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<p>In order to remove the dyes Rhodamine B (R-B) and Congo Red (C-R), this study examines the use of raw grape marc (RGM) and ZnCl₂-activated grape marc (ACGM) as inexpensive adsorbents. The materials were characterized using point of zero charge (pHpzc) testing, scanning electron microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR). The consequences of temperature, initial dye concentration, interection time, adsorbent dosage, and solution pH were assessed in batch adsorption tests. While Langmuir, Freundlich, and Dubinin– Radushkevich (D-R) isotherm models have been applied to examine equilibrium data, pseudo-first-order (P-1), pseudo-second-order (P-2), Elovich, Bangham, intraparticle diffusion, and external diffusion models were used for kinetic investigations.</p><p>The results demonstrate that during the first phases of the adsorption process, external diffusion is crucial. The excellent fit of the pseudo-second-order model for both dyes (R² = 0.99) indicates that the surface response rate in this model is greater than the external diffusion surrounding the adsorbent particles. Other rate-controlling mechanisms were found in addition to intraparticle diffusion. Maximum adsorption potential on RGM and ACGM were found to be 22 and 46&#xa0;mg•g⁻¹ for R-B and 17 and 62&#xa0;mg•g⁻¹ for C-R, according to the Langmuir model.</p><p>For adsorbent mass, 2&#xa0;g of RGM removed 97% R-B and 96% C-R, whereas 1&#xa0;g of ACGM removed 99% of both dyes. The adsorption’s spontaneous nature process was validated by thermodynamic data, which displayed negative Gibbs free energy values (ΔG°). This study demonstrates the promise of ACGM as an affordable, efficient adsorbent for wastewater treatment.</p> Graphical abstract <p></p>

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Kinetic and isotherm modelling of cationic dyes adsorption onto raw and ZnCl2-activated wine waste adsorbents

  • 期刊论文

  • 发表日期：

    2026年3月21日

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  • Yamina Chergui,
  • Fouzia Ouazani,
  • Soumia Benkhatou,
  • Samia Benhammadi,
  • Abdelkader Iddou

摘要

In order to remove the dyes Rhodamine B (R-B) and Congo Red (C-R), this study examines the use of raw grape marc (RGM) and ZnCl₂-activated grape marc (ACGM) as inexpensive adsorbents. The materials were characterized using point of zero charge (pHpzc) testing, scanning electron microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR). The consequences of temperature, initial dye concentration, interection time, adsorbent dosage, and solution pH were assessed in batch adsorption tests. While Langmuir, Freundlich, and Dubinin– Radushkevich (D-R) isotherm models have been applied to examine equilibrium data, pseudo-first-order (P-1), pseudo-second-order (P-2), Elovich, Bangham, intraparticle diffusion, and external diffusion models were used for kinetic investigations.

The results demonstrate that during the first phases of the adsorption process, external diffusion is crucial. The excellent fit of the pseudo-second-order model for both dyes (R² = 0.99) indicates that the surface response rate in this model is greater than the external diffusion surrounding the adsorbent particles. Other rate-controlling mechanisms were found in addition to intraparticle diffusion. Maximum adsorption potential on RGM and ACGM were found to be 22 and 46 mg•g⁻¹ for R-B and 17 and 62 mg•g⁻¹ for C-R, according to the Langmuir model.

For adsorbent mass, 2 g of RGM removed 97% R-B and 96% C-R, whereas 1 g of ACGM removed 99% of both dyes. The adsorption’s spontaneous nature process was validated by thermodynamic data, which displayed negative Gibbs free energy values (ΔG°). This study demonstrates the promise of ACGM as an affordable, efficient adsorbent for wastewater treatment.

Graphical abstract