Abstract
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•Fabrication of magnetite modified carbon paste electrode (Fe3O4/CPE).•Excellent electrocatalytic activity toward ClO2− electrochemical oxidation.•A low detection limit of 8.6×10−9M for ClO2− was achieved.•The method is fast, simple, highly sensitive, selective, and economically viable.
The magnetite nanoparticles (Fe3O4), synthesized by surfactant aided hydrolysis of the stoichiometric amounts of ferrous (Fe2+) and ferric (Fe3+) ions, were dispersed in carbon paste (CP) to fabricate magnetite modified carbon paste electrode (Fe3O4/CPE). The field emission scanning electron microscopy (FESEM) was used to evaluate the morphology of the synthesized powder in the pure phase and its distribution in the CP that revealed the well-dispersed Fe3O4 nanoparticles in the graphite sheet with a mean size of 10nm. The microstructure analysis of the synthesized magnetite was performed by high-resolution transmission electron microscopy (HRTEM). The phase purity of the synthesized magnetite was evaluated by x-ray diffraction (XRD) analysis. After initial assessment of charge transport in the fabricated electrode by electrochemical impedance spectroscopy (EIS) that exhibited a substantial decrease of 87% in the charge transfer resistance, the suitability of the Fe3O4/CPE was assessed for the detection and determination of chlorite ion (ClO2−) in the aqueous medium. The modified CPE loaded with the optimized amount of Fe3O4 showed considerably enhanced oxidation current as compared to pure CPE for the oxidation of ClO2− and exhibited a near-reversible peak at ∼+0.73V in 0.1M pH 7 phosphate buffers, at a scan rate of 50mV/s. The optimum analytical conditions for the nanomolar detection of ClO2− by square wave voltammetry (SWV) were established. Likely interferences influencing the detection of ClO2− were also investigated. The excellent performance of the fabricated electrode was also established for the real tap and bottled water samples.