Degradation of chlorpyriphos in water by advanced oxidation processes.

The degradation of chlorpyriphos by different advanced oxidation processes such as photo-Fenton, TiO 2 , TiO 2 /H 2 O 2 , O 3 and O 3 /H 2 O 2 was investigated. The photo-Fenton and TiO 2 processes were optimized using a solar chamber as light source. The optimum dosages of the photo-Fenton treatment were: [H 2 O 2 ]=0.01 M; [Fe 3 +  ]=10 mg l −1 ; initial pH = 3.5. With these optimum conditions total degradation was observed after 15 minutes of reaction time. The application of sunlight was also efficient as total degradation was achieved after 60 minutes. The optimum dosage using only TiO 2 as catalyst was 1,000 mg l −1 , obtaining the maximum degradation at 20 minutes of reaction time. On the other hand, the addition of 0.02 M of H 2 O 2 to a lower dosage of TiO 2 (10 mg l −1 ) provides the same degradation. The ozonation treatment achieved complete degradation at 30 minutes of reaction time. On the other hand, it was observed that the degradation was faster by adding H 2 O 2 (H 2 O 2 /O 3 molar ratio = 0.5). In this case, total degradation was observed after 20 minutes.