Removal Of Cu-EDTA From Aqueous Solution By Electrocoagulation Using Al And Fe Electrodes

In this paper, the electrocoagulation using Al and Fe electrodes was investigatedfor the removal of Cu-EDTA from simulated wastewater. It mainly had carried on thefactor experiments, response surface optimization and its removal mechanism. Thefactor experiments mainly studied the reaction time, electrode arrangement, currentdensity, initial pH, NaCl concentration, aeration rate and initial Cu concentration onCOD and Cu removal. The central composite design (CCD) method was adopted tooptimize the electrocoagulation process. Five operating parameters were setedincluding current density, aeration rate, NaCl concentration, initial pH and reactiontime. Response values were seted as the removal efficient of COD and Cu.Environmental scanning electron microscope/energy spectrum analysis and Fouriertransform infrared spectroscopy analysis were used to explore the COD and Curemoval mechanism.The factor experiments showed that, the high removal efficient of COD and Cuwere obtained under the condition of2anodes of Al and2cathodes of Fe, initial pH3,NaCl0.5g/L, micro aeration (0.2-0.7L/min), low initial Cu concentration (below100mg/L), long reaction time and great current density. In the CCD system of CODremoval by electrocoagulation using Al and Fe electrodes, the quadratic model wassignificant, which can well fit to the COD removal actions. In the CCD system of Curemoval by electrocoagulation using Al and Fe electrodes, the quadratic model wasnot significant, so the Cu removal actions cannot be fitted well. The predictive valueof COD removal reached83.5%under the condition of current density17.05mA/cm2,aeration rate0.29L/min, NaCl concentration0.93g/L, initial pH4.32and reactiontime182.03min. The confirmatory experiment showed that, under those optimumconditions, the removal efficient of COD can reach83.12%. At the same time, theremoval efficient of Cu was99.89%. The environmental scanning electronmicroscope/energy spectrum analysis and Fourier transform infrared spectroscopyanalysis suggested that, the major EDTA removal mechanism was oxidation byhypochlorite in acidic condition, while in alkaline condition, co-precipitation withAl/Fe oxyhydroxides and charge neutralization by monomeric and polymeric Alspecies were the main mechanisms; co-precipitation with Al/Fe oxyhydroxides andelectrodeposition by Fe electrodes were the major removal mechanisms of Cu.Based on the results above, it was concluded that EC with an electrodearrangement including2anodes of Al and2cathodes of Fe could be a promisingtechnology for removal of both organic and metallic pollutants from wastewater.