Selective adsorption of bacterial cells onto zeolites

Zeolites adsorb microbial cells on their surfaces and selective adsorption for specific microorganisms was seen with certain zeolites. Tests for the adsorption ability of zeolites were conducted using various established microbial cell lines. Specific cell lines were shown to selectively absorb to certain zeolites, species to species.

In order to understand the selectivity of adsorption, we tested adsorption under various pH conditions and determined the zeta-potentials of zeolites and cells. The adsorption of some cell lines depended on the pH, and some microorganisms were preferentially adsorbed at acidic pH. The values of zeta-potentials were used for calculating the electric double layer interaction energy between zeolites and microbial cells. There was a correlation between the experimental adsorption results and the interaction energy. Moreover, we evaluated the surface hydrophobicity of bacterial cells by using the microbial adherence to hydrocarbon (MATH) assay. In addition, we also applied this method for zeolites to quantify relative surface hydrophobicity. As a result, we found a correlation between the adsorption results and the hydrophobicity of bacterial cells and zeolites. These results suggested that adsorption could be explained mainly by electric double layer interactions and hydrophobic interactions.

Finally, by using the zeolites Na-BEA and H-Y, we succeeded in clearly separating three representative microbes from a mixture of Escherichia coli, Bacillus subtilis and Staphylococcus aureus. Zeolites could adsorb each of the bacterial cell species with high selectivity even from a mixed suspension. Zeolites can therefore be used as effective carrier materials to provide an easy, rapid and accurate method for cell separation.     

Selective adsorption of thiophene and 1-benzothiophene on metal-ion-exchanged zeolites in organic medium

Adsorption of the organic sulfur compounds thiophene (TP) and 1-benzothiophene (1-BTP) in an organic model solution of hydrodesulfurizated gasoline (heptane with 1 wt% toluene and 0.156 mM (5 ppmw as sulfur) TP or 1-BTP) was studied by a batch method at 80 degrees C using metal-ion-exchanged Y-zeolites. Although NaY-zeolite or its acid-treated material rarely adsorbed the organic sulfur compounds, NaY-zeolites exchanged with Ag+, Cu2+, and Ce3+ ions and NH(4)Y-zeolites exchanged with Ce3+ ions showed markedly high adsorptive capacities for TP and 1-BTP. The sulfur uptake increased in the order CuY-zeolite(Na)相似文献   

Selective cyclodehydration of diols on zeolites

1,4-Butanediol, 2,5-hexanediol and 1,5-pentanediol were selectively converted to tetrahydrofuran and tetrahydropyran in the presence of LaHY, CaHY and H-ZSM-6 zeolites. The advantage of these zeolites is in their high stability and faster regeneration.     

Selective dehydrogenation of tetralin on zeolites

The dehydrogenation of tetralin on two zeolite catalysts has been studied, the experiments were planned statistically according to the Orthogonal Central Composite Design. In order to determine the influence of coke deposits, the time-on-stream theory of catalyst decay is applied too.

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Factors affecting drug adsorption on beta zeolites

The adsorption behaviour of three commonly used drugs, namely ketoprofen, hydrochlorothiazide and atenolol, from diluted aqueous solutions on beta zeolites with different SiO₂/Al₂O₃ ratio (i.e. 25, 38 and 360) was investigated by changing the ionic strength and the pH, before and after thermal treatment of the adsorbents. The selective adsorption of drugs was confirmed by thermogravimetry and X‐ray diffraction. The adsorption capacity of beta zeolites was strongly dependent on both the solution pH and the alumina content of the adsorbent. Such a remarkable difference was interpreted as a function of the interactions between drug molecules and zeolite surface functional groups. Atenolol was readily adsorbed on the less hydrophobic zeolite, under pH conditions in which electrostatic interactions were predominant. On the other hand, ketoprofen adsorption was mainly driven by hydrophobic interactions. For undissociated molecules the adsorption capability increased with the increase of hydrophobicity.     

CuCl改性Y型分子筛的CO吸附性能研究

利用自发单层分散原理,讨论了在NaY,NH4Y,CuY分子筛上CuCl分散改性情况,并对所得到的改性分子筛进行了CO吸附性能研究。实验结果表明,在低CuCl担载量时,CuCl可在这三种载体表面达到原子水平分散,其分散容量分别为0.58g/gNaY,0.68g/gNH4Y和0.41g/gCuY。由于CO与Cu^+可生配位化合物,经CuCl改性的Y型分子筛对CO显示出较高吸附性能。其中,0.6gCuCl/gNH4Y分子筛表现出最高的CO吸附容量,在室温、常压下可达123mL/gNH4Y.     

Selective hydroisomerization of n-dodecane over platinum supported on zeolites

In this study, in order to develop catalysts for the selective isomerization of higher paraffin, the hydroisomerization reaction of n-dodecane was performed as a model reaction. Pt/ZSM-48, Pt/HZSM-5, Pt/HY, and Pt/SAPO-11 were examined for the selective hydroisomerization of n-dodecane. The catalysts were characterized via X-ray powder diffraction, N₂ adsorption, and the temperature-programmed desorption of ammonia. Among the catalysts studied, the Pt/HZSM-48 catalyst exhibited the best isomerization selectivity in the hydroisomerization reaction of n-dodecane, which is attributed to the moderate acid sites and medium-sized pores present in the HZSM-48. The highest iso-dodecane yield was obtained at a reaction temperature of 280 °C in the Pt/HZSM-48 catalyst. The optimal selectivity of the n-dodecane hydroisomerization over the Pt/SAPO-11 catalyst was obtained at approximately 300 °C, which was slightly higher than that of the Pt/HZSM-48 catalyst.     

Propene adsorption and reaction on zeolites and pillared clays

Comparative IR and UV-Vis spectroscopic studies of propene adsorption and reaction on H-mordenite, dealuminated H-mordenite, dealuminated mazzite, montmorillonite and Al₁₃-pillared montmorillonite have been carried out. On all systems propene is first transformed into polymeric species (C_nH_2n+1 ⁺). On HMOR (both as such and dealuminated), allylic carbocations are successively produced by loss of H₂, the monoenic species (C_nH_2n?1 ⁺) being formed at room temperature and the dienic (C_nH_2n?3 ⁺) and trienic (C_nH_2n?5 ⁺) species at higher temperatures. These species are not observed on the other systems, although they are presumably formed as unstable intermediates. In fact, on all the zeolites studied here two cyclic penta-atomic and hexa-atomic allylic carbocations have been observed for the first time. On all systems, the final products of reaction are polyaromatic species which, on the basis of their reaction with NH₃ still exhibit unsaturated carbocation behaviour. The activity of the various samples depends on their pore dimensions and on the nature of acidic sites involved: the larger the available pore space, the more branched is the polymer and the more difficult it is to observe allylic carbocations. Evidence is provided for a Brønsted-induced mechanism.     

Statistical modeling of equilibrium adsorption of non-ideal mixtures on zeolites

A new model for equilibrium adsorption of a binary mixture on zeolites that takes into account the energy nonuniformity of the adsorption field in the zeolite cavities was developed on the basis of statistical thermodynamics. The nonuniformity of the adsorption field produces rearrangement of molecules in the cavity volume, decreasing the entropy, internal energy, and Helmholz free energy. A procedure for calculation of the thermodynamic functions from the data on the adsorption of pure components was proposed. The limiting cases of maximum ordering of the molecules in the cavity and their random distribution were considered. The approach proposed was exemplified by the substantially non-ideal system nitrogen--argon--zeolite NaX at 160 K. The proposed model describes the behavior of this mixture much better than that of the ideal adsorbed solution theory.     

The effect of complexation with biopolymers on the adsorption of quercetin on silica

It is shown that the interaction of polyvinylpyrrolidone and human serum albumin with a natural flavonoid quercetin in aqueous medium results in the formation of 1 : 1 supramolecular complexes. As a result of complexation, the optical and protolytic properties of the flavonoid change and its concentration in solution increases considerably. The adsorption of quercetin on silica particles in the presence of polymers is discussed.     

Detailed process of adsorption of alkanes and alkenes on zeolites

The adsorption of alkanes and alkenes on zeolites is investigated by comparing the adsorption characteristics for three types of zeolite: ferrierite, ZSM-5, and mordenite. The activation energy for the diffusion of propane and n-butane on ferrierite and the heat of adsorption of C(2)-C(4) alkanes and alkenes on zeolites and silica are estimated based on Fourier transform infrared spectroscopy, and the diffusion processes in the micropores are elucidated by comparing the results with previously reported activation energies for n-butene diffusion. The adsorption of 1-butene on mordenite is also examined. The structure and process of experimentally observable adsorption is found to differ depending on the type of zeolite and adsorbing molecule, reflecting differences in the sizes of molecules and pores. This differing behavior is utilized to interpret the elementary adsorption processes of alkanes and alkenes on zeolites.     

Selective conversion of methanol to p-xylene on modified high-silica zeolites

A procedure was proposed for preparation of p-xylene from a nonhydrocarbon material, methanol, in the presence of a modified ultrasil. It was shown that ultrasils modified by multiple-charge cations actively catalyze synthesis of xylenes from methanol at atmospheric pressure, and their properties can be controlled by varying the nature, charge, and size, as well as the procedure of introduction of the modifier cation. Modification of H-ultrasil with gallium led to enhanced para-selectivity (70%) of the catalysts, which was attributed to an increase in the ratio of the Lewis to Brønsted acid sites and to a decrease in the effective channel diameters of the zeolite.