Removal of Inorganic Contaminants Using Sodalite Synthesized From Alum Sludge

ABSTRACT The growing concern over water contamination by potentially toxic metals underscores the need for sustainable and cost‐effective remediation strategies. In this study, sodalite (SOD‐Na) was synthesized from alum sludge (AS), a by‐product of water treatment plants rich in Si and Al, through a hydrothermal process in an autoclave. Zeolitic concentrate was characterized by x‐ray diffraction (XRD), scanning electron microscopy (SEM), x‐ray fluorescence (XRF), Brunauer Emmet Teller (BET) method, and zeta potential analysis, confirming the formation of sodalite with mesoporous structure and surface charge favorable to cation adsorption. Adsorption experiments demonstrated high affinity for Pb 2+ (189 mg g −1 ), Cd 2+ (121 mg g −1 ), and Ni 2+ (58.4 mg g −1 ), whereas limited adsorption was observed for Cr 6+ (Cr 2 O 7 2− ) (8.2 mg g −1 ), consistent with the material's negative surface charge and ion‐exchange mechanism. Tests with real wastewater confirmed the material's applicability, showing Ni 2+ removal capacity of 26.5 mg g −1 despite competitive interactions with coexisting ions. These findings highlight the potential of sodalite synthesized from alum sludge as an effective and sustainable adsorbent for wastewater treatment, contributing to circular economy strategies and reducing environmental liabilities.