<p>The development of effective treatment technologies capable of complete color degradation rather than mere transfer or partial removal has garnered substantial attention. In this work, bipolymeric chitosan-polyethyleneimine supported Nano Zero valent Cobalt (Chitosan-PEI/nZvCo) and Nano Zero valent Copper (Chitosan-PEI/nZvCu) were successfully synthesized and thoroughly characterized. The prepared Chitosan-PEI/nZvCo and Chitosan-PEI/nZvCu nanocomposites were analyzed using SEM, EDX, TEM, FT-IR, TGA/DTG, and XRD techniques. SEM images revealed a wide distribution of nZvCu and nZvCo nanoparticles onto bipolymeric chitosan-polyethyleneimine surface. TEM images exhibited spherical nanocomposites. EDX analysis revealed that 4.38% of copper and 7.84% of cobalt were present in the elemental composition of chitosan-PEI/nZvCu and chitosan-PEI/nZvCo, respectively. FT-IR spectra of the prepared nanocomposites showed major changes in the intensity of the main absorption peaks and chemical shifts in the amine and hydroxyl positions, and new absorption peaks were observed at 701–458&#xa0;cm^− 1. Chitosan-PEI/nZvCu revealed the existence of new peaks at 2θ = 44°, 51°, and 74° which were identified to be (111), (200) and (220) plans. However, chitosan-PEI/nZvCo, showed a broad peak around 2θ = 20° related to chitosan and a small peak at 43° corresponding to (111) Co crystal plane. The residual mass values, after thermal decomposition, were equal to 39.5% and 33.5% for chitosan-PEI/nZvCu and chitosan-PEI/nZvCo, respectively. EC/PEI/nZVCu nanocomposite was capable to degrade 100% of methylene blue solution after only 06&#xa0;min of reaction (pH = 6, NaBH₄ = 1&#xa0;M, C₀ = 35&#xa0;mg/L). The decolorization process was influenced by NaBH₄ concentration, initial methylene blue concentration, time, and temperature. The low calculated Ea value (3.19&#xa0;kJ/mol) confirmed that the studied catalytic system was efficient. The decolorization system was non-spontaneous, endothermic, with a reduced disorder.</p>