DEGRADATION OF SULFUR-CONTAINING S-TRIAZINES DURING WATER CHLORINATION

The reactions of four sulphur containing s-triazines (prometryne, terb utryne, ametryne and desmetryne) with hypochlorous acid (HClO) and chl orine dioxide (ClO2) have been investigated using an 11 ppm/3 ppm oxid ant/herbicide ratio. The main objective of the study was the identific ation of by-products. Additionally, to study the effect of oxidant con centration on the reaction rate, two more oxidant/herbicide ratios (3 ppm/3 ppb and 11 ppb/3 ppb) have been investigated only for prometryne . Oxidation reactions were monitored by high performance liquid chroma tography (HPLC), while, the identification of by-products was initiall y carried out by low resolution HPLC-mass spectrometry (HPLC-MS) and c onfirmed by accurate mass measurement. Under the experimental conditio ns (T = 20 degrees C, pH = 8, reaction time = 48 h), the results indic ate that all the investigated triazines react in the same way with eac h oxidant. The reactions with HClO occur much faster than those with C lO2 and give rise to three identified oxidation by-products: the sulfo xide, the sulfone and the sulfone's hydrolysis product. The reactions with ClO2, instead, give rise to a sole oxidation by-product: the sulf oxide. With both oxidants, as expected, the lower the oxidant concentr ation the slower the oxidation rate. Based on the obtained results, a general pathway for the oxidation of sulphur containing s-triazines is proposed.