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<p>This study demonstrates the synthesis and utilized of an environmentally friendly an alumina–chitosan (α-AO@CS) composite as a very effective and economical adsorbent for the removal of humic acid (HA) from water. The composite was prepared through in-situ dispersion and alkaline gelation, ensuring uniform incorporation of alumina nanoparticles within the polymeric matrix. Structural and surface characterizations (FTIR, XRD, SEM–EDX, and pHpzc) confirmed the successful integration of alumina into chitosan, yielding a material with enhanced surface heterogeneity and stability. Batch adsorption experiments demonstrated that AO@CS achieved maximum HA removal of 91.7% at near-neutral pH (pH ≈ 7), outperforming bare Al<sub>2</sub>O<sub>3</sub> (49.2%) and pristine chitosan (74.9%). The point of zero charge of the composite (pHpzc = 7.3) enabled effective adsorption across a broad pH range, with optimum performance under conditions relevant to natural waters. The maximum adsorption capacity, derived from nonlinear Langmuir isotherm fitting, was 8.23&#xa0;mg g<sup>−1</sup>, while Freundlich modeling indicated multilayer adsorption on heterogeneous sites. Kinetic data conformed to the pseudo-second-order model (R² ≈ 1.0), confirming chemisorption as the dominant mechanism. Thermodynamic parameters revealed that adsorption onto α-AO@CS is spontaneous (ΔG° = − 45.14 to − 84.27&#xa0;J mol<sup>−1</sup>) and endothermic (ΔH° = 18.2&#xa0;kJ mol<sup>−1</sup>), with increased randomness at the solid–solution interface (ΔS° = 70.1&#xa0;J mol<sup>−1</sup> K<sup>−1</sup>). Importantly, the composite retained 83% of its initial capacity after five regeneration cycles, highlighting superior reusability compared with Al<sub>2</sub>O<sub>2</sub> (47%) and chitosan (43%). These results demonstrate that combining alumina’s hydroxyl-rich surfaces with chitosan’s amino functionalities improves their performance, making AO@CS a strong, scalable, and eco-friendly material for enhanced water purification.</p>

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Sustainable α-AO@CS composite for effective humic acid elimination from water

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年1月17日

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  • Bandar A. Al-Mur,
  • Mamdoh T. Jamal

摘要

This study demonstrates the synthesis and utilized of an environmentally friendly an alumina–chitosan (α-AO@CS) composite as a very effective and economical adsorbent for the removal of humic acid (HA) from water. The composite was prepared through in-situ dispersion and alkaline gelation, ensuring uniform incorporation of alumina nanoparticles within the polymeric matrix. Structural and surface characterizations (FTIR, XRD, SEM–EDX, and pHpzc) confirmed the successful integration of alumina into chitosan, yielding a material with enhanced surface heterogeneity and stability. Batch adsorption experiments demonstrated that AO@CS achieved maximum HA removal of 91.7% at near-neutral pH (pH ≈ 7), outperforming bare Al2O3 (49.2%) and pristine chitosan (74.9%). The point of zero charge of the composite (pHpzc = 7.3) enabled effective adsorption across a broad pH range, with optimum performance under conditions relevant to natural waters. The maximum adsorption capacity, derived from nonlinear Langmuir isotherm fitting, was 8.23 mg g−1, while Freundlich modeling indicated multilayer adsorption on heterogeneous sites. Kinetic data conformed to the pseudo-second-order model (R² ≈ 1.0), confirming chemisorption as the dominant mechanism. Thermodynamic parameters revealed that adsorption onto α-AO@CS is spontaneous (ΔG° = − 45.14 to − 84.27 J mol−1) and endothermic (ΔH° = 18.2 kJ mol−1), with increased randomness at the solid–solution interface (ΔS° = 70.1 J mol−1 K−1). Importantly, the composite retained 83% of its initial capacity after five regeneration cycles, highlighting superior reusability compared with Al2O2 (47%) and chitosan (43%). These results demonstrate that combining alumina’s hydroxyl-rich surfaces with chitosan’s amino functionalities improves their performance, making AO@CS a strong, scalable, and eco-friendly material for enhanced water purification.