Heterogeneous and homogeneous photocatalytic degradation of chlorophenols in aqueous titanium dioxide and ferrous ion

Photocatalytic degradation of 100 mg/l chlorophenols was studied using TiO2 and Fenton reagent as catalysts. P-chlorophenol, 4-chlorophenol, and 2,4-d ichlorophenol were selected as the target compounds. Results showed that di rect photolysis of chlorophenols was faster than that in the TiO2-amended s ystem. The photodegradation of 2CP followed a first-order rate relationship and the rate constants were 0.022 and 0.0103 min(-1) in direct photolysis and TiO2/UV systems, respectively. The apparent-first-order reaction rate f or decomposition of 4-chlorophenol was higher than that for 4-chlorophenol and 2,4-dichlorophenol under acidic conditions, while 2,4-dichlorophenol wa s higher than 2-chlorophenol and 4-chlorophenol in an alkaline medium. Both the TiO2 catalyst system and direct photolysis process were faster in basi c medium than acidic and neutral medium processes. The Fenton system is exc ellent for the degradation of chlorophenols and its activity has become low in high pH medium.