Photolysis of aqueous H2O2:: Quantum yield and applications for polychromatic UV actinometry in photoreactors

Methanol is used to measure the yield of center dot OH radicals produced in the photolysis of H2O2 in aqueous solutions The UV photolysis of H2O2 generates center dot OH radicals, which in the presence of methanol, oxygen, and phosphate buffer form formaldehyde, namely, (D(HCHO) = (D(Phi(center dot OH). The quantum yield of center dot OH has been redetermined in view of literature inconsistencies resulting in (D(center dot OH) = 1.11 +/- 0.07 in the excitation range of 205-280 nm. The constancy of Phi)-(center dot OH) and the ease and sensitivity of the formaldehyde product analysis makes the H2O2/CH3OH system suitable for polychromatic UV actinometry. In addition, the relatively low cost of the main components and the possibility of destroying the methanol before disposal qualify the system for both monochromatic and polychromatic actinometry in a large volume of water. The H2O2/CH3OH system was applied in different commercial UV photoreactors.