Ozonation of drinking water: part I. Oxidation kinetics and product formation.

Advanced oxidation processes (AOPs), defined as those technologies that utilize the hydroxyl radical (·OH) for oxidation, have received increasing attention in the research and development of wastewater treatment technologies in the last decades. These processes have been applied successfully for the removal or degradation of toxic pollutants or used as pretreatment to convert recalcitrant pollutants into biodegradable compounds that can then be treated by conventional biological methods. The efficacy of AOPs depends on the generation of reactive free radicals, the most important of which is the hydroxyl radical (·OH). The authors summarize the formation reactions of ·OH and the mechanisms of pollutants degradation. They cover six types of advanced oxidation processes, including radiation, photolysis and photocatalysis, sonolysis, electrochemical oxidation technologies, Fenton-based reactions, and ozone-based processes. Controversial issues in pollutants degradation mechanism were discussed. They review t...

Advanced Oxidation Processes for Wastewater Treatment: Formation of Hydroxyl Radical and Application

Ozone is a powerful antimicrobial agent that is suitable for application In food in the gaseous and aqueous states. Molecular ozone or its decomposition products (for example, hydroxyl radical) inactivate microorganisms rapidly by reacting with intracellular enzymes, nucleic material and components of their cell envelope, spore coats, or viral capsids. Combination of ozone with appropriate initiators (for example, UV or H 2 O 2 ) results in advanced oxidation processes (AOPs) that are potentially effective against the most resistant microorganisms; however, applications of AOPs in food are yet to be developed. When applied to food, ezone is generated on-site and it decomposes quickly, leaving no residues. Ozone is suitable for decontaminating produce, equipment, food-contact surfaces, and processing environment. L'ozone est un puissant antimicrobien, adapte a l'etat gazeux et aqueux, a l'application sur les aliments. L'ozone moleculaire ou ses produits de decomposition inactivent rapidement les microorganismes en reagissant avec les enzymes intracellulaires, les materiaux nucleiques et les composants de la membrane cellulaire. La combinaison de l'ozone avec des initiateurs appropries (UV ou H 2 O 2 ) engendre des procedes d'oxydation avances, potentiellement efficaces contre les microorganismes les plus resistants.

Microbiological aspects of Ozone applications in food: A review

The ozonation of model systems and several natural waters was examined in bench-scale batch experiments. In addition to measuring the concentration of ozone (O3), the rate of depletion of an in situ hydroxyl radical probe compound was monitored, thus providing information on the transient steady-state concentration of hydroxyl radicals (√OH). A new parameter, Rct , representing the ratio of the √OH-exposure to the O3-exposure was calculated as a function of reaction time. For most waters tested, including pH-buffered model systems and natural waters, Rct was a constant value for the majority of the reaction. Therefore, Rct corresponds to the ratio of the √OH concentration to the O3 concentration in a given water (i.e. Rct = [√OH]/[O3]). For a given water source, the degradation of a micropollutant (e.g. atrazine) via O3 and √OH reaction pathways can be predicted by the O3 reaction kinetics and Rct .

Hydroxyl Radical/Ozone Ratios During Ozonation Processes. I. The Rct Concept

Reference LCIB-ARTICLE-2007-010doi:10.1021/cr030726oView record in Web of Science Record created on 2007-02-14, modified on 2017-05-12

Inorganic and bioinorganic solvent exchange mechanisms.

L'etape d'initiation serait O 3 +OH − →HO 2 − +O 2 qui correspond a un processus de transfert de 2 electrons

Kinetics and mechanism of ozone decomposition in basic aqueous solution

Nuclear magnetic resonance study of the kinetics of the water exchange process in the equatorial positions of uranyl complexes

The exchange reactions of dimethyl sulfoxide (DMSO) with UO2(acac)2dmso and UO2(dbm)2dmso (acac=acetylacetonate, dbm=dibenzoylmethanate) have been studied by the NMR method in CD3COCD3 and CD2Cl2. ...

A Nuclear Magnetic Resonance Study of the Kinetics of Ligand Exchange Reactions in Uranyl Complexes. III. Dimethyl Sulfoxide Exchange in Bis(β-diketonato)(dimethyl sulfoxide)dioxouranium(VI)

The 17O NMR spectrum of uranyl oxygens enriched with 17O gave three peaks. These peaks are assigned to the signals of three isotopomers, [16O=U=17O]2+, [17O=U=17O]2+, and [18O=U=17O]2+. Chemical shifts for the signals of [17O=U=17O]2+ and [18O=U=17O]2+ were −0.054±0.002 and −0.108±0.002 ppm relative to [16O=U=17O]2+, respectively.

Oxygen Isotope Shifts in 17O NMR Spectra of the Uranyl Ion

Two-phase emf titrations have been performed for the extraction of hydrochloric acid from aqueous solution containing 1 M NaCl (M=mol dm−3) by trioctylamine (TOA) dissolved in cyclohexane, toluene, benzene, chlorobenzene, nitrobenzene, cyclohexane–benzene mixtures, and benzene–nitrobenzene mixtures. It has been found that the extraction is accompanied with the formation of monomeric trioctylammonium chloride and its successive aggregation from dimer to micell (n-mer) in organic phase: ‾TOA+H++Cl−=‾TOAHCl, Kd; (‾TOAHCl)i−1+‾TOAHCl=(‾TOAHCl)i, \barKi(i=2,3,···,n), where the concentration quotients of successive aggregation, \barKi, satisfy the relation 2 \barK2=3\barK3⁄2=···=n\barKn⁄(n−1). The quotients Kd and \barK2 vary with the total volume fraction of TOA in organic phase, ΨR°, according to equations, In Kd=1nKd°+gΨR° and 1n \barK2=1n\barK2°+h\barΨR°. Diluent effect on the equilibrium constants Kd° and \barK2° are discussed in detail based on the theory of regular solution.

Hiroshi Fukutomi

Papers

Kinetics and mechanism of ozone decomposition in basic aqueous solution

Nuclear magnetic resonance study of the kinetics of the water exchange process in the equatorial positions of uranyl complexes

A Nuclear Magnetic Resonance Study of the Kinetics of Ligand Exchange Reactions in Uranyl Complexes. III. Dimethyl Sulfoxide Exchange in Bis(β-diketonato)(dimethyl sulfoxide)dioxouranium(VI)

Oxygen Isotope Shifts in 17O NMR Spectra of the Uranyl Ion

Extraction Equilibria of Hydrochloric Acid by Trioctylamine in Low-Polar Organic Solvents