A straightforward strategy is designed for the fabrication of a magnetically separable NiFe2O4-graphene photocatalyst with different graphene content. It is very interesting that the combination of NiFe2O4 nanoparticles with graphene sheets results in a dramatic conversion of the inert NiFe2O4 into a highly active catalyst for the degradation of methylene blue (MB) under visible light irradiation. The significant enhancement in photoactivity under visible light irradiation can be ascribed to the reduction of GO, because the photogenerated electrons of NiFe2O4 can transfer easily from the conduction band to the reduced GO, effectively preventing a direct recombination of electrons and holes. The results of the kinetic study indicated that the rate-determining stage is the adsorption process of MB molecules. NiFe2O4 nanoparticles themselves have a strong magnetic property, which can be used for magnetic separation in a suspension system, and, therefore, the introduction of additional magnetic supports is no longer necessary. (c) 2011 American Institute of Chemical Engineers AIChE J, 2012