Synthesis and formation mechanism of flowerlike architectures assembled from ultrathin NiO nanoflakes and their adsorption to malachite green and acid red in water

Abstract

The flowerlike architectures assembled from ultrathin NiO nanoflakes have been synthesized by a hydrothermal reaction of Ni(NO3)2 with H2O in the presence of glycerin and subsequent annealing at 400°C 2h in air. The NiO flowerlike architectures with diameters of 7–10μm are assembled from the nanoflakes with thicknesses of 20–30nm. The formation of ultrathin Ni(OH)2·0.75H2O nanoflakes results from the selective adsorption of glycerin on the (100) prismatic faces. The secondary nucleation and growth of Ni(OH)2·0.75H2O nanoflakes result in the formation of flowerlike architectures. When the NiO flowerlike nanoarchitectures are served as the adsorbent for malachite green (MG) and acid red (AR) in water, the adsorption capacity for MG and AR are 142.08 and 64.23mg/g, respectively. The high adsorption capacity of the as-prepared NiO flowerlike architectures for the MG removal could be attributed to the unique hierarchical structure and high surface area of the adsorbents as well as molecule structure of MG.