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 p roduct has been applied to the photodegradation kinetics of four chlorophen ols (CPs) undergoing photolysis (lambda > 300 nm) at a TiO2 film. The effec ts on the rate of photomineralisation of (i) varying CP concentration, (ii) O-2 concentration, (iii) flow rate, (iv) light intensity and (v) supportin g electrolyte, have been examined. Of particular note are the accelerative effects of increasing [O-2] and removing background electrolyte. The kineti cs 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], thi s model proves inadequate and a mixed-control model, incorporating mass tra nsfer as an additional parameter, is shown to be necessary. The approach de veloped allows the conditions under which mass transfer is important in con trolling photomineralisation rates to be identified. (C) 2001 Elsevier Scie nce B.V. All rights reserved.