<p>The electrochemical detection of cadmium ions (Cd²⁺) in aqueous media was investigated using a carbon paste electrode modified with a geomaterial (zeolite/geopolymer composite). Electrochemical measurements including, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to assess the performance of the fabricated electrode. The results revealed that the electrode composed of 20 mass% geomaterial exhibited the highest detection sensitivity, while hydrochloric acid was identified as the most suitable supporting electrolyte. Under these conditions, the electron transfer process was quasi-reversible. Furthermore, the increase of the solution pH causes a notable decrease in the anodic current density, which can be due to the partial immobilization of cadmium species (Cd²⁺ and Cd(OH)⁺) on the negatively charged surfaces of the zeolite/geopolymer particles. Additionally, at scan rates higher than 100 mV/s, the electrochemical system transitions from quasi-reversible to irreversible behavior, as evidenced by the disappearance of the cathodic peak, likely due to limited electron transfer kinetics. Electrochemical impedance modeling showed that the electrode/solution interface could be represented using an equivalent electrical circuit consisting of a constant phase element (CPE) in parallel with a charge transfer resistance (<i>R</i>_<i>ct</i>), coupled with a Warburg element that accounted for diffusion-controlled processes.</p> Graphical abstract <p></p>