A new strategy for determination of current efficiency during electro-oxidation of aromatic compounds in a packed-bed system

The electro-oxidation of aromatic compounds in 4,4′-diaminostilbene-2,2′-disulfonic (DSD) acid wastewater on IrO₂–Ta₂O₅/Ti anodes was studied. The current efficiency was evaluated in terms of chemical oxygen demand (COD) by introducing a new factor, the fraction of the Faradaic current to the total cell current (β) through the network analysis of packed bed electrode system (PBEs). Experimental results using an up-flow PBEs at current intensities ranging from 5 to 16 A m⁻², flow rates ranging from 20 to 80 L h⁻¹ and inter-electrode distance of 5 to 50 cm are in good agreement with the proposed equation. In addition, lower current density, increasing flow rate and larger inter-electrode distance are beneficial to enhance the current efficiency.