Fly ash and TiO2 modified fly ash as adsorbing materials for removal of Cd(II) and Pb(II) from aqueous solutions
Kaman Singh, Alok Singh, Arun Kumar, Ankita Agarwal
Abstract
The FA and MFA had been sued to adsorb heavy metals on their surface in this work. For this purpose, fly ash alone is efficient for adsorption, but its efficiency increases when modified with TiO2. TiO2 enhanced the adsorption site of the FA. The study of the surface morphology of FA and MFA by SEM and XRD provides information about their morphology and crystallinity, which is enhanced by modification with TiO2. The crystallinity calculated by Debye-Scherrer's equation was 49.36% for FA, which increased to 79.70%, modifying it with TiO2. The BET analysis reveals that the adsorbent surface area increases after treatment from SBET = 10.79 m2 g−1 (FA) to SBET = 30.59 m2 g−1 (MFA). The adsorption parameters to define the adsorption, such as contact time, temperature, adsorbate concentration, and the adsorbent mass ratio, have been optimized. The TEM analysis revealed that the mean diameter of FA and MFA was 19.45 and 57.71 nm, respectively. The percentage removal of Cd(II) onto FA and MFA was found to be 78.10% and 94.30% and of Pb(II) onto FA and MFA was found to be 75% and 93.10%, respectively at 308 K. The adsorption capacity, qm of Cd(II) onto FA and MFA was found to be 59.20 and 68.80 mg/g, and of Pb(II) onto FA and MFA was found to be 75.30 and 62.70 mg/g, respectively at 308 K. The experimental data had been applied to various adsorption and kinetic models for both FA and MFA, and the order of the best-fitted model was Temkin > Langmuir > Freundlich > Dubinin-Radushkevich isotherm for the adsorption model and pseudo-second-order >pseudo-first-order > intraparticle diffusion for kinetic models.