Effect of pH,charge separation and oxygen concentration in photoelectrocatalytic systems:active chlorine production and chlorate formation

摘要

In this study,photoanodic chlorine generation and chlorate formation were investigated using a nanoporous TiO_2 photo-electrode under an illumination intensity of 7.4 mW/cm~2UV and biased at +1.0 V vs.SCE.Chlorine formation increased over time finally reaching a steady-state concentration of 42 mg/1 in 45 min.On the other hand,chlorate formation was observed after only 5 min irradiation and increased over time.The effect of pH,oxygen concentration and charge separation on chlorine generation and chlorate formation was also investigated.Chlorine production was practically constant over a pH range of 4.0-8.0,but decreased slightly at higher pH values.Chlorate production could be detected at pH values >7.0.A significant effect of oxygen concentration on chlorate formation was observed.Chlorate was significantly reduced under nitrogen gas.Chlorine production in the separated photoanode compartment was about 10 fold higher than that in a combined photoanode-cathode system.