'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles