Research Note: Penetration of Ozone Gas Across the Shell of Hen Eggs

Increasing evidence indicates that ozone gas is effective against Salmonella on and within shell eggs. However, information on the penetration of ozone across egg shell is limited. In this study, whole hen egg shells, filled with indigotrisulfonate solution (OD₆₀₀ ～1), were exposed to ozone gas (12–14% wt/wt O₃ in O₂) at 1.5 liters/min and atmospheric pressure for ≤ 40 min with appropriate controls. Ozone penetrated the shells over time (r²?=?0.9974) causing indigo decoloration and increasing its transmittance from 16 to 28% after gas exposure for 40 min. This study confirms ozone penetration through egg shell using a simple qualitative technique.     

The Reaction of Ozone with Bisulfide (HS−) in Aqueous Solution – Mechanistic Aspects

The ozone demand to oxidize HS^?/H₂S [pK_a(H₂S) = 6.9, k(HS^? + O₃) = 3 × 10⁹ M^?1 s^?1, k(H₂S + O₃) = 3 × 10⁴ M^?1 s^?1] to SO₄ ^2? is only 2.4 mol ozone per mol SO₄ ^2? formed, much lower than stoichiometric 4.0 mol/mol if a series of O-transfer reactions would occur. As primary step, the formation of an ozone adduct to HS^?, HSOOO^–, is suggested that decomposes into HSO^– and singlet oxygen (16%) or rearranges into peroxysulfinate ion, HS(O)OO^– (84%). Potential reactions of the above intermediates are discussed. Some of these can account for the low ozone demand.     

Steady State Disinfection of Water By Ozone and sonozone

Steady State laboratory flow equipment is used to disinfect Coxsackievirus, E. coli, S.lutea and the plate count flora of natural water, by means of dissolved and gaseous ozone, alone and simultaneous with ultrasound (sonozone).Distilled, surface and waste water are used as media. By ozonation, a three stage inactivation kinetics is observed. Inactivation of 3 & 4 decades is obtained, at 10–95% lower ozone concentrations, and by 57–96% lower gaseous ozone dosage by the sonozonation process compared to ozonation alone. Ultrasound increases the gas–liquid ozone transfer, and decomposes the dissolved ozone. It also disaggregates the viable microbial units.     

Ozone Application during Coagulation of Wastewater: Effect on Dissolved Organic Matter

The aim of this work was to determine the effect of ozone on dissolved organic matter (DOM) during wastewater coagulation using alum. Adding ozone to the coagulation treatment (O₃ECT) enhanced the quality of the final effluent in comparison to conventional coagulation treatment (CT). Final effluents were analyzed by Fourier transform infrared Spectroscopy (FTIR) and UV-Vis spectroscopy. The hydrophilic polar fraction was separated from the hydrophobic fraction using fractionation resins XAD-8 and XAD-4. Wastewater hydrophilic DOM was characterized by molecular weight distribution (MWD), and, BOD₅, TOC and DOC parameters. Results show that FTIR spectra for both effluents were very similar in the frequency range 7000 to 1400 cm^?1; however, some differences occurred in the O₃ECT effluent in the range 1100 to 700 cm^?1, which indicated that amines and aromatics groups were affected. In the same way, the UV-Vis spectra showed that there was an increase in absorbance within the wavelength range 285 to 300 nm for the O₃ECT effluent (when compared with CT) while the absorbance decreased in the range 210 to 455 nm, particularly at 380 nm. With regards to the hydrophilic polar compounds of DOM, the most abundant fraction in raw wastewater was found in the 3–10 kDa range. After CT, the effluents fraction concentrations decreased in all cases, but for O₃ECT the 10–30 kDa range exhibited a marked increase while the smaller (<3 kDa, 3–10 kDa) and larger fractions (>30 kDa) decreased. The ozone application during coagulation slightly increased TOC and DOC percentage removals, 84.4% to 89.1% and 80% to 82.5%, respectively. This suggests that the small dose of ozone transferred (1.47 mg/L) caused only minor changes in DOM. Finally, the O₃ECT effluent exhibits 10 mg/L more of biological oxygen demand (BOD₅) than a single CT.     

Ozonation and Advanced Oxidation of Wastewater: Effect of O3 Dose,pH, DOM and HO•-Scavengers on Ozone Decomposition and HO• Generation

The decomposition of ozone in wastewater is observed starting 350 milliseconds after ozone addition. It seems not to be controlled by the autocatalytic chain reaction, but rather by direct reactions with reactive moieties of the dissolved organic matter (DOM). A larger ozone dose increases ozone consumption prior to 350 milliseconds but decreases the rate of ozone decomposition later on; this effect is predicted by a second-order kinetic model. Transferred Ozone Dose (TOD) is poorly correlated with ozone exposure (= ∫[O₃]dt) indicating that TOD is not a suitable parameter for the prediction of disinfection or oxidation in wastewater. HO^? concentrations (> 10^?10 M) and R_ct (=∫[HO^?]dt/∫[O₃]dt > 10^?6) are larger than in most advanced oxidation processes (AOP) in natural waters, but rapidly decrease over time. R_ct also decreases with increasing pre-ozonation doses. An increase in pH accelerates ozone decomposition and HO^? generation; this effect is predicted by a kinetic model taking into account deprotonation of reactive moieties of the DOM. DOC emerges as a crucial water quality parameter that might be of use to normalize ozone doses when comparing ozonation in different wastewaters. A rapid drop of absorbance in the water matrix—with a maximum between 255–285 nm—is noticeable in the first 350 milliseconds and is directly proportional to ozone consumption. The rate of absorbance decrease at 285 nm is first order with respect to ozone concentration. A kinetic model is introduced to explore ozone decomposition induced by distributions of reactive moieties at sub-stoichiometric ozone concentrations. The model helps visualize and comprehend the operationally-defined “instantaneous ozone demand” observed during ozone batch experiments with DOM-containing waters.     

The Benefits of Small Quantities of Nitrogen in the Oxygen Feed to Ozone Generators

This paper reports the ozone generation in pulsed multichannel dielectric barrier discharge. The influence of nitrogen addition (0.1%–10%) on ozone concentration and ozone generation efficiency in nitrogen–oxygen gas mixtures is studied. Results show that adding 0.1% N₂ would not seriously increase the ozone production. Meanwhile, 1% N₂ content exhibits the highest ozone production efficiency in low SIE (J/L, defined as the ratio of power to gas flow rate) region (0–200 J/L) while adding 0.3% N₂ would lead to the highest ozone generation efficiency in high SIE region (300–800 J/L). The increase of ozone production induced by N₂ addition is more significant in low SIE region compared with that in high SIE region. At 100 J/L, ozone production efficiency increases 26.9% to 201.6 g/kWh with 1% N₂ addition when compared with that in oxygen. At 18 J/L, the observed maximum ozone generation efficiency reaches 252 g/kWh at 1.3 g/Nm³ with 1% N₂ addition. An increase of ozone production can be obtained with 0.3%–2% N₂ addition in all explored SIE ranges.     

Performance evaluation of ozonation and an ozone/hydrogen peroxide process toward development of a new sewage treatment process—Focusing on organic compounds and emerging contaminants

Performance of ozonation and an ozone/hydrogen peroxide process under a new concept centering on ozonation and/or ozone/hydrogen peroxide processes in sewage treatment processes comprising only physical and chemical processes are discussed, with focus on the removal of matrix organic compounds and emerging contaminants. Matrix organic compounds of filtrated primary sewage effluents were removed to as low as 3.2 mgC/L in the ozone/hydrogen peroxide process at an ozone consumption of around 400 mg/L. Linear relationships between ozone consumption and removal amounts of organic compounds were observed, in which the amounts of ozone required to remove 1 mg of organic carbon were 9.5 and 8.3 mg (2.4 and 2.1 mol-O₃/mol-C) in ozonation and the ozone/hydrogen peroxide process, respectively. Ratios of hydroxyl radical exposure to ozone exposure were in the order of 10^–9 to 10^–8 for ozonation and 10^–7 to 10^–6 for the ozone/hydrogen peroxide process. Experiments and a kinetic evaluation showed that ozonation and/or the ozone/hydrogen peroxide process have high elimination capability for emerging contaminants, even in primary sewage effluent with the thorough removal of matrix organic compounds. Newly found reaction phenomena, the temporal increase and decrease of dissolved ozone and accumulation of hydrogen peroxide in the early stage of oxidation with the continuous feeding of hydrogen peroxide, were presented. Possible reaction mechanisms are also discussed.     

The Effect of Gaseous Diluents on Ozone Generation from Oxygen

Ozone generation in a negative corona discharge has been experimentally investigated using both a pure oxygen and in binary mixtures of oxygen with several gases. The concentration of ozone (O₃) in such mixtures is found to be dependent both on the input energy density η, dissipated in unit volume of gas mixture and on the type and the concentration of the additives. The experimentally measured dependencies of ozone concentration on the input energy density (O₃) = f(η) have been fitted using the Vasiliev–Kobozev–Eremin formula and the specific rate coefficients for ozone formation K_f and ozone decomposition K_d have been calculated. Using Ar, N₂ or CO₂ as admixtures, an increase in the specific rate coefficient for ozone generation was observed for increasing concentrations of added gaseous impurity into oxygen. In contrast, admixtures with SF₆ or CCl₂F₂ caused a substantial reduction of K_f values. The absolute values of ozone concentration at constant input energy density were observed to decrease with decreasing concentrations of oxygen in all mixtures.     

Inactivation of Bacillus cereus and Salmonella enterica serovar typhimurium by Aqueous Ozone: Modeling and UV-Vis Spectroscopic Analysis

Antibacterial efficacy of aqueous ozone (O₃) against B. cereus vegetative cells and S. typhimurium by was studied by using GInaFiT tool and results were validated using UV-Vis spectroscopy. Ozone gas was generated using a domestic ozone generator. Buffer solutions containing known amounts (≈10⁸–10⁹ cfu/mL) of bacterial pathogens were treated with aqueous ozone (200 mg/hr or 0.1 mg/l) for 16 min with sampling at 0-, 0.5-, 1-, 2-, 4-, 8- and 16-min intervals. A reduction of 4.6 log of B. cereus and 7.7 log cycle reduction of S. typhimurium was obtained in 16 min. Biphasic shoulder and double Weibull models were good fit for the experimental inactivation kinetics data. Principal Component Analysis showed discrete grouping based on the time of treatment. The highest correct classification results for SIMCA were achieved for both B. cereus and S. typhimurium after 1 and 8 min of treatment, respectively. In partial least squares regression analysis, maximum R² values for calibration and validation were found to be 0.84, 0.80 for B. cereus and 0.90, 0.89 for S. typhimurium, respectively.     

A Study of Ozone Formation on the Surfaces of Electrodes

It had been previously thought that ozone production occurred in gaseous space, especially the space between electrodes. However, based on our research, we believe that may only be one of the ozone-producing processes. In this study, we aimed to confirm that a third body, which is present at the interface between oxygen gas and a metal electrode, works to compose ozone. Ozone was not observed in pure oxygen (400x10^?6 Nm³/min flow rate) when electrical discharge was supplied after approximately 6 months. The concentration of ozone increased (approximately 0.07 ppm) when nitrogen (approximately 20x10^?6 Nm³/min flow rate) was added to a gas-mixing chamber. A third body was required to produce ozone when an oxygen molecule and an oxygen atom collided. The same phenomenon was observed on the surface of a copper anode. A simulation confirmed this. Using an industrial ozone generator which utilized ceramic dielectrics and expanded metal electrodes, an increase in the temperature of the cooling water led to a proportional decrease in ozone concentration. After changing from the titanium electrode to a nickel electrode and an antimony electrode, we observed the difference in the enthalpy changes which were calculated using van't Hoff's formula. The antimony electrode increases the efficiency of the ozone generator to produce ozone. We have come to believe that ozone can be composed on the surface of a metal electrode.     

Kinetic Modeling of Ozone Generation via Dielectric Barrier Discharges

A mathematical model combining chemical kinetic and reactor geometry is developed for ozone synthesis in dry O₂ streams with a wire-tube dielectric barrier discharge (DBD) reactor. Good agreement is found between the predicted ozone concentrations and experimental data. Sensitivity analysis is conducted to elucidate the relative importance of individual reactions. Results indicate that the ground-state oxygen atom is the most important species for O₃ generation; however, ozone generation will be inhibited if the O atom is overdosed. The excited species, that is, O(¹ D) and O₂(b ¹Σ), can decompose O₃ and suppress ozone synthesis. The model developed is then applied to modify the original DBD reactor design for the enhancement of ozone yield. With a thinner dielectric thickness, more than 10% increase of ozone concentration is achieved.     

The Impact of Traces of Hydrogen Peroxide and Phosphate on the Ozone Decomposition Rate in “Pure Water”

To obtain an idea of the magnitudes of the ozone loss rates r_O3 in practical applications of ozone, an overall determination of the ozone decay profiles and rate constants was carried out in four different systems. These systems resemble different conditions for industrial application of ozone and the peroxone process, such as in the field of micro electronics, drinking water purification, disinfection, etc. Therefore, the behavior of ozone was monitored in the pH range from 4.5 to 9.0, in pure water and phosphate buffered systems in absence and presence of small amounts of hydrogen peroxide (10^?7 M to 10^?5 M H₂O₂). First the reproducibility of the ozone decay profiles was checked and from the various kinetic formalism tests, the reaction order 1.5 for the ozone decay rate has been selected. As expected, hydrogen peroxide increases the decay rates. In pure systems, added concentrations of 10^?7M H₂O₂ already cause a remarkable acceleration of the ozone decay in the acidic and neutral pH range compared to the pure systems. However for alkaline pH conditions almost no effect of the low hydrogen peroxide concentrations was noticed. Contradictory to literature data, in the absence of hydrogen peroxide, ozone displays faster decays in the buffered systems of low ionic strength of 0.02 compared to pure water. This acceleration is more pronounced for acidic pH conditions. Low concentrations of phosphate may indeed accelerate the ozone decay in the presence of organic matter. Adding H₂O₂ concentrations below 10^?5M to phosphate buffered solutions has a negligible effect on the ozone decay rate compared with pure water systems, except for pH 7. It appears that phosphate masks the effect of hydrogen peroxide below 10^?5 M as tested here. Thus the application of AOP's by adding low concentrations of hydrogen peroxide is not well feasible in the presence of phosphate buffers in pure water systems.     

Ultraviolet-Enhanced Ozonation of Organic Compounds: 1,2-Dichloroethane and Trichloroethylene as Model Substrates

1,2–Dichloroethane (DCE) and trichloroethylene (TCE) were used as model compounds to study the oxidation of organic chemicals by ozone/ultraviolet radiation, ozone, and hydrogen peroxide/ultraviolet radiation. It was found that ozone/ultraviolet radiation oxidized both 1,2–dichloroethane and trichloroethylene in batch systems, at pH = 2 (phosphate buffer). At ozone concentrations in the 1 to 5 mg/L range, the reaction was first order in both ozone and substrate. At pH = 2 and initial ozone concentration 2.2–2.6 mg/L, rate constants (k)Q = 25 and 130 M^-1sec^-1 were observed for the ozone/ultraviolet radiation oxidation of DCE and TCE, respectively. The rat e constants for ozone oxidation of DCE and TCE without ultraviolet radiation were 4.3 and 47 M^-1sec^-1, respectively.

The higher rate of TCE oxidation implies that direct reaction occurs with the double bond. Finite reaction rate of DCE with ozone, and substantial increases in rate at higher pH imply the participatation of hydroxyl radicals in the oxidation of both compounds. For example, at pH = 7, initial ozone concentration of 2.3 mg/L, the k_o for TCE oxidation by ozone/ultraviolet radiation is approximately 500 M^?1 sec^?1 almost too fast to measure in a batch system.The rate also is increased by increased ultraviolet radiation intensity, and by the presence of hydrogen peroxide, which acts as a catalyst.     

Ozone Production in a High Frequency Dielectric Barrier Discharge Generator

Factors that affect the performance of an expanded-mesh dielectric barrier discharge ozone cell were investigated. A gas feed pf 94% O₂, 4% Ar and 1% N₂ was used. An improvement in the productivity (g ozone/kWh) of about 20 % was achieved by doubling the gas flow rate through the cell. Decreasing the cell operating frequency (in the range 72 kHz to 19 kHz) increased the productivity of the ozone generator at constant power. The ozone production increased approximately in proportion to the input power; however productivity did not vary significantly with power above a minimum level. As the cell voltage was increased the dependence of productivity on power or frequency was reduced. Changing the feed gas temperature between ? 5^°C and + 42^°C had no effect on productivity. Finer meshes drew more power than coarser ones for a given voltage. Using a thinner mesh for the centre electrode increased productivity. The best results were obtained with a 6 × 3 × 1.86 mm titanium mesh giving a productivity of 110 g ozone/kWhr at 30–60 W, 1500–1900V and 23 KHz.     

Enhanced mechanical properties and bactericidal activity of polypropylene nanocomposite with dual‐function silica–silver core‐shell nanoparticles

Dual‐function silica–silver core‐shell (SiO₂@Ag) nanoparticles (NPs) with the core diameter of 17 ± 2 nm and the shell thickness of about 1.5 nm were produced using a green chemistry. The SiO₂@Ag NPs were tested in vitro against gram‐positive Staphylococcus aureus (S. aureus) and gram‐negative Escherichia coli (E. coli), both of which are human pathogens. Minimal inhibitory concentrations of the SiO₂@Ag NPs based on Ag content are 4 and 10 μg mL^?1 against S. aureus and E. coli, respectively. These values are similar to those of Ag NPs. SiO₂@Ag NPs were for the first time incorporated to a commodity polypropylene (PP) polymer. This yielded an advanced multifunctional polymer using current compounding technologies i.e., melt blending by twin‐screw extruder and solvent (toluene) blending. The composite containing 5 wt % SiO₂@Ag NPs (0.05 wt % Ag) exhibited efficient bactericidal activity with over 99.99% reduction in bacterial cell viability and significantly improved the flexural modulus of the PP. Anodic stripping voltammetry, used to investigate the antibacterial mechanism of the composite, indicated that a bactericidal Ag⁺ agent was released from the composite in an aqueous environment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of Ozone Treatment on the Reduction of Chlorpyrifos Residues in Fresh Lychee Fruits

The effect of ozone on the reduction of chlorpyrifos residue in lychee cv. Chakapat (Litchi chinensis Sonn.) was studied. Lychee fruits were dipped in the solution of chlorpyrifos at a concentration of 10 mg L^?1 for 10 min. Then, they were exposed to ozone gas (O₃) at concentrations of 80, 160, 200, 240 mg L^?1 and dipped in ozone-containing water, at concentrations of 2.2, 2.4, 3.4 and 3.2 mg. L^?1 for 10, 20, 30 and 60 min, respectively. Both ozone gas and ozone-containing water reduced pesticide residue in lychee, but exposure to ozone gas for 60 min was most effective. When lychee fruits were stored at 25 °C for 6 days, both processes did not show significant differences in weight loss, total soluble solids (TSS) and titratable acidity (TA). However, ozone-containing water decreased the eating quality of lychees after storage, compared with the ozone-fumigated groups.     

Experimental Study of Ozone Generation by Negative Corona Discharge in Mixtures of N2 and O2

Ozone generation by negative DC corona discharge in N₂-O₂ mixtures has been experimentally investigated using a coaxial wire-cylinder corona reactor operating at room temperature and atmospheric pressure. The experiments have been carried out under different gas flows (15 cm³ min^?1 to 200 cm³ min^?1) and gas compositions (5% to 90% of O₂), and the effect of these parameters on the corona current, the ozone density and the efficiency of the ozone generator have been analyzed. The global rate coefficients for ozone formation and destruction have also been evaluated, and their values compared with those reported by other authors. The maximum efficiency for ozone production was found in gas mixtures with oxygen content about 70–80%.     

Destruction of Helminth (Ascaris suum) Eggs by Ozone

Based on the properties of ozone as a strong germicidal agent, the inactivation kinetics or disintegration of Ascaris suum eggs in water were studied. Ozone was applied in synthetic samples, the concentration of dissolved ozone in the liquid phase was typically between 3.5 to 4.7mg/L, pH 5, 9. The value of 90% inactivation (t₉₀) obtained was at 1 h, the remaining 10% being inactivated in 2 h. A linear correlation between the logarithm of bacterial or yeast concentration (N) and contact time was found, being the linear significant correlation coefficient (r of 0.95). That 2-log inactivation occurred at a CT value near 4.7mg/min/L. The best reduction percentage was of 99.00 in 120min. It therefore could be demonstrated that ozone indeed induces effects on the helminth eggs.     

Modified Indigo Method For Gaseous And Aqueous Ozone Analyses

The indigo method developed by Bader and Hoigné for aqueous ozone analysis was modified to allow for both gaseous and aqueous ozone determination. Gas or water samples were extracted with a gas-tight syringe containing a known volume of indigo reagent. The modified procedure provided a more consistent basis for gaseous and aqueous ozone determination allowing for more accurate ozone mass balance calculations. Direct gaseous ozone UV absorbance with molar absorptivity of 3,000 M^?1cm^?1 at 258 nm was used as primary standard to determine the molar absorptivity of the indigo reagent. The molar absorptivity of indigo reagent, assuming a 1:1 stoichiometric ratio for the reaction between indigo and ozone, was determined to be 23,150 ± 80 M^?1cm^?1, or approximately 16 percent higher than that of 20,000 M^?1cm^?1 suggested by Bader and Hoigné. An independently calibrated membrane-electrode ozone monitor showed good correlation with indigo method results using the molar absorptivity value determined in this study. The apparent molar absorptivity of aqueous ozone at the wavelength of 258 nm measured by the modified indigo method increased from 2,400 to 3,600 M^?1cm^?1 in the investigated ozone concentration range of 0.4 to 11.0 mg/L. This variation might have been caused by the inherent interference of unidentified ozone byproducts, which presence was supported with scanning spectra in the wavelength range of 200 to 300 nm.