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<p>In this work, two prepared adsorbents Na-bentonite (Na-Bnt) and nano-ZnO-bentonite composite (ZnO-Bnt) were used to study the adsorption of Congo red (CR) dye from aqueous solutions. Several analytical methods, such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM), were used to characterize the adsorbents. The effects of several operational parameters such as initial pH, adsorbent dosage, temperature, and initial dye concentration were optimized. The results showed that ZnO-Bent exhibited a higher adsorption efficiency (64.66%) compared to Na-Bent (40%) at an initial dye concentration of 5&#xa0;mg/L. Optimal removal was achieved at natural pH (pH = 7), with an adsorbent dose of 0.008&#xa0;g, a contact time of 40&#xa0;min, and a temperature of 25&#xa0;°C. Kinetic, isotherm, and thermodynamic studies were also performed. The adsorption process followed the pseudo-second-order (PSO) kinetic model, with rate constants (K₂) of 0.0082 and 0.0048&#xa0;g mg⁻¹ min⁻¹ for Na-Bent and ZnO-Bent, respectively. The Langmuir model provided the best fit to the equilibrium data, with maximum adsorption capacities (qₘₐₓ) of 71.43&#xa0;mg g⁻¹ and 23.8&#xa0;mg g⁻¹ for ZnO-Bent and Na-Bent, respectively. Thermodynamic parameters indicated that the adsorption process was endothermic. In comparison to Na-Bent, the synthesized ZnO-Bent nanocomposite showed promising adsorption performance and a higher potential for removing Congo red dye, according to the results.</p> Graphical Abstract <p></p>

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Adsorption of Congo red dye from aqueous phase using ZnO-bentonite nanocomposite and exchanged bentonite: a competitive study

  • 期刊论文

  • 发表日期：

    2026年1月12日

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  • Imen Harbi,
  • Nacéra Zabat

摘要

In this work, two prepared adsorbents Na-bentonite (Na-Bnt) and nano-ZnO-bentonite composite (ZnO-Bnt) were used to study the adsorption of Congo red (CR) dye from aqueous solutions. Several analytical methods, such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM), were used to characterize the adsorbents. The effects of several operational parameters such as initial pH, adsorbent dosage, temperature, and initial dye concentration were optimized. The results showed that ZnO-Bent exhibited a higher adsorption efficiency (64.66%) compared to Na-Bent (40%) at an initial dye concentration of 5 mg/L. Optimal removal was achieved at natural pH (pH = 7), with an adsorbent dose of 0.008 g, a contact time of 40 min, and a temperature of 25 °C. Kinetic, isotherm, and thermodynamic studies were also performed. The adsorption process followed the pseudo-second-order (PSO) kinetic model, with rate constants (K₂) of 0.0082 and 0.0048 g mg⁻¹ min⁻¹ for Na-Bent and ZnO-Bent, respectively. The Langmuir model provided the best fit to the equilibrium data, with maximum adsorption capacities (qₘₐₓ) of 71.43 mg g⁻¹ and 23.8 mg g⁻¹ for ZnO-Bent and Na-Bent, respectively. Thermodynamic parameters indicated that the adsorption process was endothermic. In comparison to Na-Bent, the synthesized ZnO-Bent nanocomposite showed promising adsorption performance and a higher potential for removing Congo red dye, according to the results.

Graphical Abstract