The research of 4-chlorobiphenyl in aqueous solution was conducted in two parts. The first part of the study explored the adsorption of 4-chlorobiphenyl onto glass. When the initial concentration of 4-chlorobiphenyl was below 25 µg/L, the sample concentration became undetectable after 24 h. With respect to 4-chlorobiphenyl adsorbed onto glass, the adsorption rate constant k was 18 µg/h L, the adsorption equilibrium constant K was nearly 10(-3) µg/L using the Langmuir first-order reaction model, and the monolayer saturated density, using the BET model, was 1200 µg/m2. In the second half of this study, the photocatalytic oxidation (UV/TiO2) of 4-chlorobiphenyl was investigated using its adsorption characteristics. The UV/TiO2 process decreased the 4-chlorobiphenyl concentration (initial concentration = 500 µg/L) by 77% within 120 min. The ratio between the TiO2 adsorption rate constant and the UV/TiO2 process degradation rate constant was 1/10(5). Copyright 1997 Academic Press.