Pulse radiolytic induced transient electrical conductance in liquid solutions. Part 2.—Radiolysis of aqueous solutions of NO–3, NO–2 and Fe(CN)3–6

Comparisons of the predictions of stochastic diffusion kinetic calculations using electron track structures with experimental scavenger data show that the precursor to the hydrated electron, e pre -, plays a role in determining the total yield of electrons scavenged in a number of systems. The significance of e pre -scavenging on yields depends on the scavenger of interest and on the rate coefficient of the scavenger's reaction with the hydrated electron, e aq -. For Cd 2+ , where the reaction (e aq -+ Cd 2+ ) is fast, the consequences of e pre -scavenging are experimentally not apparent, for NO 3 -, a less efficient e aq -scavenger, the effects of e pre -reaction are apparent in concentrated solutions, and for SeO 4 2-, an inefficient e aq -scavenger, e pre -scavenging is obvious even in dilute solution.

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“…59 The production of NO 2 -occurs via a multistep mechanism involving the intermediates NO 3 2-and NO 2 , as follows…”

Section: Results and Analysismentioning

confidence: 99%

On the Radiation Chemical Kinetics of the Precursor to the Hydrated Electron

Pimblott

LaVerne

1998

J. Phys. Chem. A

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“…This is a logical consequence of the high reactivity of ozone and hydroxyl radical with nitrite. 13,14 However, ozonation increases the ef®-ciency of a subsequent biological treatment to remove nitrogenous compounds. There are several possible explanations for this behavior.…”

Section: Discussionmentioning

confidence: 99%

Integration of continuous biological and chemical (ozone) treatment of domestic wastewater: 2. Ozonation followed by biological oxidation

Beltrán

García‐Araya

Álvarez

1999

J. Chem. Technol. Biotechnol.

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A combined chemical±biological treatment, ozonation plus activated sludge, of domestic wastewater was studied and the results were compared with those shown in a previous study where the sequence of oxidation was reversed. Experimental results indicated wastewater preozonation to be an effective pretreatment step for domestic sewage. The goals of ozonation were the improvement in ef¯uent biodegradability and the removal of certain biorefractory organics as aromatic and unsaturated compounds. The percentage of biodegradability was measured by the BOD/COD ratio (eg 0.69 was obtained for an ozonated ef¯uent (D O3 = 40 g m À3) while a ratio of 0.57 was measured for raw sewage). Based on continuous experiments of a single activated sludge system (hydraulic retention time = 5 h; mixed liquor volatile suspended solids = 1.6 g dm À3) the combined oxidation leads to an improvement of BOD and COD percentage reductions (88% and 66% observed after the combined process for BOD and COD, respectively, compared with 80% and 47% obtained without preozonation). Preozonation also improves the total kjeldahl nitrogen (TKN) removal during subsequent single stage activated sludge treatment. The fraction of autotrophic biomass (f nit ) was more important when preozonation took place, so nitri®cation rates were enhanced in the combined process. The ef®ciency for the individual and combined process was computed and compared. Among the three processes studied, the sequence of ozonation plus biological oxidation resulted in the highest percentage COD, TKN and UV 254 reduction.

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“…In the nitrite actinometer solution, a large fraction of the OH radical was expected to react with the nitrite ion based on the large value of its second-order rate constant (1.1 X 10'" M-I s-I) (29). Because of this high rate constant and the limited solubility of BA in water, complete scavenging of the OH radical was not achieved.…”

Section: Hplc the Hplc System Consisted Of An Eldex Model B-1004mentioning

confidence: 99%

Nitrate and Nitrite Ultraviolet Actinometers

Jankowski¹,

Kieber²,

Mopper³

1999

Photchem. Photbio.

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We developed nitrate and nitrite actinometers to determine radiant fluxes from 290 to 410 nm. These actinometers are based on the reaction of the photochemically generated OH radical with benzoic acid to form salicylic acid (SA) and p-hydroxybenzoic acid (pHBA). Actinometer development included determination of the temperature and wavelength dependence of the quantum yield for formation of SA and pHBA from nitrate and nitrite photolysis in air-saturated solutions. Quantum yields (at 25°C) for SA production from nitrate photolysis ranged from 0.00146 to 0.00418 between 290 and 350 nm, and from 0.00185 to 0.00633 for nitrite photolysis between 290 and 405 nm. The quantum yields for SA production were approximately 50-60% greater than quantum yields for pHBA production from nitrate and nitrite photolysis. For both actinometers, SA and pHBA formation was temperature dependent, increasing by approximately a factor of 2.2 from 0 to 35°C. Activation energies for SA formation varied with wavelength, ranging from 14.7 to 16.5 kJ mol-' between 290 and 330 nm for the nitrate actinometer and 12.3 to 17.8 kJ mol-1 between 310 and 390 nm for the nitrite actinometer. Activation energies for pHBA formation were 211% higher. Wavelengthdependent changes in the quantum yield and activation energy for SA and pHBA formation from nitrate photolysis suggest multiple electronic transitions for nitrate from 290 to 350 nm. Quantum yields for OH radical formation from nitrate and nitrite photolyses were estimated from SA and pHBA quantum yields at 25°C. Wavelength-dependent OH quantum yields ranged from 0.007 to 0.014 for nitrate photolysis between 290 and 330 nm and from 0.024 to 0.078 for nitrite photolysis between 298 and 390 nm. The nitrate and nitrite actinometers can maintain initial rate conditions for hours, are insensitive to laboratory lighting, easy to use and extremely sensitive; the minimum radiant energy that can be detected in our irradiation system is approximately einsteins.(4) occurring in the far UV ( E , , , = 9500 M-l cm-I at 201 nm), while the second is a weak absorption band centered at 302 nm (emax = 7.14 M-

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Pulse radiolytic induced transient electrical conductance in liquid solutions. Part 2.—Radiolysis of aqueous solutions of NO–3, NO–2 and Fe(CN)3–6

Cited by 42 publications

References 0 publications

On the Radiation Chemical Kinetics of the Precursor to the Hydrated Electron

On the Radiation Chemical Kinetics of the Precursor to the Hydrated Electron

Integration of continuous biological and chemical (ozone) treatment of domestic wastewater: 2. Ozonation followed by biological oxidation

Nitrate and Nitrite Ultraviolet Actinometers

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