Ultra-Violet Absorption Spectra of the Molecules H2O, HDO and D2O

A study of enhanced performance of VUV/UV process for the degradation of micropollutants from contaminated water

“…Furthermore, the reflection, refraction, and absorption of photons within the air gap (separating the lamp and the quartz sleeve region) and on the quartz sleeve were incorporated within the radiation sub-model. Moreover, to account for the dependency of 185 nm water absorption coefficient on temperature (+0.05 cm −1 / • C), a linear function which corresponds to 1.4 cm −1 at 25 • C [12,25] was coupled to the radiative transfer equation [3,4]. Measured UV 254 transmittance of the samples was found to be 98% and this value was used in the simulations.…”

“…Lack of studies demonstrating the removal efficacy of the VUV/UV process under continuous flow reactors are among the key factors hindering their practical implementation. This is of paramount importance since the very high absorption coefficient of water for 185 nm radiation limits the oxidation power of the process to a thin film optical path (e.g., less than 1 cm) [11,12]. Furthermore, the extent to which background water constituents limit the AOP performance of VUV/UV systems needs to be analyzed under continuous flow operation.…”

Theory and applications of charge-transfer-to-solvent spectra

“…If spectra are recorded above 51,000 cm-1, then the optical path should be flushed with dry nitrogen to remove the Schumann-Runge absorption bands of oxygen. 41 Serveral double-beam spectrophotometers having synthetic silica optical components are available for spectra up to 62,500 cm-l.…”

Computational fluid dynamics (CFD) modeling of VUV/UV photoreactors for water treatment

“…To calculate the mixture diffusion coefficient of the solution, dilute approximation theory which accounts for each species diffusion in pure water was utilized [20,23]. Moreover, to account for the dependency of 185 nm water absorption coefficient on temperature (+0.5 cm -1 /ºC) [24], a linear function which corresponds to 1.4 cm -1 at 25ºC [24,25] was coupled to the radiative transfer equation. Assuming a constant temperature for the air trapped between the sleeve and water, decadic absorption coefficient of oxygen was set to 0.166 atm -1 cm -1 [26].…”

“…7b). The more significant decay of the 185 nm radiation is mainly due to the very high absorption coefficient of water at this wavelength (1.4 cm -1 at 25 °C [24,25]) which results in a large dark zone area in the VUV/UV photoreactor. Therefore, the 185 nm direct-photolysis of the target contaminant occurs predominantly in the area with less than 1 cm distance from the quartz sleeve.…”