Decomplexation and subsequent reductive removal of EDTA-chelated Cu^II by zero-valent iron coupled with a weak magnetic field: Performances and mechanisms

The feasibility of EDTA-chelated Cu^II (Cu^II-EDTA) removal by zero-valent iron (Fe⁰) in the presence of a weak magnetic field (WMF) and the involved mechanisms were systematically investigated. Fe⁰ combined with WMF (Fe⁰/WMF) was very effective for removing Cu^II-EDTA at pH 4.0-6.0 with the rate constants ranging from 0.1190min^-1 to 0.0704min^-1. Little passivation of Fe⁰ was observed during Cu^II-EDTA removal by Fe⁰/WMF in 8 consecutive runs when 10.0mgL^-1 Cu^II-EDTA was dosed before the initiation of each run. The evidences presented in this study verified that Cu^II-EDTA was removed by decomplexation followed by reduction/adsorption. In brief, Fe^II released from Fe⁰ corrosion was rapidly oxidized by oxygen to Fe^III to chelate with EDTA and release free Cu^II, and the detached Cu^II ions were subsequently reduced/removed by Fe⁰/Fe^II and co-precipitated by the generated iron (hydr)-oxides. To advance the application of Fe⁰/WMF technology in real practice, a magnetic propeller agitator was designed to offer WMF inside the reactor, which could greatly improve Cu^II-EDTA removal by Fe⁰ and be easily amplified.