Silver-loaded Zeolite Research Articles

Preparation of 4A-Type Silver-Loaded Zeolite and Antibacterial Papers

4A-type silver-loaded zeolite antibacterial agents, prepared by ion-exchanging method, were added into 2 % PVA solutions with the concentration of 0.0 %, 0.1 %, 0.3 %, 0.5 %, 0.7 %, 0.9 %, 1.0 %, 1.5 %, 2.0 %, 2.5 % and 3.0 %, and then coated on different papers to prepare antibacterial papers. Physical and mechanical properties, whiteness and smoothness of these papers were studied. The results show that the properties of the papers are not seriously affected.

Effect of Silver-Loaded Zeolite on the Susceptibility of <i>Escherichia Coli</i> Against Antibiotics

We investigated the effect of silver-loaded zeolite (Ag-Z) on antibacterial activity of some antibiotics against Es-cherichia coli against antibiotics. We treated the bacterial suspension of E. coli by Ag-Z to be the level which the decrease of viable cell count was not observed. Susceptibility test of E. coli treated with Ag-Z was carried out against four antibiotics with different mode of action. Apparent increase in susceptibility was found in the case of rifampicin, not in others. The result suggests that application of Ag-Z to ward environment might give a good outcome at the treatment with rifampicin and at the treatment for pathogenic microbe spread through the air, such as tubercle bacilli.

Antibacterial activity of silver-loaded zeolite A prepared by a fast microwave-loading method

Silver ion was loaded into zeolite A by a rapid synthesis method, microwave loading, to obtain an antibacterial agent suitable for use in biological applications. Antibacterial activity of silver-loaded zeolite A against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus was determined by minimum inhibitory concentration, revealing its potential as a strong bactericide.

A Novel Zeolite Coating for Protection of Concrete Sewers from Biological Sulfuric Acid Attack

Microbial growth inhibition and resistance to biological deterioration of concrete specimens coated with silver-loaded zeolite was evaluated by measuring the time course of bacterial growth, biological sulfur oxidation, and sulfate production using Acidithiobacillus thiooxidans as a corrosive agent. Live bacterial cells declined from an initial inoculum concentration of 1.1 × 104 cell ml-1 to zero in 10 days, during which only 0.5–1% of the initial sulfur concentration of 10 g l-1 was biologically oxidized, corresponding to sulfate production rates of 35–42 mg SO 4 2 − g − 1 S − 1 . Leaching coefficients of calcium and silicon in the specimens coated with silver-loaded zeolite of 1.6 × 10 − 4 to 4.6 × 10 − 2 cm 2 d − 1 respectively, were only 0.8% and 1% of the uncoated specimens.

Catalytic oxidation of butyl acetate over silver-loaded zeolites

The performance of silver-loaded zeolite (HY and HZSM-5) catalysts in the oxidation of butyl acetate as a model volatile organic compound (VOC) was studied. The objective was to find a catalyst with superior activity, selectivity towards deep oxidation product and stability. The catalyst activity was measured under excess oxygen condition in a packed bed reactor operated at gas hourly space velocity (GHSV) = 15,000–32,000 h −1, reaction temperature between 150 and 500 °C and butyl acetate inlet concentration of 1000–4000 ppm. Both AgY and AgZSM-5 catalysts exhibited high activity in the oxidation of butyl acetate. Despite lower silver content, AgY showed better activity, attributed to better metal dispersion, surface characteristics and acidity, and its pore system. Total conversion of butyl acetate was achieved at above 400 °C. The oxidation of butyl acetate followed a simple power law model. The reaction orders, n and m were evaluated under differential mode by varying the VOC partial pressure between 0.004 and 0.018 atm and partial pressure of oxygen between 0.05 and 0.20 atm. The reaction rate was independent of oxygen concentration and single order with respect to VOC concentration. The activation energies were 19.78 kJ/mol for AgY and 32.26 kJ/mol for AgZSM-5, respectively.

Light Irradiation Is a Factor in the Bactericidal Activity of Silver-Loaded Zeolite

Silver loaded zeolite (Ag-Z) was previously found to have effective bactericidal activity against Escherichia coli. To understand the mechanisms of bactericidal activity of Ag-Z, role of light irradiation was focused and investigated in this study. In this study, we focused on light irradiation. Antibacterial assay and spectroscopic study revealed that light irradiation enabled Ag-Z to reduce dioxygen to form a reactive oxygen species, which led to bactericidal activity. These results indicate that the onset of bactericidal activity can be controlled by light irradiation.

Antimicrobial action and efficiency of silver-loaded zeolite X

To synthesize silver-loaded zeolite X and establish the extent to which it persist in its antimicrobial action against strains of Escherichia coli K12W-T, Pseudomonas aeruginosa NCIMB8295 and Staphylococcus aureus NCIMB6571. The antimicrobial action and efficacy of silver-loaded zeolite X on Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were investigated. Zeolite X was synthesized and loaded with Ag(+) by ion exchange. This resulted in 2.0% (w/w) loading of Ag(+) in the zeolite framework and 5.8% (w/w) on the zeolite. Escherichia coli and Pseudomonas aeruginosa and Staphylococcus aureus suspended in tryptone soya broth were exposed to 0.15, 0.25, 0.5 or 1.0 g l(-1) of silver-loaded zeolite X for a period up to 24 h. No viable cells were detected for any of the three micro-organisms within 1 h. Silver-loaded zeolite X, retrieved three times from the first exposure cultures, was washed with de-ionized water and added to fresh bacterial suspensions. The results showed that the silver-loaded zeolite X retained its antimicrobial action. Silver-loaded zeolite X persisted in its antimicrobial action against all three micro-organisms. The results are significant for the longevity of antimicrobial action of silver-loaded zeolite X.

Bactericidal activity of Ag–zeolite mediated by reactive oxygen species under aerated conditions

The bactericidal activity induced by the introduction of silver ions into zeolite was studied. Escherichia coli was used as the test microorganism. Silver ions were loaded into zeolite by the ion-exchange method. Silver-loaded zeolite was demonstrated the strong bactericidal activity. Dissolved oxygen was an essential factor for the occurrence of the bactericidal activity because the activity was observed only under aerated condition. Superoxide anions, hydrogen peroxide, hydroxyl radicals and singlet oxygen were formed. Scavengers of these each reactive oxygen species (ROS) inhibited the bactericidal activity. This means that all ROS contributed to the activity.

Bactericidal allophanic materials prepared from allophane soil: II. Bactericidal activities of silver/phosphorus–silver-loaded allophanic specimens

Bactericidal activities against Escherichia coli and Staphylococcus aureus in water for two sterilizing allophanic specimens prepared by loading silver or phosphorus along with silver on an allophane soil carrier, were examined in comparison to those of silver-loaded zeolite specimens. The sterilizing allophanic specimens were added to bacteria suspensions (1×10 6–1×10 7 cells of E. coli or S. aureus/1 cm 3 of suspension) and stirred for a fixed period. Then bactericidal activities were evaluated from survival ratio of bacteria in liquid phase by batch method. Obvious and strong bactericidal activities of the sterilizing allophanic specimens were observed for both bacteria. These sterilizing allophanic specimens also showed immediate pronounced effects for bactericidal activity than that of silver-loaded zeolite specimens. For these allophanic specimens, it was understood that the contribution of insoluble silver in the specimens to bactericidal activity was remarkably high in comparison to those of silver-loaded zeolite specimens. Co-loading of phosphorus enhances the amount of silver loading and had a great effect in controlling silver elution from these allophanic specimens.

The mechanism of antibacterial activity of silver-loaded zeolite

The mechanism of antibacterial activity of silver-loaded zeolite

127I Mössbauer spectra of iodine adsorbed on zeolites

The adsorption behavior of iodine on zeolites and silver-loaded zeolites has been studied by127I Mossbauer spectroscopy. Iodine is adsorbed on zeolites in two forms. One is a physically adsorbed species and the other is a dissociative species. The former is the major form and their intermolecular interactions are suggested to be weakened. Iodine is converted to silver iodide on the surface of silver-loaded zeolites, although some portion is physically adsorbed.

Epoxidation of Ethylene on Silver-Loaded Zeolites

Epoxidation of Ethylene on Silver-Loaded Zeolites