Synthesis of hierarchical structured flower-like Ni(OH)2 and NiO and their application in waste water treatment

Flower-like Ni(OH)₂ and NiO with hierarchical structures were synthesised by a template- and surfactant-free, environmentally friendly chemical precipitation method. The X-ray powder diffraction result indicated that α-Ni(OH)₂ and cubic NiO were synthesised. A scanning electron microscope and a high-resolution transmission electron microscope showed that flower-like Ni(OH)₂ and NiO with good dispersity had an average diameter of ca. 5 m and were composed of leaf-like building blocks. The Brunauer Emmett Teller results showed that flower-like Ni(OH)₂ and NiO possessed high surface areas. Adsorption of congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The equilibrium adsorption data of CR on the as-prepared samples were analysed by Langmuir models, suggesting that the Langmuir model provides a better correlation of the experimental data. The adsorption capacities for removal of CR were determined by using the Langmuir equation and found to be 636.9 and 303 mg/g for flower-like Ni(OH)₂ and NiO, respectively. The as-prepared flower-like Ni(OH)₂ and NiO showed excellent adsorption capacities for CR pollutant from wastewater because of their hierarchical flower-like structures and high specific surface areas.