Photocatalytic degradation of chlorobenzene by TiO2 in high-temperature and high-pressure water

Abstract

A fluidized-bed-type flow reactor available for the photocatalytic treatment of the suspension of model soil under high-temperature, high-pressure conditions was designed. An aqueous suspension containing hydrogen peroxide (H 2 O 2) as an oxidizer and inorganic oxides as a model soil, titania (TiO 2), silica (SiO 2), or kaoline (Al 2 Si 2 O 5 (OH) 4) was continuously fed into the reactor with the temperature and the pressure controlled to be T = 20 400 °C and P =30MPa, respectively. The degradation of chlorobenzene (CB) in water was chosen as a model oxidation reaction. It appeared that most of the model soils are not so harmful to the SCWO treatment of CB in solutions. When the TiO 2 suspension containing H 2 O 2 was irradiated with near-UV light, the promotion of the degradation caused by photocatalytic actions of TiO 2 was observed at all temperatures. Persistence of the photocatalytic activity in the oxidation reaction in high-temperature, high-pressure water would open up a possibility of the development of the hybrid process based on the combination of SCWO process and TiO 2 photocatalysis for the treatment of environmental pollutants in soil and water, which are difficult to handle by conventional SCWO process or catalytic SCWO process alone.