Vacuum-UV photolysis of aqueous solutions of nitrate: effect of organic matter I. Phenol
| Autor: | AndréM. Braun, Mónica C. Gonzalez |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
inorganic chemicals
chemistry.chemical_classification Reaction mechanism Aqueous solution General Chemical Engineering Inorganic chemistry Oxalic acid food and beverages General Physics and Astronomy chemistry.chemical_element General Chemistry Mineralization (soil science) Photochemistry Oxygen Redox chemistry.chemical_compound chemistry Phenol Organic matter |
| Zdroj: | Journal of Photochemistry and Photobiology A: Chemistry. 93:7-19 |
| ISSN: | 1010-6030 |
| DOI: | 10.1016/1010-6030(95)04127-3 |
| Popis: | Water homolyses on vacuum-UV excitation (λ The rates of oxidative degradation of phenol and its oxidation products strongly depend on the dissolved oxygen concentration. The formation of dihydroxybenzenes, trihydroxybenzene and oxalic acid as oxidation intermediates was observed in irradiation experiments with oxygen- and air-saturated solutions, but no significant concentrations of these compounds were observed in experiments with argon-saturated solutions. The depletion rates of NO3− have been reported previously to be slow yielding mainly nitrite and N2O as reaction products. Vacuum-UV irradiation of aqueous solutions containing NO3− and phenols results in the simultaneous mineralization of phenol and depletion of NO3−, yielding mainly NH4+ and, in much lower yields, NO2−. The experimental observations indicate that the nitrogen-containing inorganic ions formed during NO3− depletion promote the oxidation of the dissolved organic matter independent of the presence of oxygen. A possible reaction mechanism is discussed, in which the interaction of O2NOOH, ONOOH, NO. and NO. with organic matter is proposed as being mainly responsible for the overall observed behaviour. The interaction between organic substrates and NO. seems to favour further reduction to NH4+, whereas a one-electron reduction yielding N2O is observed in the absence of organic substrates. The effect of CO32− on these reactions is also discussed. Under continuous irradiation, NH4+ is subsequently re-oxidized. Complete oxidation to NO3− is observed only in experiments with oxygen-saturated solutions. Experiments with air- or argon-saturated solutions show only 30% and 10% NO3− formation respectively due to the simulataneous formation of N2. The reduction of NO3− to NH4+ and the oxidation of NH4+ to NO3− seem to involve a series of common intermediates interrelated by many redox reactions and reaction equilibria where the pH, availability of electrons and the presence of protons or hydrogen donors and molecular oxygen determine their importance. |
| Databáze: | OpenAIRE |
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