Photomineralisation kinetics of aqueous chlorophenols at a supported TiO2 surface studied by the channel-flow method with electrochemical detection

The channel flow method with electrochemical detection (CFMED) of Cl- ion product has been applied to the photodegradation kinetics of four chlorophenols (CPs) undergoing photolysis (lambda > 300 nm) at a TiO2 film. The effects on the rate of photomineralisation of (i) varying CP concentration, (ii) O-2 concentration, (iii) flow rate, (iv) light intensity and (v) supporting electrolyte, have been examined. Of particular note are the accelerative effects of increasing [O-2] and removing background electrolyte. The kinetics have been shown to fit models derived from Langmuir-Hinshelwood kinetics; at high [CP], the rates fit a surface-limited model, but at low [CP], this model proves inadequate and a mixed-control model, incorporating mass transfer as an additional parameter, is shown to be necessary. The approach developed allows the conditions under which mass transfer is important in controlling photomineralisation rates to be identified. (C) 2001 Elsevier Science B.V. All rights reserved.