Antimicrobial Properties of Zeolite-X and Zeolite-A Ion-Exchanged with Silver,Copper, and Zinc Against a Broad Range of Microorganisms

Zeolites are nanoporous alumina silicates composed of silicon, aluminum, and oxygen in a framework with cations, water within pores. Their cation contents can be exchanged with monovalent or divalent ions. In the present study, the antimicrobial (antibacterial, anticandidal, and antifungal) properties of zeolite type X and A, with different Al/Si ratio, ion exchanged with Ag⁺, Zn²⁺, and Cu²⁺ ions were investigated individually. The study presents the synthesis and manufacture of four different zeolite types characterized by scanning electron microscopy and X-ray diffraction. The ion loading capacity of the zeolites was examined and compared with the antimicrobial characteristics against a broad range of microorganisms including bacteria, yeast, and mold. It was observed that Ag⁺ ion-loaded zeolites exhibited more antibacterial activity with respect to other metal ion-embedded zeolite samples. The results clearly support that various synthetic zeolites can be ion exchanged with Ag⁺, Zn²⁺, and Cu²⁺ ions to acquire antimicrobial properties or ion-releasing characteristics to provide prolonged or stronger activity. The current study suggested that zeolite formulations could be combined with various materials used in manufacturing medical devices, surfaces, textiles, or household items where antimicrobial properties are required.     

Adsorptive removal of halo-olefinic impurities from 1,1,1,3,3-pentafluoropropane over ion-exchanged Y zeolites

Various metal cations exchanged Y zeolites were prepared via the exchange of NaY zeolite with aqueous solutions containing K⁺, Ca²⁺, Cu²⁺, La³⁺ and Ce³⁺ cations, respectively. The influence of the extra-framework cations nature of these ion-exchanged Y zeolites on their adsorption performance for a low content of halo-olefinic impurities, mainly including 1-chloro-3,3,3-trifluoro-1-propene (HCFC-1233zd), 1-chloro-1,3,3,3-tetrafluoro-1-propene (HFC-1224zb) and 2-chloro-1,3,3,3-tetrafluoro-1-propene (HFC-1224xe), in the 1,1,1,3,3-pentafluoropropane (HFC-245fa) product after distillation was investigated. HCFC-1233zd impurity can be substantially removed from HFC-245fa product feed via the adsorption over multivalent metal cations and Cu⁺ cation exchanged Y zeolites, which is ascribed to the formation of π-adsorption complexes between HCFC-1233zd and zeolites, rather than over alkaline metal cations exchanged Y zeolites. Among multivalent metal cations exchanged Y zeolites, CeY has the highest adsorption capacity for HCFC-1233zd and best regeneration performance, due to its lowest density of strong Brønsted and weak Lewis acid sites as well as high framework stability during the regeneration. Regardless of the cations introduced in Y zeolite used as an adsorbent, HCFC-1224zb and HCFC-1224xe impurities are not obviously removed from HFC-245fa product feed via the adsorption, maybe due to more halogen atoms linked with the double bond in them comparing with HCFC-1233zd.     

Thermodynamics of the Exchange Processes between K+, Ca2+ and Cr3+ in Zeolite NaA

In this paper it was analyzed the ion exchange isotherm of K⁺, Ca²⁺ and also Cr³⁺ ions with NaA zeolites at three temperatures: 30, 45 and 60°C. The NaA isotherms were favorable for the metal cations studied. Differences in shape are due to the different influence of temperature in the interaction of the in-going cation with the zeolite framework. As a consequence, sites of different energies were used in the exchange process, which provided non linear Kielland plots. Equilibrium constant, standard free energy, enthalpy and enthopy changes were measured and tabulated. Equilibrium constant is directly proportional to the in-going ion charge. Concerning enthalpy, endothermic and exothermic exchanges were observed due to differences in the cation-framework interaction. The selectivity order based on the standard free energy over the entire temperature range was K⁺ < Cr³⁺ < Ca²⁺, a consequence of different ion exchange mechanisms. It was also noted that the entropy change increases with the polarizibility of the cations.     

Atmospheric pressure laser desorption/ionization of plant metabolites and plant tissue using colloidal graphite

Colloidal graphite is a promising matrix for atmospheric pressure laser desorption/ionization mass spectrometry. Intact [M+H]⁺ and [M–H]^? ions are readily produced from a wide range of small molecule plant metabolites, particularly anthocyanins, fatty acids, lipids, glycerides, and ceramides. Compared with a more traditional organic acid matrix, colloidal graphite provides more efficient ionization for small hydrophobic molecules and has a much cleaner background spectrum, especially in negative ion mode. Some important metabolites, e.g., fatty acids and glycosylated flavonoids, can be observed from Arabidopsis thaliana leaf and flower petal tissues in situ. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and adsorption investigations of zeolites MCM-22 and MCM-49 modified by alkali metal cations

Ion exchange was made on MCM-22 and MCM-49 zeolites with different Si/Al molar ratios, with Li⁺, Na⁺, K⁺, and Cs⁺ ions and the study of the influence of alkali metal cations on CO₂ adsorption properties was performed. The degree of ion-exchange decreased for larger cations (Cs⁺) apparently due to steric hindrances. The exchange with different cations led to a decrease in the surface area and the micropore volume. Our study shows that the adsorption capacity of the tested zeolites depends significantly on the nature and the concentration of the charge-compensating cations. The highest CO₂ adsorption capacity was obtained on the MWW zeolites with the lowest Si/Al molar ratio and the Li⁺ or K⁺ cations.     

Mesopores in USY Zeolites II

Microporous zeolites Na‐Y and K‐Y were converted into the NaNH₄‐Y and KNH₄‐Y modifications by ion exchange being active in dealumination. Removal of framework aluminium and silicon is accompanied by formation of secondary mesopores. Internal mesopores are formed in the centre of zeolite crystals and external pores at their surface. Formation of mesopores changes the sorption behaviour.Residual alkali metal cations as Na⁺ or K⁺ stabilise, however, the framework ≡Si‐O‐Al≡ bonds. Because of inhomogeneous distribution of sodium ions, in NaNH₄‐Y less internal but more external mesopores are formed. Potassium ions of KNH₄‐Y are more homogeneous distributed over the framework why a more balanced formation of secondary pores takes place.     

Photophysical and photochemical processes in zeolite cavities: The effects of ion-exchanged alkalimetal cations on the excited states of xanthone and the photolysis of 2-pentanone

The characteristics properties of xanthone phosphorescence and of 2-pentanone photolysis in alkali metal cation-exchanged zeolites have been investigated to clarify the effect of the micro-environment of host-adsorbents on the photophysical and photochemical properties of guest-molecules in restricted void spaces. The enhancement of the phosphorescence yields of xanthone included in zeolites is observed by changing the exchangeablealkali metal cation from Li⁺ to Cs⁺. Simultaneously, the phosphorescence lifetimes were observed to continuously shorten by changing the cation from Li⁺ to Cs⁺. These results suggest that the external heavy-atom effect deriving from the alkali metal cations on the singlet-triplet transitions of xanthone molecules stabilized on alkali metal cations in the order of Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺. The yields for the photolysis of 2-pentanone included in zeolites increase with changing the alkali metal cation from Li⁺ to Cs⁺. IR investigations of the adsorption state of 2-pentanone indicate that strength of the interaction between the alkali metal cations and 2-pentanones decreases by changing the cation from Li⁺ to Cs⁺, which results in a longer lifetime of 2-pentanone. The selectivity of propylene formation is dramatically increased by changing the cation from Li⁺ to Cs⁺. The enhanced formation of propylene is asociated with the hydrogen absorption from propyl radicals by lattice oxygen, their basicity increasing by changing the cation from Li⁺ to Cs⁺. Thus, these changes in the zeolite cavities modified by exchanging cations caused significant effects not only on the excited state but also on the following chemical reactions of ketones.     

Evaluation of Co/SSZ-13 Zeolite Catalysts Prepared by Solid-Phase Reaction for NO-SCR by Methane

Co/SSZ-13 zeolites were prepared by heating the finely dispersed mixture of NH₄-SSZ-13 and different cobalt salts up to 550 °C. Investigations by thermogravimetry – differential scanning calorimetry – mass spectrometry provided new insight into details of the solid-state reaction. Formation of Co carrying hydrate melt or volatile species was shown to proceed from chloride, nitrate, or acetylacetonate Co precursor salts upon thermal treatment. This phase change allows the transport of the Co species into the zeolite pores. The reaction of the NH₄⁺ or H⁺ zeolite cations and the mobile Co precursors generates vapor or gas products, readily leaving the zeolite pores, and cobalt ions in lattice positions suggesting that solid-state ion-exchange is the prevailing process. The obtained catalysts are of good activity and N₂ selectivity in the CH₄/NO-SCR reaction. The thermal treatment of acetate or formate salts give solid intermediates that are unable to get in contact and react with the cations in the zeolite micropores. These catalysts contain mainly Co-oxide clusters located on the outer surface of the zeolite crystallites and have poor catalytic performance.     

Determination of alkali metal ion binding selectivities of calixarenes by matrix-assisted laser desorption ionization and electrospray ionization in a quadrupole ion trap

Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS) are used to evaluate the alkali metal ion binding selectivities of a series of calixarenes. Each calixarene of interest is mixed with one or more alkali metal salts (1:100 ratio of calixarene to metal), either in the ESI solution or on the MALDI probe surface, and the relative binding selectivities are directly determined from the intensities of the calixarene/metal complexes in the mass spectra. For t-butylcalix[4]arene-tetraacetic acid tetraethyl ester (calixarene 1), complexation of Na⁺ is favored over complexation of K⁺, in agreement with prior solution results obtained by conventional methods. For the three calixarenes that do not have t-butyl groups on the upper rims, the calixarenes preferentially bind K⁺ over Na⁺, thus demonstrating that size selective complexation can be probed with both the ESI and MALDI methods. Collision-activated dissociation results indicate that the phenyl oxygens, but not necessarily the ethoxy ethyl oxygens of the lower rims, are the primary binding sites for the alkali metal ions.     

Highly active and reusable heterogeneous catalysts for acylation of anisole

In the present study, non-conventional solid acid catalysts such as NaY, metal ion exchanged zeolite NaY (Zn²⁺, Fe³⁺, Ce³⁺, La³⁺ and Nd³⁺), H-mordenite, H-β and HZSM-5 were used in order to overcome the disadvantages of conventional Friedel-Crafts catalysts for the acylation of anisole with acetic anhydride. Among the various zeolites studied, the HY zeolite shows an intermediate activity. Zeolite containing transition metal ions (Zn²⁺ and Fe³⁺) are less active and zeolite NaY is nearly inactive. The catalysts exhibit the activity in the order H-β>transition metal ions (Zn²⁺ and Fe³⁺)>HY>NaY zeolite. The highest catalytic activity of H-β could be due to its larger pore size. The type of acidity and the acid strength in zeolite Y were determined by FTIR and differential scanning calorimetric (DSC) studies on the pyridine adsorbed catalysts. The correlation of catalytic activity with acidity reveals that Brönsted acid sites in zeolite promote the acylation of anisole.     

Monovalent cation-promoted ordering of a glycine-rich cyclic peptide

This report describes an accelerated self-assembly of a synthetic cyclic hexapeptide in the presence of alkali metal ions. Time-dependent aggregation of hexapeptide was considerably influenced upon co-incubation with monovalent metal ions, of which K⁺ afforded the most significant effect both on the time-scale required for self-assembly and on the morphology of aged structures. Metal ion adducts formation ability of the hexapeptide was confirmed by electrospray ionization mass spectrometry measurements and ¹³C NMR spectrometry. The effect of metal ion binding on peptide structure was also probed by circular dichroism, optical microscopy, and scanning electron microscopy. K⁺ ions not only interacted more efficiently with the hexapeptide enabling it to reach conformational state(s) conducive for self-assembly, but also altered the morphologies of the aged peptide fibers, when compared to the unmetalated peptide.     

Desilication mechanism revisited: highly mesoporous all-silica zeolites enabled through pore-directing agents

The role of pore‐directing agents (PDAs) in the introduction of hierarchical porosity in silicalite‐1 in alkaline medium was investigated. By incorporation of various PDAs in aqueous NaOH, homogenously distributed mesopores were introduced in 2.5 μm silicalite‐1 crystals. It was proven for the first time that framework aluminum is not a prerequisite for the introduction of intracrystalline mesoporosity by desilication. The pore‐directing role is not directly exerted by framework trivalent cations metals, but by species on the external surface of the zeolite. The inclusion of metal complexes (Al(OH)₄^?, Ga(OH)₄^?) and tetraalkyl ammonium cations (tetramethyl ammonium (TMA⁺), tetrapropyl ammonium (TPA⁺)) in the alkaline solution led to distinct mesopore surface areas (up to 286 m² g^?1) and pore sizes centered in the range of 5–20 nm. In the case alkaline treatment was performed in the presence of Al(OH)₄^?, all aluminum partially integrated in the zeolite giving rise to both Lewis and Brønsted acidity. Apart from the concentration and location, the affinity of the PDA to the zeolite surface plays a crucial role in the pore formation process. If the PDA is attracted too strongly (e.g., TMA⁺), the dissolution is reduced dramatically. When the pore‐directing agent is not attracted to the zeolite’s external surface, excessive dissolution occurs (standard alkaline treatment). TPA⁺ proved to be the most effective PDA as its presence led to high mesopore surface areas (>200 m² g^?1) over a broad range of PDA concentrations (0.003–0.1 M ). Importantly, our results enable to extend the suitability of desilication for controlled mesopore formation to all‐silica zeolites.     

Fe+ chemical ionization of peptides

Laser-desorbed peptide neutral molecules were allowed to react with Fe⁺ in a Fourier transform mass spectrometer, using the technique of laser desorption/chemical ionization. The Fe⁺ ions are formed by laser ablation of a steel target, as well as by dissociative charge-exchange ionization of ferrocene with Ne⁺. Prior to reaction with laser-desorbed peptide molecules, Fe⁺ ions undergo 20–100 thermalizin collisions with xenon to reduce the population of excited-state metal ion species. The Fe⁺ ions that have not experienced thermalizing collisions undergo charge exchange with peptide molecules. Iron ions that undergo thermalizing collisions before they are allowed to react with peptides are found to undergo charge exchange and to form adduct species [M + Fe⁺] and fragment ions that result from the loss of small, stable molecules, such as H₂O, CO, and CO₂, from the metal ion-peptide complex.     

Catalytic Activity of Boron-Beta Zeolite Modified with Indium in the Epoxidation of Cinnamyl Alcohol

Liquid-phase epoxidation of cinnamyl alcohol was carried out with hydrogen peroxide as oxidizing agent using indium-containing boron- and aluminium-beta zeolites. It was proved that InO⁺ ions, created by oxidation of univalent indium cations incorporated into beta zeolite by reductive solid-state ion exchange, play an important role in the activation of hydrogen peroxide. The indium-hydroperoxo complex formed in beta zeolite pores was found to be accessible by the bulky cinnamyl alcohol molecules. Among the applied catalysts In/H[B]-beta (containing 7.6% In₂O₃/g) showed the highest selectivity in cinnamyl alcohol epoxidation.     

Influence of electronic and molecular structure on the fragmentation dynamic of even‐electron carbocationic triangulenes and helicenes in the gas phase

Stable, long‐lived organic cations are directly transferred by electrospray ionization (ESI) from solution into the gas phase where their collision‐induced dissociations (CID) are studied by tandem mass spectrometry. Three related types of triphenyl carbenium ions are investigated, in which the meta positions are either substituted by methoxy groups or tertiary nitrogen bridges, including tetramethoxyphenylacridinium (TMPA⁺), dimethoxyquinacridinium (DMQA⁺), and triazatriangulenium (TATA⁺) cations. These ions are triangular in shape with increasing degrees of planarity. Fragmentation occurs at the periphery of the triangular molecule, involving the methoxy groups and the substituent of the nitrogen bridge. Each initial precursor cation is an even electron (EE) system and shows competing dissociations into both even (EE) and odd electron (OE) fragment ions. The latter reaction is a breach of the classic ‘even‐electron rule’ in mass spectrometry. While the EE fragment dissociates similar to the precursor, the OE fragment ion shows a rich radical‐induced fragmentation pattern. Two driving forces direct the fragmentation of the EE precursor ion toward OE fragment ions, including the release of stabilized radicals and the extension of the π‐system by increasing planarization of the triangulene core. Copyright © 2017 John Wiley & Sons, Ltd.     

Selective Determination of Dimethyl Sulfide in Seawater Using Reactive Extractive Electrospray Ionization Mass Spectrometry

Reactive extractive electrospray ionization mass spectrometry was used for the rapid, sensitive determination of dimethyl sulfide in seawater without sample pretreatment. Using silver cations (Ag⁺) as the ionic reagent, the analyte was selectively extracted from seawater to form adduct ions of [CH₃SCH₃?+?Ag]⁺. The characteristic product ions of Ag⁺, generated from parent ions of [CH₃SCH₃?+?Ag]⁺ by tandem mass spectrometry, were used for quantitative analysis. A linear calibration curve was obtained from 1 to 10,000 pg/mL with acceptable relative standard deviations of 3.2–8.1%. This method provided a low limit of detection (0.3 pg/mL), reasonable recovery (82–111%), and acceptable precision (3.9 and 4.2% for intraday and interday measurements). Trace dimethyl sulfide was determined in seawater by this method. These results demonstrate that reactive electrospray ionization mass spectrometry is suitable for the rapid, reliable, and sensitive determination of dimethyl sulfide in seawater. Further investigations will improve our understanding on the relationship between global climate change and dimethyl sulfide concentrations in the ocean.     

Laser-based ion mobility spectrometer for the direct analysis of aromatic compounds in liquids

A laser-based ionization source for the direct analysis of liquid samples in ion mobility (IM) spectrometry is presented and characterized. Ionization of aromatic substances in liquids is achieved, analogous to atmospheric pressure laser ionization (APLI) in mass spectrometry, by vaporizing the liquid and subsequently ionizing the aromatic substances by resonance-enhanced multiphoton ionization (REMPI). The effects of parameters, such as composition and flow rate of the solvent as well as laser wavelength and pulse energy, are systematically investigated. The characterization of the IM spectrometer is carried out by means of selected substances from diverse fields of applications, e.g., polycyclic aromatic hydrocarbons (PAH), pesticides, wood preservatives and drug compounds. Limits of detection (LOD) down to 10 fmol and linear ranges up to three orders of magnitude are established. In addition to direct laser ionization, indirect laser ionization via dopants (toluene) for substances with low ionization efficiencies is investigated. Ionization occurs as a result of proton transfer from toluene radical cations to substances of sufficiently high proton affinities. As a result of indirect laser ionization, LOD could be decreased by up to two orders of magnitude. Ionization products are investigated by means of a combination of IM and mass spectrometer. Depending on the substance investigated primary ions (radical cations) and secondary ions (protonated molecules) resulting from ion molecule reactions are formed.     

Role of metal co-cations in improving CuY zeolite performance for DMC synthesis: A theoretical study

First principle calculations based on density functional theory are conducted to investigate the influence of metal cations including Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, La (OH)²⁺ and Ce (OH)²⁺ in the small cage of zeolite on the electronic environment of adjacent active center, Cu⁺ in CuY zeolite as well as the process of CO insertion into CH₃O to form CH₃OCO for oxidative carbonylation of methanol. The study explains the theoretical reasons for the effects of metal cations on the catalytic activity of zeolites. It was found that, the presence of co-cations in the small cage can affect the electronic properties and also the catalytic activity in two ways. Firstly, the presence of co-cations, viz., Ca²⁺, Sr²⁺, Mg²⁺, Ba²⁺ and La species in small cage hinders the migration of active Cu⁺ cations from the super cage to small cage. Secondly, the co-cations greatly affect the charge transfer from zeolite framework to Cu⁺ present in the adjacent super cage, leading to the increase of the net charge and binding energy of Cu⁺. The findings can improve the CO adsorption and insertion efficiencies, and the stability of transition states, which results in the enhanced catalytic activity of corresponding zeolites.     

Schwermetallausgetauschte Zeolithe als Katalysatoren für die Selektivoxidation

Transition Metal Zeolites as Catalysts for the Partial Oxidation of Methanol Zeolites containing cations of the 4th period of the periodical system from Ti to Cu have been prepared by ion exchange of a NaY zeolite in aqueous solutions. Structural and surface chemical properties of the zeolites were characterized by adsorption, DTA, thermogastitrimetry, x-ray, ESR, IR, and UV-V is spectroscopy. It could be shown that both localization and coordination state of transition metal ions is fairly different and depends on the thermal treatment of the zeolites. By exchanging sodium ions the acidic properties as well as the ability of the zeolites to interact with H₂O or CO₂ is changed and depends on the kind of transition metal ion. VO and Cr exchanged zeolites proved to be selective catalysts for the oxidative dehydrogenation of methanol to formaldehyde with a maximum selectivity of 70%. It is concluded that in contrast to oxides where a redox mechanism is assumed the reaction on zeolites occurs via an associative mechanism.     

Equilibria and heats of exchange of alkaline-earth metal ions on the Na form of mordenite

Sorption-analytic studies of ion exchange equilibria combined with direct calorimetric measurements of the heats of ion exchange sorption of the Ca²⁺, Sr²⁺, and Ba²⁺ cations were performed over the whole range of solid phase fillings with sorbed cations on the Na forms of two mordenites prepared from natural specimens rich in Na⁺ and Ca²⁺ cations. Ion exchange constants were determined and the Gibbs energies and entropies of ion exchange were calculated. The thermodynamic characteristics obtained were analyzed taking into account the preferable localization of alkaline-earth metal ions on certain exchange centers in the structure of mordenite. The presence of natural mordenite memory effects with respect to extra-framework Ca²⁺ cations in the presence of which these zeolites were crystallized in nature was established.