Accessibility to quality water around the world has become a major concern as a result of the contamination of water resources from untreated effluents being discharged by some industries into the environment and water bodies. In this study, the efficacy of nanosilica prepared from corn cob ash to remove crystal violet (CV) and acid blue (AB) dyes from aqueous solutions was investigated. Characterisations of the nanosilica adsorbent were achieved using Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy-Energy Dispersive X-ray Spectroscopy (TEM-EDS), Nitrogen adsorption-desorption and X-ray Diffraction (XRD). Effects of adsorption variables, such as pH, adsorbent dosage, contact time, initial concentration and temperature, on the adsorption process were studied using batch adsorption technique. The experimental kinetic data were subjected to non-linear pseudo first order, pseudo second order, and Elovich models as well as intraparticle diffusion model. The equilibrium data were equally subjected to non-linear Langmuir, Freundlich, Dubinin-Radushkevich and Liu models. The average particle size of the nanosilica obtained from TEM image is 40 nm. The specific surface area of the nanosilica, obtained from the Brunauer Emmett Teller (BET), is (65 m2/g). The data showed that adsorption of both dyes was pH dependent and the equilibrium times of CV and AB are 30 and 60 min, respectively. The adsorption process followed pseudo second order kinetic model while the equilibrium data were best fitted into Liu model. The maximum adsorption capacity of the nanosilica for removal of CV is 90.912 mg/g while that of AB is 7.286 mg/g at 28 °C and 0.02 g adsorbent dosage. Increase in temperature did not favour the removal of both dyes and the negative values of thermodynamic parameters ∆Ho and ∆Go indicate exothermicity and spontaneity of adsorption processes, respectively. The nanosilica obtained from corn cob has tendency to be deplored for treatment of textile effluents that are laden with dyes.
Ajayi et al. (Wed,) studied this question.