Kinetics Of Adsorption-desorption Research Articles

Synthesis, Characterisation and Utilisation of Magnetic Fe3O4 – TGT Nanocomposite in the Removal of Pb(II) from Aqueous Solutions

Magnetic Adsorption Separation (MAS) method is an ideal substitute for the environmental clean-up process. Magnetic material embedded with natural litter material is a facile route to achieve maximum adsorptive ability at a lower dosage, contact time and increased chance of metal-laden adsorbents’ recovery from aqueous matrices. In the present study, the synthesis of Fe3O4–TGT composite (TGT- C2) by the auto combustion method and its employment for Pb(II) removal from aqueous solutions is discussed. TGT- C2 is characterised using VSM (Vibrating Sample Magnetometer), SEM (Scanning Electron Microscope), Particle Size Analyzer, EDAX (Energy Dispersive X-ray Spectrometer) and FTIR (Fourier Transform Infra Red Spectrophotometer) techniques. TGT- C2 is found to be magnetic in nature and their saturation magnetization (Ms)/ Coercivity (Hc) values are calculated as 1.54 emu g-1/139.83 G, respectively, being less than bare Fe3O4. The synthesised nanocomposite registered a maximum of 98% sequestration of Pb(II) ions under the optimised conditions of 100 mg/L initial metal ion concentration, 10 min agitation time, 50 mg dosage and pH 5 environment. Isothermal verification, the kinetics of adsorption and successive desorption/ regeneration cycles were performed. The outcomes support the preparation of bio-nanocomposites from animal waste was successful in the efficient trapping of divalent metal ions.

Hg0 Conversion over Sulfureted HPMo/γ-Fe2O3 with HCl at Low Temperatures: Mechanism, Kinetics, and Application in Hg0 Removal from Coal-Fired Flue Gas

Recently, sulfureted metal oxides have been developed for the catalytic oxidation of Hg0 to HgCl2 using HCl as an oxidant at low temperatures, and they exhibit excellent Hg0 removal performance. Owing to the lack of reaction mechanisms and kinetics, further improvement in their performance for Hg0 conversion is extremely restricted. In this study, the reaction mechanism of Hg0 conversion over sulfureted HPMo/γ-Fe2O3 with HCl at low temperatures was investigated using Hg balance analysis and transient reaction. The chemical adsorption of Hg0 as HgS and the catalytic oxidation of Hg0 to HgCl2 both contributed to Hg0 conversion over sulfureted HPMo/γ-Fe2O3. Meanwhile, the formed HgCl2 can adsorb onto sulfureted HPMo/γ-Fe2O3. Then, the kinetics of Hg0 conversion, Hgt adsorption, and HgCl2 desorption were developed, and the kinetic parameters were gained by fitting the Hg balance curves. Subsequently, the inhibition mechanism of H2O and SO2 on Hg0 conversion over sulfureted HPMo/γ-Fe2O3 was determined by comparing the kinetic parameters. The kinetic model suggested that both HgCl2 resulting from Hg0 oxidation and unoxidized Hg0 can be completely adsorbed on sulfureted HPMo/γ-Fe2O3 with a moderate mass hourly space velocity. Therefore, sulfureted HPMo/γ-Fe2O3 can be developed as a reproducible sorbent for recovering Hg0 emitted from coal-fired power plants.

Compositional effect on humidity self-regulation functionality in gibbsite-based ceramic tiles

This paper analyses the effect of the starting composition on the humidity regulating capacity of a gibbsite-based composition successfully tested for the manufacture of ceramic tiles. For this purpose, the proportion of gibbsite and quartz has been varied and the effect of these two ingredients of the composition on the moisture regulating capacity and on the kinetics of adsorption-desorption of sintered tiles has been studied. To explain the effect, the microstructure of the sintered bodies has been also characterised. It has been found that increasing the proportion of gibbsite in the starting composition produces a significant increase in the moisture regulating capacity as a consequence of the higher proportion of transition alumina in the sintered bodies that provide a larger mesopore reservoir. In contrast, the addition of quartz does not affect the moisture regulating capacity but does affect the rate at which moisture adsorption and desorption phenomena take place by increasing the fraction of larger pores in the structure. In both cases, the kinetic model tested corroborates the observed relationship between microstructure and moisture regulating capacity.

Effect of the Porosity, Roughness, Wettability, and Charge of Micro-Arc Coatings on the Efficiency of Doxorubicin Delivery and Suppression of Cancer Cells

Porous calcium phosphate coatings were formed by the micro-arc oxidation method on the surface of titanium for the loading and controlled release of the anticancer drug doxorubicin. The coatings’ morphology and microstructure were examined by scanning electron microscopy. The phase composition was determined with the help of X-ray diffraction analysis. Studies of the hydrophilic properties of the coatings and their zeta potential were carried out. Data on the kinetics of doxorubicin adsorption-desorption were obtained. In addition, the effect of calcium phosphate coatings impregnated with doxorubicin on the viability of the Neuro-2a cell line was revealed. The coating formed at low voltages of 200–250 V contained a greater number of branched communicating pores, and therefore they were able to adsorb a greater amount of doxorubicin. The surface charge also contributes to the process of the adsorption-desorption of doxorubicin, but this effect is not fully understood and further studies are required to identify it.

Barrier kinetics of adsorption-desorption of alcohol monolayers on water under constant surface tension.

The desorption of spread decanol and dodecanol monolayers at controlled constant surface tension is shown to proceed under mixed barrier-diffusion control; the role of the convective diffusion is also discussed. The desorption rate is measured as a function of the density of the monolayer and the temperature. The rate of barrier desorption increases as the monolayer approaches the collapse point, reaching an infinite value. The average desorption time of an adsorbed dodecanol molecule increases linearly with the area per molecule, and is phase-specific - it is higher for the liquid condensed state of the monolayer than for the liquid expanded. The desorption rate increases with temperature; the activation energy for desorption is independent of the compression and the surface phase. The increase of the intensity of convection is shown to produce a vanishingly thin diffusion layer and causes the desorption to proceed under pure barrier control. A schematic map of the adsorption-desorption regimes acting as a function of time and intensity of the convection is constructed. General expressions for the rate of adsorption and desorption of alcohols are formulated.

Adsorption kinetics of tannic acid onto an albumin-terminated multilayer thin films

The protein-polyphenol multilayer film is a promising material for protection functional food ingredients from gastric digestion and their targeted delivery to small intestine. Here, we study the process of layer-by-layer assembly of bovine serum albumin—tannic acid (BSA-TA) multilayer films by precision ellipsometry. We demonstrate that TA adsorption has both irreversible and reversible components which contribute to 43% and 57% of bound TA molecules, respectively. The kinetic of TA adsorption/desorption process is analyzed using a phenomenological function approach. The rate-limiting stage of the process is the kinetics of molecules adsorption (desorption) to (from) a planar surface and not diffusion of TA molecules from (to) a solution bulk. For irreversible adsorption, the rate constant is 3.9 × 103 M−1 s−1. For the reversible process, the adsorption rate constant, Kads is 5.14 × 103 M−1 s−1; desorption rate constant, Kdes is 79.4 s−1; and equilibrium constant, K is 64.7 M−1.

Ice XVII as a Novel Material for Hydrogen Storage

Hydrogen storage is one of the most addressed issues in the green-economy field. The latest-discovered form of ice (XVII), obtained by application of an annealing treatment to a H 2 -filled ice sample in the C 0 -phase, could be inserted in the energy-storage context due to its surprising capacity of hydrogen physisorption, when exposed to even modest pressure (few mbars at temperature below 40 K), and desorption, when a thermal treatment is applied. In this work, we investigate quantitatively the adsorption properties of this simple material by means of spectroscopic and volumetric data, deriving its gravimetric and volumetric capacities as a function of the thermodynamic parameters, and calculating the usable capacity in isothermal conditions. The comparison of ice XVII with materials with a similar mechanism of hydrogen adsorption like metal-organic frameworks shows interesting performances of ice XVII in terms of hydrogen content, operating temperature and kinetics of adsorption-desorption. Any application of this material to realistic hydrogen tanks should take into account the thermodynamic limit of metastability of ice XVII, i.e., temperatures below about 130 K.

B134 シリンダ型細孔構造をもつメソポーラスシリカの水の吸脱着速度に関する研究(OS-6: マイクロ・ナノ熱工学(3))

The adsorption-desorption isotherm of water on mesoporous silicas with pore diameters of 3.8 nm was measured at 298 K using a gravitational method. Type V adsorption-desorption isotherm with significant hysteresis was obtained. Capillary condensation was initiated around 0.4 - 0.6 relative pressure and complete pore filling with water occurred near the saturated vapor pressure. The kinetics of water adsorption-desorption was also investigated. The relaxation rate of water uptake in the capillary condensation state was much smaller than that in the layer adsorption or pore filling state. However, he relaxation rate increased with increasing the amount of stepwise change in relative humidity. This result suggests that, in the capillary condensation state, water transport mechanism in mesopores should be different from simple diffusion. Similar trend could also be observed in the desorption process.

Comparison of the mass transfer in totally porous and superficially porous stationary phases in liquid chromatography

The characterization of mass-transfer processes in a chromatographic column during a separation process is essential, since the influence of the mass-transfer kinetics on the shape of the chromatographic band profiles and on the efficiency of the separation is crucial. Several sources of mass transfer in a chromatographic bed have been identified and studied: the axial dispersion in the stream of mobile phase, the external mass-transfer resistance, intraparticle diffusion, and the kinetics of adsorption-desorption. We measured and compared the characteristics and performance of a new brand of shell particles and those of a conventional brand of totally porous silica particles. The shell stationary phase was made of 2.7-microm superficially porous particles (a 1.7-microm solid core is covered with a 0.5-microm-thick shell of porous silica). The other material consisted of totally porous particles of conventional 3.5-microm commercial silica. We measured the first and second central moments of the peaks of human insulin over a wide range of mobile phase velocities (from 0.02 to 1.3 mL/min) at 20 degrees C. The plate height equations were constructed and the axial dispersion, external mass transfer, as well as the intraparticle diffusion coefficients were calculated for the two stationary phases.

N-hexane soot oxidation reactivity in N2/O2and N2/O2/NO2atmospheric pressure pulsed corona discharges

This paper discusses some aspects of n-hexane soot reactivity in a multi-pin to plate pulsed corona discharge working in the nanosecond regime at atmospheric pressure. The soot-discharge interaction was quantified by measuring the densities of CO, CO 2 , O 3 and NO 2 out-coming from the discharge cell. Results showed that CO 2 is the major product of soot oxidation. They also showed a strong enhancement of soot oxidation for O 2 percentage greater than 10% and cathode temperatures above 425 K. The soot reactivity is significantly enhanced when the discharge frequency is increased. The results obtained were interpreted in term of the competition between the kinetics of plasma active species adsorption and oxidation product desorption.

Kinetics of phosphine adsorption and phosphorus desorption from gallium and indium phosphide ( [formula omitted

The kinetics of phosphine adsorption and phosphorus desorption from gallium and indium phosphide (0 0 1) has been determined using reflectance difference spectroscopy to monitor the phosphorus coverage in real time. Assuming a Langmuir adsorption mechanism, phosphine exhibited an initial reactive sticking coefficient at 500 °C of 8.7 ± 1.0 × 10 −2, 3.5 ± 1.0 × 10 −2 and 1.0 ± 0.2 × 10 −3 on the GaP (2 × 4), GaP (1 × 1) and InP (2 × 4) reconstructions, respectively. The sticking coefficient increased with temperature on the gallium phosphide surfaces, exhibiting an activation energy of 0.5 ± 0.2 eV, while on indium phosphide, no temperature dependence was observed. The desorption of phosphorus from the GaP (2 × 1) surfaces was first-order in coverage with rate constants of 5.0 × 10 15 (s −1) exp(−2.6 ± 0.2 (eV)/kT). These results may be used to estimate the feed rate of phosphine relative to the group III precursors during the metalorganic vapor-phase epitaxy of gallium and indium phosphide.

Kinetics of tertiarybutylphosphine adsorption and phosphorus desorption from indium phosphide ( [formula omitted

The kinetics of tertiarybutylphosphine adsorption and phosphorus desorption from indium phosphide ( 0 0 1 ) have been determined using reflectance difference spectroscopy for real-time monitoring of the phosphorus coverage. The precursor adsorption rate depends linearly on the coverage, and the initial sticking coefficient varies from 0.007 to 0.001 as the temperature increases from 420 to 520 °C. The phosphorus desorption rate is first order in the coverage and exhibits an activation energy and pre-exponential factor of 2.4 ± 0.2 eV and 10 14.7 ± 1.5 s −1. These reaction kinetics play an important role in the growth of phosphide-based alloys by metalorganic vapor-phase epitaxy.

Binding and Dissociation Kinetics of Wild-Type and Mutant Streptavidins on Mixed Biotin-Containing Alkylthiolate Monolayers

The kinetics of adsorption and competitive desorption of wild-type streptavidin (WT SA) and three genetically engineered mutants (S27A, N23E, and W120A) was studied at gold surfaces functionalized with mixed alkylthiolates, some terminated with biotin headgroups and the rest with oligo(ethylene oxide) using surface plasmon resonance (SPR). The saturation coverage of the protein varied strongly with surface biotin concentration (XBAT) and was independent of mutation (except at very low and very high XBAT, where a weak dependence was seen). Initial adsorption rates were nearly diffusion-limited except at extremely low XBAT, where the rate varied weakly between mutants in accordance with their differing strengths of binding to biotin. Initial sticking probabilities were estimated to be between ∼1−6 × 10-6 per collision with the surface. The adsorbed SA desorbs upon introduction of solution-phase biotin. For XBAT below 1%, the desorption rate constants of the SA variants closely follow their off-rate constants measured in homogeneous solution (which at 25 °C are WT = 4 × 10-6 sec-1, N23E = 1.6 × 10-3 sec-1, S27A = 1.2 × 10-3 sec-1, and W120A estimated to be ca. 23 s-1). This proves that SA is mainly bound to the surface by a single SA-biotin link at very low XBAT. Importantly, for XBAT between 10 and 40%, where desorption is 30- to >1000-fold slower and the saturation coverage maximizes, the ratios of off-rate constants between mutants (W120A/N23E and W120A/S27A) are approximately the square of their ratios for XBAT below 1%. This squaring strongly suggests that the dominant species at these coverages is doubly bounded SA (i.e., immobilized via two surface biotins). The kinetics are explained with a mechanism involving only two first-order rate constants, that is, for (1) the slow dissociation of any bond between an SA site and a surface-immobilized biotin and (2) the fast reforming of this bond in the special case that it was released from a doubly bonded SA whose other site is still linked to one surface-immobilized biotin. The rate constant for (2) is almost independent of the SA mutant, as it is for adsorption. For XBAT > 60%, the desorption rates again approach the singly bound SA values, and the ratios of rate constants for the SA variants drop to slightly less than below 1% biotin. This is due to the dominance of singly bonded SA, plus a contribution from nonspecific binding, consistent with structural studies of these alkylthiolate films.

Adsorption of atomic and molecular oxygen and desorption of silicon monoxide on Si(111) surfaces

Quantum chemical theoretical calculations were performed to investigate the adsorption reaction of an ${\mathrm{O}}_{2}$ molecule or an O atom with a single dangling bond on the Si(111) surface and the desorption reaction of SiO gas from the O-adsorbed Si surface. The dissociative reaction of an ${\mathrm{O}}_{2}$ molecule requires an activation energy of $58 \mathrm{k}\mathrm{c}\mathrm{a}\mathrm{l}/\mathrm{m}\mathrm{o}\mathrm{l},$ whereas no potential-energy barrier exists in the reaction of an O atom. The most stable O-adsorbed species has a Si-O-Si bridging configuration. This configuration is formed by a conversion from the preceding metastable species where an O atom directly attaches to a surface dangling bond. It was revealed in the SiO desorption that the dissociation of two Si-Si bonds and one Si-O bond was responsible for the SiO generation. The activation energy of each dissociation was estimated to be $89$ and $44 \mathrm{k}\mathrm{c}\mathrm{a}\mathrm{l}/\mathrm{m}\mathrm{o}\mathrm{l},$ respectively. In addition, the consistency of the theoretical calculations for the kinetics of the oxygen adsorption and subsequent SiO desorption was examined under change in the size of the computational model clusters.

In situ optical second-harmonic-generation monitoring of disilane adsorption and hydrogen desorption during epitaxial growth on Si(001)

The kinetics of disilane adsorption and hydrogen desorption during low-temperature, ultrahigh vacuum chemical vapor deposition on Si(001) is investigated in situ in real time by monitoring the instantaneous hydrogen coverage using optical second-harmonic generation. A simple two-site adsorption model and first-order desorption are used to establish a reactive sticking coefficient and to predict the Si(001) epitaxial growth rate. The reactive sticking coefficient is temperature independent between 740 and 920 K and equal to 0.04±0.01. Predicted growth rates are in agreement with published growth rates obtained from gas-source molecular-beam epitaxy of Si(001).

Equilibrium and Kinetics of Borate Adsorption‐Desorption on Pyrophyllite in Aqueous Suspensions

AbstractThis study was conducted to elucidate the dynamic aspects of the adsorption‐desorption of borate ions on edge surfaces of 2:1 clay minerals. A pressurve‐jump relaxation method was used to evaluate the elementary processes involved in the adsorption‐desorption of borate ions by pyrophyllite in aqueous media at pH 9 and ionic strength of 0.01 (NaNO3). This clay was selected because of the small deviation from the ideal structural formula of the dioctahedral 2:1 clay minerals. At pH 9, 37% of the total B in solution is in the B(OH)−4 form, whereas of the total adsorbed B, the fraction of the adsorbed B(OH)−4 is assumed to be ≈ 0.99 at all levels of adsorbed B studied. This high fraction is probably due to the absence of repulsive forces associated with the planar surfaces. A linear correlation (R2 = 0.94) between the reciprocal value of the relaxation time, τ−1, and the sum of concentrations of the free adsorption sites and borate ions in solution at equilibrium was determined. The forward rate constant, k1, for the adsorption was 104.26 L mol−1 and the backward rate constant, k‐1, for the desorption was 101.11 s−1. The desorption rate constant was three orders of magnitudes smaller than the adsorption rate constant. The intrinsic equilibrium constant obtained from the kinetic measurements (log10 Kkinetic = 3.15) agreed relatively well with that calculated from the static studies (log10 Kstatic = 3.51). The suggested reaction scheme for the B‐pyrophyllite interaction is: urn:x-wiley:03615995:saj2sssaj199403615995005800040016x:equation:saj2sssaj199403615995005800040016x-math-0001 or urn:x-wiley:03615995:saj2sssaj199403615995005800040016x:equation:saj2sssaj199403615995005800040016x-math-0002

Comparison of the various kinetic models of non-linear chromatography

It is not possible to separate simply the influences of a slow mass transfer kinetics and of a slow kinetics of adsorption-desorption on the elution profile of a component. Four Kinetic models of chromatography are studied: (i) the Thomas or reaction model, which assumes Langmuir Kinetics of adsorption-desorption and no axial dispersion; (ii) the reaction-dispersive model, which uses the same Langmuir kinetics as the Thomas model but assumes a finite axial dispersion; (iii) a transport model, which uses the linear solid film driving force model to account for a slow kinetics of mass transfer and assumes no axial dispersion; and (iv) a transport-dispersive model, using the same mass transfer kinetics as the transport model and assumes finite axial dispersion. The analytical solution of the Thomas model can be fitted, with an accuracy which exceeds the precision of experimental measurements, on bands calculated using either one of the other three kinetic models of chromatography. Thus, the Thomas model, which assumes a slow adsorption-desorption kinetics and infinetely fast mass transfer kinetics, accounts very well for profiles calculated with a model making the reverse assumption. However, the values of the lumped kinetic coefficient obtained by curve fitting depend on the sample amount. Thus, the examination of an elution profile and its fitting to a model do not permit an easy solution of the inverse problem of chromatography.

The kinetics of adsorption and thermal desorption of NO on stepped Pt single crystal surfaces

The kinetics of adsorption and thermal desorption of nitric oxide on Pt field emitter surfaces has been studied by means of pulsed field desorption mass spectrometry (PFDMS). Adsorption on the high index planes with terraces of (111) orientation occurs molecularly with high initial sticking probabilities S=0.65,...,0.9. By varying the repetition frequency of the desorbing field pulses, i.e., by varying the field free reaction time tR (100 μs to 1 s), the mean lifetimes before thermal desorption of the NOad have been measured. The temperature dependence of the mean lifetimes has been evaluated. An activation energy of 139 kJ/mol and a preexponential of 3.8×10−15 s are found. These rate parameters are dominated by adsorption at step sites as verified on the basis of a model comprising multiple state adsorption and desorption. Dissociation of NOad has not been observed on stepped Pt(111), but has been on stepped Pt(100).

Interactions of sulfur with nickel surfaces: Adsorption, diffusion and desorption

The kinetics of adsorption, surface diffusion and thermal desorption of sulfur on Ni surfaces have been studied using field electron emission microscopy methods. The sticking probability for elemental sulfur sublimed onto a Ni specimen is approximately unity for Ni substrate temperatures from 77 to 530 K. The maximum average work function for ~ monolayer coverage of S ranged from 4.7 to 5.05 eV in different experiments; for fractional monolayer doses of S, surface diffusion was rapid at T 400 K, with activation energies ranging from 15 to 28 kcal mol . For multilayer adsorption of sulfur, diffusion occurs without motion of a sharp boundary, and there is evidence of extensive surface reaction between S and Ni (emission from small “crystallites” is evident in the field emission patterns). Sulfur desorbs from Ni at temperatures above 1500 K.

Study of the kinetics of adsorption-desorption of lead(2+) ion on a .gamma.-aluminum oxide surface by means of relaxation techniques

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudy of the kinetics of adsorption-desorption of lead(2+) ion on a .gamma.-aluminum oxide surface by means of relaxation techniquesKazuaki. Hachiya, Minoru. Ashida, Minoru. Sasaki, Haruki. Kan, Tadaomi. Inoue, and Tatsuya. YasunagaCite this: J. Phys. Chem. 1979, 83, 14, 1866–1871Publication Date (Print):July 1, 1979Publication History Published online1 May 2002Published inissue 1 July 1979https://doi.org/10.1021/j100477a015RIGHTS & PERMISSIONSArticle Views141Altmetric-Citations43LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts