Electrochemical sensing probe for chemical oxygen demand (COD) assay in waste water: molecular-scale particle design, electrode engineering and system integration

点击翻译按钮获取中文摘要

The chemical oxygen demand (COD) is the amount of oxidant necessary to fully decompose organic compound in water and is critical for purifying drinking water from hazardous and/or biologically active substances. Conventionally this is carried out by mineralization of organic contaminants in the mixture of very toxic and corrosive digesters, which generate safety and environmental concerns. The proposed Discovery Grant research has been targeted at a new class of materials that have electrochemical, photo-electrochemical and pyro-electrochemical reactivity toward oxidation of organic pollutants. Thus they will be integrated into a reagent-free sensor system which can outperform the existing commercial COD assay. This will be accomplished by applying additional initiation and activation methods such as ultrasound, light, polarization and/or temperature. This Discovery program will have three complementary objectives: (1) molecular-scale particle design that delivers catalyst with a high surface area targeting multiple redox active centers, (2) understanding of the synergy electrochemical-photochemical-pyroelectric catalysis toward COD detection, and (3) the sensor prototyping with integrated excitation modes: light, temperature and ultrasound.***We will introduce for the first time ZnO as the catalytic anode for COD detection. Similar to the photocatalytic approach, the organic compounds will be oxidized through excitation of a semiconductor (photo mineralization). In the advanced phase of the project, the ZnO will be modified with metal clusters or metal oxide (ZnO-Zu-Cu2O heterojunctions) in order to initiate photo-electrochemical mineralization in visible light.***The second near-term objective is to adapt a completely new class of catalysts such as pyroelectric LiNbO3 and LiTaO3 and ferroelectric BaTiO3 powders and thin films. In principle, the polar crystal structures of these materials exhibit a spontaneous polarization that can be changed by temperature difference. This results in the formation of surface charges that, in turn, are the sources of pyro-electrochemical activity. In this context, we will synthesize pyroelectrics and investigate the impact of thermal excitation by conventional temperature control or by applying ultrasound as the excitation/activation tool, on the formation of reactive oxygen species (hydroxyl radicals). These reactive species participate in mineralization of organic contaminants.****Each anode will be validated in amperometric, voltammetric and coulometric sensing modes in the integrated a light-ultrasound-temperature-controlled electrochemical cell. This will allow us to examine: (i) fundamentals of electrode kinetic, (ii) mass transport effects studied by rotating disc electrode voltammetry, (iii) the electrode engineering, and (iv) the reactor prototyping and system integration.**