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Herein, activated semi coke (ASC) adsorbents were prepared and tested for SO2 adsorption-desorption process in a rotary reactor. The experiment results showed that the nitric acid activated semi coke (ASC-1) had a higher SO2 adsorption capacity and a better SO2 removal ability in the SO2 adsorption-desorption dynamic process. And the SO2 adsorption efficiency of ASC-1 in the dynamic SO2 removal process was increased from 57.5% to 88.3% at 200 °C with the extension of desorption time from 60 s to 180 s. Increasing the desorption temperature was an effective method to improve SO2 removal efficiency in the rotary reactor. The SO2 adsorption efficiency of ASC could be improved from 52.5% to 80.7% with the desorption temperature increasing from 100 °C to 300 °C. Moreover, the mechanisms of SO2 adsorption-desorption dynamic process over ASC in rotary reactor at different temperatures were also summarized. There were two desorption paths for SO2 species adsorbed on the ASC surface under the purge of desorption gas CO. One of the paths was that the weakly adsorbed SO2 and some –SO3- species were directly desorbed from ASC surface under the purge of CO, which was the dominant SO2 desorption path. And the other path, which was not activated at low temperature (

The injection of CO2 into a coal seam can effectively improve the recovery efficiency of coalbed methane. Existing CO2-enhanced coalbed methane(ECBM) is mainly focused on improving the physical recovery efficiency of free CH4. In macro experiments, it is difficult to simultaneously separate adsorbed CH4 and free CH4; therefore, there are few studies on using CO2 to improve the recovery efficiency of coal seams. In this study, the LF-NMR method was used to evaluate the transformation law of adsorbed and free CH4 during the CO2 injection process, and the enhancement of adsorbed CH4 recovery efficiency using CO2 was quantified. The results showed that adsorbed CH4 and free CH4 formed separate T 2 peaks, allowing them to be distinguished. The T 2 spectra of adsorbed CH4 (adsorbed on pore surfaces) were distributed between 0.01 and 2.247806 ms, whereas the T 2 spectrum of free CH4 (existing between the coal particles and the inner walls of sample cavities) were distributed between 15.702901 and 714.942899 ms. CO2 injection increased the total desorption efficiency of adsorbed CH4 by 19.89%, the desorption efficiency of adsorbed CH4 per unit time by 14.108% and the amount of CH4 desorption per unit mass of coal by 35.23%. The results of the study demonstrate that CO2 injection into a coal seam can significantly improve the recovery efficiency of adsorbed CH4 and shorten the CH4 desorption time; findings that are highly significant in relation to enhancing coalbed methane exploitation and CO2 geological storage.

Adsorption of heavy metal ions on chitosan-based adsorbents has been extensively investigated. However, few studies explored the feasibility of desorbing and regenerating chitosan. Adsorbents used after adsorption of heavy metals are discarded, and this practice exacerbates the solid treatment problem. Regeneration and reuse of exhausted adsorbents should be considered to operate environment-friendly and cost-effective adsorption. This review was performed to summarize the desorption of heavy metal ions and possible regeneration of chitosan-based adsorbents using various desorption agents such as acids, alkalis, salts, and chelating agents. It was found that the highest desorption efficiencies obtained by acidic eluents. The percentage use of desorption agents for desorbing followed the order of acids (49.3%) > chelators (26.9%) > alkalis (14.9%) > salts (8.9%). Moreover, the proper desorption time were estimated to be 0.84 by 1.37 h. Beneficial information is provided for regeneration and recovery of chitosan adsorbents.

This study evaluated the NOx adsorption and desorption performance as well as the casual relationship underlying a Mn-incorporated catalyst (Pt/Ba/Ce/xMn/γ-Al2O3). NOx adsorption and desorption are regarded as a prominent index for the NOx removal performance of NOx storage and reduction; we utilized NOx storage experiments with various inlet NO and O2 concentrations and cycling adsorption/desorption experiments with a couple of adsorption time protocols for performance evaluation. In-suit DRIFT and NOx-TPD tests were implemented to reveal the instant stored species and their thermal stability. Eight percent of Mn catalyst at 350 °C was adopted in the described experiments for its desirable NOx adsorption characteristics. The optimal NOx storage performance was found under 10% O2, deteriorating when the concentration was further increased. Furthermore, elevating NO concentration impaired the NOx adsorption due to the low NO2/NOx ratio. It was also found that shorter adsorption time facilitated NOx removal via maintaining an unsaturated state for active storage components in terms of a fixed desorption time. The stored species existed as nitrites and nitrates with a good low-temperature thermal stability which however decayed at higher temperatures as exhibited in the DRIFT and NOx-TPD tests. These findings provided invaluable information for the application of Mn-incorporated catalyst for NOx removal in diesel exhaust purification to relieve the aerial pollution.

In this study, preparation and regeneration of methyl cellulose/calcium alginate beads (MC/CABs), a thermo-sensitive adsorbent material, have been introduced. The effects of preparation parameters, including mass ratio of methyl cellulose to calcium alginate, CaCl2 concentration, stirring speed and calcification time, on the adsorption property and the compressive strength of MC/CABs have been investigated in detail. The optimum parameters were obtained as follows: mass ratio of MC to SA was 1:1; CaCl2 concentration of calcification solution was 0.05 g/mL; stirring speed was 200 r/min; and calcification time was 240 min. As for the MC/CABs prepared under the optimum conditions, its difference of adsorption ratio of MB between 30 and 60 °C was about 57.84%, and its compressive strength reached 0.710 N. The formation mechanism and regeneration mechanism of MC/CABs have been presented in the work. In addition, CaCl2 as the desorption agent has better regenerative properties than Ca(C3H5O3)2 and Ca(CH3COO)2. Under the regeneration conditions of calcium concentration 0.01 g/mL, deionized water 50 mL, desorption temperature 60 °C and desorption time 15 min, both adsorption capacity and compressive strength of the used MC/CABs could be basically recovered to the level of fresh MC/CABs after the regeneration. The effects of preparative parameters on the property of MC/CABs, a thermo-sensitive adsorbent material, have been investigated. The optimal preparation and regeneration conditions were obtained, and the formation mechanism and regeneration mechanism of MC/CABs were also presented.

A method for the hydrocarbon content in nanometer size pores adsorbed gas in unconventional reservoir rocks using gas chromatography (GC-FID) has been established in this paper. The experiment of gas desorption from nanometer size pores using a device for preparing nanometer size rock samples and gas desorption has been carried out to determine the most favorite experiment conditions. The result shows that the best desorption time is about 20 min with the temperature at 80°C and the sample weight of 20 g. The test conditions for gas chromatography are as follows: an OV-101 GC column with carrier gas flow rate at 40 mL/min; the temperature of GC oven began at 50°C for 0.5 min and then increased to 100°C at 10°C/min, with the final temperature being maintained for 5 min. The parallel test shows that the method introduced here is characterized by quickness, accurateness, and high sensibility with relative testing error less than 9.99% (the least is 2.18%). We have tested 19 rock samples from 11 wells...

International audience; In this paper are reviewed the main reported trends of Al incorporation as a function of the main 4H-SiC epitaxial growth parameters. Al incorporation was found to be limited by its high desorption rate for all the parameters investigated. Due to the lack of a general model describing reasonably the processes of Al incorporation, the concept of surface vacancy induced incorporation was proposed and applied to explain these experimental results. In this model, Al incorporation is mainly driven by the transient formation of Si vacancies at the surface or sub-surface of terraces. It was shown that for increasing Al incorporation, one needs to improve its stability upon adsorption on Si vacancy and/or to reduce its desorption time. In this model, the transient formation of C vacancies at the surface or sub-surface (favored at low C/Si ratio) is proposed to play also a role by destabilizing the incorporated Al atoms.

This paper deals with nitrogen dioxide gas sensor based on multi-wall carbon nanotubes functionalized by carboxyl groups. The carbon nanotubes were non-covalent modified by lead phthalocyanine. The modification showed improvement of important sensor properties. Sensitivity change is 50 % from original value under exposure to 10 ppm of nitrogen dioxide. The dynamic properties of sensor are much better in comparison with non-modified carbon nanotubes. Gas desorption was accelerated by UV illumination and desorption time is shortened to several seconds.

In this work, Tenax consecutive extractions of polycyclic aromatic hydrocarbons (PAHs) were conducted in two spiked sediments to investigate the influence of different Tenax addition amounts and desorption times on the rapidly desorbing fraction of PAHs, and to determine a reliable method for estimating PAHs bioavailability. The results indicated that a large Tenax addition amount has a positive effect on the desorption of PAHs from sediments. The desorption amounts of target PAHs compounds (3-ring phenanthrene and 4-ring fluoranthene) increased as the Tenax: sediment ratios increased from 0.25 to 2 in two spiked sediments. The highest desorption percentages of phenanthrene and fluoranthene were 48.91% and 34.70% for Jialing industrial park sediment, and 43.36% and 33.24% for Huanghuayuan bridge sediment, respectively. The results of desorption kinetics were suitably fitted with first order three-compartment model to estimate the rapidly desorbing fraction, Moreover, the Tenax: sediment ratio of 1 and desorption time of 24 h were found to be suitable for the desorption of phenanthrene and fluoranthene from sediments. The PAHs in sediments were biodegraded well by the bacterial strain J1-q. Comparing the maximum biodegraded amount of target PAHs in 30 days and the desorbed fraction over 400 h, the results showed that Tenax had better correlation with the high molecular weight fluoranthene than with the low molecular weight phenanthrene.

A novel solar water-bath solid adsorption ice-making system with activated carbon-methanol as adsorption working pairs was designed and constructed. The experimental results demonstrated that the desorption temperature and the desorption time had important influences on performance of the ice-making system. The daily ice-making capacity of 5.1 kg and refrigeration cycle coefficient of performance (COP) of 0.0322 could be obtained when the desorption temperature was maintained at 94 °C. However, there were no ice-making phenomenon when the desorption temperature was respectively maintained at 85 °C and 75 °C. With the increasing of desorption time from 7 h to 12 h when the desorption temperature was maintained at 94 °C, the COP of the system dropped gradually from 0.0507 to 0.0370, and the heat utilization efficiency decreased from 0.5969 to 0.4608 due to the gradual increase of energy imported into the system. The daily ice-making capacity increased rapidly from 5.5 kg to 7.6 kg when the desorption time increased from 7 h to 10 h, however, the daily ice-making capacity increased slightly from 7.6 kg to 7.7 kg when the desorption time was increased from 10 h to 12 h. There was an optimal desorption time of 10 h for the system.

A solid-phase microextraction procedure followed by analysis by gas chromatography is proposed to determine surface flavouring content in encapsulated flavouring. The method showed a good selectivity, as well as good intraday and interday precision, CVs

Experimental data on the sorption extraction of uranium from fluorine-containing solutions on different types of modern ion-exchange absorbers and structures in order to improve the technological schemes for reprocessing wastes from radiochemical production are presented. The primary technological relations are studied and the optimal indices in static and dynamic regimes of sorption-desorption extraction of uranium from model systems simulating production fluorine-containing solutions are determined. A chelate-forming aminophosphonic cation-exchanger Purolite S950 with uranium capacity up to 20% is recommended. It is shown that uranium concentration in the waste ≤0.003 g/liter can be obtained. It is found that uranium desorption by a 15% solution of sodium carbonate is a highly efficient process with desorption time 10 h and degree of uranium desorption 99.92%.

Mixed amine solvents have gained increasing attention in recent years. The absorption and desorption performance of mixed amine solvents for CO2 were analyzed by experiments. The absorption rate, absorption load, and desorption rate were used as the evaluating index. The experiment results show that the smaller proportion of MDEA/DETA solvents is the higher absorption load and absorption rate are, but the final desorption degree does not rise. When the rate of TETA is high, it is helpful to improve absorption rate and reduce desorption time of MDEA + TETA, but it is not necessary to add excessive TETA into mixed amine solvents.

Based on spontaneous desorption characteristic, the correlation of desorption time and gas content was analyzed and the application of it in production was researched. The desorption of high rank coalbed methane in Qinshui basin was periodic, and isotope fractionation effect also exists in the process. Δδ13C1 can be used to distinguish the stabilization of coalbed methane wells, associated with desorption rate, the individual well recoverable reserves can be calculated. Economically recoverable time can be predicted according to the logarithmic relationship between desorption gas content per ton and desorption time. The error between predicted result and numerical simulation result is only 1.5%.

In this paper, feather was used to adsorb lead ions as a new type of adsorbent materials. For recycling feather, NaOH solutions as the desorption solutions were adopted to desorb feather after adsorption of lead ions, and then the factors which affect the desorption effect, such as desorption time, concentration of desorption solutions, temperature and so on were studied. It was found that the optimum desorption conditions are: the desorption time of 60min, the concentration of NaOH solutions of 30mmol/L, the temperature of 40°C.

Adsorption and desorption experiments for the binary mixture (N2/O2; 79:21 vol%) on zeolite 5A, 10X, and 13X beds were performed to study the dynamic characteristics of air separation adsorption processes. Because the breakthrough and desorption curves showed a tail by temperature variance in the beds, a nonisothermal dynamic model incorporating mass and energy balances was applied to the simulation of adsorption dynamics using the Langmuir–Freundlich model and the LDF approximation. The breakthrough and desorption results were compared among three different beds with respect to the breakthrough and desorption times, tailing effect, and temperature variation with the effects of pressure and flow rate. On the basis of the similar bed density, the order of breakthrough time and desorption time was zeolite 10X, 13X, and 5A beds. Also, the O2 MTZ of the zeolite 10X bed was slightly sharper than those of the zeolite 5A and 13X beds due to more favorable N2 isotherm of zeolite 10X. Furthermore, the breakthrough...

In the first of this two-paper series, a new model is presented that simulates the effects of a temperature perturbation on the rate of slow desorption as a function of mass remaining. The model assumes slow desorption is controlled by one-dimensional diffusion from a single or many hydrophobic micropores and that the micropores of a geosorbent are defined by a γ distribution of diffusion rate constants. Simulation results indicate that during slow desorption the relative increase in flux upon heating increases with decreasing micropore width. Simulation results also indicate that the relative increase in flux upon heating increases with desorption time when diffusion occurs from successively smaller width micropores with decreasing mass remaining. In paper 2, the model is tested and used to examine micropore geometry in natural and model solids by simulating results from temperature stepped desorption (TSD) experiments.

Sorption effects of a number of combinations of indoor materials and volatile organic compounds have been investigated. A limited number of experiments have been conducted to investigate the influence of parameters such as the adsorption time, the desorption time, the concentration of the pollutants and the temperature, on the sorption. Experiments were performed with vapours of single compounds and with mixtures of VOCs. All parameters have an influence on the sorption. A relatively quick screening method can be applied with mixtures of VOCs with a limited adsorption time and desorption time (6 h each). Air samples should be collected at the end of the adsorption time and during the desorption time. © Indoor Air (1998).

In this study, the use of capillary isoelectric focusing (cIEF) as a micropreparative tool for protein analysis by matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF-MS) is demonstrated. A newly designed, automated, collection interface equipped with a fiber-optic UV detector and a sheath flow connection was employed for collection of protein fractions. Multiple fractions were collected during a single cIEF run and further analyzed by MALDI-TOF-MS for mass assignment. The feasibility of the method was tested with a mixture of model proteins with different isoelectric points and molecular masses, and with variants of human hemoglobins differing in pI, but with negligible difference in Mr. Some practical considerations of the collection procedure and subsequent TOF analysis are presented.

Three systems of trace separation are used as case studies to investigate the effect of mass transfer during the blowdown step. The systems are simulated from start (clean columns) to cyclic steady state with the desorption step period equal to the adsorption step period as a base case. There is no difference between the case where mass transfer is accounted for and the case where the frozen solid condition is assumed. However, in the context of optimal operation there is a significant effect for some combinations of the desorption time period and the blowdown time period, but this effect depends on the specific system and the specification of the product purity. There is also a possible effect when the repressurization step is performed with product instead of feed.

Laser desorption time-of-flight (LD-TOF) mass spectrometry was utilized to determine the metabolic intermediates in microbial degradation of phenol. The identified components were in good agreement with the well-documented pathway. This technique also demonstrated excellent precision. Analytical merits, instrumentation and methodology are discussed.

The kinetics rule of adsorption and desorption of imazethapyr on Black soil and Planosol soil was studied. According to 10∶1 ratio of water and soil, adsorption-desorption kinetics of imazethapyr on Black soil and Planosol soil was studied by the batch equilibrium method at 25±2°C. The results showed that dual constant equation can describe well the adsorption and desorption kinetics of imazethapyr. Comparing with Planosol soil, the capacity of adsorption and desorption on Black soil was higher. Adsorption rate of Imazethapyr on two kinds of soil was higher than desorption rate. Adsorption rate and desorption rate of imazethapyr with higher initial concentration were higher than those with lower initial concentration. The adsorption rate and desorption rate of imazethapyr on Black soil were higher than those on Planosol soil. The desorption capacity of imazethapyr on Black soil and Planosol soil increased with the adsorption capacity before desorption, which showed significantly square power functional relationship between them. There was the same rule in kinetics of adsorption and desorption of imazethapyr on Black soil and Planosol soil. In the case of the same adsorption or desorption time, the adsorption or desorption capacity and adsorption or desorption rate of imazethapyr on Black soil were higher than those on Planosol soil. The desorption capacity of imazethapyr on Planosol soil was higher than that on Black soil, when the adsorption capacity before desorption was same. It was due to the organic matter content, pH vale and initial capacity of adsorption or desorption in the soil.

A multi-residual method is described for the simultaneous determination of 23 personal care products (PCPs), which display a wide range of physicochemical properties, present at trace levels in water samples. A one-step procedure was developed based on solid-phase microextraction (SPME) coupled with GC-MS analysis. A chemometric approach consisting of an experimental design (design of experiments) was applied to systematically investigate how four operating parameters--extraction temperature and time and desorption temperature and time--affect extraction recovery of PCPs in water. The optimum SPME procedure operating conditions, those yielding the highest extraction recovery for all the compounds, were determined; they correspond to an extraction time of 90 min and temperature of 80 °C and a desorption time of 11 min and temperature of 260 °C. Under these optimized conditions, the SPME procedure shows good analytical performance characterized by high reproducibility (RSD% intra-day accuracy varying in the 0.01-1.3% range) as well as good linearity and low detection limits (LODs lower than 2 ppb for most of the investigated PCPs).

We report on the kinetics of hydrogen absorption and desorption in magnetocaloric La(Fe,Si)13 materials based on experimental results and model calculations. In the model, the diffusion process is considered to take place dominantly in a hydriding or dehydriding reaction. An important parameter “characteristic absorption/desorption time” is introduced to predict the kinetics of hydriding/dehydriding reaction in a simple way. The application of the model on the La0.9Ce0.1Fe11.44Si1.56 compound gives coincident kinetic results with those determined from experiments. It indicates that the model provides an efficient guidance for measuring and comparing the kinetic property of the magnetocaloric La(Fe,Si)13Hy materials.

A complete fourth-order quantum-statistical calculation of the isothermal desorption time ${t}_{d}$ in a gas-solid system is presented showing localized physisorption including all one-phonon and two-phonon processes in fourth order. The multiphonon interaction terms arising from higher-order derivatives of the surface potential turn out to contribute significantly to the desorption rate. Extensive numerical work confirms that the relaxation time approach to desorption phenomena is acceptable for weakly coupled systems for which $\frac{h}{|{E}_{0}|}\ensuremath{\ll}{t}_{d}$ where ${E}_{0}$ is the energy of the bound state. Second-order calculations are sufficient as long as $|{E}_{0}|\ensuremath{\lesssim}{k}_{B}T\ensuremath{\lesssim}\ensuremath{\hbar}{\ensuremath{\omega}}_{D}$, where $\ensuremath{\hbar}{\ensuremath{\omega}}_{D}$ is the Debye energy of the solid. Fourth-order contributions become important for $|{E}_{0}|l\ensuremath{\hbar}{\ensuremath{\omega}}_{D}$ and ${k}_{B}T\ensuremath{\gtrsim}\ensuremath{\hbar}{\ensuremath{\omega}}_{D}$. Moreover, for $\ensuremath{\hbar}{\ensuremath{\omega}}_{D}\ensuremath{\le}|{E}_{0}|\ensuremath{\le}2\ensuremath{\hbar}{\ensuremath{\omega}}_{D}$ fourth-order terms are essential because second-order contributions are zero in this region of bound-state energies.

Event mixing, i.e. the effect of secondary ions being ascribed wrong desorption events and thus wrong flight times in fast heavy-ion-induced desorption time-of-flight mass spectrometry, is treated theoretically. It is shown to produce a considerable part of the background for start rates and data collection times typically used. Experiments with a modified data collection system support the theoretical predictions and result in lower background levels.

Caracterisation de polyoxyde d'ethylene ou de propene, de polyethyleneimine et de melanges d'oligomere

Certain important aspects of experimental design for the measurement of permeation time lags are considered, with particular reference to downstream desorption time lags of permanent gases permeating through microporous plugs. Some problems of earlier designs are discussed, a new one is given and its performance in practice is illustrated.

A two-dimensional hydrodynamic model of adsorbate behavior is modified by including the isothermal desorption. It is shown that for mobile adsorbates at reasonable temperatures and coverages it is the desorption which provides the dominant momentum nonconserving process and that the short-wavelength sound modes can propagate in the adsorbate provided desorption time is not too short.

Helium desorption is treated in a model where the film is assumed to have the thermodynamic properties of bulk liquid and the vapor is described by kinetic theory. Equations for energy and mass conservation determine the dynamics of the system. The model resolves some puzzling features of a number of experiments, and predicts a thermally activated desorption time constant in reasonable agreement with experiment, without adjustable parameters.

The subject of laser-stimulated desorption (LSD) has recently attracted considerable attention both experimentally and theoretically. Much of this attention comes from the prospects of possible applications of laser-stimulated catalytic processes at various solid surfaces. Should such processes (for example selective cleaning of the surface) require low power and be selective they would be enormously important technologically, particularly in microelectronics.

11 pages, 9 figures, 10 references., The reversibility of the adsorption of phosphate on goethite was measured by diluting suspensions of goethite on which phosphate was adsorbed with large volumes of phosphate-free solution at the same ionic strength. The effect on the reversibility of various adsorption and desorption conditions was studied, particularly pH, temperature, ionic strength and time of reaction. The apparent irreversibility of the adsorption reaction seems to be due to a slow adsorption reaction of part of the phosphate after a very rapid initial adsorption, with a similar behaviour when the phosphate is desorbed. When the total adsorption plus desorption time is long enough, both adsorption and desorption points tend to lie on a single curve which corresponds to the isotherm calculated according to the Stern double-layer theory.