Photooxidation kinetics reactions

Bhowmick and Semmens (1994) studied the photooxidation kinetics of five halogenated VOCs, including chloroform (CHL), carbon tetrachloride (CTC), trichloroethylene (TCE), tetrachloroethylene (PCE), and 1,1,2-trichloroethane (TCA) by UV/ozone. In the low to intermediate concentration range of 0.07 to 1.11 mg/L, the reactivities of the organics rank in the following order TCE > PCE > CTC > CHL > TCA. This order indicates that the reaction between ozone and saturated hydrocarbons is much slower than that of ozone with unsaturated compounds such as alkenes. For CHL, TCA, and CTC, an increase in ozone concentration had little effect on the rate constant. By comparison, the rates of oxidation for TCE and PCE increased with added... 

Hoigne, J. 1990. Formulation and calibration of environmental reaction kinetics Oxidations by aqueous photooxidants as an example. In W. Stumm, ed., Aquatic Chemical Kinetics Reaction Rates of Processes in Natural Waters, pp. 43-70. Wiley-Interscience, New York. 

A pseudo first-order reaction with a half-life of 2 h was deduced for the photooxidation kinetics of anthracene in aqueous media under simulated solar radiation conditions [11]. Bertilsson and Anneli report that photochemical degradation of anthracene and phenanthrene in water proceeds rapidly (half-lives 1 and 20.4 h, respectively) while that of naphthalene (half-life > 100 h) does not [12], In the presence of humic substances, the anthracene degradation rate was unaffected while that of phenanthrene was slowed down considerably. Differences in the spectral absorbance of anthracene and... 

As it is seen from Figure 2.6 (curve 2) at the moment of light source switching off the rate of O2 absorption decreases up to stationary rate in dark process and oxidation reaction proceeds for some time. This effect is the effect of photochemical aftereffect or post-effect. It is explained [173] by lasting radical-chain process of oxidation, consisting of two stages reactions of continuation and breaks of chain of photooxidation. Kinetic curve of oxygen... 

Photooxidation kinetics are generally interpreted in terms of free radical reactions. A typical scheme is given below ... 

Surface vs Solution Reactions, Anotliei issue of debate in pliotocatalyzed mineialization of oiganic substrates is whether the initial oxidation occurs on the photocatalyst s surface or in solution. Kinetic data of photooxidations and photoreductions have often been fitted to the simple... 

Kinetics of the photooxidation of organic water impurities on illuminated titania surfaces has been generally regarded to be based on the Langmuir-Hinshelwood equation with first-order reaction kinetics vs. initial substrate concentration was established univocally by many authors... 

Cox, R. A., The Photolysis of Gaseous Nitrous Acid—A Technique for Obtaining Kinetic Data on Atmospheric Photooxidation Reactions, Ini. J. Chem. Kinet. Symp., 1, 379-398 (1975). 

Paulson, S. E., R. C. Flagan, and J. H. Seinfeld, Atmospheric Photooxidation of Isoprene. 1. The Hydroxyl Radical and Ground State Atomic Oxygen Reactions, hit. J. Chem. Kinet., 24, 79-101 (1992a). 

For the kinetics and mechanisms of the gas-phase reactions of other 2- to 4-ring PAHs with OH radicals, N03 radicals, and 03, see, e.g., phenanthrene, Kwok et al. (1994a), and indan, indene, fluorene, and 9,10-dihy-droanthracene, Kwok et al. (1997) for dibenzo-thiophene, a volatile S-PAC that is ubiquitous in polluted ambient air environments and forms mutagenic photooxidation products, see Kwok et al. (1999) see also Kwok et al. (1994b) for a review of gas-phase NO-, radical reactions with aromatics. 

Kinetic Approach for Reactions with Well-Defined Photooxidants Illustrative Example 16.1 Estimating Near-Surface Hydroxyl Radical Steady-State Concentrations in Sunlit Natural Waters Reactions with Hydroxyl Radical (H0 )... 

Kinetic Approach for Reactions with Well-Defined Photooxidants... 

A number of workers have looked at the effect of photooxidation and photodynamic sensitizers on DNA. Rose Bengal photosensitizes strand breaks in double-stranded, supercoiled, pBR322 DNA the effect follows first-order kinetics with respect to light fluence and dye concentration. The reaction is substantially more efficient in the absence of oxygen, but the quantum yield of strand breaks in air is only 10 8. The results are consistent with the initiation of chain scission by Rose Bengal triplet, with some additional mechanism coming into play in the presence of oxygen. 

In connection with the antioxidant properties of L-ascorbic acid and its stability, many kinetic and mechanistic studies have been performed. For instance, it has been shown a role as a radical scavenger in the autooxidation of methyl linoleate, and its synergistic effect when used with vitamin E.362 The photooxidation,363 superoxide-mediated oxidations,364 reactions with radicals,365 and the influence of other agents, including ultrasound and y-rays,366 have been reported. 

After [9], numerous papers were published related to the low-temperature photooxidation of P700 in the PS1 reaction centres of plants and the reverse process of recombination of P700+ and a reduced electron acceptor (see e.g. Refs. [208-211]). In these works controversial data on the kinetics of the dark decay of P700 + were obtained. Therefore in Ref. [212] the kinetics of charge recombination in the PS1 reaction centres was investigated in detail over a broad range of times and temperatures. 

PS1, containing still part of its own light harvesting complex, has provided excellent kinetic results on the energy transfer to the reaction centre, with the subsequent photooxidation of P700, and the time of this whole process. 

Maldotti A, Chiorboli C, Bignozzi CA, et al. 1980. Photooxidation of 1,3-butadiene containing systems rate constant determination for the reaction of acrolein with hydroxyl radicals. Int J Chem Kinet 12 905-913. 

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