Finite Bath Research Articles

Visualising intraparticle protein transport in porous adsorbents by confocal microscopy

Confocal scanning microscopy was used to study protein uptake to porous adsorbents during batch experiments in a finite bath. By coupling of a fluorescent dye to the protein molecules the penetration of single adsorbent particles at different times during batch uptake could be observed visually. Intensity profiles of the protein distribution within a single particle were obtained by horizontal scanning. After integration of the profiles the overall fluorescence within a bead could be calculated. Relating the overall fluorescence at different incubation times to the value at equilibrium allowed the construction of the fractional approach to equilibrium versus time. These data were compared to uptake curves, which had been obtained by measurements of the protein concentration in the supernatant and an excellent agreement of the curves was detected. The procedure was performed for two different proteins (lysozyme and human IgG) on two different media for protein adsorption (SP Sepharose Fast Flow and SP Sepharose XL; Pharmacia Biotech) and in all cases it could be shown, that the results from the direct measurements by confocal microscopy correspond very well to the data obtained from the indirect measurements in the fluid phase.

Effect of Poly(ethylene glycol) on Dyeing Properties of Vinylon Fiber with Milling Acid Dye.

The effect of poly (ethylene glycol) (PEG) on the dyeing properties of vinylon fiber with a milling acid dye, Kayanol Milling Red RS 125 (C. I. Acid Red 114), has been investigated in dye-PEG-sodium chloride aqueous solutions at 80 and 90°C. Each dyeing was made in a finite bath (liquor ratio 1:1, 500) with1×10-4 mol/L of the dye in the presence of 0.1mol/L of sodium chloride. The reduced viscosities of dye-PEG (0.1g/dL) aqueous solutions increased with increasing dye concentrations and showed a maximum value. The absorption maximum (λmax) of the dye shifted to shorter wavelength and the equilibrium sorption of dye (C∞) gradually decreased with an increase in the concentration and weight-average molecular weight (_??_W) of PEG. The results are attributed to dye-PEG complex formation. The Apparent diffusion coefficient (D) and apparent rate constant (K) of dyeing varied in an opposit tendency from C∞

Time-Resolved Mass Spectrometric Studies of Fullerenes and Endohedral Fullerenes

The energetics and dynamics of C2 evaporations from fullerene radical cations Cn •+ were studied with and without ion trapping techniques. Electron space charge trapping was applied in electron ionization experiments. RF trapping in a Paul type ion source was applied for Laser MPI. Appearance energies, kinetic energy releases and metastable fractions were determined. the experimental data were modeled by finite heat bath theory (FHBT) and by RRKM/QET. Evaporation (binding) energies as well as conventional and intrinsic kinetic shifts were deduced. Our results support the following conclusions: (a) C60 sits on the leading edge of a magic shell, with C58 only slightly less stable and C62 considerably less stable than C60; (b) Dissociative decay is able to compete with radiative decay of C60 •+ only at internal energies in excess of 37.6 eV (Tb>2300 K); (c) a Ne endohedral atom has a slightly stabilizing effect on the C60 •+ cage whereas La is strongly stabilizing the C82 •+ cage; (d) C2 loss is a true evaporation in the sense of having a loose transition state with no reverse activation energy; (e) the C2 evaporations are statistical in nature and theories such RRKM/QET and FHBT are in excellent agreement with experimental observations.

Relative dissociation energies of singly and doubly charged fullerene ions, C nz+ , for n = 52 to 70

Relative activation energies for dissociation of fullerene ions C n z+ into C n−2 z+ + C 2 have been determined for z = 1 and 2, covering the size range 52 ≤ n ≤ 70. These data are derived from measured appearance energies of fragment ions, obtained by electron impact ionization of C 70, with the help of the finite heat bath theory. The present results are compared with experimental and theoretical values for C 2 loss reported in the literature.

Kinetic energy losses and vibrational excitation in hyperthermal C 60-surface scattering: dependence on vibrational energy of the incident molecule

Kinetic energy losses and vibrational excitation in scattering of a polyatomic molecule from a surface at hyperthermal energies were studied for the first time as a function of the average vibrational energy of the incident molecule. C 60 molecules with variable amounts of vibrational energy in the range of < E v = 7–15 eV and fixed kinetic energy were prepared in a helium seeded beam and scattered from a carbonized nickel surface. The primary beam kinetic energies and kinetic energy losses were measured with an accuracy of ± 0.1 eV while vibrational energies before and after the scattering event were measured with an accuracy of ± 0.25 eV (most probable values of the corresponding energy distributions). The vibrational thermometry method employed is shown to be practically independent of the specific model relating vibrational temperature to average vibrational energy (canonical vs. finite heat bath). Experiments were done at two different scattering angles corresponding to near normal and near grazing conditions, and for both angles it was found that the kinetic energy loss is independent of the initial vibrational energy to within 0.2 eV. The collisional vibrational excitation showed a weak inverse dependence on initial vibrational energy for both scattering angles. For the lowest incident C 60 vibrational energy (< E v = 9.8 eV) and near normal scattering (30.7 eV in the normal impact energy component) this excitation was found to be about 5% of the impact kinetic energy. We discuss these results in relation to possible mechanisms for normal and tangential energy transfer in a single C 60-surface collision at the hyperthermal (10–50 eV) energy range.

REMOVAL OF COPPER ELECTROLYTE CONTAMINANTS BY ADSORPTION

- Selective adsorbents have become frequently used in industrial processes. Recent studies have shown the possibility of using adsorption to separate copper refinery electrolyte contaminants, with better results than those obtained with conventional techniques. During copper electrorefinning, many impurities may be found as dissolved metals present in the anode slime which forms on the electrode surface, accumulated in the electrolyte or incorporated into the refined copper on the cathode by deposition. In this study, synthetic zeolites, chelating resins and activated carbons were tested as adsorbents to select the best adsorbent performance, as well as the best operating temperature for the process. The experimental method applied was the finite bath, which consists in bringing the adsorbent into contact with a finite volume of electrolyte while controlling the temperature. The concentration of metals in the liquid phase was continuously monitored by atomic absorption spectrophotometry (AAS)

ETHANOL-WATER ADSORPTION ON COMMERCIAL 3A ZEOLITES: KINETIC AND THERMODYNAMIC DATA

Dehydration of ethanol via adsorption using molecular sieves has recently been suggested as a promising alternative to the conventional separation methods for ethanol-water mixtures. 3A zeolites possess selective micropores whereon, due to the small size of their pores, the water molecules are adsorbed while the ethanol molecules are excluded. The scope of this work was, hence, the thermodynamic and kinetic study of ethanol-water adsorption on commercial zeolites of different origins, with the aim to select the best one. For the thermodynamic study, a thermostated bath was used at four different temperatures, where the data obtained by the static method could be correlated by means of a nonlinear isotherm. The kinetic data were obtained in a circulating finite liquid bath cell, where the effect of the temperature and of the mean diameter of the adsorbent particles on the rate of adsorption was studied. The results obtained in this way, expressed through uptake rate curves, showed that the adsorption rates were strongly dependent on the parameters studied. On comparing the adsorption rates among the adsorbents (commercial 3A zeolites), it could be concluded that, under the same operational conditions, exists a pronounced difference among them

The effects of pregrafting cotton fabrics with MAA/MAM on the dyeing kinetics of direct dyes in a finite bath

The influence of pregrafting of cotton fabrics with mixed monomer on the dyeing kinetics of direct dyes was investigated. The results of this research show that the equilibrium absorption (ae) and activation energy (ΔE*) in the dyeing of grafted fabrics are smaller than those of ungrafted fabrics. The experimental results show that the value of the equilibrium absorption is smallest when the molar ratio of MAA/MAM (methacrylic acid/methylacryl amide) is 4/6. However, the rate constant (k′) is larger for grafted fabrics than for ungrafted fabrics. No significant difference was observed between the structural diffusion resistance constant (n) of grafted and ungrafted fabrics. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1139–1142, 1997

The effects of pregrafting cotton fabrics with MAA/MAM on the dyeing kinetics of direct dyes in a finite bath

The influence of pregrafting of cotton fabrics with mixed monomer on the dyeing kinetics of direct dyes was investigated. The results of this research show that the equilibrium absorption (ae) and activation energy (ΔE*) in the dyeing of grafted fabrics are smaller than those of ungrafted fabrics. The experimental results show that the value of the equilibrium absorption is smallest when the molar ratio of MAA/MAM (methacrylic acid/methylacryl amide) is 4/6. However, the rate constant (k′) is larger for grafted fabrics than for ungrafted fabrics. No significant difference was observed between the structural diffusion resistance constant (n) of grafted and ungrafted fabrics. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1139–1142, 1997

Analysis of Protein Adsorption to Ion Exchangers in a Finite Bath

The adsorption of proteins to ion exchangers was investigated by finite bath experiments and by computer simulations using existing rate models. Experimental data were obtained for the binding of bovine serum albumin at different feed concentrations to both cation and anion exchangers. The results were interpreted together with model predictions and the values of the parameters characterizing the mass transfer mechanisms as well as the interaction rates of the adsorbate–adsorbent complex were estimated. The best agreement between theory and experiment throughout the whole period of adsorption process was obtained with a complex model where several steps of the overall mechanism were simultaneously controlling the overall rate. The simplified models, which offer rapid solution requiring less computational power, can be used at low feed concentrations of the proteins where the mechanisms controlling the adsorption rate are less complex. As the interaction rate mechanism and the intraparticle mass transfer mechanism in the adsorbent particles are the same in both finite bath and column adsorption systems, the information presented in this paper can be used to predict the protein adsorption in a column chromatography system. © 1997 SCI.

Analysis of Protein Adsorption to Ion Exchangers in a Finite Bath

Analysis of Protein Adsorption to Ion Exchangers in a Finite Bath

Sorption of diffusants by polymeric cylinders under isothermal, finite bath conditions: Advances in mathematical modeling

Diffusion-controlled, isothermal sorption (or desorption) of diffusants by cylindrical polymeric materials can be modeled for finite bath conditions by the use of the conventional diffusion equation solutions of Wilson or Crank when certain limiting assumptions apply. Iterative determination of diffusion coefficients by the use of these advanced equations, however, requires accurate “seed roots” for efficient solution. An empirical seed root generating function has been found that is so very accurate that it can be used in place of the conventional diffusion equation solutions for all but the most extreme levels of definitude. The parameters of the empirical equation as functions of equilibrium bath exhaustion are given, and values of fractional equilibrium uptake, M1/Mx, as a function of dimensionless time, Dt/r2, found by the use of both the diffusion equation solutions and the empirical equation are compared. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1237–1242, 1997

Absorption Kinetics of Direct Dye on Cotton from Finite Baths

Absorption time curves from finite baths are determined for untreated and cross-linked cotton fabrics dyed with Direct Red 81 under different conditions. A new method is described for kinetic analysis of absorption time curves. Structural coefficients, electrical coefficients, and dyeing rate constants are determined from the time curves. Crosslinking reduces the electrical coefficients, dyeing rate constants, and activation energy, but increases the structural coefficients (decreases the pore size). The structural coefficient is only affected by crosslinking in this study. The electrical coefficient and dyeing rate constant values are affected very little by dye concentration in aqueous solution in the cases of crosslinked and untreated cotton. However, both electrical coefficient and dyeing rate constant are affected by dyeing temperature and liquor ratio in the two cases.

Affinity adsorption of adsorbates into spherical monodisperse and bidisperse porous perfusive and purely diffusive adsorbent particles packed in a column parameter estimation in the Laplace transform domain

A novel mathematical method for parameter estimation is proposed and used to estimate in the Laplace transform domain the values of the parameters that characterize the mechanisms of intraparticle diffusion and convection in spherical perfusive or purely diffusive adsorbent particles with a monodisperse or with a bidisperse porous structure when the adsorbent particles are packed in a column. The parameter estimation method in the Laplace transform domain presented in this work is significantly simpler, easier to use and dramatically faster than the conventional parameter estimation procedure in the time domain, which requires the repeated numerical solution of the partial differential equations that describe the dynamic behaviour of the adsorption of an adsorbate in a column. Furthermore, since the value(s) of the parameter(s) that characterize the diffusional mass transfer mechanism(s) in the porous adsorbent particles is independent of the mode of operation, then the value(s) of the effective pore diffusion coefficient(s) determined by the mathematical method presented in this work could be used to describe the diffusional mass transfer rate of the adsorbate in operational modes other (finite bath (batch) operation, periodic countercurrent column operation, fluidized bed operation) than fixed-bed column operation.

Pore diffusivities in deactivated unimodal and bimodal coal liquefaction catalysts

This work investigated coke induced physical changes in pore geometry and intraparticle diffusivities of deactivated unimodal and bimodal catalysts withdrawn from a 4 ton/day direct coal liquefaction ebullated bed reactor. Porosimetry, surface area, equilibrium adsorption, and pore diffusivity measurements were performed on fresh, spent, and regenerated catalysts. Equilibrium adsorption experiments showed the loss in adsorption sites in the spent catalysts to be significantly greater than indicated by the decrease in overall BET surface areas. Pore diffusivity measurements performed using solute adsorption from a finite bath surrounding the catalyst particles yielded pore diffusivities two orders of magnitude lower than would be expected based on the measured average pore characteristics of the spent catalysts. This observation was postulated to result from a nonuniform radial distribution of coke deposits within the spent catalyst particles. A mathematical diffusion model incorporating the nonuniform coke deposition aspect of the deactivation process was formulated and used to simulate experimental diffusional uptake experiments. The model yielded results in satisfactory agreement with experimental measurements and provided a reasonable rationalization for the low diffusivities in the spent catalysts using physically realistic parameter values.

Neutralization and delayed ionization in fullerene surface collisions: Fragmentation and ionization rates as a route to activation energies

The interaction of C+60 and C+70 ion beams with a surface of highly oriented pyrolitic graphite was investigated by probing the ionization and fragmentation rates of scattered species within a time window of 20 μs following impact. Neutralization/reionization and fragmentation behavior was observed and followed by a pulsed deflection field applied to the surface at variable delays after the collision event. An almost complete collisional neutralization of the incident projectile was found. For an impact energy of 140–180 eV, a significant part of the scattered species was found to reionize by delayed electron emission within the experimental time window. The associated reionization and fragmentation kinetics were modeled with a system of differential equations assuming a simple unimolecular reaction diagram. Rate constants for delayed ionization and fragmentation were calculated as functions of internal energy and respective activation energies with the ‘‘finite heat bath’’ model (Klots) and the Rice–Ramsperger–Kassel–Marcus expression, respectively. The calculated and measured (deflection field delay dependent) ion intensities were compared in a fit procedure. The best fit led to an activation energy for the fragmentation of C+60 (C+60→C+58+C2) of 6.6±0.5 eV. This translates to an activation energy of 7.1±0.5 eV for the fragmentation of neutral C60 (using the experimentally determined ionization potential of C58). For C+70 we obtained an identical (within error) activation energy for fragmentation (C+70→C+68+C2) of 6.6±0.5 eV.

Self-consistent determination of fullerene binding energies BE (C+n–C2), n=58⋅ ⋅ ⋅44

Using recently measured accurate relative partial ionization cross section functions for production of the C60 fragment ions C+58 through C+44 by electron impact ionization, we have determined the respective binding energies BE(C+n–C2), with n=58,...,44, using a novel self-consistent procedure. Appearance energies were determined from ionization efficiency curves. Binding energies were calculated from the corresponding appearance energies with the help of the finite heat bath theory. Then using these binding energies we calculated with transition state theory (TST), the corresponding breakdown curves, and compared these calculated ones with the ones derived from the measured cross sections. The good agreement between these breakdown curves proves the consistency of this multistep calculation scheme. As the only free parameter in this procedure is the binding energy C+58–C2, we studied the influence of different transition states chosen in the determination of this binding energy via TST theory and iterative comparison with breakdown curve measurements. Based on this study we can conclude that extremely loose transition states can be confidently excluded, and that somewhat looser transition states than those used earlier result in an upward change of the binding energy of less than 10% yielding an upper limit for the binding energy C+58–C2 of approximately 7.6 eV.

Sorption Kinetics of Citric Acid from Aqueous Solutions by Macroporous Resins Containing a Tertiary Amine.

The rates for the sorption of citric acid from relatively concentrated aqueous solutions (0.05–0.2 mol/dm3) with macroporous resins containing tri-n-octylamine (TOA) were measured in finite bath. Experiments were carried out as functions of citric acid concentration in the aqueous phase, TOA concentration in the resin phase, and temperature. It was shown that the kinetic data could be well described by the Elvoich equation. Rate equations for the sorption processes were obtained and the activation energy was also determined.

Kinetic energy releases upon dissociation of endohedral fullerene cations

Kinetic energy release distributions are reported for the emission of C 2 from the positive ions of C 60, Ne@C 60, C 82 and La@C 82. Finite heat bath theory was applied to deduce the C 2 binding (vaporization) energies, ΔE vap. The results obtained are: ΔE vap(C 60 +) = 7.1 ± 0.5 eV, ΔE vap(Ne@C 60 +) = 7.4 ± 0.5 eV; ΔE vap(C 82 +) = 6.1 ± 0.4 eV and ΔE vap(La@C 82 +) = 7.3 ± 0.4 eV. The endohedral neon atom has a minor effect on the cage binding, while lanthanum has a relatively strong effect.

Real‐time monitoring of diffusion in polymer films using fluorescent tracer

AbstractA method for real‐time nondestructive monitoring of small molecules diffusion in polymeric films was developed. The method was based on detection of a fluorescent tracer eluting from the investigated polymer film into the solution in which this film was immersed. The kinetics of the tracer elution, monitored by the increase in solution fluorescence intensity, was used to deduce tracer diffusivity in polymer film. The data were treated using a straightforward mathematical model, describing diffusion from an infinite plane of a certain thickness immersed into a finite solvent bath. Fluorescent 7‐diethylamino‐4‐methyl coumarin was used as a tracer. The diffusion of this tracer within plasticized poly(methyl methacrylate) and styrene‐isoprene‐styrene block copolymer matrices was monitored. The diffusion coefficients equal to 2 × 10−9 cm2/s and 1 × 10−9 cm2/s, respectively, were obtained. © 1995 John Wiley &amp; Sons, Inc.