Res. Chem. Intermed.
, Vol. 30, No. 6, pp. 663–672 (2004)
Also available online - www.vsppub.com
Titanium-dioxide-mediated photocatalysis reaction of three
selected pesticide derivatives
, M. QAMAR
and D. BAHNEMANN
Department of Chemistry, Aligarh Muslim University, Aligarh 202 002, India
Institut für Technische Chemie, Universität Hannover, Callinstr. 3, D-30167 Hannover, Germany
Received 15 October 2003; accepted 17 March 2004
Abstract—The photocatalysis reaction of three selected pesticide derivatives, namely methoxy-
chlor (1), chlorothalonil (2) and disulfoton (3), has been investigated in an acetonitrile/water mixture
in the presence of titanium dioxide and oxygen. The change as a function of irradiation time has been
monitored using the UV spectroscopic analysis technique. An attempt has been made to identify the
product formed during the photooxidation process through GC/MS analysis technique. The photolysis
of methoxychlor (1) led to the formation of methoxychlor oleﬁn (4) and 4,4
(9), whereas chlorothalonil (2) gave rise to 2,3,4,5-tetrachlorophenol (17) as the only product. On the
other hand, the photolysis of disulfoton (3) under analogous conditions gave disulfoton sulfoxide (25)
and phosphorodithioic acid (21). All the products have been identiﬁed by comparing the molecu-
lar ion and mass fragmentation peaks of the products with those reported in the library. A probable
mechanism for the formation of the products has been proposed.
Keywords: Photocatalysis; titanium dioxide; pesticides; methoxychlor; chlorothalonil; disulfoton.
A large number of chemicals are applied on agricultural sites, which due to their
chemical stability, resistance to biodegradation and sufﬁcient water solubility pen-
etrate deep into the ground water [1– 3]. Their toxicity, stability to natural decom-
position and persistence in the environment has been the cause of much concern
by the society and regulating authorities around the world [4, 5]. Biodegradation,
which is the major mechanism in the wastewater treatment, is quite inefﬁcient at
low levels of substrate concentration . Earlier studies have shown that irradiation
in presence of a semiconductor powder (most commonly of the inexpensive tita-
nium dioxide) is an appealing method for the oxidation of organic molecules. Such
To whom correspondence should be addressed. Tel.: (49-511) 762-5560. Fax: (49-511) 762-2774.