Study of the potential of composite material based on zeolite and geopolymer as an adsorbent of toxic metals

Abstract

The uncontrolled disposal of effluents generated by the electroplating industry represents significant environmental challenges due to the toxicity and persistence of toxic metals present. The present study evaluated a geopolymer-zeolite A composite adsorbent, synthesized from fly ash of steel mill furnaces, for the removal of Cu 2+ , Ni 2+ , and Zn 2+ from aqueous solutions. The produced material exhibited properties (structural and morphological) of both components, which were confirmed by physicochemical characterizations. Batch adsorption studies were performed in a synthetic solution (simulating a galvanic effluent). Kinetic studies revealed satisfactory adsorption rates for Cu 2 ⁺ and Zn 2 ⁺, while Ni 2 ⁺ showed low performance. The experimental adsorption isotherm data were best described by the Sips model, indicating the heterogeneity of the material’s surface. The maximum adsorption capacities were 162,393 mg·g⁻ 1 (Zn 2 ⁺), 99,801 mg·g⁻ 1 (Cu 2 ⁺), and 63,266 mg·g⁻ 1 (Ni 2 ⁺). The removal efficiencies relative to the initial concentration (0.8 mmol L⁻ 1 ) were 34.7% (Cu 2+ ), 32.67% (Zn 2+ ), and 17.12% (Ni 2+ ). Textural analysis revealed that the composite exhibits intermediate behavior between the base phases, with an increased surface area (SBET = 7 m 2 ·g −1 ) and pore volume, which enhances active site accessibility, while FTIR spectra confirmed the structural integrity of the aluminosilicate framework post-adsorption. The dominant mechanism of ion exchange was verified, due to the substantial increase in Na + concentration (from 800 to 1112 mg·L −1 ). The results suggest that the developed composite is a promising route for valorizing legacy coal fly ash, demonstrating strong adsorptive properties for specific heavy metals in simulated aqueous systems. Clinical trial number : Not applicable.

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