Phase-controlled synthesis of 3D flower-like Ni(OH)2 architectures and their applications in water treatment

Abstract

3D flower-like Ni(OH)₂ architectures including α- and β-Ni(OH)₂ phases, respectively, have been successfully synthesized via a facile microwave-assisted hydrothermal method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N₂ adsorption, respectively. The possible mechanism of Ni(OH)₂ architectures has been discussed and found that the reaction temperature plays a critical role in the formation of two kinds of products. Specifically, flower-like β-Ni(OH)₂ with monolayer petals and α-Ni(OH)₂ with bilayer petals were prepared at 120 °C and 150 °C, respectively. It was suggested that both architectures hold the advantages of large surface-exposure areas and can be readily separated for wastewater treatment due to their particular surface microstructures. Adsorption results showed that both samples exhibited significantly different selectivities for cationic/anionic dyes such as methylene blue (MB) and acid fuschine in aqueous solutions. The hydrophilic properties of two samples were investigated at room temperature. Furthermore, the relationships among the adsorption abilities, the hydrophilic properties and their applications in wastewater treatment of Ni(OH)₂ architectures have been discussed in detail.