High performance ferrocenium tetrachloromagnesate modified MWCNTs electrode for trace level detection of bismuth(III) in aqueous pollution

This study presents the fabrication of a ferricenium tetrachloromagnesate(FTM) modified multi-walled carbon nanotubes(MWCNTs) electrode for the voltammetric determination of bismuth ions (Bi(III)) in aquatic environments. The FTM was synthesized from the reaction of magnesium chloride with ferrocene. The incorporation of FTM , a redox-active species, was shown to markedly improve electron transfer kinetics and overall electrochemical conductivity. Structural and morphological characterizations via Fourier transform infrared spectroscopy(FTIR), transmission electron microscopy(TEM), energy dispersive x-ray(EDX), field emission scanning electron microscopy(FESEM), and x-ray diffraction(XRD) confirmed the successful embedding of FTM within the electrode matrix. Electrochemical assessment using cyclic voltammetry, electrochemical impedance spectroscopy, and chronocoulumetry revealed that a 10% (w/w) FTM loading provided the most optimal charge transfer and interfacial behavior. Differential pulse stripping voltammetry further demonstrated the high sensitivity of the developed electrode, achieving an ultralow detection limit of 0.543 nM across a broad linear range of 1.0 nM to 0.1 mM of Bi(III). The sensor also exhibited remarkable reproducibility(RSD 8.67%) and stability(RSD 7.77%). Furthermore, excellent selectivity towards Bi(III) was maintained in the presence of potentially interference ions such as Mn(II), La(III), Ni(II), Li, Zn(II), Fe(II), Cd(II), Cu(II), Er(II), and Ca(II). Real water sample analyses produced recoveries between 89% and 104%, confirming the practical feasibility of the electrode for the environmental monitoring.