sorption and desorption experiments

Top PDF sorption and desorption experiments:

CEC-normalized clay-water sorption isotherm

CEC-normalized clay-water sorption isotherm

[ 22 ] Water sorption in porous media almost ubiquitously exhibits hysteresis. This behavior may arise from any of the following effects: (a) capillary condensation, (b) changes in clay morphology, (c) effects of pore topology in which the filling and emptying pathways differ [Dontsova et al., 2004], and (d) contact angle dynamics on chemically heterogene- ous and rough surfaces [Tuller and Or, 2005]. The general character of hysteresis in the wetting/drying loop is such that the desorption isotherm exhibits higher water content than its adsorption counterpart at the same relative humidity. Indeed, there is some variability observed in the hysteresis, which may indicate the cumulative influence of the afore- mentioned affects in sequential experiments [see Aochi and
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Competitive sorption and desorption of phosphate and citrate in clayey and sandy loam soils.

Competitive sorption and desorption of phosphate and citrate in clayey and sandy loam soils.

SUMMARY The increase of organic acids in soils can reduce phosphorus sorption. The objective of the study was to evaluate the competitive sorption of P and citrate in clayey and sandy loam soils, using a stirred-flow system. Three experiments were performed with soil samples (0-20 cm layer) of clayey (RYL-cl) and sandy loam (RYL-sl) Red Yellow Latosols (Oxisols). In the first study, the treatments were arranged in a 2 × 5 factorial design, with two soil types and five combinations of phosphorus and citrate application (only P; P + citrate; and citrate applied 7, 22, 52 min before P); in the second, the treatments were arranged in a 2 × 2 factorial design, corresponding to two soils and two forms of P and citrate application (only citrate and citrate + P); and in the third study, the treatments in a 2 × 2 × 6 factorial design consisted of two soils, two extractors (citrate and water) and six incubation times. In the RYL-cl and RYL-sl, P sorption was highest (44 and 25 % of P application, respectively), in the absence of citrate application. Under citrate application, P sorption was reduced in all treatments. The combined application of citrate and P reduced P sorption to 25.8 % of the initially applied P in RYL-cl and to 16.7 % in RYL-sl, in comparison to P without citrate. Citrate sorption in RYL-cl and RYL-sl was highest in the absence of P application, corresponding to 32.0 and 30.2 % of the citrate applied, respectively. With P application, citrate sorption was reduced to 26.4 and 19.7 % of the initially applied citrate in RYL-cl and RYL-sl, respectively. Phosphorus desorption was greater when citrate was used. Phosphorus desorption with citrate and water was higher in the beginning (until 24 h of incubation of P) in RYL-cl and RYL-sl, indicating a rapid initial phase, followed by a slow release phase. This suggests that according to the contact time of P with the soil colloids, the previously adsorbed P can be released to the soil solution in the presence of
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Chemical associations and sorption capacity of Pb and Zn: column experiments on a polluted soil from the Amizour mining district (Algeria)

Chemical associations and sorption capacity of Pb and Zn: column experiments on a polluted soil from the Amizour mining district (Algeria)

2013 ; Neal and Guilarte 2013 ). Soils have a finite capacity to attenuate trace metal concentrations through their mul- tiple reactive mineral and organic components, which are involved in metal retention through forming inner and outer-sphere complexes (Evans 1989 ). Clay minerals, metal (hydr)oxides and organic matter are key constituents of soil particle surfaces and contain distinct metal retention sites; consequently, metals may be found in various forms within the solid soil phase, namely: (a) on non-specific ion exchange sites; (b) on functional groups of organic matter and metal oxides; and (c) in the structure of primary and secondary minerals (Bradl 2004 ). The metal sorptiondesorption process in both natural soils and different model minerals plays a significant role in controlling the aqueous concentrations of metal species in soils. Metal sorption is typically described in terms of two basic mechanisms: specific sorption, e.g. surface complexation; and non- specific sorption such as ion exchange.
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Correcting for Electrocatalyst Desorption and Inactivation in Chronoamperometry Experiments

Correcting for Electrocatalyst Desorption and Inactivation in Chronoamperometry Experiments

Chronoamperometric experiments with adsorbed elec- trocatalysts are commonly performed either for analytical purposes or for studying the catalytic mechanism of a redox enzyme. In the context of amperometric sensors, the current may be recorded as a function of time while the analyte concentration is being increased to determine a linearity range. In mechanistic studies of redox enzymes, chronoamperometry proved powerful for untangling the effects of electrode potential and time, which are convo- luted in cyclic voltammetric measurements, and for studying the energetics and kinetics of inhibition. In all such experiments, the fact that the catalyst’s coverage and/or activity decreases over time distorts the data. This may hide meaningful features, introduce systematic er- rors, and limit the accuracy of the measurements. We propose a general and surprisingly simple method for correcting for electrocatalyst desorption and inactivation, which greatly increases the precision of chronoampero- metric experiments. Rather than subtracting a baseline, this consists in dividing the current, either by a synthetic signal that is proportional to the instant electroactive coverage or by the signal recorded in a control experi- ment. In the latter, the change in current may result from film loss only or from film loss plus catalyst inactivation. We describe the different strategies for obtaining the control signal by analyzing various data recorded with adsorbed redox enzymes: nitrate reductase, NiFe hydro- genase, and FeFe hydrogenase. In each case we discuss the trustfulness and the benefit of the correction. This method also applies to experiments where electron trans-
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Magnetorheological Elastomers: Experiments and Modeling

Magnetorheological Elastomers: Experiments and Modeling

HAL Id: hal-00592692 https://hal.archives-ouvertes.fr/hal-00592692 Submitted on 3 May 2011 HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

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Sorption of CO₂/CH₄ mixtures in TZ-PIM, PIM-1 and PTMSP: experimental data and NELF-model analysis of competitive sorption and selectivity in mixed gases

Sorption of CO₂/CH₄ mixtures in TZ-PIM, PIM-1 and PTMSP: experimental data and NELF-model analysis of competitive sorption and selectivity in mixed gases

3 1. Introduction Polymers are used as membrane materials in several industrial, medical and environmental applications dealing with separation and purification of gases and liquids, including desalination, dialysis, food processing and packaging, sensor development, and gas separation. Nowadays, gas separation with membranes is employed industrially for hydrogen recovery, nitrogen production, air dehydration, and natural gas sweetening [1 –4]. However, in order to promote a larger market penetration of this gas separation technology, better membranes are needed. One of the challenges posed by the use of polymeric materials as membranes is that they are subject to a trade-off between permeability and selectivity: for every gas pair the log of selectivity versus the log of the permeability of the most permeable gas has been shown to lie at or below a limiting line, customarily referred to as the Robeson upper bound [5,6]. Ultra-permeable materials usually lack in selectivity, whereas highly-selective materials exhibit lower permeability [6]. Therefore, the efficiency that can be achieved by the operation in terms of purity and productivity is limited and it is always necessary to find the right compromise between these factors [7,8] in order to maximize the process economy.
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Unfolding in the Empirical Sciences: Experiments, Thought-experiments and Computer Simulations

Unfolding in the Empirical Sciences: Experiments, Thought-experiments and Computer Simulations

not  aimed  at  refining  them  nor  at  providing  radically  new  information  about  these  systems. Kelly and alii explicitly say that they are after a molecular device functioning as  a ratchet – something that could lead to a violation of the second law. While they could  simply  try  to  identify  physically  unknown  systems  having  the  right  behavior,  they  choose known molecules having the right properties in term of structure (helicity) and  energetic barriers to rotation and use their existing knowledge about them to compute  their  energy  landscapes  (figure  4)  in  order  to  recreate  in  material  form   an  adequate  token of the target scenario and investigate its behavior. Accordingly, their work is best  seen as unraveling how some well‐described systems do behave in some circumstances.  Their  conclusion  is  that  this  known  physical  system,  though  exhibiting  an  asymmetry  (key  element  of  the  characterization),  does  not  lead  to  a  violation  of  the  second  law  (behavior).  This  only  makes  sense  if  the  observed  behavior,  though  not  accessible  by  mathematical  means,  is  believed  to  be  covered  by  the  provided  characterization.  In  other  words,  the  statements  describing  their  results  are  presumably  analytical  even  if  this  belief  might  be  false  because  the  system  does  not  instantiate  the  target  scenario,  something  has  gone  wrong  in  the  E  or  the  behavior  is  in  fact  not  covered  by  the  characterization. 
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Retinal waves: experiments and theory

Retinal waves: experiments and theory

i) Across species Rabbit Mouse Chick Turtle Godfrey et al.. Variability within retinal waves Zheng et al. 2004 i) Across species Rabbit Mouse Chick Turtle ii) Development Godfrey et al..[r]

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Uptake and sorption of aluminium and fluoride by four green algal species.

Uptake and sorption of aluminium and fluoride by four green algal species.

Abstract Background: We examined the uptake and sorption of aluminium (Al) and fluoride (F) by green algae under conditions similar to those found in the effluents of the aluminium industry. We took into account the speciation of Al in the medium since Al can form stable complexes with F and these complexes may play a role in the uptake and sorption of Al. We compared the capacity of four species of green algae (i.e. Chlamydomonas reinhardtii, Pseudokirchneriella subcapitata, Chlorella vulgaris, and Scenedesmus obliquus) to accumulate and adsorb Al and F. The selected algae were exposed during 4 days, covering all growth phases of algae, to a synthetic medium containing Al and F at pH 7.0. During this period, dissolved Al as well as cellular growth were followed closely. At the end of the exposure period, the solutions were filtered in order to harvest the algal cells. The cells were then rinsed with enough ethylene diaminetetraacetic acid to remove loosely bound ions from the algal surface, determined from the filtrates. Finally, the filters were digested in order to quantify cellular uptake.
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Desorption behaviour of regular adsorbed polyampholytic layers

Desorption behaviour of regular adsorbed polyampholytic layers

Figure 1. Chemical structure of the investigated polyampholyte PMAA-b-PDMAEMA. The silicon wafers were alkaline pretreated by using a mixture of NH3 and H2O2 in MilliQ water. After this cleaning procedure the IEP of the silicon substrate was determined to be pHIEP = 3.8[38,39]. For all desorption experiments the adsorbed polyam-pholyte layers were prepared using the same procedure. At first an aqueous adsorption solution containing 0 13 g/L polyampholyte and 0.01 mol/L NaCl was prepared. The pH of these polymer solutions was set to values around pH ≈ 6.8 The silicon substrates were placed in this solution for at least 10 hours, which is quite long enough to reach the equilibrium in adsorption [33, 40]. Afterwards the wafers were taken out of the solution, rinsed with MilliQ water and dried with nitrogen Under the used adsorption conditions the adsorbed
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Simulation of adsorption and desorption phenomena in a gas chromatography microcolumn

Simulation of adsorption and desorption phenomena in a gas chromatography microcolumn

being + . = + 79: ⁄ . + ,- The implemented adsorption model is the largely used Langmuir adsorption isotherm [ 7 ]. Since we are interested in the transport of the pollution molecules of the BTEX group by the carrier gas flow, the main aim is to describe the variation of the species concentration along the column in order to evaluate the so called retardation factor. The description of the concentration of species along the column can be done by two different ways: using the simplified model, considering constant velocity and diffusion coefficient along the column, and using the complete model, where velocity of carrier gas and diffusion coefficient varies along the column because of the pressure gradient.
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Comparison of the Saturated Salt Solution and the Dynamic Vapor Sorption techniques based on the measured sorption isotherm of barley straw

Comparison of the Saturated Salt Solution and the Dynamic Vapor Sorption techniques based on the measured sorption isotherm of barley straw

HAL Id: hal-01708203 https://hal.archives-ouvertes.fr/hal-01708203 Submitted on 13 Feb 2018 HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

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Comparison Between Static and Dynamic Methods for Sorption Isotherm Measurements

Comparison Between Static and Dynamic Methods for Sorption Isotherm Measurements

Both models were used to fit the experimental data curves plotted in Figure 4. The optimized parameters are summarized in Table 2. When compared to the literature, the same order of magnitude is found for the optimized parameters of the GAB model. For instance, under desorption conditions at 20°C (Rahman, 1995), the GAB monolayer moisture content is 0.058 kg of water/kg of dry matter and the two constant parameters C’ and K are estimated at 24.38 and 0.805. As it was observed by several authors

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Characteristics of sorption and expansion isotherms of reactive limestone aggregate

Characteristics of sorption and expansion isotherms of reactive limestone aggregate

This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur. Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

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Native Desorption Electrospray Ionization Liberates Soluble and Membrane Protein Complexes from Surfaces

Native Desorption Electrospray Ionization Liberates Soluble and Membrane Protein Complexes from Surfaces

on surfaces and desorbed in solutions that retain their native state interactions. Despite considerable progress in applica- tions of non-denaturing or native MS (nMS) of soluble [7–9] and membrane embedded proteins [10] the possibility of effectively “lifting” intact complexes from surfaces is desirable since many high throughput technologies then become accessi- ble. [11] Moreover the lipid distribution in natural membranes is essentially planar and asymmetric with varying spatial and temporal arrangements in the vicinity of embedded protein complexes. [12] The lipid distribution and the desire for a sur- face technology that is also able to analyse membrane proteins motivated us to develop a modified DESI approach capable of releasing folded protein molecules from planar surfaces and to construct an interface that we could couple to a high-resolution Orbitrap MS optimised for high mass transmission [13] of membrane proteins. [14] We demonstrate the potential of this methodology in three ways 1) by capturing transient protein substrate products 2) by screening for optimal solution/purification conditions using picoMoles of membrane and soluble proteins and 3) by carrying out ligand binding experiments on planar surfaces.
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Kinetic and Sorption isotherms of cadmium, copper and nickel ions on two synthetic hydroxylapatites

Kinetic and Sorption isotherms of cadmium, copper and nickel ions on two synthetic hydroxylapatites

Kinetic and Sorption isotherms of cadmium, copper and nickel ions on two synthetic hydroxylapatites.. Authors[r]

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Intracrystalline Sorption of Water and Organic Substances in Tetracalcium Aluminate Hydrate

Intracrystalline Sorption of Water and Organic Substances in Tetracalcium Aluminate Hydrate

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous. https://doi.org/10.4224/20331487 Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

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Sorption of Eu(III) on Attapulgite Studied by Batch, XPS and EXAFS Techniques.

Sorption of Eu(III) on Attapulgite Studied by Batch, XPS and EXAFS Techniques.

Sorption of Eu(III) on Attapulgite Studied by Batch, XPS and EXAFS Techniques Q.H. FAN †,‡, , X.L. TAN †, , J.X. LI † , X.K. WANG †* , W.S. WU ‡* , G. Montavon &* Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, P.O. Box 1126, Hefei, 230031, P.R. China; Radiochemistry Laboratory, Lanzhou University, Lanzhou, 730000, P.R. China; and Laboratory SUBATECH, UMR 6457 Ecole des Mines de Nantes/IN2P3-CNRS/Université de Nantes, 4 rue A. Kastler, BP 20722, 44307 Nantes cedex 03, France

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Zn sorption modifies dynamically the layer and interlayer structure of vernadite

Zn sorption modifies dynamically the layer and interlayer structure of vernadite

et al., 2007; Grangeon et al., 2008; Lanson et al., 2008). The uncertainty on the b lattice parameter is ±0.001 A ˚ (Grangeon et al., 2008), and the uncertainty on the sum of DC and TC site occupancy is ±0.01 atom per octahedral site. Note that diffraction does not allow the differentiation of DC and TC complexes, because their positions are crys- tallographically equivalent (Grangeon et al., 2008). When CSDs include 2–4 layers, as in vernadite, the precision from XRD on their size is likely better than 0.2 layer, a fivefold intensity increase being observed for the 0 0 1 reflection when the average number of layers in CSDs increases from 2.1 to 3.4 (Grangeon et al., 2010). The precision of the CSD size in the a–b plane is estimated to ±10%. The sensitivity of XRD to this parameter was demonstrated in Fig. 6 of Vill- alobos et al. (2006), which shows that reducing the CSD size from 60 to 30 A ˚ dramatically modifies the XRD profile.
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Acid gases absorption/desorption by alkanolamines aqueous solutions

Acid gases absorption/desorption by alkanolamines aqueous solutions

Les résultats obtenus indiquent qu’il est possible de représenter les flux de transfert de dioxyde de carbone avec des solutions aqueuses de DEA et de MDEA et des mélanges [r]

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