The reported rate constants in this study were of the same order of magnitude with smaller nZVI dosages of 5 and 10 mg/L, and the kSA determined for nZVI dosage of 20 mg/L was one order of magnitude lower. The nZVI nanoparticles with their very high surface areas, can enhance the reduction efficiencies remarkably. However, nZVI prepared in this study tend to agglomerate rapidly because of their high surface area and high reactivity, resulting in the formation of much larger particles and loss in