Nanosized MnFe2O4 particles were prepared by using amorphousδ-FeOOH as a precursor.Structure and magnetic properties of the samples were investigated by XRD,TEM and VSM.It is found that the size of as-prepared manganese ferrite particles varies from 30 to 60nm.The as-prepared manganese ferrite particles have selective adsorption for Cr(Ⅵ)ions in wastewater.Based on the strong magnetism,the manganese ferrite particles adsorbed Cr(Ⅵ)ions can be easily separated from the solution.