Rare shungite carbon, carbon nanotubes and magnesium oxide nanoparticle based composite paste electrode for electrochemical lead ion detection

Abstract

Composite paste was synthesized using magnesium oxide nanoparticles with shungite carbon and multi-walled carbon nanotubes, to formulate two-electrode sensor, facilitating lead detection in aqueous stream. A uniform and homogeneously dispersed composite paste was obtained using the powder with a binder, i.e., silicone oil. Working electrode only comprises magnesium oxide nanoparticles, which was paired with reference electrode to measure potential against various lead concentration. Various factors including concentration of MgO, electrolyte pH, temperature, electrode-separation, detection time and real water sample analysis were examined to optimize sensor's performance. Most effective sensor was then chosen for electrochemical characterizations, which include, cyclic voltammetry, electrochemical impedance spectroscopy, differential pulse voltammetry across different electrolyte concentrations, i.e., lead. Amperometric analysis evaluated influence of co-existing ions, whereas leachate solution studies quantified ion content from working electrode. Electrochemically active surface area and surface coverage areas were measured as 0.022 cm2 and 0.036 cm2, and 2.85 mM.cm−2 and 2.39 mM.cm−2 for unmodified and modified electrodes. Sensor exhibited quasi-reversible behavior with sensitivities of 2.75 mA.cm−2.mg.L−1 and 0.0275 mA.cm−2.mg.L−1, along with detection limits of 0.3 μg.L−1 and 57 μg.L−1 over dynamic ranges. This performance, combined with low fabrication cost (~31.6 US$.g−1), presents a competitive and economical alternative against different commercial lead sensors.