Res. Chem. Intermed.
, Vol. 28, No. 7–9, pp. 857–870 (2002)
Also available online - www.vsppub.com
Fundamental photochemical approach to the concepts
of uence (UV dose) and electrical energy ef ciency
in photochemical degradation reactions
JAMES R. BOLTON
and MIHAELA I. STEFAN
Bolton Photosciences Inc., 628 Cheriton Cres., NW Edmonton, AB, Canada, T6R 2M5
Present address: Trojan Technologies Inc., 3020 Gore Rd., London, ON, Canada, N5V 4T7
Abstract—For photochemical reactions in a quasi collimated beam, derivations are presented that
introduce ‘rate constants’ based on the
(UV dose) received within the irradiated solution.
These uence-based ‘rate constants’ are shown to be fundamental and depend only on the quantum
yield and the molar absorption coef cient at the irradiation wavelength. An experimental example
is given, where the quantum yield for the photolysis of atrazine is determined to be 0.033. The new
concepts are developed further to analyze the Figure-of-Merit
Electrical Energy per Order
it is shown that the E
depends on the same fundamental photochemical parameters. An example of
the photolysis of N-nitrosodimethylamine (NDMA) is presented, and it is shown that the E
decrease (increased electrical energy ef ciency) as the radius of the UV reactor increases (increased
path length), and should increase as the percent transmittance of the water decreases.
The theory of quantum yield determination for both monochromatic and polychro-
matic light has been extensively covered in the literature [1– 6]. In general, it has
been developed for low concentrations of the light absorber, such that the rate law
is rst order in the absorber concentration.
The rst-order rate constants derived
from these studies are often given in units of time
; however, unless several para-
meters of the photolysis experiments (e.g. irradiance, absorbance, path length, etc.)
This paper is dedicated to Prof. Henry Linschitz. The content and the style are very much in tune
with the fundamental approach that he always took to studies in Photochemistry.
To whom correspondence should be addressed.
However, if the concentration is high, so that almost all the incident light is absorbed, zero-order
kinetics can be observed.