Methylene Blue Removal by Copper Oxide Nanoparticles Obtained from Green Synthesis of Melia azedarach: Kinetic and Isotherm Studies

In this study, Melia azedarach fruit extract was used as a reducing agent and copper chloride dihydrate (CuCl2·2H2O) was used as a precursor in the synthesis of copper oxide nanoparticles (CuO NPs). The UV–visible spectrum showed a characteristic absorption peak of CuO NPs at 350 nm. The surface properties of the adsorbent were analyzed through various techniques, indicating the successful formation of CuO NPs. The impacts of several factors, including initial pH (4 to 8), a dose of CuO NPs adsorbent (0.01–0.05 g), dye initial concentration (10–50 mg·L−1), and contact times ranging from 5 to 120 min, were examined in batch adsorption studies. Based on the experimental results, the Langmuir isotherm is well-fitted, indicating MB dye monolayer capping on the CuO NPs surface with 26.738 mg·g−1 as a maximum adsorption capacity Qm value. For the pseudo-second-order kinetic model, the experimental and calculated adsorption capacity values (qe) exhibited good agreement.