Nanoscale zero-valent iron (nZVI) was prepared by continuously pumping aqueous FeCl2 center dot 4H(2)O (0.1 mol/L) and NaBH4 (0.2 mol/L) into a rotating packed bed (RPB) with blade packings. A rotational speed of 1400 rpm, liquid flow rates of 0.6 L/min, and a temperature of 21 degrees C were used. nZVI that was prepared in this way had a mean grain size of 11.5 nm and a BET surface area of 17.1 m(2)/g. The reactivity of the thus prepared nZVI was measured using the degradation of Reactive Red 2 (RR2) in the presence of dissolved oxygen. At pH 4 and 30 degrees C with an nZVI dosage of 0.30 g/L, the prepared nZVI degraded approximately 92% of the RR2 in 5 min; this efficiency of degradation greatly exceeded that obtained using nZVI that was purchased from Centron Biochemistry Technology (CBT). (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.