A Sensitive Electrochemical Sensor Using a Dolomite-Graphite Composite for the Simultaneous Detection of Pb2+ and Cd2+

A sensitive electrochemical method for the detection of trace heavy metal ions such as lead Pb (II) and cadmium Cd (II) using a Carbon Graphite Electrode (CPE) chemically modified by a dolomite powder was applied. Firstly, local Moroccan dolomite was deeply characterized  in order to understand its chemical composition and morphological structure. The performance of this sensor is revealed by three electrochemical methods Square Wave Voltammetry (SWV), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). The effect of preconcentration time, concentration effect, media pH, and interference ionic response to the electrochemical response of the working electrode were all investigated under various experimental settings. The SWV determination coefficient (R² (Pb (II)) = 0.8385 and R² (Cd (II)) = 0.9307) is lower than the cyclic voltammetry result (R² (Pb (II)) = 0.989 and R² (Cd (II)) = 0.977), showing the latter's superior predicting ability. Even in the presence of interfering ions, the suggested electrochemical sensor exhibits good repeatability and selectivity, with detection limits of 0.10113 μM and 0.22227 μM for Pb2+ and Cd2+, respectively. These values ​​obtained from the calibration curves of the substances studied reveal that the developed sensor showed excellent electroanalytical performances for the detection of heavy metal ions. According to Atomic Absorption Spectroscopy (AAS), the prepared electrode from CPE-dolomite showed a highly sensitive capacity toward cadmium detection with a content of 178.43 mM after mineralization of the electrode immersed in CdSO4 solution. The same electrode was used to reduce the lead in which the resulting solution was analyzed involving a value of 125.23 mM.