Photodegradation of new herbicide HW-02 in organic solvents.

HW-02 is a new organophosphates herbicide which is discovered and developed in China. The kinetics and mechanism of HW-02 photodegradation in the organic solvents were studied at 25 degrees C under the irradiation of ultraviolet light. The results showed that photochemical reaction of HW-02 in organic solvents such as n-hexane, methanol, dimethyl benzene and acetone under UV light could be well described by the first kinetic equation, and the photodegradation efficiency decreased with a order of n-hexane > methanol > xylene > acetone. The photodegradation efficiency constant of HW-02 in n-hexane, methanol, xylene and acetone were 4.951 x 10(-2), 3.253 x 10(-2), 2.377 x 10(-2) and 1.628 x 10-2 min(-1), and the corresponding half-lives were 13.99, 21.20, 29.15 and 42.56 min, respectively. By separation and identification of photoproducts using GC-MS, it could be concluded that HW-02 was photolyzed through ester cleavage, photo-dechlorination and photoisomerization of the molecule itself.