Cerium oxide nanoparticles were prepared by a novel simple microemulsion procedure and sol-gel method. Using the Taguchi design method, the effective parameters were determined and optimized for CeO2 nanoparticle synthesis. These nanoparticles were characterized by XRD, SEM, TEM, DLS, and BET. The data obtained by these analyses indicated that the microemulsion procedure produces finer particles (3.9 nm) with higher specific surface area in comparison with the sol-gel method. In addition, photocatalytic degradation behavior of the Reactive Orange 16 in aqueous solution with cerium oxide nanoparticles was studied successfully. (C) 2013 Elsevier B.V. All rights reserved.