Paired removal of color and COD from textile dyeing wastewater by simultaneous anodic and indirect cathodic oxidation.

The anodic and indirect cathodic removals of color and COD from real dyeing wastewater were investigated simultaneously using a stacked Pt/Ti screen anode and a graphite packed-bed cathode in a divided flow-by electrochemical reactor. The anodically generated hypochlorite and cathodically generated hydrogen peroxide were the main species used to remove color and COD in the wastewater. Various experimental operating factors that can affect the removal efficiency were investigated, including the applied current density, the amount of NaCl added, the solution pH in alkaline ranges and the temperature. The color and COD removal efficiencies in the anodic chamber were much higher than those in the cathodic chamber. The overall (anodic plus cathodic) removal efficiencies increased with the applied current density, the amount of NaCl added and the temperature. In contrast, increasing the solution pH decreased the overall removal efficiency. The anodic and cathodic current efficiencies at 20 mA/cm(2) were 63.50% and 19.57%, respectively. In this work the total treatment cost for removing 1g COD was US $0.643 when an air cylinder was used.