Electrocatalytic decomplexation of Cu-EDTA and simultaneous recovery of Cu with Ni/GO-PAC particle electrode

Cu-ethylenediaminetetraacetic acid (Cu-EDTA) has strong stability in water and is hard to remove by conventional methods. Fixed bed of particle electrodes was investigated on decomplexation of Cu-EDTA and simultaneously recovery of Cu in the present study. Particle electrode of Ni/GO-PAC was prepared, using powder AC (PAC) and graphene oxide (GO) as carrier, and Ni as catalyst. Results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) revealed that catalyst Ni was mainly composed by Ni-0 and Ni2+. Decomplexation of Cu-EDTA and total complexing copper (TCCu) nearly reached to more than 99%, with more than 94.0% of total copper (TCu) deposited and recovered, at 1 mmol Cu-EDTA, 1.6 mA cm(-2), pH of 3.15 and 1:1 molar ratio of Cu2+:EDTA. The acidic condition was beneficial to decomplexation, while excessive Cu2+ or EDTA brought about the negative impacts. Electron spin resonance (ESR) and free radical quenching experiments confirmed that (OH)-O-center dot had no contribution to the decomplexation of Cu-EDTA. Results of linear sweep voltammetry (LSV) and cyclic voltammetry (CV) discovered that Cu(II) in Cu-EDTA was first reduced to Cu(I), then reduced to Cu(0) through one electron transfer process. The decomplexation of Cu-EDTA was realized through electro-reduction. EDTA was gradually oxidized to small organic species and NO3-