Kinetic studies of sulfentrazone herbicide dechlorination by Fe/Ni nanoparticles were performed in the presence of different electrolytes such as: Cl-, SO 4 2-, NO 3-, Cu 2+ , Na + and Zn 2+. In the presence of Cland SO 4 2the reaction occurred efficiently, reaching approximately 100% of dechlorination after 30 minutes of reaction. In the presence of NO 3 and Cu 2+ ions the sulfentrazone dechlorination was significantly inhibited, because these ions tend to compete with the substrate for the electrons donated by Fe 0. In the presence of Na+ ions, the dechlorination efficiency remained approximately 100%, however, this electrolyte provided an increase on the reaction rate, due to the increase of the ionic strength in the system. The Zn 2+ ions has no influence on the dechlorination efficiency, but the reaction rate was reduced due to the formation of a protective layer formed by the sorption of Zn 2+ ions on the surface of the nanoparticles.