Formation of volatile halogenated by-products during chlorination of isoproturon aqueous solutions

The present paper deals with the formation of volatile halogenated by-produ cts (POX) during the chlorination (160 mg/l) of aqueous solutions of the he rbicide isoproturon (40 mg/l). Chlorination reactions have been carried out over 48 h, at ambient temperature, at two pHs (6 and 9) and in the presenc e or not of bromide ions (80 mg/l). The main results obtained have been as follows: (1) in the presence of bromide, isoproturon degradation is rather fast and it results affected by pH, complete isoproturon degradation is ach ieved within 1 and 15 min at pH 6 and 9, respectively; (2) in the absence o f bromide herbicide degradation is slow (complete degradation is achieved w ithin 180 min) and it is not affected by pH; (3) at pH 6, regardless of the presence of bromide, the maximum amount of POX formed is low (similar to 1 5 mu mol X-/l) and remains constant during the reaction; (4) at pH 9 the am ount of POX formed is far greater and continuously increases during the rea ction, reaching a value of about 110 mu mol X-/l after 48 h; (5) two differ ent groups of by-products have been identified by solid phase micro extract ion (SPME)-gas chromatography (GC)-mass spectrometry (MS) for the reactions carried out with or without bromide; among them, aliphatic as well as arom atic byproducts containing chlorine, bromine or both halogens are present e ven though the most abundant are halogenated-methane derivatives (haloforms ); pH value affects the amount of these by-products but does not modify the ir chemical nature. (C) 2001 Elsevier Science Ltd. All rights reserved.