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<p>This work investigates the effects of hydrochar (HC) derived from <i>Cuscuta</i> (dodder), an invasive plant, on the textural, structural, morphological, and porosity properties, as well as the adsorptive performance of pozzolan-based alkali-activated geopolymers for the removal of crystal violet (CV) dye from saline water. The geopolymer-hydrochar composites GP<sub>0</sub>, GP<sub>2.5-HC</sub>, and GP<sub>5-HC</sub> were prepared by replacing 0%, 2.5%, and 5% of the pozzolan with hydrochar, respectively. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N<sub>2</sub> adsorption, and scanning electron microscopy (SEM) analyses were used to assess the effects of HC on the mineralogical profile, functional groups, structure, morphology, and texture of the pozzolan-based geopolymers. Batch adsorption experiments were conducted to evaluate CV removal by these composites. Incorporation of 2.5% and 5% HC produced morphologically distinct composites but did not affect the geopolymerization reaction, as no new mineralogical phases were observed. The addition of 5% HC resulted in ~ 27% decrease in specific surface area, from 20.00 to 14.66 m<sup>2</sup>/g, while achieving ultrahigh adsorption capacities ranging from 24 to 5896&#xa0;mg/g in saline water. Salinity enhanced the adsorption capacity 7–11-fold compared with non-saline water, attributed to decreased CV solubility, shifts in ion-exchange equilibrium favoring cation uptake, and electrostatic shielding in saline media. R<sup>2</sup> values ≥ 0.90 and low χ<sup>2</sup> error function values indicated that the Langmuir–Freundlich and Genuine Halsey isotherms best fit the equilibrium data in both non-saline and saline water. Overall, the results demonstrate that geopolymer–hydrochar composites are promising candidates for the removal of CV from saline water.</p> Graphical abstract <p></p>

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Pozzolan and dodder based geopolymer-hydrochar composites with ultrahigh adsorption capacity for crystal violet removal in saline water

  • 期刊论文

  • 发表日期：

    2026年1月5日

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  • H. T. Dzoujo,
  • P. A. Ondiek,
  • V. O. Shikuku,
  • S. Tome,
  • W. Pokam,
  • C. Janiak,
  • Z. M. Getenga,
  • D. D. J. Dina

摘要

This work investigates the effects of hydrochar (HC) derived from Cuscuta (dodder), an invasive plant, on the textural, structural, morphological, and porosity properties, as well as the adsorptive performance of pozzolan-based alkali-activated geopolymers for the removal of crystal violet (CV) dye from saline water. The geopolymer-hydrochar composites GP0, GP2.5-HC, and GP5-HC were prepared by replacing 0%, 2.5%, and 5% of the pozzolan with hydrochar, respectively. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), N2 adsorption, and scanning electron microscopy (SEM) analyses were used to assess the effects of HC on the mineralogical profile, functional groups, structure, morphology, and texture of the pozzolan-based geopolymers. Batch adsorption experiments were conducted to evaluate CV removal by these composites. Incorporation of 2.5% and 5% HC produced morphologically distinct composites but did not affect the geopolymerization reaction, as no new mineralogical phases were observed. The addition of 5% HC resulted in ~ 27% decrease in specific surface area, from 20.00 to 14.66 m2/g, while achieving ultrahigh adsorption capacities ranging from 24 to 5896 mg/g in saline water. Salinity enhanced the adsorption capacity 7–11-fold compared with non-saline water, attributed to decreased CV solubility, shifts in ion-exchange equilibrium favoring cation uptake, and electrostatic shielding in saline media. R2 values ≥ 0.90 and low χ2 error function values indicated that the Langmuir–Freundlich and Genuine Halsey isotherms best fit the equilibrium data in both non-saline and saline water. Overall, the results demonstrate that geopolymer–hydrochar composites are promising candidates for the removal of CV from saline water.

Graphical abstract