Formation of volatile halogenated by-products during chlorination of isoproturon aqueous solutions.
The present paper deals with the formation of volatile halogenated by-products (POX) during the chlorination (160 mg/l) of aqueous solutions of the herbicide 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 presence 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 achieved within 1 and 15 min at pH 6 and 9, respectively; (2) in the absence of bromide herbicide degradation is slow (complete degradation is achieved within 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 (approximately 15 micromol X-/l) and remains constant during the reaction; (4) at pH 9 the amount of POX formed is far greater and continuously increases during the reaction, reaching a value of about 110 micromol X-/l after 48 h; (5) two different groups of by-products have been identified by solid phase micro extraction (SPME)-gas chromatography (GC)-mass spectrometry (MS) for the reactions carried out with or without bromide; among them, aliphatic as well as aromatic by-products containing chlorine, bromine or both halogens are present even though the most abundant are halogenated-methane derivatives (haloforms); pH value affects the amount of these by-products but does not modify their chemical nature.
Lopez
A
A
Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche, Bari, Italy. an.lopez@area.ba.cnr.it
Mascolo
G
G
Ciannarella
R
R
Tiravanti
G
G
D002713:Chlorine / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006219:Halogens / Q000032:analysis / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008782:Methylurea Compounds / Q000737:chemistry*; D010671:Phenylurea Compounds; D013696:Temperature; D014835:Volatilization; D014874:Water Pollutants, Chemical / Q000032:analysis; D018508:Water Purification
D006219:Halogens; D006540:Herbicides; D008782:Methylurea Compounds; D010671:Phenylurea Compounds; D014874:Water Pollutants, Chemical; D002713:Chlorine; C028904:isoproturon