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High-capacity removal of crystal violet using ZIF-8/graphene quantum dot composite with RSM optimization and explainable machine learning
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  • Published: 14 February 2026

High-capacity removal of crystal violet using ZIF-8/graphene quantum dot composite with RSM optimization and explainable machine learning

  • Minaam Hussaini1,
  • Sagheer A. Onaizi2,3 &
  • Muhammad S. Vohra1,4 

Scientific Reports , Article number:  (2026) Cite this article

We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

Subjects

  • Chemistry
  • Environmental sciences
  • Materials science

Abstract

Synthetic dyes are persistent pollutants resistant to conventional treatment, necessitating effective removal strategies. This study examines the adsorption of Crystal Violet (CV) onto a ZIF-8/graphene quantum dot (Z8GD) composite under varying conditions. Batch experiments revealed strong sensitivity to operational parameters, with capacities ranging from 76 to 971 mg/g. Adsorption capacity increased from 195 to 460 mg/g as the dose decreased (0.10 → 0.04 g/L), from 200 to 401 mg/g with higher CV concentration (25 → 75 ppm), and from 162 to 971 mg/g with longer shaking time (3 → 24 h). Response Surface Methodology identified these factors as highly significant (p < 0.0001) and yielded a robust predictive model (R² = 0.9869). Kinetic analysis showed that the Avrami model (R² = 0.9993) best described the process, suggesting multi-mechanistic uptake. The maximum adsorption capacity reached ~ 7162 mg/g, with the Redlich–Peterson isotherm providing the best fit (R² = 0.9969). Thermodynamic analysis indicated an endothermic process (ΔH = 20.9 kJ/mol), with Gibbs free energy becoming more negative at higher temperatures (ΔG = − 30.6 to − 33.9 kJ/mol). Post-adsorption XRD and FTIR confirmed Z8GD’s structural stability and revealed multiple interactions, including π–π/CH–π stacking, hydrogen bonding, and electrostatic attraction. Machine learning models further enhanced predictive capability, with the SVR + XGB hybrid achieving the highest accuracy (R² = 0.9986). Shapley Additive Explanations identified shaking time and initial dye concentration as the most influential variables. Overall, Z8GD demonstrated exceptional adsorption capacity and mechanistic versatility, while the integration of RSM and ML provided both optimization and interpretability for adsorption behavior.

Data availability

Data will be made available on request from the corresponding author.

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Acknowledgements

This work was supported by the Interdisciplinary Research Center for Construction and Building Materials (IRC-CBM) at the King Fahd University of Petroleum & Minerals (KFUPM) under Research Grant # INCB2512. The authors would also like to thank the Civil and Environmental Engineering Department and the Chemical Engineering Department at KFUPM for providing the lab facilities.

Funding

This work was supported by the Interdisciplinary Research Center for Construction and Building Materials (IRC-CBM) at the King Fahd University of Petroleum & Minerals (KFUPM) under Research Grant # INCB2512.

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Authors and Affiliations

  1. Civil and Environmental Engineering Department, King Fahd University of Petroleum & Minerals, Dhahran, 31261, Saudi Arabia

    Minaam Hussaini & Muhammad S. Vohra

  2. Department of Chemical Engineering, King Fahd University of Petroleum & Minerals, Dhahran, 31261, Saudi Arabia

    Sagheer A. Onaizi

  3. Interdisciplinary Research Center for Hydrogen Technologies and Carbon Management, King Fahd University of Petroleum & Minerals, Dhahran, 31261, Saudi Arabia

    Sagheer A. Onaizi

  4. Interdisciplinary Research Center for Construction and Building Materials, King Fahd University of Petroleum & Minerals, Dhahran, 31261, Saudi Arabia

    Muhammad S. Vohra

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  1. Minaam Hussaini
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Contributions

Author contributionsMinaam Hussaini: Writing – original draft, Formal analysis, Investigation, Methodology, Validation, Data curation, Visualization. Sagheer A. Onaizi: Writing – review & editing, Conceptualization, Methodology, Funding acquisition, Project administration, Resources, Supervision. Muhammad S. Vohra: Writing – review & editing, Conceptualization, Methodology, Funding acquisition, Project administration, Resources, Supervision.

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Correspondence to Muhammad S. Vohra.

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Hussaini, M., Onaizi, S.A. & Vohra, M.S. High-capacity removal of crystal violet using ZIF-8/graphene quantum dot composite with RSM optimization and explainable machine learning. Sci Rep (2026). https://doi.org/10.1038/s41598-026-39933-2

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  • Received: 23 September 2025

  • Accepted: 09 February 2026

  • Published: 14 February 2026

  • DOI: https://doi.org/10.1038/s41598-026-39933-2

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Keywords

  • CV adsorption
  • Machine learning
  • SHAP analysis
  • ZIF-8/GQD composite
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