Efficient preparation of nanoscale zero‐valent iron by high gravity technology for enhanced Cr(VI) removal

Abstract

AbstractOwing to its strong reducibility capacity, nanoscale zero‐valent iron (nZVI) can be widely used in the treatment of wastewater. In this study, nZVI particles with an average size of 14 nm were continuously prepared using a rotating packed bed (RPB) reactor with stainless wire mesh packing. The effects of the surfactant type and the rotating speed of the RPB reactor on the particle size of nZVI were investigated. The results indicated that the average particle size could be notably reduced with the proper addition of PVP in the preparation process. Meanwhile, the particle size could be further decreased by increasing the rotating speed of the RPB. Compared to a stirred tank reactor (STR), the RPB reactor had nZVI with a smaller particle size and a much shorter reaction time. The as‐prepared nZVI was further employed to remove Cr(VI) in the simulated sewage. The results indicated that lower pH, higher nZVI dosage, and higher temperature were beneficial to the efficient removal of Cr(VI). The removal process of Cr(VI) well conformed to a pseudo‐first‐order kinetic model. Thermodynamic studies showed that the reduction of Cr(VI) by nZVI was a spontaneous endothermic reaction process with increased entropy. In addition, nZVI prepared in the RPB displayed higher removal efficiency than the counterpart in the STR, and the removal rate was greatly increased by 17.4 times.