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<p>This study investigates the removal of the azo textile dye Bemacid Yellow E-TL01 using a [Zn-Al-Cl] layered double hydroxide synthesized by coprecipitation at pH 9. The adsorbent’s structural and morphological features were studied by X‑ray diffraction, Fourier‑transform infrared spectroscopy, scanning electron microscopy coupled with energy‑dispersive X‑ray spectroscopy, and thermal analysis. The adsorption performance was evaluated by examining the effects of initial pH, contact time, dye concentration, and temperature. Adsorption tests revealed that the highest removal efficiency (&gt; 95%) was achieved at pH 6.86, with a maximum adsorption capacity of 341.3&#xa0;mg.g⁻¹ (Langmuir model, R² = 0.9975). The kinetics followed a pseudo-second-order model (R² &gt; 0.994), indicating that the adsorption rate was controlled by both dye concentration and surface site coverage. Thermodynamic parameters (Δ<sub>ad</sub>G° from − 1.27 to − 1.53&#xa0;kJ.mol⁻¹, Δ<sub>ad</sub>H° = 2.09&#xa0;kJ.mol⁻¹, Δ<sub>ad</sub>S° = 11.33&#xa0;J.mol⁻¹.K⁻¹) confirmed that the process was spontaneous, endothermic, and governed by physisorption. Density functional theory calculations (B3LYP/6–31 + G(d), CPCM solvation) yielded: E<sub>HOMO</sub> = − 6.13&#xa0;eV, E<sub>LUMO</sub> = − 3.23&#xa0;eV, and ΔE = 2.91&#xa0;eV, suggesting high reactivity and strong electron-sharing propensity. The adsorption mechanism was primarily electrostatic with monolayer coverage on the LDH surface via hydrogen bonding and π–π stacking interactions.</p> Graphical Abstract <p></p>

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Zn–Al LDH for Rapid and Effective Azo Dye Adsorption: Integrating Kinetics, Equilibrium, Thermodynamics, and DFT Analysis

  • 期刊论文

  • 发表日期：

    2026年2月23日

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  • Adnane Seman,
  • Dalal Badreddine,
  • Abdeslam Ansari,
  • El Habib Ait Addi,
  • Ali Assabbane,
  • Omar Cherkaoui,
  • Mohammed Badreddine,
  • Ahmed Legrouri

摘要

This study investigates the removal of the azo textile dye Bemacid Yellow E-TL01 using a [Zn-Al-Cl] layered double hydroxide synthesized by coprecipitation at pH 9. The adsorbent’s structural and morphological features were studied by X‑ray diffraction, Fourier‑transform infrared spectroscopy, scanning electron microscopy coupled with energy‑dispersive X‑ray spectroscopy, and thermal analysis. The adsorption performance was evaluated by examining the effects of initial pH, contact time, dye concentration, and temperature. Adsorption tests revealed that the highest removal efficiency (> 95%) was achieved at pH 6.86, with a maximum adsorption capacity of 341.3 mg.g⁻¹ (Langmuir model, R² = 0.9975). The kinetics followed a pseudo-second-order model (R² > 0.994), indicating that the adsorption rate was controlled by both dye concentration and surface site coverage. Thermodynamic parameters (ΔadG° from − 1.27 to − 1.53 kJ.mol⁻¹, ΔadH° = 2.09 kJ.mol⁻¹, ΔadS° = 11.33 J.mol⁻¹.K⁻¹) confirmed that the process was spontaneous, endothermic, and governed by physisorption. Density functional theory calculations (B3LYP/6–31 + G(d), CPCM solvation) yielded: EHOMO = − 6.13 eV, ELUMO = − 3.23 eV, and ΔE = 2.91 eV, suggesting high reactivity and strong electron-sharing propensity. The adsorption mechanism was primarily electrostatic with monolayer coverage on the LDH surface via hydrogen bonding and π–π stacking interactions.

Graphical Abstract