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.