A novel eco-friendly procedure was developed to adsorb Pd 2+ ions from wastewaters using the green synthesized zinc oxide (ZnO) nanoparticles (NPs). ZnO NPs were easily produced using zinc nitrate through Centaurea cyanus extract as a reducing agent at ambient conditions. X-ray diffraction results demonstrated that ZnO NPs have a highly crystalline hexagonal structure. Fourier transform infrared spectral analysis indicated an active contribution of C. cyanus-derived biomolecules in zinc ions bioreduction. ZnO NPs were properly dispersed and had a hexagonal shape. The impact of process parameters like initial pH of solution, adsorption dosage, Pd 2+ ions initial concentration, and contact time on the Pd 2+ ions adsorption from the effluent of a petrochemical company was evaluated. The Freundlich isothermal model could excellently legitimize a multilayer adsorption. The adsorption process followed a pseudo-second-order reaction kinetic, i.e., chemisorption process.

ZnO nanoparticles (NPs) were easily synthesized using zinc nitrate through centaurea cyanus extract (as a reducing agent) at ambient conditions. XRD results demonstrated that ZnO NPs have a high-crystalline hexagonal structure with an average size of 48 nm in diameter. FT-IR spectral analysis indicated an active contribution of centaurea cyanus-derived biomolecules in zinc ions bioreduction. According to SEM analysis, ZnO NPs were properly dispersed and had a hexagonal shape. Batch experiments were performed to investigate the impact of several process parameters such as initial pH of solution, adsorption dosage, Pd2+ ions initial concentration and contact time on the Pd2+ ions adsorption from the solution. The Freundlich isothermal model could excellently legitimize a multilayer adsorption. Furthermore, the adsorption process followed a pseudo-second-order reaction kinetic. The maximum adsorption (99.24%) was experimentally found at pH of 5.5, adsorption dosage of 1.63 g.L-1, Pd2+ ions initial concentration of 77.5 mg.L-1 and contact time of 91.25 min.