Sorption of aliphatic alcohols, acetates, and their mixtures by corn starch cryotextures depending on concentrations of sorbates and starch in initial sols

The sorption of a mixture ofn-hexanol,n-octanol, andn-hexyl andn-octyl acetates from aqueous solutions by corn starch cryotextures was studied using capillary gas chromatography at different initial concentrations of the sorbates (1–25 mmol L⁻¹) and corn starch (2–6%). The amounts of compounds sorbed by cryotextures are proportional to the increase in their concentration in the initial sol and the length of the alkyl substituent. Linear equations describing the concentration dependence were proposed. The sorption ofn-hexanol from a mixture of substances containingn-octanol increases as compared to that from the individual alcohol. It was shown that the degree of sorption of aroma by cryotextures was independent of the content of starch in the initial sol. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1496–1501, August, 1999.     

Binding of cyclic compounds by starch cryotextures from aqueous solutions

Binding of cyclohexanol, 2-, 3-, and 4-methylcyclohexanones, and isomeric fenchone and camphor bicycles by the corn starch cryotextures from aqueous solutions in a concentration range of 1—16 mmol L^–1 was studied using capillary gas chromatography. Cyclohexanone is not sorbed by the cryotexture. All substances except fenchone exhibit linear plots of the amount of substances bound by the cryotexture vs.their concentration in the corn starch gel. The empirical constants in the linear dependence of the concentration of cryotexture-bound odorants on their initial concentration in the gel were calculated. The presence and position of methyl substituents in the ring affect the degree of binding of the cyclic compounds. The sorption isotherms of the cycles have different shapes. The apparent binding constants and the number of binding sites were determined for compounds reaching the saturation stage on sorption. Cooperative interactions between the binding sites were found. The most part of compounds are irreversibly bound by the cryotexture pointing to the formation of supramolecular complexes.     

Sorption of aliphatic alcohols from aqueous solutions by starch cryotextures

Capillary GLC was applied to study the sorption ofn-butanol,n-hexanol,n-octanol, and linalood from aqueous solutions by com starch cryotextures. The concentrations of alcohols in aqueous solutions were varied from 0.5 to 15 mmol L⁻¹. The sorption of alcohols by crytotextures formed of sols containing these alcohols and the coefficients of their. distribution depend on the initial concentration and structure of the alcohols.n-Butanol is not sorbed by the corn starch cryotextures over the range of 0.5–80 mmol L⁻¹. The sorption of other alcohols increases with increasing length of the alkyl substituent and the concentration of the alcohol. The highest sorption capacity of the cryotexture (88%) was observed forn-octanol. The sorption of linalool decreases due to the double bonds and branching in its molecules. Translated fromIzestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 734–737, April, 1999.     

Sorption of CO2, C2H4, N2O and their binary mixtures in poly(methyl methacrylate)

Sorption of carbon dioxide, ethylene, and nitrous oxide in poly(methyl methacrylate) (PMMA) at 35°C has been characterized for each gas as a pure component and for mixtures of carbon dioxide/ethylene and carbon dioxide/nitrous oxide. Pressures up to 20 atm were examined. Pure-component sorption isotherms are concave to the pressure axis for each of the gases. This behavior is accurately described by the dual-mode sorption model. Using only the purecomponent dual-mode parameters and the generalization of the model for gas mixtures, one can predict the total concentration of gas sorbed in the polymer to within an average deviation of ±2.01% for the CO₂/C₂H₄/PMMA system and ±0.98% for the CO₂/N₂O/PMMA system. In both systems, for each component of the mixture, sorption levels were lower than corresponding pure-component sorption levels at pressures equal to the partial pressure of the respective components in the mixture. Depression of the sorbed concentration in mixture situations appears to be a general feature of the above systems and can be substantial in some situations. For the CO₂/C₂H₄/PMMA system, use of pure-component sorption data to estimate the total sorbed concentration in the mixture would be in error by as much as 40% if one failed to account for competition phenomena responsible for depression in mixed-gas situations. Mixture pressures as high as 20 atm were studied for both systems and in the CO₂/N₂O/PMMA system sorbed concentrations reach 33.90 [cm³(STP)/cm³ polymer] without any significant deviation from model predictions.     

Multimodal sorption of nonionic dyes with two amino groups by various polymers from water

Sorption isotherms of nonionic dyes with two amino groups (one anthraquinone dye and two azo dyes) on various polymers from water were measured at 40–90°C (Nylon-6 and cellulose film) and at 95°C (polyester microfiber). The isotherms were curved, convex to upward, in the range of low dye concentration C_s in water and almost linear in the range of medium to saturated C_s. The isotherms measured at low temperature (40°C for cellulose, 40–60°C for Nylon-6, and at 95°C for polyester) were satisfactorily described by considering three concurrent modes of sorption. They are Nernst type partitioning and bimodal Langmuir sorption (sorption by the higher affinity sites with a small saturation value and that by the lower affinity sites with a large saturation value). However, for the sorption of the anthraquinone dye and one azo dye by Nylon-6 film at high temperature (80–90°C), the amount of dye sorbed by the high affinity site decreased to negligibly small. Accordingly, the isotherms were expressed well by simple dual-sorption model. © 1995 John Wiley & Sons, Inc.     

Gravimetric study of high-pressure sorption of gases in polymers

A gravimetric method for determining precisely the solubility of gases in polymers at high pressure is described. The solubilities of N₂ and CO₂ in low-density polyethylene (LDPE); CO₂ in polycarbonate (PC); and N₂, CH₄, C₂H₆, and CO₂ in polysulfone (PSUL) have been measured as a function of pressure up to 50 atm. Most of the measured sorption isotherms agreed closely with published data, but reproducible and time-dependent hysteresis in the sorption of CO₂, C₂H₆, and CH₄ in glassy polymers, PC, and PSUL, was observed in this study for the first time. Like the well known conditioning effect of high-pressure CO₂ on the sorption capacity of glassy polymers, these hysteresis phenomena are believed to be due to the plasticizing effect of sorbed gases. On the basis of the current data, the dual-mode sorption model including the plasticization by sorbed gas is discussed and a primitive equation for the concentration of sorbed gases in a quasiequilibrium state of sorption or desorption is proposed.     

Sorption of alkyl acetates from aqueous solutions by corn starch cryotextures

Capillary gas chromatography was used to study noncovalent sorption ofn-butyl,n-hexyl, andn-octyl acetates from aqueous solutions by corn starch cryotextures. In the concentration range of 0.5–15.0 mmol L⁻¹, about 38%n-butyl acetate, 70%n-hexyl acetate, and 98%n-octyl acetate are extracted from aqueous solutions. The sorption of the alkyl acetates depends on the alkyl chain length, indicating the hydrophobic character of their interaction with the corn starch cryotexture. No competitive sorption between acetates in the mixture was observed. Binding of alkyl acetates occurs during the cryosponge formation, due probably to the templation at the stage of starch sol, fixation in the cryosponge, and sorption on the surface of its walls. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1943–1945, October, 1998.     

Thermodynamic characteristics of supramolecular complexes of aroma compounds with ordered structures of polysaccharides of corn starch and its cryotextures

Supramolecular complexes of organic odorants (n-octanol and n-octyl acetate) with polysaccharides of corn starch, its cryotextures, and waxy corn starch cryotextures were studied by differential scanning microcalorimetry. It was shown that complexes are formed with amylose-containing starch and no complexes are formed with amylopectin starch. The melting enthalpies of the complexes were determined. It was shown that complexes of the odorants with native corn starch and its cryotextures have different thermodynamic characteristics.     

On the interaction of anionic detergents and montmorillonite clays

Summary The interaction of sodium decane sulfonate and sodium dodecyl sulfate with sodium and calcium montmorillonite was investigated byx-ray diffraction. Sorption of detergent by clay was calculated from the decrease in detergent concentration and from carbon analysis of the solids.The two detergents did not interact with sodium montmorillonite either below or above their critical micelle concentrations. Calcium montmorillonite sorbed both detergents, but metathesis, leading to the precipitation of some calcium alkyl sulfate and sulfonate, and hydrolysis of dodecyl sulfate complicated the situation.Thex-ray patterns of calcium montmorillonite treated with detergent solutions and dried contained two sets of (00l) reflections. One, rather broad, belonged to unmodified clay. Like untreated dry clay, its basal spacing increased by 6 Å on exposure to 85% relative humidity, owing to insertion of two monolayers of water between adjacent clay lamellae. The other set consisted of narrow reflections; their basal spacing, which did not increase on exposure to 85% relative humidity, exceeded that of unmodified clay by a distance equal to the extended length of the C₁₀H₂₁SO₃- and C₁₂H₂₅OSO₃-anions, respectively. Therefore, the sorbed, intercalated detergent molecules were fully extended, with their chain axis perpendicular to the plane of the clay lamellae.Sorption may have occurred in two steps: (1) binding of alkyl sulfonate and sulfate anions by calcium counterions of the clay, followed by (2) sorption of sodium alkyl sulfonate and sulfate molecules by association between their hydrocarbon tails and those of previously sorbed detergent anions throughvan der Waals forces.

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Zusammenfassung Die Aufnahme von Natriumdecylsulfonat und Natriumdodecylsulfat in Natrium- und Calcium-Montmorillonit wurde durch Analyse der Gleichgewichtslösungen und der Bodenkörper untersucht. Aus röntgenographisch bestimmten Schichtabständen wurde auf die Anordnung der Detergentienmoleküle im Schichtzwischenraum geschlossen.

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With 5 tables     

The solvent dependence of the sorptive abilities of tetracyanocomplexes

The two different types of tetracyanocomplexes [ZnNi(CN)₄·nH₂O] and [Cd(en)Pd(CN)₄·2C₆H₆] have been examined as sorptive materials in a simple contact with benzene, after their modification with auxiliary solvents and their use in gas chromatographic experiments. All forms of sorption experiments show identical characteristics from the view of the sorption of aromatic compounds as exemplified by benzene. The tetracyanocomplexes exhibit a permanent capability of sorption, even when heated to a temperature of 260°C and show a separation ability towards sorbed materials depending on the solvent used and on the degree of thermal degradation of the tetracyanocomplex. The prducts of the modification and sorption (in static and dynamic) experiments have been characterized by IR spectroscopy, X-ray patterns and by thermal analysis.     

Analysis of hydrocarbon gas sorption and transport in ethyl cellulose using the dual sorption/partial immobilization models

Low pressure sorption and transport data reported by Barrer et al. [1] for various C₄ and C₅ hydrocarbons in ethyl cellulose are analyzed in terms of current models of sorption and transport in glassy polymers. The popular dual sorption model, which was first qualitatively justified by these investigators, is used to estimate the frozen free volume fraction in the polymer which can accommodate Langmuir sorption. New CO₂ sorption data in ethyl cellulose are also presented and shown to be consistent with the dual sorption model and the frozen free volume fraction estimated from the hydrocarbon sorption. p]Transport of the hydrocarbons in ethyl cellulose is adequately described in terms of the partial immobilization model which attributes mobilities to each of the two sorbed species. The ratio of the mobility of the Langmuir species to that of the Henry's law species was found to be considerably less than unity for all of the gases.     

Effect of sorbed molecules on the resistivity of alkali metal-graphite intercalation compounds

Alkali metal-graphite intercalation compounds with the composition of MC₂₄ (M=K, Rb, Cs) were prepared by heating a mixture of MC₈ (saturated compound) and graphite sheet (Grafoil) at 350-450 °C. The resistivity perpendicular to the layer planes (ρ_c) of the resulting compounds was determined by the two-terminal method. The anisotropy factor of the resistivity, (ρ_c/ρ_a), of KC₂₄ prepared from Grafoil was ∼130, being about 1/6-1/10 in magnitude compared with that of KC₂₄ prepared from highly oriented pyrolytic graphite. The resistivity change during sorption of hydrogen (at 90 K), ethylene (at 194 K) and acetylene (at 194 K) was determined. The resistivity of MC₂₄ increased with increase of the sorbed amount of H₂. The magnitude of the increase was in the order KC₂₄>RbC₂₄>CsC₂₄. This resistivity increase was considered to be due to the expansion along c-direction which reduces the charge-transfer interaction between the carbon layers and potassium ions, resulting in the decrease of the density of the conduction electron. The resistivity of MC₂₄ increased extensively during sorption of C₂H₄ and C₂H₂. It was discussed in connection with the in-plane structural transition and chemical interaction between alkali metal ions and sorbed molecules.     

Temperature dependence of the free energy of sorption ofn-alkanes and energy contribution of their methylene groups on columns with fullerene C60

The partial molar free energy, enthalpy, and entropy of sorption of C₁₁−C₂₃ n-alkanes were calculated on the basis of the GC data obtained on the glass capillary column coated with fullerene C₆₀ (Ful-60) as stationary phase. The thermodynamic parameters ofn-alkane sorption on a column with Ful-60 and a fused silica capillary column with polydimethylsiloxane OV-1 were determined and compared. The enthalpy-entropy compensation effect for the sorption ofn-alkanes on Ful-60 and OV-1 was found. A linear dependence of the partial molar free energy ofn-alkane sorption on the temperature of analysis and carbon chain length was found. The free energy contributions of the methylene groups were calculated, and their temperature dependences were studied. The differences in the temperature dependences of the energy contributions of methylene groups ofn-alkanes on Ful-60 and OV-1 were revealed. The entropy contribution is 68–82% of the enthalpy contribution which indicates a substantial role of the number of contacts with Ful-60 in retention ofn-alkanes. The ability of Ful-60 for dispersive interactions is similar to those of nonpolar liquid phases and substantially differs from that for carbon adsorbents. Fullerene columns were shown to be convenient for analysis of highly boiling organic substances in aqueous and organic solutions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1490–1495, August, 1999.     

Steps toward the synthesis of a geodesic C60H12 end cap for a C3v carbon [6,6]nanotube

Several shape-persistent carbon-rich nanomolecules with diameters exceeding 1.7 nm have been prepared by the aldol trimerization of 20-carbon aromatic ketones bearing chlorine atoms at various sites. These C₆₀H₂₇Cl₃ and C₆₀H₂₄Cl₆ polycyclic aromatic compounds represent attractive intermediates for the synthesis of a geodesic C₆₀H₁₂ end cap of a C_3v carbon [6,6]nanotube.     

The mass spectra of some phenyl pyridyl ketones

The mass spectra of phenyl 2-pyridyl, phenyl 3-methoxy-2-pyridyl, phenyl 4-methoxy-2-pyridyl, phenyl 5-methoxy-2-pyridyl, phenyl 6-methoxy-2-pyridyl ketones, phenyl 3-pyridyl and phenyl 6-methoxy-3-pyridyl ketones, and phenyl 4-pyridyl ketone were studied. The major fragmentation pathway of all the ketones results in the formation of[C₆H₅CO]⁺ and [C₅H₄NCO]⁺ type ions. Another fragmentation path is the loss of carbon monoxide with formation of an [M ? CO]⁺ ion after skeletal rearrangement.     

Hydration mechanism of polysaccharides: A comparative study

Water sorption was studied at 20 °C on films composed of different natural polymers. Three polysaccharides were investigated: chitosan, cellulose, and alginate. The major differences between these polymers, from a structural point of view, lay in the substitution of an OH group by an NH₂ function for chitosan and by an ionic COO^?Na⁺ group for alginate. An analysis of the experimental water sorption isotherms, expressed as the number of water molecules sorbed per repeating unit in the amorphous phase, associated with an analysis of the enthalpy profile related to the water sorption allowed us to propose a water sorption mechanism in two steps for all the polymers: water sorption on polymer‐specific sites in the first step and water clustering around the first sorbed water molecules in the second step. It was determined that two water molecules interacted with the polymer chains for cellulose and chitosan, whereas four water molecules were bonded to alginate chains. The specific sorption sites were identified as OH groups for cellulose, OH and NH₂ groups for chitosan, and ionic and OH groups for alginate. A systematic reduction of the half‐sorption time was observed in the activity range corresponding to this first sorption step, and it was explained by a water plasticization effect. On the other hand, an increase in the half‐sorption time was observed in the second sorption step, at a high activity (>0.8), for chitosan and alginate. A modelization associating the Guggenheim–Anderson–de Boer model and the clustering theory, applied to our systems, allowed us to relate the occurrence of this last phenomenon to the formation of water clusters containing more than two water molecules. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 48–58, 2005     

Structures and bonding patterns of nanoannular carbon clusters (C4–C20) through AIM analyses

Structures, binding energies, harmonic frequencies, dipole moments, HOMO–LUMO energy gaps and particularly atoms in molecules (AIM) analyses of some nanoannular carbon clusters (C₄–C₂₀) are investigated at B3LYP/6-31+G(d) level of theory. No correlation is found by plotting the calculated binding energies as a functional number of carbon atoms of carbon clusters. The calculated binding energies sharply increase from C₄ to C₁₀ while slowly from C₁₀ to C₂₀. The binding energies of C_4n+2 clusters including C₆, C₁₀, C₁₄, and C₁₈ have a clear increase when compared with others indicating their aromatic characters which is confirmed by results of HOMO–LUMO energy gaps and geometrical parameters. AIM analyses show that most of our carbon clusters are topologically normal (non-conflict) with stable structures. Nevertheless, the topological networks of small antiaromatic rings, C₄ and C₈, at their equilibrium geometries may change via molecular vibrations. The existence of straight bond paths in 3D molecular graphs of carbon clusters with n > 10 implies that ring strains are decreased as the ring sizes grow. Except for C₄ and C₈, the ellipticity values for the remaining carbon clusters are small indicating that the C–C bond is conserved in these clusters. Dipole moments of even-numbered structures are negligible, whereas odd-numbered ones have μ values of 0.09−0.73 D.     

Specific Sorption Sites for Nitrogen in Zeolites NaLSX and LiLSX

Specific sorption sites for nitrogen, N₂, in NaLSX and LiLSX zeolites were investigated using a DRIFT spectroscopic method. Sorption of molecular hydrogen, H₂, by NaLSX or LiLSX zeolite at 77 K with DRIFT control of perturbation of sorbed molecules allowed to discriminate two or three different types of specific sorption sites in the respective zeolites. Their H–H stretching frequencies are 4077 and 4081 cm^–1 for NaLSX, and 4061, 4084 and 4129 cm^–1 for LiLSX. With reference to an independent investigation by methods of both sorption thermodynamics and molecular modeling for N₂ sorption on LiLSX, the first two of the corresponding bands were ascribed to H₂ sorption on lithium cations, Li⁺, localized in supercages of the faujasite, FAU, zeolite framework at sites SIII and SIII, while the latter band most likely belongs to H₂ sorption on Li⁺ cations at sites SII, and on hydroxyl groups, OH. Sorption of N₂ by Li⁺ cations at sites SIII and SIII is the strongest, resulting in a decrease of intensity of the corresponding DRIFT bands that stem from subsequent H₂ sorption. Nitrogen sorption by Li⁺ cations at sites SII is much weaker. Sorption of N₂ on Na⁺ cations at sites SIII in NaLSX zeolite is also stronger than by Na⁺ cations at sites SII.     

The influence of humic acid on the pH-dependent sorption of americium(III) onto kaolinite

This work investigates the sorption of americium [Am(III)] onto kaolinite and the influence of humic acid (HA) as a function of pH (3–11). It has been studied by batch experiments (V/m = 250:1 mL/g, C _Am(III) = 1 × 10⁻⁵ mol/L, C _HA = 50 mg/L). Results showed that the Am(III) sorption onto the kaolinite in the absence of HA was typical, showing increases with pH and a distinct adsorption edge at pH 3–5. However in the presence of HA, Am sorption to kaolinite was significantly affected. HA was shown to enhance Am sorption in the acidic pH range (pH 3–4) due to the formation of additional binding sites for Am coming from HA adsorbed onto kaolinite surface, but reduce Am sorption in the intermediate and high pH above 6 due to the formation of aqueous Am-humate complexes. The results on the ternary interaction of kaolinite–Am–HA are compared with those on the binary system of kaolinite–HA and kaolinite–Am and adsorption mechanism with pH are discussed. Effect of different molecular weight of HA, with three HA fractions separated by ultrafiltration techniques, on the Am sorption to kaolinite were also studied. The results showed that the enhancement of the sorption of Am onto kaolinite at the acidic pH conditions (pH 3–4) was higher with HA fractions of higher molecular weight. Also, the Am sorption over a pH range from 6 to 10 decreased with decreasing molecular weight of HA.     

Tefluthrin Sorption to Mineral Particles: Role of Particle Organic Coatings

Abstract

The sorption of tefluthrin was studied on “pure” clay minerals and those that had been coated with aquatic humic substances over a mass percent carbon range of 0.02 to 2.15. Tefluthrin sorption onto humic-coated minerals was significantly greater than on to the clean minerals and increased with increasing quantities of sorbed humic substances. Humic acid, the most aromatic coating, was the strongest sorbent, followed by fulvic acid, hydrophilic macromolecular acid and natural coatings on estuarine suspended particles. This shows the significant impact of humic coatings on the sorptive capacity of mineral particles. The sorption was linear, also consistent with the operation of a partition process. The partition coefficient normalised to organic carbon (K_oc) after deduction of the contribution from the clean mineral, ranged from 120000 to 770000 and was highest for the most aromatic humic acid fraction.