Effective decontamination of Ca2+ and Mg2+ hardness from groundwater using innovative muscovite based sodalite in batch and fixed-bed column studies; dynamic and equilibrium studies

Abstract

A novel form of sodalite was synthesized from muscovite (M.SD) as low-cost softening material for both Ca²⁺ and Mg²⁺ ions from real groundwater in batch and column studies. The sodalite sample showed significant surface area (105 m²/g) and ion exchange capacity (87.3 meq/100 g) which qualifies it strong for softening applications. The incorporation of the M.SD as a fixed bed in column system at a fixed thickness of 4 cm and flow rates of 5 mL/min resulted in removal percentages of 90.5% and 92.2% for Ca²⁺ and Mg²⁺, respectively at pH 7.6. Considering the real concentrations of the ions (Ca²⁺ (233 mg/L) and Mg²⁺ (114 mg/L)), the M.SD bed has the ability to reduce their concentrations according to the recommended limits (75 mg/L for Ca²⁺ and 50 mg/L for Mg²⁺). These conditions resulted in purification of about 8.1 L and 8.7 L with breakthrough intervals of 1380 min and 1440 min; and saturation interval more than 1620 min for Ca²⁺ and Mg²⁺, respectively. The M.SD columns' performances were described considering the assumption of the Thomas model, Adams-Bohart model, and Yoon-Nelson model. The batch studies demonstrate the uptake of both Ca²⁺ and Mg²⁺ ions according to the Pseudo-First order kinetics and Langmuir equilibrium behaviour. Considering the values of Gaussian energies (0.77 KJ/mol (Ca²⁺) and 1.36 KJ/mol (Mg²⁺)), the uptake of these ions occurred by homogenous reactions of monolayer form and physical nature. The thermodynamic studies declared the spontaneous properties of the reactions and their exothermic properties.

Keywords: Adsorption; Batch; Fixed bed; Hardness; Muscovite; Sodalite.