A study of the photocatalytic degradation of metamitron in ZnO water suspensions Original Research Article

The photocatalytic degradation of the herbicide metamitron in water using ZnO under Osram ULTRA-VITALUX® lamp light was studied. The effect of the operational parameters such as initial concentration of catalyst, initial metamitron concentration, initial salt concentration (NaCl, Na2CO3 and Na2SO4) and pH was studied. The optimal concentration of catalyst was found to be 2.0 g/l. First-order rate constants were calculated for the uncatalysed reactions. On the base of the Langmuir–Hinshelwood mechanism, a pseudo first-order kinetic model was illustrated and the adsorption equilibrium constant and the rate constant of the surface reaction were calculated (0.119 l mg− 1 and 0.836 mg l− 1 min− 1, respectively). The photodegradation rate was higher in acidic than in alkaline conditions. When salt effect was studied, it was found that sodium carbonate was the most powerful inhibitor used, while sodium chloride was the weakest one. A negligible inhibition was observed when the concentration of sodium chloride was 20 mM.