Modification of Surface and Structural Properties of Ordered Mesoporous Silicates

Two simple modification methods for ordered mesoporous silicas were examined and compared. MCM-41 molecular sieve was physically coated with 4-cyano-4-biphenyl [4(4-pentenyloxy)]benzoate (CBPB) and chemically modified using trimethylethoxysilane. The structural and surface properties of the obtained materials were characterized using elemental analysis, thermogravimetry and nitrogen adsorption over a wide pressure range.It was shown that the pore size of the MCM-41 material was not decreased significantly after the coating procedure, even for high loadings of CBPB. Moreover, low pressure adsorption measurements indicated that significant fractions of the MCM-41 surface were not covered by CBPB, even for high CBPB loadings, which suggests that the attained coverage may be very nonuniform. The chemical bonding procedure led to a marked decrease in the pore size and change of surface properties.It was demonstrated that nitrogen adsorption measurements provide a means of a thorough characterization of modified MCM-41 materials, allowing to estimate the surface area, pore volume and pore size distribution. Moreover, low pressure adsorption data can be used to qualitatively or semiquantitatively assess the surface coverage of the coated/bonded organic groups, which may be used to estimate the uniformity of the coverage and therefore, the usefulness of the modification procedure.     

THERMODYNAMIC STUDY OF ADSORPTION OF PHENOLIC COMPOUNDS FROM AQUEOUS SOLUTION BY A WATER-COMPATIBLE HYPERCROSSLINKED POLYMERIC ADSORBENT

Equilibrium data for the adsorption of phenolic compounds, i.e., phenol, p-cresol, p-chlorophenol and p-nitrophenol from aqueous solutions by a water-compatible hypercrosslinked polymeric adsorbent (NJ-8) within temperature range of 283-323 K were obtained and correlated with a Freundlich-type of isotherm equation, so that equilibrium constants KF and n were obtained. The capacities of equilibrium adsorption for all the four phenolic compounds on the NJ-8 from aqueous solutions are around 2 times as high as those of Amberlite XAD-4, which may be attributed to the unusual micropore structure and the partial polarity on the network. The values of the enthalpy (always negative) are indicative of an exothermic process, which manifests the adsorption of all the four phenolic compounds on the two polymeric adsorbents to be a process of physical adsorption. The negative values of free energy change show that the solute is more concentrated on the adsorbent than in the bulk solution. The absolute free energy values of adsorption for NJ-8 are always higher than those for Amberlite XAD-4, which indicates that phenolic compounds are preferentially adsorbed on NJ-8. The negative values of the adsorption entropy are consistent with the restricted mobilities of adsorbed molecules of phenolic compounds as compared with the molecules in solution. The adsorption entropy values of phenolic compounds for NJ-8 are lower than those for Amberlite XAD-4, which means the micropores of NJ-8 require more orderly arranged adsorbate.     

Affinity adsorption of recombinant human interferon-α on a porous dye-affinity adsorbent

Interferons are potent biologically active proteins synthesized and secreted by somatic cells of all mammalian species. Dye-affinity adsorption is increasingly used for protein separation. Hollow fibers have several advantages as adsorbents in comparison to conventional bead supports because they are not compressible and they eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of polyamide hollow fibers to which Cibacron Blue F3GA was attached for adsorption of recombinant interferon-α (rHuIFN-α). The hollow fiber was characterized by scanning electron microscopy. These dye-carrying hollow fibers (35.8 μmol/g) were used in the rHuIFN-α adsorption-elution studies. The effects of initial concentration of rHuIFN-α, medium pH, ionic strength and temperature on the adsorption efficiency of dye-attached hollow fibers were studied in a batch system. The non-specific adsorption of rHuIFN-α on the hollow fibers was 1.2 mg/g. Cibacron Blue F3GA attachment significantly increased the rHuIFN-α adsorption up to 99.8 mg/g. Significant amount of the adsorbed rHuIFN-α (up to 94.8%) was eluted in 1 h in the elution medium containing 1.0 M NaCl. In order to determine the effects of adsorption conditions on possible conformational changes of rHuIFN-α structure, fluorescence spectrophotometry was employed. We resulted that dye-affinity hollow fibers can be applied for rHuIFN-α adsorption without causing any significant conformational changes. Repeated adsorption/elution processes showed that these dye-attached hollow fibers are suitable for rHuIFN-α adsorption.     

后交联型St-DVB大孔吸附树脂对低级醇类的吸附性能研究

分别在静态和动态条件下研究了Friedel—Crafs后交联型聚苯乙烯-二乙烯基苯(St-DVB)大孔吸附树脂对水溶液中多种低级一元醇的吸附性能，测定静态吸附等温线和动态吸附曲线，并分别按照Langmuir和Freundlich模型进行拟合．结果显示，树脂对水中低浓度低级一元醇的吸附过程属于放热的物理吸附过程，树脂吸附能力随着一元醇碳原子数的增加，即分子内疏水基团质量的增加而增加；树脂对直链醇的吸附能力稍强于同分异构的支链醇．     

Reaction of 2,6-dibenzylidenecyclohexanone with phosphorus pentachloride: Triple functionalization of the isosemiquinoid system

The reaction of 2,6-dibenzylidenecyclohexanone with PCl₅ occursvia the sequential stages of desoxychlorination and substitutional phosphorylation to form (after oxidation, methoxylation, and hydrolysis on the surface of the chromatographic SiO₂ adsorbent) organophosphorus products of the 1-(a-chloro-, a-hydroxy-, or -alkoxy)benzyl-2-chloro-3-(-(dimethylphosphoryl)benzylidene)cyclobex-1-ene series.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 441–443, February, 1996.     

大孔树脂吸附法处理含苯肼工业废水的研究

以Hz-841大孔树脂为吸附剂,95%乙醇为脱附剂处理含苯肼4000~5000mg/L的工业废水,取得了理想的分离效果,苯肼吸附率>99.8%,树脂工作吸附量40~50g/L。     

大孔吸附树脂处理含磺胺废水的研究

利用大孔吸附树脂处理含磺胺废水。实验表明，DRHⅢ树脂对磺胺具有良好的吸附－解吸效果。原废水中磺胺浓度约为17.2g/L,COD约为13750mg/L，经树脂吸附处理后，废水中COD去除率约86％，磺胺的吸附率88．2％，树脂的解吸率为97．5％，磺胺的回收率约86．0％，其纯度达99．8％。在废水有效处理的同时实现了废物资源化，具有良好的环境效益和较高的经济效益。     

Estimation of micropore size distribution in active carbons from adsorption isotherms of water vapor

A possibility of estimation of the micropore size distribution in the carbon adsorbents with the developed micro-and mesoporous structure by analysis of the adsorption isotherms of water vapors was considered. At saturation water condenses in micropores in a form of a weakly compressed liquid. However, water molecules in micropores are packed not so closely as in the liquid because of steric hindrance. Therefore, the real density of water adsorbed in the micropores is lower than that of water adsorbed on an open surface and lower than the density of the normal liquid. An analysis of the adsorption isotherms of water vapors with account for the both opposite effects on the water density gives reliable data on the micropore sizes of the carbon adsorbents. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 40–43, January, 2007.     

Stability of workroom air volatile organic compounds on solid adsorbents for thermal desorption gas chromatography

The storage stability of the occupationally frequently occurring compounds, methylethylketone, methylisobutylketone, benzene, toluene, tetrachloroethylene, n-butylacetate, -pinene, β-pinene, limonene and n-decane, has been investigated on the adsorbents Tenax TA, Chromosorb 106 and Carbotrap using thermally desorbable tube type samplers, commonly utilized in ambient and workroom atmospheric measurements. Fifty and 500 ng of each compound were loaded on the various adsorbents tubes, stored at both ambient (20 °C) and refrigerated (4 °C) temperatures and analysed by means of thermal gas chromatography with mass spectrometric detection on days 0, 7, 14 and 28 after exposure. A 90% storage recovery was chosen as acceptance criteria for storage stability, and statistical testing by Student's t-test, analysis of variance and Bonferroni post hoc tests were employed to investigate the effect of the categorical variables storage time, storage temperature and analyte loading on the different adsorbents. Chromosorb 106 showed the overall best behaviour with recoveries of 90% or better for all analytes during the 28-day test period. Tenax TA and Carbotrap yielded lower recoveries and were more influenced by variations in storage time, storage temperature and analyte loading. Refrigerated temperatures were best avoided for storage on Tenax TA, but may increase the recovery of some compounds on Carbotrap (e.g. n-butylacetate). The blank build-up on the adsorbents was also investigated, and Carbotrap and Tenax TA showed no signs of artefact development over time. Chromosorb 106, however, contained inherently more artefacts that build up over time, which in spite of the excellent storage capability, may limit its use in field studies where long storage times are normal.     

Universal system for liquid stationary phase classification on the basis of thermodynamical data

Summary Equations modifying Rohrschneider's relationship between I and thermodynamical characteristics values are derived. Polarity in chromatography is discussed as a possibility of stationary phases or absorbents to enter into intermolecular interactions and is determined on the basis of the partial molar free energies of solution (G) of six test substances. A simple method for the calculation of stationary phase polarity in terms of G from retention indices and McReynolds constants is given. Equations are presented for the calculation of stationary phase selectivity utilizing G data tabulated for selected test substances. The thermodynamical basis of selecting a reference phase for a unified system expressing the selectivity of stationary phases which can also be applied for adsorbents is suggested. The energy equivalent to an index unit, G_i.u., is discussed.