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<p>The present work aimed to synthesize pillared clays with titanium (Ti-PILC) and aluminum (Al-PILC) from montmorillonite (LG-PILC) and to verify their efficiency in removing the anionic diazo dye Congo red via adsorption. The clays were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, zeta potential, Brunauer–Emmett–Teller (BET) surface area, and energy-dispersive X-ray spectroscopy (EDS). In the adsorption tests, the kinetics of equilibrium, adsorption dosage, and adsorption isotherms were studied, as well as the recovery and reutilization of the adsorbents. The results of the adsorption tests indicated that the process reached equilibrium after 90&#xa0;min; the amount of dye removed per gram of adsorbent (<i>q</i><sub><i>e</i></sub>, mg.g<sup>−1</sup>) was 23.01, 34.92, and 25.45 for the clays LG-PILC, Ti-PILC, and Al-PILC, respectively. In the kinetic studies of adsorption, all samples followed the pseudo-second-order model. The optimal adsorbent dosage for removing Congo red across all samples was 0.5&#xa0;g.L<sup>−1</sup>. Among the adsorption isotherm models tested, the isotherms found in LG-PILC and Al-PILC samples were closest to the Henry isotherm (<i>R</i><sup>2</sup> = 0.94 and 0.84 for LG-PILC and Al-PILC, respectively). In contrast, the isotherm found in Ti-PILC clay was closest to the Langmuir model in linear form (<i>R</i><sup>2</sup> = 0.98). XRD results showed that the clay composition is mainly montmorillonite, and all other characterization results indicated that the pillars formed within the clay. In the recovery and reuse of clays (with post-treatment), it was observed that the clays maintained the ability to remove Congo red at each reuse stage. Still, they decrease after each cycle (reaching stability as the cycles go by). The clays studied in this research demonstrated high potential for removing Congo red, with the most promising being titanium pillared clay (Ti-PILC). The Ti-PILC clay showed superior adsorption properties to other adsorbents reported in the current literature.</p>

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Adsorption of Congo red on montmorillonite modified with titanium and aluminum pillars

  • 期刊论文

  • 发表日期：

    2025年12月22日

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  • Marcos Vinícius A. Colares,
  • Gabriela Tuono Martins Xavier,
  • Wagner Alves Carvalho,
  • Maria del Rosario Sun-Kou,
  • Yvan Jesús Olortiga Asencios

摘要

The present work aimed to synthesize pillared clays with titanium (Ti-PILC) and aluminum (Al-PILC) from montmorillonite (LG-PILC) and to verify their efficiency in removing the anionic diazo dye Congo red via adsorption. The clays were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, zeta potential, Brunauer–Emmett–Teller (BET) surface area, and energy-dispersive X-ray spectroscopy (EDS). In the adsorption tests, the kinetics of equilibrium, adsorption dosage, and adsorption isotherms were studied, as well as the recovery and reutilization of the adsorbents. The results of the adsorption tests indicated that the process reached equilibrium after 90 min; the amount of dye removed per gram of adsorbent (qe, mg.g−1) was 23.01, 34.92, and 25.45 for the clays LG-PILC, Ti-PILC, and Al-PILC, respectively. In the kinetic studies of adsorption, all samples followed the pseudo-second-order model. The optimal adsorbent dosage for removing Congo red across all samples was 0.5 g.L−1. Among the adsorption isotherm models tested, the isotherms found in LG-PILC and Al-PILC samples were closest to the Henry isotherm (R2 = 0.94 and 0.84 for LG-PILC and Al-PILC, respectively). In contrast, the isotherm found in Ti-PILC clay was closest to the Langmuir model in linear form (R2 = 0.98). XRD results showed that the clay composition is mainly montmorillonite, and all other characterization results indicated that the pillars formed within the clay. In the recovery and reuse of clays (with post-treatment), it was observed that the clays maintained the ability to remove Congo red at each reuse stage. Still, they decrease after each cycle (reaching stability as the cycles go by). The clays studied in this research demonstrated high potential for removing Congo red, with the most promising being titanium pillared clay (Ti-PILC). The Ti-PILC clay showed superior adsorption properties to other adsorbents reported in the current literature.