Green microwave-assisted synthesis of hierarchical NiO architectures displaying a fast and high adsorption behavior for Congo red

Abstract Well dispersed NiO architectures with in-built nanostructure were successfully achieved via a green microwave-assisted aqueous chemical reaction followed by a calcination process. The as-prepared products were characterized by XRD, FESEM, TEM, HRTEM, and N 2 adsorption/desorption isotherms. The results indicated that the three-dimensional (3D) flower-like microspheres with 400–600 nm in diameter are assembled by the pure cubic NiO nanosheets with the thickness of about 10 nm. It should be noted that the interconnecting ultrathin nanosheets have intercrystal mesoporosity and the inhomogeneous multimodal mesopores are ranging from 2.3 to 30.4 nm. A formation mechanism for NiO architectures was simply proposed. In addition, for dye removal in water, the as-obtained NiO as adsorbent exhibited a fast and high adsorption behavior for Congo red (CR), suggesting a promising application in water treatment.