Alumina-silica nano-sorbent from plant fly ash and scrap aluminium foil in removing nickel through adsorption

The alumina-silica nano-sorbent with different alumina-silica ratio were synthesized from thermal power plant fly ash and scrap aluminium foil by alkali extraction, followed by precipitation and calcination. The adsorbent were used successfully for Ni(II) adsorption. The nano-sorbent was characterized by X-ray fluorescence analysis (XRF), X-ray diffraction analysis (XRD), Fourier Transform Infrared spectroscopy (FTIR), Brunauer-Emmet-Teller (BET) analysis, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM). In the BET analysis, the proposed nano-sorbent was found to be mesoporous type with a surface area of 136.18 m2/g, which was about 65 times greater than that of fly ash. The adsorption isotherm confirmed a monolayer adsorption and the kinetic result explained that the chemisorption was predominating in presence of external film and intra-particle pore diffusion. The nature of the adsorption process was observed to be spontaneous and endothermic, at low Ni(II) initial concentration by thermodynamic analysis. The optimal values of the process parameters of equilibrium isotherms, namely pH, initial concentration and temperature were determined. The maximum adsorption capacity of proposed alumina-silica adsorbent for Ni(II) was found to be of 49.754 mg/g.