| dc.description.abstract | Chemical oxygen demand (COD) is a critical indicator for assessing the organic pollutant levels in environmental water bodies and is widely used for water quality monitoring. However, traditional COD analysis methods have several drawbacks, including time-consuming, limited oxidation capability, and secondary pollution due to the use of highly toxic reagents. In contrast, electrochemical methods offer several advantages, such as rapid analysis, low cost, high sensitivity, excellent selectivity, and environmental friendliness, making them increasingly attractive for COD analysis, especially for on-site monitoring and analysis.
In this study, TiO2/SWCNT nanocomposites were synthesized using the sol-gel method and utilized to modify electrodes for COD analysis using linear sweep voltammetry (LSV). Both single-species and dual-species water samples were investigated. The single-species samples were prepared using potassium hydrogen phthalate (KHP), 4-nitrophenol (4-NP), glycine, and salicylic acid (SA), while the dual- species samples were composed of two compounds mentioned above. The study discussed the interactions between organic species on the electrode under varying theoretical oxygen demand (ThOD) ratios.
The results demonstrated that the prepared electrodes exhibited excellent correlation for all organic compounds in single-species systems in a concentration range of 10-100 mg/L. In dual-species systems, the KHP+SA mixture revealed potential competitive interactions at +0.3 V, weakening the oxidation of SA dimers while increasing the oxidation currents of SA at +0.7 V and +1.1 V. For the KHP+4-NP mixture, the oxidation current of KHP was reduced and that of 4-NP enhanced, which suggested that 4-NP inhibited the adsorption of KHP onto the electrode surface, and there might be synergistic effects between 4-NP aromatic groups. Additionally, there was competition between 4-NP and SA in the mixture, which lead to an increased oxidation current of 4-NP and a decrease in the oxidation current of SA. Finally, both oxidation currents of SA and glycine reduced after they were mixed, which suggested that there might be competition. | en_US |