Photodegradation of chlorpyrifos in water by UV/H2O2 treatment: toxicity evaluation.

Chlorpyrifos (CP) is an organophosphorus pesticide widely used in agriculture. Due to its toxicity, it has been necessary to develop a treatment to eliminate the environmental wastes generated by this substance. The combination of UV radiation and hydrogen peroxide seemed an interesting option to reduce the concentration of CP in water, as it has proved to be a simple and effective method to degrade other similar pesticides. The purpose of this work is to study the effect of different initial concentrations of H2O2 on the degradation of commercial CP in water using UV/H2O2. Conversions of 93% were achieved in 20 min with 450 mg L(-1) of H2O2 initial concentration (0.16 mg of CP degraded per mg of H2O2 consumed). The total organic carbon analysis showed interesting mineralization values, reaching a 70% conversion after 4 h of reaction. In addition, this degradation procedure leads to a clear reduction of the toxicity of the reaction mixture over Vibrio fischeri.