Facile preparation of mesoporous nickel oxide microspheres and their adsorption property for methyl orange from aqueous solution

Mesoporous NiO microspheres with the average diameters of 1.5 μm, 2 μm, 5 μm and 10 μm were successfully prepared by the direct thermal transformation of nickel oxalate microspheres as the sacrificial oxalate template, which was facilely synthesized by simple precipitation reaction with controllable size in the control of polyvinyl alcohol. The obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption measurement. Specific surface area of the mesoporous NiO microspheres with the average diameters of 10 μm was calculated as 110.2 m2 g−1 by BET method. The mesoporous NiO microspheres as adsorbents exhibited rapid adsorption rate for methyl orange and high adsorption capacity of 113.64 mg g−1 for methyl orange. Batch kinetic experiments showed that pseudo-second-order kinetic equation can better describe the adsorption kinetics, and the experimental data of equilibrium adsorption fitted very well to Langmuir model. The thermodynamic parameters of ΔG°, ΔH° and ΔS° showed that adsorption of methyl orange on mesoporous NiO microspheres was an exothermic and spontaneous in nature.