In this study, cobalt molybdate (CoMoO4) nanoparticles were synthesized by precipitation and microemulsion methods. The effective parameters for these two methods were determined and optimized using Taguchi design method. The obtained nanopartides were characterized by XRD, SEM, TEM, DLLS and BET analysis. By comparing the results of the two methods, it was found that the microemulsion procedure produces finer particles (11.7 nm) with higher specific surface area than that obtained by precipitation method. Moreover, the CoMoO4 nanoparticles were successfully applied to eliminate Reactive Black (RB) 8 dye from aqueous solution with decolorization efficiency of 91.47%. (C) 2013 Elsevier B.V. All rights reserved.