Light degradation, case study

Case Study A.9 Scaled-Up Light Degradation and LC/MS and NMR Characterization... 

The quantity R is proportional to the number of chain scissions per original macromolecule. For both PBS and PHS, for all solvents studied (1,4-dioxane, acetonitrile, chloroform, tetrahydrofuran, toluene and 2-butanone) the scattered light intensity decreases after irradiation. The amount of degradation R° for the same polysulfone is higher for solvents with larger yield of radicals. R° is larger for PHS than for PBS in the case of the solvents 1,4-dioxane and acetonitrile, which have the highest yield of radicals ... 

Ti02. However, in the case of ZnO, photocorrosion frequently occurs with the illumination of UV lights. This phenomenon is considered as one of the main reasons for the decreased photocatalytic activity of ZnO in aqueous solutions [209,210], But for gas-phase applications, this disadvantage should not exist [211], Additionally, some studies have confirmed that ZnO exhibits a better efficiency than Ti02 in the photocatalytic degradation of some dyes, even in aqueous solutions [212,213],... 

To study the effect of the protease treatment cell-free suspension, with or without protease treatment, was subjected to gel-filtration chromatography on Sephadex G-75 and the elution patterns were compared (Fig. 1). In each case, two major peaks were detected by monitoring column fractions with absorbance at 280 nm. Degradation activities on mexacarbate, in the presence of FMN and light under anaerobic condition, were measured for each fraction. It was found that the highest activity was associated with peak II. It is interesting to note that protein (s) associated with peak II were detected with or without protease treatment these will be referred to as natural flavoprotein (B, Fig. 

A basic requirement of the ESR technique is the presence of molecules or atoms containing unpaired electrons. Such species can be generated in polymeric systems by homolytic chemical scission reactions or by polymerization processes involving unsaturated monomers. These reactions can be initiated thermally, photochemically, or with a free-radical initiator, and, in the case of scission, by mechanical stress applied to the system. Therefore, ESR can be used to study free-radical-initiated polymerization processes and the degradation of polymers induced by heat, light, high-energy radiation, or the application of stress. 

In the case of semiconductor assisted photocatalysis organic compounds are eventually mineralized to carbon dioxide, water, and in the case of chlorinated compounds, chloride ions. It is not unusual to encounter reports with detection of different intermediates in different laboratories have been observed. For example, in the degradation of 4-CP the most abundant intermediate detected in some reports was hydroquinone (HQ) [114,115,123], while in other studies 4-chloro-catechol, 4-CC (3,4-dihydroxychlorobenzene) was most abundant [14,116-118, 121,163]. The controversy in the reaction intermediate identification stems mainly from the surface and hydroxyl radical mediated oxidation processes. Moreover, experimental parameters such as concentration of the photocatalyst, light intensity, and concentration of oxygen also contribute in guiding the course of reaction pathway. The photocatalytic degradation of 4-CP in Ti02 slurries and thin films... 

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