Adsorption isotherms, thermodynamics, kinetics and mechanism for the removal of Ca2+, Mg2+ and Cu2+ ions onto Nosean prepared by using Coal Fly Ash

Abstract

The disposal of Coal Fly Ash (CFA) is a serious environmental issue everywhere in the world. At the same time adulterated and metal ion contaminated water and inadequate amount of good quality water is another environmental problem. To overcome these challenges, this paper is the first of its kind that reports the alkali fusion of CFA followed by hydrothermal synthesis of alumino-silicate sulphate sodalite (Nosean), Na8[AlSiO4]6(SO4)H2O. The Nosean was analysed by XRD, FT-IR, SEM and BET surface area. The adsorption of Ca2+, Mg2+ and Cu2+ ions onto alumino-silicate Nosean was investigated in aqueous medium by batch method. The adsorption of metal ions increased largely with increasing initial concentration of Ca2+, Mg2+ and Cu2+ ions. Pseudo-first, second order, Bangham’s model and intra-particle diffusion models were applied to compute experimental data collected from batch studies and helps to simplify kinetics and mechanism of adsorption process. The equilibrium adsorption data obtained is fitted satisfactorily into different isotherm models given by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich. The thermodynamic parameters and activation energy were evaluated and the results obtained in the present study confirmed that the present adsorption process is a spontaneous and endothermic physisorption.