Development and Application of Nanostructured Mn3O4 Based Sensor in the Determination of Heavy Metals in Water and Wastewater

In this work, a novel nanostructured Mn3O4-based electrochemical sensor was developed for the determination of heavy metals in aqueous media. The Mn3O4 nanostructure was solvothermally synthesized in the sole presence of propylene glycol (PG). Under the specific synthetic conditions, PG provided surface coating and stabilization by decomposition products and/or residual PG molecules that have been adsorbed on Mn3O4 NPs surfaces, creating a thin organic layer. This imparts a negative surface charge (zeta potential), enhancing colloidal stability in dispersions and electrochemical performance. The physicochemical properties of the resulting NPs were characterized via X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Thermogravimetric Analysis (TGA), and Dynamic light scattering (DLS) and ζ-potential measurements, as well as SEM imaging of the modified electrode surface, confirming its successful formation and favorable structural properties. The LODs of Cd2+, Pb2+, Zn2+, and Cu2+ for their simultaneous determination are 2.9 μg·L−1, 5.2 μg·L−1, 7.1 μg·L−1, and 2.5 μg·L−1, respectively, with relative standard deviations of about 5.24%, 4.43%, 7.74%, and 4.53%, respectively. As a result of this study, a simple, sensitive, and reproducible electrochemical sensor based on a carbon paste electrode (CPE) modified with novel synthesized manganese nanoparticles and employing voltammetric techniques was applied in water and wastewater.