Water irradiation

Properties of T2O. Some important physical properties of T2O are Hsted in Table 2. Tritium oxide [14940-65-9] can be prepared by catalytic oxidation of T2 or by reduction of copper oxide using tritium gas. T2O, even of low (2—19% T) isotopic abundance, undergoes radiation decomposition to form HT and O2. Decomposition continues, even at 77 K, when the water is fro2en. Pure tritiated water irradiates itself at the rate of 10 MGy/d (10 rad/d). A stationary concentration of tritium peroxide, T2O2, is always present (9). AH of these factors must be taken into account in evaluating the physical constants of a particular sample of T2O. 

Similar spatial distribution of active bubbles has been observed in partially degassed water and in pure water irradiated with pulsed ultrasound [67]. For both the cases, the number of large inactive bubbles is smaller than that in pure water saturated with air under continuous ultrasound, which is similar to the case of a surfactant solution. As a result, enhancement in sonochemical reaction rate (rate of oxidants production) in partially degassed water and in pure water irradiated with pulsed ultrasound has been experimentally observed [70, 71]. With regard to the enhancement by pulsed ultrasound, a residual acoustic field during the pulse-off time is also important [71]. 

Photolytic. Photolysis of 2,4-D in distilled water using mercury arc lamps (A, = 254 nm) or by natural sunlight yielded 2,4-dichlorophenol, 4-chlorocatechol, 2-hydroxy-4-chlorophenoxyacetic acid, 1,2,4-benzenetriol, and polymeric humic acids. The half-life for this reaction is 50 min (Crosby and Tutass, 1966). A half-life of 2 to 4 d was reported for 2,4-D in water irradiated at 356 nm (Baur and Bovey, 1974). 

Photolytic. Distilled water irradiated with UV light (X = 290 nm) yielded the following photolysis products 2-chloro-l-propanol, allyl chloride, allyl alcohol, and acetone. The photolysis half-life in distilled water is 50 min, but in distilled water containing hydrogen peroxide, the half-life decreased to <30 min (Milano et al, 1988). 

Yamamoto TA, Seino S, Katsura M, Okitsu K, Oshima R, Nagata Y (1999) Hydrogen gas evolution from alumina nanoparticles dispersed in water irradiated with gamma ray. Nanostructured Mater 12 1045... 

OH radical polycrystalline H20 irradiated by y-rays at 77K show signals of OH radicals. The same is observed by UV-irradiation of ice frozen from water irradiated by y-rays as shown in Figure 5 (a) with a spectrum of a computer simulation. 

This is an electron transfer to the solvent, in which a hydrated electron is formed. In this complex there are well defined d-d transitions in the VIS and near UV (NUV), and CT bands in the UV regions. Irradiation in the d-d bands leads to ligand exchange, for instance to photoaquation in water. Irradiation in the CT bands results in electron transfer to the solvent. This provides a very good example of the dependence of the nature of photochemical reactions on irradiation wavelength in metal complexes. 

Approximately 2 mg dissolved in 2 mL of water Irradiate with simulated sunlight produced by a xenon arc lamp for 20 hr Visible exposure 3 million lx hr UV exposure 1500 W hr/m2 8.1... 

Solution in unbuffered water irradiated with simulated sunlight Solution in unbuffered water irradiated with simulated sunlight (control)... 

Lin and Kringstad (7) confirmed Leary s results in an experiment with a solution of milled wood lignin (MWL) in methylcellusolve water. Irradiation of this solution in a vacuum produced no colour. This solution, opened to air and irradiated, produced the same amount of colour as a solution of milled wood lignin initially irradiated in air. The effect of oxygen on light-induced yellowing of newsprint is further illustrated by the accompanying effect on methoxyl content. Leary found that the methoxyl content of newsprint after irradiation in a vacuum decreased by only 0.1% whereas the same irradiation in air decreased the methoxyl content by 0.4% (6). 

The choice of the saturation gas is critical. When Ar and Kr were sparged in water irradiated at 513 kHz, an enhancement in the production of OH radicals of between 10% and 20%, respectively, was observed, compared with 02-saturated solutions [22]. The higher temperatures achieved with the noble gases upon bubble collapse under quasi-adiabatic conditions account for the observed difference. Because the rate of sonochemical degradation is directly linked to the steady state concentration of OH radicals, the acceleration of those reactions is expected in the presence of such background gases. The use of ozone as saturation gas (in mixtures with 02) provided new reaction pathways in the gas phase inside the bubbles, which also increase the measured reaction rates (see Sect. IV.G.l). 

Figure 3 Energy deposition for water irradiated with electrons of various energies. 

A further difference between isotope gamma rays and electrons is penetrating ability. As charged particles, electrons have short ranges in matter. Fig. 3 shows energy deposition curves for water irradiated with electrons of various energies. 

Continuous water irradiation by e-beam is conducted on a bench scale at the Austrian Research Center, Seibersdorf. A 500-keV, 25-mA ICT accelerator (Vivirad-Eligh Voltage Corp.) is used as the electron source [52]. A 3-mm horizontal layer of water is irradiated. Low penetration by the lower energy electrons produced by this smaller accelerator is compensated for by irradiating a turbulent water flow. Dose distribution in the turbulent stream is not uniform, but the overall volume of water treated to an average dose is increased. A schematic of the system is shown in Fig. 5. 

ETFE exhibits excellent dielectric properties. Its dielectric constant is low and essentially independent of frequency. The dissipation factor is low but increases with frequency and can be also increased by cross-linking. Dielectric strength and resistivity are high and are unaffected by water. Irradiation and cross-linking increase dielectric loss [64],... 

The high temperatures and pressures produced lead to the formation of free radicals and other compounds thus, the sonication of pure water causes its thermal dissociation into H atoms and OH radicals, the latter forming hydrogen peroxide by recombination [9,11,12]. Table 3.1 shows the main reactions occurring in water irradiated with ultrasounds. If the water contains some salt such as potassium iodide, iodine free radicals are also released in addition to the previous species [4]. 

There is bleaching of resonances close to the water irradiation frequency (which is where the HQ resonances of peptides and proteins are often found). 

In the water column, the downwelling irradiance ( d) of the solar light field diminishes with depth due to absorption and scattering processes. In optically homogeneous waters, irradiance decreases exponentially and can be described using the vertical attenuation coefficient (K ) ... 

Figure 3. Spectra of single crystals of 2,4-hexadiindol-bisiphenylurethane) depending on irradiation time at 25°C. (a) Modification I (crystallized from dioxane water) irradiated at 330 nm with monochromatic light, (b) Modification II (crystallized from anisol) irradiated at 310 nm. (c) Modification HI (from Modification II at 130°C) irradiated at 330 nm.

The radiolysis products are clustered in spurs (Fig. 7.1) i.e., they are inhomogeneously distributed in the water and proceed to diffuse out of the spur volume. During this "spur diffiision process, recombination reactions take place leading to the formation of molecular or secondary radical products. The spur expansion is complete within 10 s, at which time the radiolysis products are those shown in Figure 7.5. Spur reactions are listed in Table 7.2. G-values for the radiolysis products in water irradiated with different types of radiation are givoi in Table 7.3. It is seen that, as the LET of the radiation increases, the G-values... 

In the absCTce of solutes, reactions between radical and molecular species occur in the bulk water. In pure water irradiated with 7 or X-rays, water is reformed via the reactions... 

Appleby, A., Schwarz, H. A. 1969. Radical and molecular yields in water irradiated by gamma-rays and heavy ions. J. Phys. Chem. 73 (6) 1937-1941. 

A soln. of 2.57 g. ll, 17/ -dihydroxy-5-oxo-3,5-jeco-A-norandrostan-3-oic acid f-lactone 17-acetate in dioxane-water irradiated 7.5 hrs. at 25-30° with a 200 w. high-pressure Hg-lamp 0.761 g. 9 -acetoxydodecahydro-5,9ay -dimethyl-2-oxo-2H-indeno[5,6-b]oxepine-6a-propionic acid. W. Koch, M. Carson, and R. W. Kier-stead, J. Org, Chem. 33, 1272 (1968). 

A soln. of methanesulfonyl azide in isopropanol-water irradiated 80 min. in a slow Ng-stream with a high-pressure Hg-arc lamp until gas-evolution ceases -> methane-sulfonamide. Y 99.8%. F. e., also in the presence of benzophenone as sensitizer, s. M. T. Reagan and A. Nickon, Am. Soc. 90, 4096 (1968). 

Azauracil and 1-cyclohexenyl acetate in 70%-acetone-water irradiated 2-4 hrs. with the Corex-filtered light of a 450 w. Hanovia medium-pressure lamp, and the intermediate treated with water product, Y 70%. F. e. s. J. S. Swenton and R. J. Balchunis, J. Heterocyclic Chem. 11, 453 (1974). 

A soln. of 3-diazo-l,5,5-trimethyl-2,4-pyrrolidinedione in ether, presatd. at 0° with water, irradiated 2.5 hrs. with the Pyrex-filtered light of a 450 w. medium-pressure Hg-arc lamp 3-carboxy-l,4,4-trimethyl-2-azetidinone. Y 98%. F. e. s. G. Stork and R. P. Szajewski, Am. Soc. 96, 5787 (1974). 

N-Debenzylation. N-Benzylpyrrolidine and a little 9,10-dicyanoanthracene as electron acceptor in 7 3 acetonitrile/water irradiated for 6-10 h in a Pyrex tube with a 450 W Hanovia lamp (405 nm) fitted with a CuS04 NH3 soln. filter - pyrrolidine, Y 90%. The method is not applicable to deprotection of a-aminoacids. F.e.s. G. Pandey, K.S. Rani, Tetrahedron Letters 29, 4157-8 (1988) N-demethylation with N,N -dimethyl-2,7-diazapyrenium fluoroborate as electron acceptor s. J. Santamaria et al., ibid. 30, 2927-8 (1989) review of photo-induced electron transfer s, J, Mattay, Synthesis 1989, 233-52 review of single electron transfer (SET) s. E.C. Ashby, Acc. Chem. Res. 21, 414-21 (1988) review of new developments in photochemical synthesis s. M. Demuth, G. Mikhail, Synthesis 1989, 145-62. 

In the experiments reported by Lucas (1985) the influence of additives to the solution and the gas phase on radiolytic oxidation of 1 was studied. At a composition of the test solution which was claimed to be quite similar to that assumed for the containment sump water, irradiation was carried out using a dose rate of 4 kGy/h. The results showed that in a closed vessel an h saturation concentration is reached at an integrated radiation dose of about 60 kGy the presence of CO2 in the gas phase resulted in an increase of the saturation level to about 20% I2 formation, while the presence of H2 did not significantly affect the results. By contrast, in an open system where I2 evolved from the test solution was trapped in a NaHCOs solution, no saturation I2 yield was obtained under such conditions, the I2 yield increased linearily with the dose rate, reaching about 55% at an integrated radiation dose of 0.24 MGy. 

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