In this study, a biocompatible sorbent based on copper nanoparticles was synthesised from the extract of cinnamon. The sorbent was characterised by X-ray diffraction, field emission electron microscopy, and Fourier transform infrared spectroscopy. Then, the capability of the prepared sorbent was evaluated for the removal of the Janus Green B (JGB) azo dye from the aqueous media. Initially, the sorbent showed a very fast sorption rate that gradually became slower. Thus, with an initial dye concentration of 200 mg L−1, pH of 6.0, and 10 mg of sorbent, about 84% of the dye is removed in 2 minutes, and the maximum removal efficiency is achieved after 15 minutes (>95%). The sorption data were best fitted with the Langmuir isotherm model with a maximum sorption capacity of 193.62 mg g−1. A pseudo-second-order kinetic model was suitable for explaining the JGB dye sorption rate on the sorbent. [ABSTRACT FROM AUTHOR]