Scalable and facile preparation of optical-magnetic dual function 3D Ni@graphene-ZnO for high efficiency removal of hexavalent chromium

For the first time, ZnO nanoparticles decorated three-dimensional (3D) Ni@graphene (Ni@GE) composites with uniform size and magnetic separation properties were synthesized by a simple and scalable one-step sol-gel method. The photocatalysts were characterized by X-ray diffraction, fourier-transform infrared spectra, field-emission scanning electron microscope, transmission electron microscopy, UV-vis diffusive reflectance spectra and photo luminescence. The results indicated the ZnO nanoparticles loaded on the outsides of the Ni@GE were no significant numbers of vacancies or apparent aggregation. Meanwhile, the introduction of 3D structured graphene material resulted in the better charge separation efficiency compared with that of the pure ZnO. More significantly, the as-prepared Ni@graphene-ZnO showed superior photocatalytic activity and stability for Cr(VI) reduction to Cr(III).