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 (Fe(0)) in the presence of a weak magnetic field (WMF) and the involved mechanisms were systematically investigated. Fe(0) combined with WMF (Fe(0)/WMF) was very effective for removing Cu(II)-EDTA at pH 4.0-6.0 with the rate constants ranging from 0.1190 min(-1) to 0.0704 min(-1). Little passivation of Fe(0) was observed during Cu(II)-EDTA removal by Fe(0)/WMF in 8 consecutive runs when 10.0 mg L(-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 Fe(0) 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 Fe(0)/Fe(II) and co-precipitated by the generated iron (hydr)-oxides. To advance the application of Fe(0)/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 Fe(0) and be easily amplified.