Determination of chemical oxygen demand based on photoelectrocatalysis of nanoporous TiO2 electrodes

Here we report on a novel, rapid, and environmentally friendly methodology for the determination of chemical oxygen demand (COD) using an electrochemically reduced nanoporous TiO2 electrode. A highly ordered nanoporous structure is grown directly onto a Ti plate through a three-step anodic oxidation process. Subsequent to electrochemical reduction, the nanoporous TiO2 electrode demonstrates a significant enhancement in photoelectrocatalytic activity. An advanced photoelectrochemical method based on the reduced nanoporous TiO2 is successfully developed and employed to quantify COD values in both synthetic and actual wastewater samples. Specifically, a typical processing period of 1-2 min, a practical detection limit of 8 mg L-1, and a linear range of 20-250 mg L-1 COD are achieved. More importantly, the proposed method is in excellent agreement with the standard K2Cr2O7 COD determination technique, albeit with a more rapid analysis period. Further merits include the negation of the necessity of any toxic (Cr2O7-) and highly corrosive (H2SO4) reagents, simple and automatic operation, and environmental compatibility. (C) 2015 Elsevier B.V. All rights reserved.