Avaliação da adsorção de cátions metálicos de efluente simulado de galvanoplastia por compósito derivado de cinzas volantes e zeólita A

Abstract

The growing generation of metal-containing effluents by the electroplating industry poses environmental challenges due to the toxicity and persistence of these contaminants. This study evaluated an adsorbent composite of geopolymer and zeolite A, synthesized from steel furnace fly ash, for the removal of Cu²⁺, Ni²⁺, and Zn²⁺ ions from aqueous solutions. The proposal aims to valorize solid waste and develop alternative materials to conventional adsorbents. The synthesis resulted in a material with structural and morphological features of both components, confirmed by physicochemical characterization techniques. Batch adsorption tests were conducted using a synthetic solution representative of electroplating effluents. In kinetic studies, Cu²⁺ exhibited the highest initial adsorption rate, Zn²⁺ stood out for its higher equilibrium capacity, and Ni²⁺ showed the lowest performance in both aspects. Among the isotherm models evaluated, the Sips model provided the best fit to the experimental data, reflecting the heterogeneity of the adsorptive surface. Site saturation was observed at approximately 150 mg·L⁻¹, with maximum adsorption capacities of 162.393 mg·g⁻¹ (Zn²⁺), 99.801 mg·g⁻¹ (Cu²⁺), and 63.266 mg·g⁻¹ (Ni²⁺). The initial concentration influenced both the adsorption rate and removal efficiency, particularly for copper, which was more sensitive to ion availability. The highest removal percentages were observed at the lowest initial concentration (0.8 mmol·L⁻¹): 34.7% (Cu²⁺), 32.67% (Zn²⁺), and 17.12% (Ni²⁺). Ion exchange was identified as one of the main mechanisms, supported by the increase in Na⁺ concentration in solution from 800 mg·L⁻¹ to 1,112 mg·L⁻¹, indicating the release of this cation from the adsorbent matrix in exchange for the metal ions. The results indicate that the developed composite is a promising and sustainable alternative for the treatment of metal-laden effluents.