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<p>Developing multifunctional materials for the efficient removal and recovery of industrial dyes from aqueous solutions remains a significant challenge in environmental remediation. This study integrates experimental optimization via Response surface methodology (RSM) with theoretical insights from quantum mechanical calculations and pKa theory to predict optimal parameters and elucidate the pH-dependent mechanisms for dye removal and recovery using mesoporous silica nanoparticles and their composites. The Density functional theory (DFT) method was employed to calculate interaction energies between Methylene Blue (MB) and the silica surface, showing attractive interactions at basic pH (8–14) due to deprotonation of surface silanol groups, and repulsive interactions in acidic media, aligning with experimental data. The SiO₂ nanoparticles and composites were synthesized and characterized using XRD, AFM, SEM, EDX, DLS, and FTIR to investigate their adsorption behavior under varying conditions of pH, dye concentration, contact time, temperature, and adsorbent dosage. The composite silica and activated charcoal (SiO<sub>2</sub>/AC) showed a significantly higher adsorption capacity of 209.49&#xa0;mg/g, compared to the individual precursors, with SiO<sub>2</sub> showing an adsorption capacity of 29.09&#xa0;mg/g and activated charcoal exhibiting 118.77&#xa0;mg/g. These results were further corroborated by DFT calculations. Thermodynamics studies revealed that the process was spontaneous (∆G = -1.7&#xa0;kJ/mol) and endothermic (∆H = 1.31&#xa0;kJ/mol), following pseudo-second-order kinetics. The recyclability of the adsorbed dye was optimized using ethyl alcohol, HCl, and NaOH, with ESI–MS confirming superior recovery in acidic media. The computational modeling validated pH-dependent molecular interactions, providing mechanistic insights into the removal/recovery cycle.</p>

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Mechanistic Understanding of pH-Responsive Dye Removal/Recovery from Aqueous Media Using a SiO₂/Charcoal Nanocomposite: A Combined DFT and RSM-Based Experimental Study

  • 期刊论文

  • 发表日期：

    2026年6月1日

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  • Erum Asghar Ali,
  • Marriam Yamin,
  • Zafar Khan Ghouri,
  • Fozia Rehman,
  • Abdur Rahim,
  • Dilshad Hussain,
  • Khalid Ahmed

摘要

Developing multifunctional materials for the efficient removal and recovery of industrial dyes from aqueous solutions remains a significant challenge in environmental remediation. This study integrates experimental optimization via Response surface methodology (RSM) with theoretical insights from quantum mechanical calculations and pKa theory to predict optimal parameters and elucidate the pH-dependent mechanisms for dye removal and recovery using mesoporous silica nanoparticles and their composites. The Density functional theory (DFT) method was employed to calculate interaction energies between Methylene Blue (MB) and the silica surface, showing attractive interactions at basic pH (8–14) due to deprotonation of surface silanol groups, and repulsive interactions in acidic media, aligning with experimental data. The SiO₂ nanoparticles and composites were synthesized and characterized using XRD, AFM, SEM, EDX, DLS, and FTIR to investigate their adsorption behavior under varying conditions of pH, dye concentration, contact time, temperature, and adsorbent dosage. The composite silica and activated charcoal (SiO2/AC) showed a significantly higher adsorption capacity of 209.49 mg/g, compared to the individual precursors, with SiO2 showing an adsorption capacity of 29.09 mg/g and activated charcoal exhibiting 118.77 mg/g. These results were further corroborated by DFT calculations. Thermodynamics studies revealed that the process was spontaneous (∆G = -1.7 kJ/mol) and endothermic (∆H = 1.31 kJ/mol), following pseudo-second-order kinetics. The recyclability of the adsorbed dye was optimized using ethyl alcohol, HCl, and NaOH, with ESI–MS confirming superior recovery in acidic media. The computational modeling validated pH-dependent molecular interactions, providing mechanistic insights into the removal/recovery cycle.