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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., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)