Water Science & Technology: Water Supply Vol 1 No 2 pp 73–82 © IWA Publishing 2001
Effects of the H2O2 concentration and spectral distribution of the
UV lamp output power on the photooxidation of a water pollutant
OM Alfano*, MJ Martínez**, RJ Brandi*** and AE Cassano****
*
INTEC (Universidad Nacional del Litoral – CONICET).
Güemes 3450 (3000) Santa Fe. Fax: +54-342-4559185.
e-mail: acassano@intec.unl.edu.ar
**
INTEC (Universidad Nacional del Litoral – CONICET).
Güemes 3450 (3000) Santa Fe. Fax: +54-342-4559185.
e-mail: acassano@intec.unl.edu.ar
***
INTEC (Universidad Nacional del Litoral – CONICET).
Güemes 3450 (3000) Santa Fe. Fax: +54-342-4559185.
e-mail: acassano@intec.unl.edu.ar
****
INTEC (Universidad Nacional del Litoral – CONICET).
Güemes 3450 (3000) Santa Fe. Fax: +54-342-4559185.
e-mail: acassano@intec.unl.edu.ar
ABSTRACT
Previous kinetics studies have been extended to analyze some practical
issues concerning this process. Hence, in this work we have studied
additional aspects of the H2O2 enhanced,
UV degradation of 2,4-dichlorophenoxyacetic acid (2,4-D), namely:
(i) the effect of the H2O2/2,4-D initial molar
ratio and (ii) the effect of the irradiation power and, particularly,
the characteristics of the wavelength distribution of the lamp output
emission. The work was done on a well stirred, discontinuously operated
tank reactor irradiated from its bottom. A UV, tubular lamp and a
cylindrical reflector of parabolic cross section were used [actually,
two germicidal lamps (254 nm) of different output power per unit lamp
length and a medium pressure, mercury arc lamp with polychromatic emission
between 220 and 760 nm]. 2,4-D concentration and TOC were the main
variables used to investigate the degradation rate. There is an optimal
initial concentration ratio for each 2,4-D initial concentration. It was
also observed that increasing the lamp output power at 254 nm (output from 0.08 W/cm to 0.6 W/cm) favors the reaction rate. However, much
more significant is the effect produced by employing a polychromatic
lamp with some emission below 254 although this photonic contribution
is relatively small (just 0.21 W/cm below 250 nm). A kinetic model,
having parameters independent of the reactor configuration and derived
from mechanistic considerations was used to analyze the experimental data.
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