Synthesis of NiO nanoparticles by thermal routes for adsorptive removal of crystal violet dye from aqueous solutions

Abstract

Nickel oxide (NiO) nanoparticles were prepared by thermal decompositions of nickel acetate tetrahydrate and bis(acetylacetonato) nickel(II) complex at 500°C in air atmosphere. The thermal decomposition of nickel acetate tetrahydrate produced NiO and the thermal decomposition of bis(acetylacetonato) nickel(II) complex afforded a metal-metal oxide composite material (Ni/NiO). The prepared materials were characterised for assigning their structural and surface properties using the Fourier transform infrared (FT-IR), the X-ray diffraction (XRD), the scanning electron microscopy (SEM), the transmission electron microscopy (TEM), and the thermal analysis (TGA, DTA). The XRD analysis revealed a cubic crystalline structure of NiO and a face-centred cubic structure of Ni. The crystallite size of NiO nanoparticles found to be within 21–63 nm. The XRD analysis of the Ni/NiO composite proved a molar ratio of 10:1 for Ni/NiO. The prepared NiO nanoparticles were studied for the adsorptive removal of the crystal violet dye (CV) from the aqueous solutions as a function of pH of the aqueous solution, initial CV concentration, adsorbent dose, contact time and temperature. The highest adsorbed amount obtained is 79.13 mg/g at pH 9–10 and the adsorption reached equilibrium after 20 min. The equilibrium data was analysed using the Langmuir and the Freundlich adsorption isotherm models and the maximum monolayer adsorbed amount of 53.19 mg/g.