Advancements in rapid on-site detection of chemical oxygen demand: Insights into sensing mechanisms and practical applications

Abstract

Chemical oxygen demand (COD) serves as a primary indicator for assessing organic matter levels in water quality evaluation. Spectroscopy-based and advanced oxidation-based sensors, known for their environmental friendliness and cost-effectiveness, show significant promise for the rapid on-site detection of COD. However, the practical application of spectroscopic techniques still faces high prediction errors in water quality, while advanced oxidation techniques are hindered by incomplete oxidation efficiency. This review first summarizes the research progress of these two sensor types in terms of sensing mechanisms, applicable scenarios, and future improvement directions. Additionally, the potential integration of novel technologies, such as machine learning, portable microfluidic chips, the Internet of Things (IoT), and field-effect transistors, is explored, focusing on the current bottlenecks in practical applications of water quality monitoring. In conclusion, recent advancements in COD sensing devices, coupled with modern technologies, are emphasized to provide a thorough understanding of the challenges they face and the future prospects for sensor development.