Abstract A novel and efficient photo-Fenton catalyst of Fe(III)-5-sulfosalicylic acid (ssal) supported on Al 2O 3 was prepared and characterized by FT-IR and TEM-EDX technique. A detailed investigation of photocatalytic degradation of 2- sec-butyl-4,6-dinitrophenol (DNBP) using this catalyst and H 2O 2 under solar light irradiation was carried out. The effects of reaction parameters on photodegradation performance were investigated by examining H 2O 2 dosage, catalyst loading, solution pH, initial DNBP concentration and temperature. The optimal conditions were an initial DNBP concentration of 40 mg L −1 at pH 2.5 and temperature 30 °C with catalyst loading of 1.0 g L −1 and H 2O 2 concentration of 5 mmol L −1 under solar light irradiation for 100 min. Almost complete degradation of DNBP was observed with [Fe(III)-ssal]-Al 2O 3/H 2O 2 process under the optimal conditions. The degradation of DNBP by photo-Fenton-type process can be divided into the initiation phase and the fast phase. The kinetics of Fenton oxidation is complex and the degradation of DNBP in the two phases both can be described by a pseudo-first-order kinetic model. No obvious decline in efficiency of the [Fe(III)-ssal]-Al 2O 3 catalyst was observed after 5 repeated cycles indicating this catalyst is stable and reusable. A possible reaction mechanism was proposed on the basis of all the information obtained under various experimental conditions.