Functionalized Cu-based metal oxide nanoparticles with enhanced Cd⁺² adsorption capacity and their ecotoxicity...

In the present study, synthesis of eco-friendly Cu-based metal oxides nanoparticles [CuO, Cu₂O, and CuO&Cu₂O nanoparticles (NPs)] without and with functionalization with Diethylene glycol (DEG) has been demonstrated. The synthesized NPs were screened for their ability to adsorb multiple heavy metal ions from an aqueous solution. Based on the maximum Cadmium (Cd⁺²) ion adsorption capacity, functionalized Cu₂O (fCu₂O) NPs were selected for the detailed characterization and batch studies. The average size of fCu₂O NPs was found to be 57.4 ± 6.14 nm in comparison to NPs without capping (72.6 ± 5.19 nm). The experimental parameters viz. contact time, initial pH, and initial concentration were optimized, and the obtained results were interpreted using standard isotherms and kinetic models. The maximum Cd⁺² adsorption on fCu₂O NPs was observed at initial solution pH 7. The adsorption of Cd⁺² was found to be decreased at acidic pH due to the protonation of functional groups present on the NPs surface. A maximum Cd⁺² adsorption capacity of 204 ± 6.2 mg g^-1 was obtained from the Langmuir adsorption isotherm. The crystal structure of NPs was prepared and docked with the protein targets of selected soil microbes in order to determine their ecotoxicity. The obtained results showed that NPs exhibited low affinity towards protein targets in comparison to the standard used. It suggests that NPs have less impact on the functionality of soil microbes and are thus safe for their disposal into the soil micro-environment.