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.

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