Simultaneous electrochemical removal of copper and chemical oxygen demand using a packed-bed electrode cell

Abstract

Copper ions and chelating agents in water were treated simultaneously by using a packed-bed electrode cell. The cathode packings were graphite particles or graphite felt; the anode packings were platinum-plated titanium pellets, β-PbO₂ particles or oxidized lead spheres. The catholyte contained ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA) or glycine chelate of copper, while the anolyte contained the corresponding chelating agents. The initial concentration of chelating agents was 0.01 M in each experiment. The electrowinning of copper and the removal of chemical oxygen demand (COD) were achieved in the cathodic and the anodic chamber, respectively, under galvanostatic conditions. The COD was determined by the standard KMnO₄ method.

Of the cathodic packings, the graphite felt gave better results than the graphite particles because of the large surface area of the felt. Of the anodic packings, the platinum-plated titanium pellets and the β-PbO₂ particles showed equal suitability for COD removal. In the case of the platinum-plated titanium pellets, the current efficiency for COD removal of EDTA, NTA and IDA was 1.4, 0.7 and 0.32, respectively, in the range 0–12 kC. The removal of COD for EDTA, NTA and IDA under the same conditions was 41, 36 and 25%, respectively. In the lower pH range the electro-oxidation of EDTA proceeded more efficiently.