Heterogeneous photocatalytic degradation of monochlorobenzene in water

This investigation evaluated the photocatalytic degradation of monochlorobenzene (MCB) in an aqueous TiO 2 suspension. In accordance with the experimental results, the degradation of MCB was a function of the initial substrate concentration, incident light intensity, and TiO 2 dosage. However, the solution pH had insignificant effect on the degradation efficiency. The heterogeneous photocatalytic degradation of MCB followed the Langmuir–Hinshelwood kinetics. The adsorption coefficient of MCB ( K) and the observed degradation rate constant ( k) were calculated as 13.4 mM −1 and 0.0054 mM min −1, respectively. In addition, a 0.255 dependency of the initial degradation rate on the light intensity revealed the considerable adverse effect of e −–h + pair recombination. Both mineralization and dechlorination occurred during the photocatalytic degradation of MCB. Under the operating condition of initial MCB concentration of 0.1 mM, light intensity of 5.68 μEinstein s −1, TiO 2 dosage of 1.0 g L −1, and solution pH of 7, about 93.7% of MCB was mineralized after 240 min of irradiation. Nevertheless, 64.3% of the stoichiometric amount of Cl − ions was released into the bulk solution. The simulation results derived from the X-ray photoelectron spectroscopy (XPS) analysis was suggested that the interaction between Cl − ions and TiO 2 surface tended to lower the released amount of Cl − ions.