A Green Method to Determine VUV (185 nm) Fluence Rate Based on Hydrogen Peroxide Production in Aqueous Solution

Abstract

A mini-fluidic vacuum ultraviolet/ultraviolet (VUV/UV) photoreaction system (MVPS) was developed in our previous study. Based on the MVPS, a green method to determine VUV fluence rate has been developed using the production rate of H O when water is exposed to 185 nm VUV. The H O production followed pseudo-zero-order reaction kinetics well over the first 10 min of VUV/UV exposure. This new method was well calibrated with a standard cis-cyclooctene cis-trans photoisomerization actinometer as recommended by the International Union of Pure and Applied Chemistry. The apparent quantum yield for H O production by 185 nm VUV irradiation of water was determined to be 0.024 ± 0.002. As the solution pH increased from 5.0 to 8.0, the H O production rate decreased from 0.83 to 0.40 μm min . Dissolved oxygen had a negligible influence on the H O production. This study proposes a novel VUV fluence rate determination method with advantages of nontoxicity, low detection limits, low costs and convenience, and it can be used as a good alternative to traditional actinometers.

H2S Removal from Groundwater by Chemical Free Advanced Oxidation Process Using UV-C/VUV Radiation

“…The lamp irradiation doses at 254 nm and 185 nm as a function of the flowrate were measured with Iodide–Iodate [ 41 ] and H 2 O 2 [ 42 ] chemical actinometry, respectively. Measured photon fluxes were, respectively, (5.2 ± 1.3) × 10 15 and (7.2 ± 1.8) × 10 14 photons s −1 cm −2 for the 254 nm and 185 nm.…”

Practical Chemical Actinometry—A Review

“…The water oxygen actinometer for 185 nm VUV light. This actinometer, studied by Yang et al (195), is based on the absorption of water as the solvent in the absence of additives other than molecular oxygen.…”

“…The relative rates of these reactions determine Φ(185)(H 2 O 2 ). The effect of pH (195) must be related to the acid dissociation of HO 2 Á , given by Eq. 100.…”

“…The 184.9 nm actinometry is mostly based on the Farkas (167) actinometer Φ(185)(H 2 ) = 0.4 (171) as a reference, with the exception of 10 mM formate (170) (based on both Farkas and Hirshberg (167) and N 2 O gas, Φ(185)(-N 2 O) = 1.0) (198)) and the water-oxygen (195) actinometer (based on ciscyclooctene ( 172)). The molecular hydrogen yield Φ(H 2 ) measured in oxygen-free solutions of ethanol equals to Φ(H…”

“…All the above methods are reliable although requiring GC analysis, which is more laborious than spectrophotometry. The nontoxic water oxygen system intended for industrial-scale actinometry (195) Note: The very low penetration depth at 172 nm and below is associated with a relatively high steady-state concentrations of intermediates, products and depletion of the actinometer. Quantum yields may be affected when the photolysis involves bimolecular reactions, low actinometer concentration or high concentrations of photoactive products.…”