Bimetallic iron-copper nanoparticles (Fe-Cu-NPs) were used for decolorization of C. I. Reactive Black effluent. NPs were capped using polyvinylpyrrolidone (PVP) to prevent them from agglomeration. The NPs were characterized by particle size analysis, TEM, EDX, XRD, and zeta potential. Decolorization parameters such as pH, dye concentration, nanoparticle concentration and duration of treatment were evaluated to determine the optimum reaction parameters using response surface modeling, and the kinetic study was also undertaken. Effect of the presence of salt and alkali in the effluent was also evaluated. Reaction products formed during dye decolorization were investigated by GCMS, FTIR, and SEM. These analyses indicated that chromatogenous groups from the dye decompose which leads to dye decolorization. Recycling of NPs was also analyzed. There was 97.86% reduction in dye along with the COD, and BOD lowering was achieved with minimal sludge generation.