Diese Literaturliste wurde im August 2005 erstellt und gibt eine Übersicht über verschiedene Anwendungen von Zeolithen in Lösungen, als Reaktionskatalysator oder als Adsorbens zur Aufarbeitung.
C. J. A. Mota, D. L. Bhering, N. Rosenbach Jr., (2004). "A DFT Study of the Acidity of Ultrastable Y Zeolite: Where is the Bronstedt/Lewis Acid Synergism?" Angew Chem 116: 3112-3115.Armagan, B. (2003). "Factors affecting the performances of sepiolite and zeolite for the treatment of textile wastewater." J Environ Sci Health Part A Tox Hazard Subst Environ Eng 38(5): 883-96.
- In this study, the adsorption mechanism of three reactive azo dyes (Everzol Black B, Everzol Red 3BS, Everzol Yellow 3RS H/C) on natural porous minerals, sepiolite and zeolite, have been examined in order to identify the ability of clay minerals on the removal of colored textile dyes from aqueous solutions. High ion exchange capacity, high surface areas and importantly their relatively cheap prices make them attractive adsorbents. For this purpose, series of batch adsorption tests were carried out as a function of solids concentration, time and dye concentration using natural and modified sepiolites and zeolites. Also, experiments were conducted to determine the amount of solid to be used in adsorption tests. An optimum solids concentration was selected as 0.05 g/mL (5%). Most of the adsorption was found to take place within the first 2h of mixing, taking into account the extreme changes like pH and concentration, the mixing period was selected as 4 h for further testing. The adsorption results indicate that both natural sepiolite and zeolite have limited adsorption capacities of the reactive dyes but are substantially improved by modifying their surfaces with quaternary amines. The mechanism of adsorption process is elucidated on the basis of experimental data.
B. Armagan, O. Özdemir, M. Turan, M. S. Çelik (2003). "The removal of reactive azo dyes by natural and modified zeolites." Journal of Chemical Technology and Biotechnology 78(7): 725-732.
- The adsorption mechanism of three reactive dyes by zeolite has been examined with the aim of identifying the ability of zeolite to remove textile dyes from aqueous solutions. Towards this aim, a series of batch adsorption experiments was carried out, along with determination of the electrokinetic properties of both natural and modified zeolites. The adsorbent in this study is a clinoptilolite from the Gördes region of Turkey. The reactive dyes CI Reactive Black 5, Red 239 and Yellow 176 are typical azo dyes extensively used in textile dyeing. Adsorption tests were carried out as a function of mixing time, solids concentration, dye concentration and pH. The adsorption results indicate that the natural zeolite has a limited adsorption capacity for reactive dyes but is substantially improved upon modifying its surfaces with quaternary amines. An electrostatic adsorption mechanism involving the formation of a bilayer of amine molecules on the clinoptilolite surface onto which anionic dye molecules adsorb, depending on their polarities, is proposed. The results are also supported by electrokinetic measurements. The adsorption data were fitted to the Langmuir isotherm and it was found that the modified sepiolite yields adsorption capacities (qe) of 111, 89 and 61 mg g-1 for Red, Yellow and Black, respectively. These results are comparable to a popular adsorbent, activated carbon.
Beta, I. A., H. Jobic, et al. (2001). "Inelastic neutron scattering and infrared spectroscopic study of furan adsorption on alkali-metal cation-exchanged faujasites." Spectrochim Acta A Mol Biomol Spectrosc 57(7): 1393-403.
- Inelastic neutron scattering (INS) as well as infrared (IR) transmission and diffuse reflection infrared Fourier transform (DRIFT) spectra of furan adsorbed on Li-LSX, NaY, NaX, K-LSX, and CsNaX zeolites have been measured in the range 2000-200 and 4000-1300 cm-1, respectively. On the basis of an assignment of normal modes of furan taken from the literature and our own quantum chemical calculations of vibrational frequencies, the observed frequency shifts between bulk furan and furan adsorbed on the zeolites mentioned above have been interpreted in view of the interactions between furan and zeolite. For an explanation of frequency shifts of CH out-of-plane bendings, CH stretchings and some ring vibrations, it has to be assumed that in addition to the interaction between furan and the corresponding cation of the zeolite, a further interaction between the CH bonds and lattice oxygen atoms exists.
Bucko, T., J. Hafner, et al. (2004). "Adsorption and vibrational spectroscopy of ammonia at mordenite: Ab initio study." J Chem Phys 120(21): 10263-77.
- The adsorption of ammonia at various active centers at the outer and inner surfaces of mordenite, involving Bronsted acid (BA) sites, terminal silanol groups, and Lewis sites has been investigated using periodic ab initio density-functional theory. It is shown that ammonia forms an ammonium ion when adsorbed at strong BA sites. The calculated adsorption energies for different BA sites vary in the interval from 111.5 to 174.7 kJ/mol depending on the local environment of the adduct. The lowest adsorption energy is found for a monodentate complex in the main channel, the highest for a tetradentate configuration in the side pocket. At weak BA sites such as terminal silanol groups or a defect with a BA site in a two-membered ring ammonia is H bonded via the N atom. Additional weak H bonds are formed between H atoms of ammonia and O atoms of neighboring terminal silanol groups. The calculated adsorption energies for such adducts range between 61.7 and 70.9 kJ/mol. The interaction of ammonia with different Lewis sites is shown to range between weak (DeltaE(ads)=17.8 kJ/mol) and very strong (DeltaE(ads)=161.7 kJ/mol), the strongest Lewis site being a tricoordinated Al atom at the outer surface. Our results are in very good agreement with the distribution of desorption energies estimated from temperature-programmed desorption (TPD) and microcalorimetry experiments, the multipeaked structure of the TPD spectra is shown to arise from strong and weak Bronsted and Lewis sites. The vibrational properties of the adsorption complexes are investigated using a force-constant approach. The stretching and bending modes of NH4(+) adsorbed to the zeolite are strongly influenced by the local environment. The strongest redshift is calculated for the asymmetric stretching mode involving the NH group hydrogen bonded to the bridging O atom of the BA site, the shift is largest for a monodentate and smallest for a tetradentate adsorption complex. The reduced symmetry of the adsorbate also leads to a substantial splitting of the stretching and bending modes. In agreement with experiment we show that the main vibrational feature which differentiates coordinatively bonded ammonia from a hydrogen-bonded ammonium ion is the absence of bending modes above 1630 cm-1 and in the region between 1260 and 1600 cm-1, and a low-frequency bending band in the range from 1130 to 1260 cm-1. The calculated distribution of vibrational frequencies agrees very well with the measured infrared adsorption spectra. From the comparison of the adsorption data and the vibrational spectra we conclude that due to the complex adsorption geometry the redshift of the asymmetric stretching is a better measure of the acidity of an active sites than the adsorption energy. (c) 2004 American Institute of Physics.
Chiku, H., M. Matsui, et al. (2003). "Zeolites as new chromatographic carriers for proteins--easy recovery of proteins adsorbed on zeolites by polyethylene glycol." Anal Biochem 318(1): 80-5.
- Zeolites are able to adsorb proteins on their surface and might be suitable as a new type of chromatographic carrier material for proteins and for their conjugates (Matsui et al., Chem. Eur. J. 7 (2001) 1555-1560). Interestingly, maximum adsorption was observed at the isoelectric point (pI) of each protein. The current study was performed to investigate the desorption of proteins from the zeolites at pI. Proteins adsorbed to zeolites could be desorbed at pI by polyethylene glycol (PEG), but not by conventional eluents. The eluted proteins still retained their activities. The zeolite Na-BEA was an especially good composite for desorption by PEG. Using this method for the adsorption and desorption of proteins at pI, we succeeded in separating various proteins. The application of zeolites to biochemistry and biotechnology is also discussed.
Cizmek, A. and Z. Ivancic (2002). "Adsorption of Paraoxon on High-silica Pentasils with Different Alkali Cations." Croatica Chimica Acta 75(1): 281-290.
- Adsorption of paraoxon (diethyl-p-nitrophenyl phosphate) on highsilica pentasils with different alkali cations (Na+, K+, NH4+) was investigated using the method of measuring the acceleration of the rate of oxidation of benzidine, and it is discussed with regard to the influence of alkali metal ions present in the system during zeolite synthesis. The rate of adsorption of paraoxon on Na-ZSM-5 was investigated at different temperatures (20, 30, 37 and 45 °C).
M. De Bruyn, S. Coman, et al. (2003). "Chemoselective reduction of complex alpha,beta-unsaturated ketones to allylic alcohols over Ir-metal particles on beta zeolites." Angew Chem Int Ed Engl 42(43): 5333-5336.
Deka, R. C., D. Ajitha, et al. (2003). "Adsorption of Small Molecules in Zeolites: A Local Hard - Soft Acid - Base Approach." J.Phys.Chem. B 107: 8574-8577.
Finch, P. and A. H. Siriwardena (1989). "Stereoselective O-glycosylation of trans-4-hydroxy-L-proline derivatives promoted by silver zeolite." Glycoconj J 6(4): 477-88.
- Trans-4-hydroxy-L-proline has been converted to four imino- and carboxyl-blocked derivatives which are suitable for the synthesis of 4-O-glycosyl conjugates. Reaction of these derivatives with 2,3,5-tri-O-benzyl-alpha-L-arabinofuranosyl chloride in the presence of a silver zeolite promoter yielded the blocked beta-furanosyl amino-acid conjugates. Deprotection gave trans-4-(beta-L-arabinofuranosyloxy)-L-proline which was characterised as its crystalline isopropyl ester. 13C-NMR Data are presented for the compounds described.
Fukuzumi, S., Y. Yoshida, et al. (2001). "Extremely slow long-range electron transfer reactions across zeolite-solution interface." J Am Chem Soc 123(45): 11331-2.
Hernandez-Malonado, A. J. and T. R. Yang (2004). "Dentirogenation of Transportation Fuels by Zeolites at Ambient Temperature and Pressure." Angew Chem 116: 1022-1024.
- Adsorption of nitrogen containing molecules on Cu-modified zeolite Y
Huttenloch, P., K. E. Roehl, et al. (2001). "Sorption of nonpolar aromatic contaminants by chlorosilane surface modified natural minerals." Environ Sci Technol 35(21): 4260-4.
- The efficacy of the surface modification of natural diatomite and zeolite material by chlorosilanes is demonstrated. Chlorosilanes used were trimethylchlorosilane (TMSCI), tert-butyldimethylchlorosilane (TBDMSCI), dimethyloctadecylchlorosilane (DMODSCI), and diphenyldichlorosilane (DPDSCI) possessing different headgroups and chemical properties. Silanol groups of the diatomite and zeolite were modified by chemical reaction with the chlorosilanes resulting in a stable covalent attachment of the organosilanes to the mineral surface. The alteration of surface properties of the modified material was proved by measurements of water adsorption capacity, total organic carbon (TOC) content, and thermoanalytical data. The surface modified material showed great stability even when exposed to extremes in ionic strength, pH, and to pure organic solvents. Sorption of toluene, o-xylene, and naphthalene from water was greatly enhanced by the surface modification compared to the untreated materials which showed no measurable sorption of these compounds. The enhanced sorption was dependent on the organic carbon content as well as on chemical characteristics of the chlorosilanes used. Batch sorption experiments showed that the phenyl headgroups of DPDSCI have the best affinity for aromatic compounds. Removal from an aqueous solution of 10 mg/L of naphthalene, o-xylene, and toluene was 71%, 60%, and 30% for surface modified diatomite and 51%, 30%, and 16% for modified clinoptilolite, respectively. Sorption data were well described by the Freundlich isotherm equation, which indicated physical adsorption onto the lipophilic surface rather than partitioning into the surface organic phase. The chlorosilane modified materials have an apparent potential for application in environmental technologies such as permeable reactive barriers (PRB) or wastewater treatment.
Jeong, H. K., S. Nair, et al. (2003). "A highly crystalline layered silicate with three-dimensionally microporous layers." Nat Mater 2(1): 53-8.
- Layered silicates with three-dimensional microporosity within the layers have the potential to enable new applications in catalysis, adsorption and ion-exchange. Until now no such materials have been reported. However, here we present the synthesis and structure of AMH-3, a silicate with three-dimensionally microporous layers, obtained in high purity and crystallinity. AMH-3 is composed of silicate layers containing eight-membered rings in all three principal crystal directions, and spaced by strontium cations, sodium cations and water molecules. Because of its three-dimensional pore structure, acid and thermal stability, this layered material could find applications in polymer-silicate composites for membrane applications, for synthesis of combined microporous-mesoporous materials, and for the formation of new zeolites and microporous films. Its existence also opens new possibilities for the synthesis of other layered silicates with multidimensional microporous framework layers.
Klint, D., P. Arvidsson, et al. (1994). "Purification of proteins by the use of hydrophobic zeolite Y." Protein Expr Purif 5(6): 569-76.
- Hydrophobic zeolite Y can be used as a fast and efficient and inexpensive matrix in the purification of proteins from crude extracts. Preferably the zeolite can be used in the first purification step, replacing the commonly used precipitation techniques with (NH4)2SO4 or ethanol. The time required for the zeolite prefractionation was a few hours compared to the much more time consuming precipitation procedure which demands centrifugation and subsequent dialysis. Proteins can be absorbed on the zeolite either in order to remove undesired proteins or to be subsequently eluted from the zeolite in order to achieve purification and concentration. Removal of undesired proteins is exemplified by the purification of horseradish peroxidase from a crude extract. The zeolite procedure enhanced the specific activity five times and provided a yield similar to that which was obtained by the use of standard procedures, (NH4)2SO4 fractionation and ion-exchange chromatography. Binding and subsequent elution of proteins from the zeolite is exemplified by the purification of monoclonal antibodies from hybridoma culture supernatants. Proteins were desorbed from the zeolite by the use of polyethylene glycol 600 and this procedure yielded a purification factor of 5.
Klint, D. and H. Eriksson (1997). "Conditions for the adsorption of proteins on ultrastable zeolite Y and its use in protein purification." Protein Expr Purif 10(2): 247-55.
- The adsorption of proteins on ultrastable zeolites was investigated. Protein binding to one of these, ultrastable zeolite Y (USY), was studied in detail. Protein binding to USY, with a Si/Al ratio of > 240, was found to be dependent on the pH of the solution, being highest at or just below the pI of the protein. The amount of protein adsorbed on the zeolite was found to be 10 times as much as the estimated binding to the external surface of the USY. We propose an adsorption mechanism involving the formation of a protein layer strongly bound to the USY surface, further protein layers being formed on top of this on the basis of protein-protein interactions. The protein-protein interactions can be disrupted by changing the pH. Ultrastable zeolite Y was used as a new matrix for protein purification. Undesired proteins can be removed from a crude preparation by adsorption on USY, increasing the purity of a specific protein, or the protein can be adsorbed on the zeolite and subsequently eluted through changing the pH. These two means of protein purification are exemplified by the purification of peroxidase from a crude horseradish extract and by the purification of lysozyme from egg white.
Kou, D. M., J. M. Wu, et al. (2001). "[Preparation and evaluation of in-situ synthesis zeolite gas-liquid modified columns]." Se Pu 19(6): 541-3.
- A new kind of NaA zeolite column has been prepared by in-situ synthesis technique. In comparing with traditional coating method, the in-situ NaA zeolite carrier is much more uniform and rigid. Several kinds of zeolite gas-liquid modified columns have been prepared with this in-situ technology, which showed satisfactory features in separation property and thermal stability. The successful utilization of mini-length and wide-bore columns showed good practical prospect of this new kind of zeolite column.
Lefebvre, F., A. d. Mallmann, et al. (1999). "Modification of the Adsorption and Catalytic Properties of Molecular Sieves by Reaction with Organometallic Complexes." European Journal of Inorganic Chemistry 1999(3): 361-371.
- Molecular sieves can be modified by organometallic complexes using two different methods: (i) OMCVD (organometallic chemical vapor deposition), where a multilayered organometallic fragment is calcined and transformed into an oxide of rather indefinite composition, and (ii) SOMC (surface organometallic chemistry), where an organometallic fragment is grafted with retention of its molecular integrity. Both methods may lead to a grafting, which can occur at the external surface and/or inside the channels of the zeolites. In the case of SOMC, by judicious choice of both the reaction conditions and the organometallic complexes, it is possible to modify only the external surface of the sieve, for example, of a mordenite. This can lead to a decrease of the surface acidity, allowing greater selectivity in catalytic reactions (such as xylene isomerization). Another application is the modification of the pore openings of the channels by grafting organometallic compounds near the pore entrances. This results in a modification of the adsorption characteristics of the molecular sieve, allowing a fine tuning of its properties. Depending on the size of the adsorbed molecule, two effects can be observed: (i) a total exclusion of the molecule from the channels of the molecular sieve, due to steric effects (thermodynamic control); (ii) a modification of the adsorption kinetics of the adsorbed molecule, depending greatly on its size and on the size of the organometallic fragment (kinetic control). Finally, the grafting reaction can, in some cases, occur inside the channels, thereby leading to effects similar to those described above and to a reduction of the adsorption capacity due to the presence of the grafted organometallic moieties within the pores.
Li, S., V. A. Tuan, et al. (2003). "MTBE adsorption on all-silica beta zeolite." Environ Sci Technol 37(17): 4007-10.
- All-silica beta zeolite is shown to be effective for MTBE removal from water. The silica beta was prepared directly from gel, and it was more effective than dealuminated beta for MTBE adsorption. Water and 2-propanol adsorption isotherms showed that the all-silica beta is more hydrophobic than dealuminated beta. The amount of MTBE adsorbed on all-silica beta increased linearly with MTBE concentration from 9.4 to 590 microg/L.
Li, Z., D. Alessi, et al. (2002). "Influence of quaternary ammonium on sorption of selected metal cations onto clinoptilolite zeolite." J Environ Qual 31(4): 1106-14.
- Clay minerals and zeolites have large cation exchange capacities, which enable them to be modified by cationic surfactant to enhance their sorption of organic and anionic contaminants. In this study, the influence of quaternary ammonium surfactants on sorption of five metal cations (Cs+, Sr+, La3+, Pb2+, and Zn2+) onto a clinoptilolite zeolite was investigated. Generally, the metal cation sorption capacity and affinity for the zeolite decreased, indicating that presorbed cationic surfactants blocked sorption sites for metal cations, as the surfactant loading on the zeolite increased. Cesium and Pb2+ sorption was affected to a small extent, indicating that selective sorption for Cs+ and specific sorption for Pb2+ play an important role in addition to cation exchange. Sorption of cationic surfactants on zeolite preloaded with different metal cations showed a strong correlation with the chain length of the surfactant tail group, while the roles of the charges and types of the metal cations were minimal. As the chain length increases, the critical micelle concentration decreases and the surfactant molecules become more hydrophobic, resulting in progressive bilayer coverage. Desorption of presorbed metal cations by cationic surfactants was strongly affected by the surfactant chain length and metal type. More metal cations, particularly Sr2+ and Zn2+, desorbed with an increase in surfactant chain length. The results, in combination with those from organic and oxyanion sorption on surfactant-modified zeolite, may be used for future surfactant modification to target sorption and desorption of a specific type of contaminant or a mixture of different types of contaminants.
Meshko, V., L. Markovska, et al. (2001). "Adsorption of basic dyes on granular activated carbon and natural zeolite." Water Res 35(14): 3357-66.
- The adsorption of basic dyes from aqueous solution onto granular activated carbon and natural zeolite has been studied using an agitated batch adsorber. The influence of agitation, initial dye concentration and adsorbent mass has been studied. The parameters of Langmuir and Freundlich adsorption isotherms have been determined using the adsorption data. Homogeneous diffusion model (solid diffusion) combined with external mass transfer resistance is proposed for the kinetic investigation. The dependence of solid diffusion coefficient on initial concentration and mass adsorbent is represented by the simple empirical equations.
Munsch, S., M. Hartmann, et al. (2001). "Adsorption and separation of amino acids from aqueous solutions on zeolites." Chem Commun (Camb)(19): 1978-9.
- The adsorption of various amino acids on zeolites with different structures was studied with regard to dependence of the pH value of the solution and the aluminum content of the zeolite in order to design tailor-made adsorbents for amino acid separations.
Nagarapu, L., N. Ravirala, et al. (2001). "A new approach toward the stereoselective synthesis of novel benzo[b][1,5]oxazepines using MCM-41(H) zeolite." Enantiomer 6(6): 339-42.
- Facile procedures have been developed for the stereoselective synthesis of novel benzo[b][1,5]oxazepines 4a-f by the condensation reaction between 2-amino phenol 2 and tert-butyl(4R)-2,2-dimethyl-4-(3-oxo-3-phenyl-1-propynyl)-1,3-oxazolane-3- carboxylate 3a-f with MCM-41(H) zeolite in acetonitrile.
Roostaei, N. and F. H. Tezel (2004). "Removal of phenol from aqueous solutions by adsorption." J Environ Manage 70(2): 157-64.
- Experiments have been conducted to examine the liquid-phase adsorption of phenol from water by silica gel, HiSiv 3000, activated alumina, activated carbon, Filtrasorb-400, and HiSiv 1000. Experiments were carried out for the analysis of adsorption equilibrium capacities and kinetics. The adsorption isotherm model of the Langmuir-Freundlich type was the best to describe adsorption equilibrium data for phenol for the adsorbents studied. Results of kinetic experiments indicated that HiSiv 1000 had the highest rate of adsorption among the adsorbents studied and therefore more detailed studies were carried out with this adsorbent. The influence of particle size, temperature, and thermal regeneration on adsorption of phenol by HiSiv 1000 was evaluated. From particle size experiments it appeared that adsorption capacity of HiSiv 1000 did not change by changing the particle size, but the rate of adsorption decreased considerably by increasing the particle size. The effect of temperature on adsorption was studied by determining equilibrium isotherms for HiSiv 1000 at 25, 40, and 55 °C. The results showed that adsorption capacity decreased with increasing temperature. Thermal regeneration of HiSiv 1000 was performed at 360 °C. It was observed that adsorption capacity of HiSiv 1000 did not change after 14 regeneration cycles. Equilibrium experiments showed that the adsorption capacities of activated carbon and Filtrasorb-400 were several times higher than that of HiSiv 1000.
Takahashi, A. and R. T. Yang (2002). "New adsorbents for purification: Selective removal of aromatics." AiChE Journal 48(7): 1457-1468.
- Adsorption of benzene and cyclohexane on various Y-zeolites was investigated to develop sorbents for the purification of aliphatics by removal of aromatics. Ag-Y showed superior benzene/cyclohexane selectivities to Na-Y, Pd-Y, and H-USY. Separation factors greater than 105 were obtained with Ag-Y at low concentrations of benzene. High selectivities were achieved by the strong interaction between benzene and Ag-Y, while the interaction with cyclohexane was not influenced by the cations. Molecular orbital calculation revealed that benzene formed a classic -complexation bond with Ag-Y: donation of electron charges from the p-orbitals of benzene to the vacant s-orbital of the silver (donation) and, simultaneously, back donation of electron charges from d-orbitals of silver to *-orbital of benzene (d-* back donation). Grand canonical Monte Carlo simulations were also performed for adsorption isotherms. Potential parameters of benzene on Ag-Y, including -complexation, were developed first. Simulation and experiments of GCMC agreed excellently for adsorption of benzene on Y-zeolites.
Turro, N. J. and P. Wan (1985). "Photolysis of Dibenzyl Ketones Adsorbed On Zeolite Molecular Sieves. Correlation Of Observed Cage Effects with Carbonyl 13C Enrichments." J Am Chem Soc 107: 678-682.
- The photolysis of 3-(4-methylphenyl)-1-phenyl-2-propanone (4-Me-DBK) and 1,3-diphenyl-2-propanone-13C (DBK-13C) has been carried out on several commonly available zeolites Dramatic changes in product distributions were observed on several zeolites. Percent cage effects were calculated and rationalized in terms of molecular mobility of photogenerated benzyl radicals in the void volumes of the zeolite.
Uglea, C. V., I. Albu, et al. (1994). "Drug delivery systems based on inorganic materials: I. Synthesis and characterization of a zeolite-cyclophosphamide system." J Biomater Sci Polym Ed 6(7): 633-7.
- Porous material of the CuX zeolite type has been synthesized and used as support for a classic antitumoral drug--cyclophosphamide (CP). The new material obtained represents a physical mixture of the two components. In vivo tests allowed biochemical and anatomopathological evaluation of antitumoral effects determined by oral administration of the CuX zeolite-CP system. Data obtained show that the intensity of the antitumoral effects of the CuX zeolite-CP system is similar as compared to that achieved by CP. A possible advantage of the CuX zeolite-CP system is the continual maintenance in the blood of a CP concentration ranging between 100 and 1,000 ng ml-1 plasma.
Walcarius, A. and R. Mouchotte (2004). "Efficient in vitro paraquat removal via irreversible immobilization into zeolite particles." Arch Environ Contam Toxicol 46(1): 135-40.
- A new efficient mineral adsorbent, zeolite ZSM-5, has been evaluated for its ability to durably immobilize the herbicide paraquat in conditions simulating acute poisoning by oral ingestion of this toxic compound. The sorption properties have been studied in water, normal saline solution, as well as in artificial and simulated human gastric juices. Uptake kinetics and capacities have been determined and compared to the ion exchange resin Amberlite IR-120. Significant advantages of ZSM-5 over the resin have been demonstrated, especially with respect to long-term retention capability of the toxic herbicide. This solid is a promising primary treatment of acute paraquat poisoning.
Xu Q. H., Z., J. H. (1985). "Ethylation of toluene on HZSM-5-Zeolites prepared without organic compounds." Acta Phy Chem 31(1-2): 181-187.
Yan, A. X., X. W. Li, et al. (2002). "Recent progress on immobilization of enzymes on molecular sieves for reactions in organic solvents." Appl Biochem Biotechnol 101(2): 113-29.
- Enzymes exhibit high selectivity and reactivity under normal conditions but are sensitive to denaturation or inactivation by pH and temperature extremes, organic solvents, and detergents. To extend the use of these biocatalysts for practical applications, the technology of immobilization of enzymes on suitable supports was developed. Recently, these immobilized biomolecules have been widely used and a variety of immobilization supports have been studied. The majority of these supports cover diverse kinds of materials such as natural or synthetic polyhydroxylic matrixes, porous inorganic carriers, and all kinds of functional polymers. Microporous molecular sieve, zeolite, has attracted extensive interest in research because of its distinctive physical properties and geochemistry. Recently, with the discovery of a new family of mesoporous molecular sieves, MCM-41, this series of materials shows great potential for various applications. Molecular sieves involve such a series of materials that can discriminate between molecules, particularly on the basis of size. As support materials, they offer interesting properties, such as high surface areas, hydrophobic or hydrophilic behavior, and electrostatic interaction, as well as mechanical and chemical resistance, making them attractive for enzyme immobilization. In this article, different types of molecular sieves used in different immobilization methods including physical adsorption on zeolite, entrapment in mesoporous and macroporous MCM series, as well as chemically covalent binding to functionalized molecular sieves are reviewed. Key factors affecting the application of this biotechnology are discussed systematically, and immobilization mechanisms combined with newly developed techniques to elucidate the interactions between matrixes and enzyme molecules are also introduced.
Zhang, P., X. Tao, et al. (2002). "Enhanced perchloroethylene reduction in column systems using surfactant-modified zeolite/zero-valent iron pellets." Environ Sci Technol 36(16): 3597-603.
- Surfactant- (hexadecyltrimethylammonium, HDTMA) modified zeolite (SMZ)/zero-valent iron (ZVI) pellets having high hydraulic conductivity (9.7 cm s-1), high surface area (28.2 m2 g-1), and excellent mechanical strength were developed. Laboratory column experiments were conducted to evaluate the performance of the pellets for perchloroethylene (PCE) sorption/reduction under dynamic flow-through conditions. PCE reduction rates with the surfactant-modified pellets (SMZ/ZVI) were three times higher than the reduction rates with the unmodified pellets (zeolite/ZVI). We speculate that enhanced sorption of PCE directly onto iron surface by iron-bound HDTMA and/or an increased local PCE concentration in the vicinity of iron surface due to sorption of PCE by SMZ contributed to the enhanced PCE reduction by the SMZ/ZVI pellets. Trichloroethylene and cis-dichloroethylene production during PCE reduction increased with the surfactant-modified pellets, indicating that the surfactant modification may have favored hydrogenolysis over beta-elimination. PCE reduction rate constants increased as the travel velocity increased from 0.5 to 1.9 m d-1, suggesting that the reduction of PCE in the column systems was mass transfer limited.
Zhang, Z., Y. Han, et al. (2001). "Mesoporous aluminosilicates with ordered hexagonal structure, strong acidity, and extraordinary hydrothermal stability at high temperatures." J Am Chem Soc 123(21): 5014-21.
- Highly ordered hexagonal mesoporous aluminosilicates (MAS-5) with uniform pore sizes have been successfully synthesized from assembly of preformed aluminosilcate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The aluminosilicate precursors were obtained by heating, at 100--140 °C for 2--10 h, aluminasilica gels at the Al2O3/SiO2/TEAOH/H2O molar ratios of 1.0/7.0--350/10.0--33.0/500--2000. Mesoporous MAS-5 shows extraordinary stability both in boiling water (over 300 h) and in steam (800 °C for 2 h). Temperature-programmed desorption of ammonia shows that the acidic strength of MAS-5 is much higher than that of MCM-41 and is comparable to that of microporous Beta zeolite. In catalytic cracking of 1,3,5-triisopropylbenzene and alkylation of isobutane with butene, MAS-5 exhibits greater catalytic activity and selectivity, as compared with MCM-41 and HZSM-5. The MAS-5 samples were characterized with infrared, UV--Raman, and NMR spectroscopy and numerous other techniques. The results suggest that MAS-5 consists of both mesopores and micropores and that the pore walls of MAS-5 contain primary and secondary structural building units, similar to those of microporous zeolites. Such unique structural features might be responsible for the observed strong acidity and high thermal stability of the mesoporous aluminosilicates with well-ordered hexagonal symmetry.
Zhu, J. H., D. Yan, et al. (2001). "Attempt to adsorb N-nitrosamines in solution by use of zeolites." Chemosphere 44(5): 949-56.
- The strong adsorption of zeolite for N-nitrosamines in solution was first revealed by use of adsorption, and temperature programmed surface reaction (TPSR) techniques. N-nitrosodimethylamine (NDMA) and N-nitrosopyrrolidine (NPYR) as well as N-nitrosohexamethyleneimine (NHMI) can be adsorbed on zeolite Y, ZSM-5 and A in the solution of methylene chloride or water, which will be helpful for removal of the N-nitrosamines pollution in environmental protection. The equilibrium data were fitted to Freundlich-type isotherms, but the adsorption capacity of zeolites mainly depended on their pore size, surface area and acid-basic properties. Molecular size of adsorbate and solute-solvent interaction also strongly affected the adsorption of N-nitrosamines on zeolite in solution. The extraordinary adsorption properties of NaA zeolite for N-nitrosamines in aqueous solution is first reported and discussed.
Für Kommentare und Anmerkungen benutzen Sie am einfachsten das Kontaktformular.
© Dr. Claudia Arnold, 2000 - 2013