Res. Chem. Intermed.
, Vol. 30, No. 3, pp. 317– 329 (2004)
Also available online - www.vsppub.com
Photodegradation of a herbicide derivative,
2,4-dichlorophenoxy acetic acid in aqueous
suspensions of titanium dioxide
H. K. SINGH and M. MUNEER
Department of Chemistry, Aligarh Muslim University, Aligarh 202002, India
Received 16 September 2003; accepted 14 November 2003
Abstract—The photocatalytic degradation of a herbicide derivative, 2,4-dichlorophenoxyacetic acid
(2,4-D, 1), has been investigated in aqueous suspensions of titanium dioxide. The degradation was
studied by monitoring the change in substrate concentration employing UV spectroscopic analysis
and decrease in Total Organic Carbon (TOC) content as a function of irradiation time in the presence
of UV light source. The degradation kinetics was investigated under a variety of conditions, such as
different types of TiO
, pH, catalyst and substrate concentrations. Higher photonic ef ciencies were
observed with Degussa P25 as compared with other photocatalysts. The degradation products were
analysed by GC-MS and probable pathways for the formation of different products were proposed.
: Photocatalysis; degradation; herbicide; 2,4-dichlorophenoxyacetic acid; titanium dioxide.
A wide variety of organic pollutants are introduced into the water system from
various sources, such as industrial ef uents, agricultural run-off and chemical
spills [1, 2]. Their toxicity, stability to natural decomposition and persistence in
the environment has been the cause of much concern to the societies and regulation
authorities around the world .
The control of organic pollutants in water is an important measure in environ-
mental protection. Among many processes proposed and/or being developed for
the destruction of the organic contaminants, biodegradation has received the great-
est attention. However, many organic chemicals, especially those that are toxic or
refractory, are not amendable to microbial degradation. Recently considerable at-
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