Magnetic zeolite from fly ash as a cost-effective adsorbent for Cu²⁺, Pb²⁺, Zn²⁺, and Cd²⁺ removal from aqueous media: a comprehensive study
Breno Aragão dos Santos, Antônia Mayza de Morais França, Luiz Thiago Vasconcelos da Silva, Andressa Gabrielle Santana Gouveia, Carla Bastos Vidal, Adonay R. Loiola, Ronaldo Ferreira do Nascimento
Abstract
In this work, we report the synthesis of magnetic zeolite A using fly ash as the main sources of SiO₂ and Al₂O₃, by hydrothermal use in the adsorption of Pb2, Cd2, Zn2⁺ and Cu2. The composite synthesis was successful, and the obtained material was characterised by using different techniques, such as X-ray diffraction (XRD), X-ray fluorescence (XRF), Infrared vibrational spectroscopy (FTIR), Electron Microscopy (SEM), and pH point of zero charge (pHpzc). XRD measurements confirm zeolites A as the main crystalline phases (98.5%), with the presence of a small amount of sodalite (1.5%). In the SEM of magnetic composite, the characteristic morphology for zeolite A was noted, with magnetite nanoparticles dispersed on its surface, resulting in a composite with magnetic properties. In the adsorption study, the magnetic composite showed a fast rate of adsorption, in which the pseudo second order model was the one that best described the experimental data of the metal ions under study. The Redlich-Peterson isotherm model best represented the experimental data of Pb2⁺ and Cd2⁺, while the Langmuir and Sips models fitted Zn2⁺ and Cu2⁺, respectively. Thus, the results showed that the magnetic composite presented high magnetic quality, facilitating its separation from the aqueous medium, as well as being a promising adsorbent in the adsorption of metal ions in aqueous medium.