Adsorption of methylene blue onto synthesized Co3O4, NiO, CuO and ZnO nanoparticles

The metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) with glutamine were synthesized and characterized by elemental analyses, IR, electronic spectra, thermal analyses (TGA and DTA), nuclear magnetic resonance (H-1 and (CNMR)-C-13), electron spin resonance and effective magnetic moments. Four coordinated complexes were formed in case of Cu(II), Ni(II) and Zn(II) ions, while Co(II) formed six coordinated species. The as-prepared metal complexes were used as precursor of Co3O4, NiO, CuO and ZnO nanoparticles after calcination at 700 degrees C. The obtained nanoparticles were characterized by (X-ray powder diffractions) XRD and transmittance electron microscope (TEM). The average particle sizes as indicated from TEM images were found to be 64, 48, 55 and 64 nm for Co3O4, NiO, CuO and ZnO, respectively. Adsorption of methylene blue on the surface of Co3O4, NiO, CuO and ZnO nanoparticles was studied. They exhibited higher adsorption capacity than those prepared by co-precipitation method. NiO showed the highest removal capacity (95.6%) among the studied compounds. Langmuir adsorption isotherm and pseudo-second-order kinetic are the best models that fit the adsorption of methylene blue onto Co3O4, NiO, CuO and ZnO nanoparticles.