[Photo-catalytical degradation of diphenylarsinic acid by TiO2 (P25)].

Diphenylarsinic acid (DPAA) is the major contaminant in environment polluted by abandoned chemical weapons. DPAA poses high risks to biota but remediation methods for this contaminant are rare. Previous research showed DPAA could be degraded within a short time by TiO2 (P25). Here the kinetics of DPAA degradation catalyzed by P25 was studied. Results showed the photo-catalytical degradation of DPAA by P25 consisted of two processes: adsorption and photo-reaction. The whole reaction could be fitted by Langmuir-Hinshelwood kinetics. Variation in pH and ionic strength caused change in adsorption of DPAA onto the TiO2 catalyst, which led to the change of reaction rate, showing a decreasing trend with the decreasing adsorption amount of DPAA. Dissolved oxygen promoted the catalytical degradation of DPAA by TiO2, and the hydroxyl free radical played the most important role in the photodegradation of DPAA, which was testified through quenching experiments with free radical scanvengers.