The degradation of Scarlet 4BS (4BS) in aqueous solution using Fe/Ni nanoparticles was investigated in this paper. Batch experiments show that the degradation of 4BS depended on an initial dye concentration, the solution pH and total Fe/Ni concentration and reaction temperature. The removal of 84.5% of 4BS was achieved when the solution contained 100 mg/L of 4BS under optimal conditions, including an 8.0 g/L nanoscale Fe/Ni, pH 5.0, 30 degrees C for 3 h. In addition, a kinetics study indicates that the degradation of 4BS was well suited to the pseudo-first-order model, where the apparent rate constant (K-obs) was 6.3 x 10(-3) min(-1). Moreover. XRD indicated that no iron and nickel oxide formed after Fe/Ni nanoparticles reacted to 4BS. However, data from FOR show that new bands appeared which corresponding to -C-H after 4BS reacted with the Ni/Fe nanoparticles. A degradation mechanism is proposed here where iron was oxidized, the hydrogen being produced was adsorbed on the catalytic nickel surface, 4BS reductively by degrading two cleaving the azo linkages. This application has much potential in that 71.2% of 4BS was removed from wastewater. (C) 2012 Elsevier Inc. All rights reserved.