Titanium dioxide-mediated photocatalysed degradation of few selected organic pollutants in aqueous suspensions W. Bahnemann a,1 , M. Muneer b,2, * , M.M. Haque c a Institut fuer Technische Chemie, Universitaet Hannover, Callinstrasse-3, D-30167 Hannover, Germany b Centre for Material Science, University of Central Lancashire, Preston PR1 2HE, UK c Department of Chemistry, Aligarh Muslim University, Aligarh 202002, India Available online 25 April 2007 Abstract The photocatalytic degradation of maleic hydrazide (1), propham (2), tebuthiuron (3), propachlor (4), chlortoluron (5), thiram (6), phenoxyacetic acid (7), 2,4,5-trichlorophenoxy acetic acid (8), 4-chlorophenoxy acetic acid (9), uracil (10), 5-bromouracil (11) and bromothymol blue (12) have been investigated in aqueous suspensions of titanium dioxide (TiO 2 ) under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics of the compounds were investigated under different conditions, such as types of TiO 2 , pH, catalyst concentration, substrate concentration, temperature and in the presence of different electron acceptors, such as hydrogen peroxide (H 2 O 2 ), potassium persulphate (K 2 S 2 O 8 ), ammonium persulphate (NH 4 ) 2 S 2 O 8 and potassium bromate (KBrO 3 ) besides molecular oxygen. TiO 2 Degussa P25 was found to be more efficient photocatalyst for the degradation of the model compounds as compared with other photocatalysts. The degradation products were analysed using GC/MS analysis technique and probable pathways for the formation of different products have been proposed. # 2007 Elsevier B.V. All rights reserved. Keywords: Photocatalytic degradation; Semiconductor; Titanium dioxide; Pesticides 1. Introduction The control of organic pollutants in water is an important measure in environmental protection. A large amount of chemicals are used in agricultural field for better quality and quantity of the crop. Hence, a wide variety of pesticides are applied on agricultural sites, which due to their chemical stability, resistance to biodegradation and sufficient water solubility penetrate deep into the ground water [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 [3]. Wastewater from the textile industry is highly colored and of a complex and variable nature. The large amount of dyestuffs used in dyeing stage of textile manufacturing processes represent an increasing environmental danger due to their refractory nature. The textile dyes and other commercial colorants have emerged as a focus of environmental remedia- tion efforts. These efforts have largely been targeted at removing colorants from wastewater effluents of textile mills and other colorant manufacturers [4–6]. A substantial amount of dyestuff is lost during the dyeing process in the textile industry [7]. The release of those colored wastewaters in the environment is a considerable source of non aesthetic pollution and eutrophication and can originate dangerous byproducts through oxidation, hydrolysis, or other chemical reactions taking place in the wastewater phase [8,9]. Decolorization of dye effluents has therefore acquired increasing attention. Development of appropriate methods for the degradation of contaminated drinking, ground, surface waters, wastewaters containing toxic or nonbiodegradable compounds is necessary. Among many processes proposed and/or being developed for the destruction of the organic contaminants, biodegradation has www.elsevier.com/locate/cattod Catalysis Today 124 (2007) 133–148 * Corresponding author. Tel.: +44 1772 893578; fax: +44 1772 892996. E-mail addresses: bahnemann@iftc.uni-hannover.de (W. Bahnemann), MMuneer@uclan.ac.in (M. Muneer), drmmhaque@gmail.com (M.M. Haque). 1 Tel.: +49 511 7625560; fax: +49 511 7623004. 2 On leave from the Department of Chemistry, Aligarh Muslim University, Aligarh, India. 0920-5861/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cattod.2007.03.031