The kinetics of photocatalytic degradation of binary mixtures of chlorophenol and nitrophenol was investigated using solution combustion synthesized nano-TiO2. The degradation rates of both organics decreased in the binary mixture compared to the individual degradation rates of the organics. This was attributed to interaction between the mother compounds, interaction between the intermediates, and competition for the active reaction site on the catalyst. A modified Langmuir-Hinshelwood kinetic model was developed, and the kinetic parameters were determined from initial rate analysis for the degradation of chlorophenol and nitrophenol. The evolution of intermediates was also investigated, and a possible pathway for degradation of chlorophenol and nitrophenol was proposed. © 2006 American Chemical Society.