- This study focuses on the development of a novel Zirconium/Cobalt/Chromium electrochemical nanocomposite (Zr/Co/CrNC) sensor for selected pollutants in groundwater. The developed Zr/Co/CrNC was prepared through biosynthesis technique using aqueous extract of Cassia fistula leaves. The precursor salts were added together with the aqueous plant extract through wet impregnation method. High resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscopy (HRTEM), X-ray Diffraction (XRD), BET, and Zetasizer were used to analyze the produced Zr/Co/CrNC. The HRSEM investigation of the Zr/Co/CrNCs revealed porous, distinct and clear morphology with irregular shapes (cube-like flake, rod-like, hexagonal, triangular, spherical, and icosahedral). The HRTEM micrograph showed different structural morphology with lattice fringes of icosahedral, hexagonal, and spherical shapes. The crystallinity of the nanocomposites was greatly influenced as indicated by SAED patterns and were further investigated by XRD pattern where the results reveals the crystalline nature of the produce Zr/Co/CrNCs Electrode Sensor with high intensity upon modifications. The BET results showed some enhanced surface properties with specific surface area as 276.3 m2 /g, pore volume of 0.136 cc/g and pore size of 2.105 nm. Zr/Co/CrNCs Electrode Sensor was used as an Electrode to detect and remove selected heavy metal pollutants in the following order Cd2+, Pd2+ , Ni2+and As3+ and (0.8eV<0.6eV<0.5eV<0.3eV) from groundwater. The detection and removal potentials of Zr/Co/CrNCs Electrode Sensor were examining via a batch mode process. The optimum condition based on each parameters was 40 min of contact time, 0.3eV of conductivity, 97o C of temperature with detection of As showing higher removal efficiency compared to other analyzed metal ions. The dynamic light scattering analysis through Zetasizer revealed the Zr/Co/CrNCs size of 46nm. Hence, it can be deduced that aqueous extract of cassia fistula act as an efficient reducer and stabilizer for the biochemical synthesis of Zr/Co/CrNC sensor. This study demonstrated that Zr/Co/CrNCs shows exceptional properties which enhanced surface area and adsorptive capacity of the prepared material for the detection and removal of selected heavy metal ion

Keywords : Biosynthesis, electrochemical, composites, sensor and groundwater