Cd(2+) Detection by an Electrochemical Electrode Based on MWCNT–Orange Peel Activated Carbon

[Image: see text] This study reports the development of a new electrochemical sensor based on a carbon paste electrode (CPE) composed of biomass-based orange peel activated carbon (ACOP) and multiwalled carbon nanotubes (MWCNTs), and this composite is used for the electrochemical detection of cadmium ions (Cd(2+)). The ACOP/MWCNT composite was characterized by FTIR, Raman, and electrochemical impedance spectroscopy. The electrochemical evaluation of Cd(2+) was performed using square wave and cyclic voltammetry. The ACOP/MWCNT–CPE electrochemical sensor exhibited a coefficient of determination r(2) of 0.9907, a limit of detection of 0.91 ± 0.79 μmol L(–1), and a limit of quantification of 3.00 ± 2.60 μmol L(–1). In addition, the developed sensor can selectively detect Cd(2+) in the presence of different interferents such as Zn(2+), Pb(2+), Ni(2+), Co(2+), Cu(2+), and Fe(2+) with a relative standard deviation (RSD) close to 100%, carried out in triplicate experiments. The ACOP/MWCNT–CPE presented high sensitivity, stability, and reproducibility and was successfully applied for the detection of Cd(2+) in river water samples with recovery rate values ranging from 97.33 to 115.6%, demonstrating to be a very promising analytical alternative for the determination of cadmium ions in this matrix.