Estudos de eletrodos à base de g-C3N4 por técnicas eletroquímicas para aplicação em sensores de metais pesados

Abstract

The increasing contamination of river and lake waters, as well as soil, by potentially toxic metals represents a threat to human and animal health, in addition to affecting natural biomes. Cations of potentially toxic metals, such as lead, cadmium, and mercury, are released into the environment through industrial activities, mining, agriculture, and improper waste disposal. Due to their high persistence, these metals do not degrade easily and tend to accumulate in living organisms. This study aims to advance the development of sensors capable of identifying Hg2+, Pb2+, and Cd2+ ions in real water samples. The sensing platforms are based on graphitic carbon nitride (gC3N4), a highly scalable and economical two-dimensional semiconductor material. Electrodes based on a paste containing carbon black were used for the detection and quantification of these ions. Anodic stripping voltammetry (ASV) results showed that the paste having g-C3N4 possesses electrocatalytic activity for the simultaneous and individual determination of Hg2+, Pb2+, and Cd2+ over a wide linear range from 0,2 to 30 μmol L-1, with a low detection limit at about 40 ppb. Electrochemical impedance spectroscopy (EIS) complements this study by providing quantitative data on charge transfer between g-C3N4 and the metal cations, through the analysis of Nyquist diagrams using equivalent circuits with constant phase elements (CPE).