Photocatalytic Degradation of Herbicide Orthosulfamuron using Zinc Oxide Nanoparticles in Water 

In the present study, the Photocatalysis of Orthosulfamuron, a new class of sulfonyl urea herbicide was investigated using ZnO nano particles in different buffer solutions of pH ranging from 4 to 9. In this study, optimum concentration of the catalyst, initial concentration of the orthosulfamuron and effect of pH of the buffer solution were studied under direct sunlight. The ZnO nano particles were synthesized by sol-gel process and characterized by using SEM, XRD and FT-IR. A commercial formulation of the herbicide having the active strength of 50% was used for the experiment. The rate of reaction followed pseudo first-order kinetics in water. The rate of reaction was 12 folds higher when compared to photolysis. The DT50 values of orthosulfamuron with ZnO nano particles in different buffer solution were 6. 42, 21.68 and 35.22 hours, respectively. The optimum concentration of nano particles to decontamination of orthosulfamuron was observed at 100 mg L-1 and the initial concentration of the orthosulfamuron used in the photocatalysis is 10 mg L-1. The fastest degradation of herbicide orthosulafamuron was observed in pH 4 buffer solution. The degradation products formed during the photocatalysis were identified by using LC-MS/MS which were N-(4,6-dimethoxypyrimidin-2-yl) urea, 2- dimet hyl carbamoylphenyl sulf amic acid and 1-(4-hydroxy-6-methoxypyrimidin-2-yl)-3-[2-(dimethylcarbamoyl) pheny lsulfamoyl] urea.