Enhanced removal of heavy metals by zerovalent iron in designed magnetic reactors

A magnetic propeller agitator and a magnetic reactor were designed to enhance the removal of heavy metals by zerovalent iron (ZVI) in comparison with the non-magnetic reactor. The weak magnetic field (WMF) applied significantly improved the CuII-EDTA removal by ZVI from 10% without WMF to 98% with WMF within 2.5 h at pHini 6.0. The pseudo-first-order rate constants of Cu(II) and As(V) removal by ZVI in the magnetic reactor were increased by 1.51-5.17 and 2.97-5.91 fold, respectively, compared to those obtained in the non-magnetic reactor. The performance of ZVI for treating practical industrial wastewater in the designed magnetic reactor was tested, and the removal of total Cu, P and Zn by ZVI was greatly accelerated. After precipitation of the practical wastewater samples, the concentrations of total Cu, P, Zn decreased to the industrial drainage standard values in 20, 3, 25 min, respectively, in the magnetic reactor, whereas the reaction time needed to eliminate total P and Zn was 10 and 60 min, and the residual total Cu still exceeded the drainage standard values in 2 h in the non-magnetic reactor. The application of magnetic reactor for industrial wastewater treatment is expected to improve the sustainability of ZVI technology.