Humic acid (HA) modifying Fe3O4 nanoparticles (Fe3O4/HA) was developed for removal of Rhodamine B from water. Fe3O4/HA was prepared by a coprecipitation procedure with cheap and environmentally friendly iron salts and HA. TEM images revealed the Fe3O4/HA (with similar to 10 nm Fe3O4 cores) were aggregated as aqueous suspensions. With a saturation magnetization of 61.2 emu/g, the Fe3O4/HA could be simply recovered from water with magnetic separations at low magnetic field gradients within a few minutes. Sorption of the Rhodamine B to Fe3O4/HA reached equilibrium in less than 15 min, and agreed well to the Langmuir adsorption model with maximum adsorption capacities of 161.8 mg/g. The Fe3O4/HA was able to remove over 98.5% of Rhodamin B in water at optimized pH. (C) 2012 Elsevier B.V. All rights reserved.