Quantum Yield of the Iodide–Iodate Chemical Actinometer: Dependence on Wavelength and Concentration¶

Abstract

The quantum yield (QY) of the iodide-iodate chemical actinometer (0.6 M KI-0.1 M KIO3) was determined for irradiation between 214 and 330 nm. The photoproduct, triiodide, was determined from the increase in absorbance at 352 nm, which together with a concomitant measurement of the UV fluence enabled the QY to be calculated. The QY at 254 nm was determined to be 0.73 +/- 0.02 when calibration was carried out against a National Institute of Standards and Technology traceable radiometer or photometric device. At wavelengths below 254 nm the QY increased slightly, leveling off at -0.80 +/- 0.05, whereas above 254 nm the QY decreases linearly with wavelength, reaching a value of 0.30 at 284 nm. In addition, the QY was measured at different iodide concentrations. There is a slight decrease in QY going from 0.6 to 0.15 M KI, whereas below 0.15 M KI the QY drops off sharply, decreasing to 0.23 by 0.006 M KI. Calibration of the QY was also done using potassium ferrioxalate actinometry to measure the irradiance. These results showed a 20% reduction in QY between 240 and 280 nm as compared with radiometry. This discrepancy suggests that the QY of the ferrioxalate actinometer in this region of the spectrum needs reexamination.

Treatment technologies for aqueous perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA)

“…The aqueous electron can reduce most halogenated contaminants at near diffusion-controlled rates [127,170,[202][203][204][205]. Electron tunneling leads to activation energies for reaction with halogenated organics that are invariable and small (6 to 30 kJ$mol -1 ) [206]. Reaction rates of the aqueous electron with fluorinated compounds have been reported [177,178,185,186,207].…”

Demonstration and evaluation of germicidal UV-LEDs for point-of-use water disinfection

“…The radiometer measurements were checked and corroborated using an iodide/iodate actinometer (Rahn et al 2003).…”

H2O2 Generation by Decamethylferrocene at a Liquid|Liquid Interface

“…I 3 À can be also detected by UV/Vis spectroscopy, as shown in Figure 2 b (sharp absorption band at l max = 352 nm). Taking a e max value of 2.76 10 4 m À1 cm À1 , [12] the concentration of I 3 À can be calculated to be 0.070 AE 0.003 mm, which corresponds to that of H 2 O 2 formed.…”