Humic acid coated Fe3O4 magnetic nanoparticles (Fe3O4/HA) were prepared for the removal of sulfathiazole from aqueous media. Fe3O4/HA exhibited high activity to produce hydroxyl ((OH)-O-center dot) radicals through catalytic decomposition of H2O2. The degradation of sulfathiazole was strongly temperature-dependent and favored in acidic solution. The catalytic rate was increased with Fe3O4/HA dosage and H2O2 concentration. When 3 g L-1 of Fe3O4/HA and 0.39 M of H2O2 were introduced to the aqueous solution, most sulfathiazole was degraded within 1 h, and >90% of total organic carbon (TOC) were removed in the reaction period (6 h). The major final products were identified as environmentally friendly ions or inorganic molecules (SO42-, CO2, and N-2). The corresponding degradation rate (k) of sulfathiazole and TOC was 0.034 and 0.0048 min(-1), respectively. However, when 3 g L-1 of bare Fe3O4 were used as catalyst, only 54% of TOC was eliminated, and SO42- was not detected within 6 h. The corresponding degradation rate for sulfathiazole and TOC was 0.01 and 0.0016 min(-1), respectively. The high catalytic ability of Fe3O4/HA may be caused by the electron transfer among the complexed Fe(II)-HA or Fe(III)-HA, leading to rapid regeneration of Fe(II) species and production of (OH)-O-center dot radicals. (C) 2011 Elsevier B.V. All rights reserved.