The degradation of organic pollutants was conducted by using persulfate as the oxidizing agent and ferrous hydroxide colloids as a heterogeneous activator. Complete degradation of sulfamonomethoxine (SMM, 0.06 mM) was achieved within 1 min in the presence of persulfate (1.2 mM) and ferrous hydroxide colloids (1.2 mM), and the apparent rate constant in this system was as high as 2.21 min(-1), being 5.3 times of that using Fe2+ ion (0.42 min(-1)) as the homogeneous activator at pH 3.0. The colloidal activator was also much superior to Fe3O4 nanoparticles, which were reported as good activator of persulfate and provided an apparent rate constant of 1.09 min(-1) under similar conditions. The combination of persulfate and ferrous hydroxide colloids also caused efficient degradation of Rhodamine B and 4-nitrophenol with high total organic carbon (TOC) removal. The highly efficient activation effect of the colloids is attributed to the intrinsic nature of colloid particles with large specific surface area, which simultaneously increase the chemical attack possibility of persulfate and the adsorption of organic pollutants on the colloidal surface. The highly efficient activation effect, easy preparation and use allow promising applications of the ferrous hydroxide colloids in removing recalcitrant organic pollutants with persulfate as green oxidizing agent. (C) 2012 Elsevier B.V. All rights reserved.