An Efficient Cost-Effective Removal of Ca²⁺, Mg²⁺, and Cu²⁺ Ions from Aqueous Medium Using Chlorosodalite Synthesized from Coal Fly Ash

Fly ash is one of the coal combustion solid wastes which causes environmental problems around the world. In this context for the first time, this paper reports the conversion of coal fly ash (CFA) into aluminosilicate chlorosodalite, Na₈[AlSiO₄]₆Cl₂. The synthesized chlorosodalite was analyzed by X-ray diffraction, Fourier transform infrared, scanning electron microscopy, and Brunauer–Emmett–Teller surface area measurements. The synthesized aluminosilicate chlorosodalite material was tested for potential applications for the removal of calcium, magnesium, and copper from their aqueous medium. The catch method was successfully used to study the effect of the initial concentration of metal ions, adsorbent dose, and contact time. The equilibrium data obtained were fitted by the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models and showed the affinity order Cu²⁺ > Ca²⁺ > Mg²⁺. The well-known thermodynamic aspects such as the variation in Gibbs free energy (ΔG), entropy (ΔS), and enthalpy (ΔH) were also evaluated. Further the kinetic parameters including the rate constant and the order of sorption process were also determined.