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<p>Aluminum ions (Al<sup>3</sup>⁺) are frequently detected in paddy field effluents due to agricultural activities, with elevated concentrations of Al<sup>3+</sup> posing risks to the environment. This study explores Al<sup>3</sup>⁺ removal using rice husk-derived activated carbon (RHAC), synthesized through Na₂CO₃ chemical treatment, followed by activation at 700&#xa0;°C for 1&#xa0;h under a continuously flowing CO₂ gas stream. RHAC exhibited BET surface area of 954.63&#xa0;m<sup>2</sup>/g, a mesoporous area of 674.52&#xa0;m<sup>2</sup>/g, and a pore diameter of 3.11&#xa0;nm. The experimental studies were conducted to evaluate the adsorption performance of RHAC for Al<sup>3</sup>⁺ ions. Batch adsorption experiments were performed under various conditions to examine equilibrium (initial Al<sup>3</sup>⁺ concentration, contact time, temperature, and pH), along with isotherm, kinetic, and thermodynamic analyses. Equilibrium studies showed that RHAC’s Al<sup>3</sup>⁺ adsorption capacity increased from 4.52 to 24.47&#xa0;mg/g with an increasing initial concentration, reaching 90.46% removal. The highest Al<sup>3</sup>⁺ uptake was observed at 30&#xa0;°C (24.47&#xa0;mg/g) and pH 7 (33.52&#xa0;mg/g). After adsorption, RHAC contained Al atomic percentage of 1.10%, equivalent to 21.03&#xa0;mg Al<sup>3</sup>⁺ per gram, as shown by EDX. Isotherm analysis with four models (Langmuir, Freundlich, Temkin, and Koble-Corrigan) showed the Freundlich model best fit (R<sup>2</sup> = 0.9841), indicating multilayer Al<sup>3</sup>⁺ coverage on RHAC. The Langmuir maximum capacity (Q<sub>m</sub>) was 42.92&#xa0;mg/g, while the heterogeneity factor (n<sub>F</sub>) was 1.62, which indicated favorable adsorption. The adsorption kinetics followed the pseudo-first-order (PFO) model and was limited by film diffusion. Adsorption of Al<sup>3</sup>⁺ onto RHAC was exothermic, spontaneous, and governed by physisorption, as revealed by the thermodynamic study.</p>

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Harnessing the Potential of Rice Husk-Derived Activated Carbon for the Remediation of Al3⁺ from Aqueous Solutions

  • 期刊论文

  • 发表日期：

    2025年4月7日

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  • Muhammad Nasri Nasehir Khan,
  • Mohd Remy Rozainy Mohd Arif Zainol,
  • Muhamad Faizal Pakir Mohamed Latiff,
  • Mohamad Firdaus Mohamad Yusop,
  • Mohd Azmier Ahmad

摘要

Aluminum ions (Al3⁺) are frequently detected in paddy field effluents due to agricultural activities, with elevated concentrations of Al3+ posing risks to the environment. This study explores Al3⁺ removal using rice husk-derived activated carbon (RHAC), synthesized through Na₂CO₃ chemical treatment, followed by activation at 700 °C for 1 h under a continuously flowing CO₂ gas stream. RHAC exhibited BET surface area of 954.63 m2/g, a mesoporous area of 674.52 m2/g, and a pore diameter of 3.11 nm. The experimental studies were conducted to evaluate the adsorption performance of RHAC for Al3⁺ ions. Batch adsorption experiments were performed under various conditions to examine equilibrium (initial Al3⁺ concentration, contact time, temperature, and pH), along with isotherm, kinetic, and thermodynamic analyses. Equilibrium studies showed that RHAC’s Al3⁺ adsorption capacity increased from 4.52 to 24.47 mg/g with an increasing initial concentration, reaching 90.46% removal. The highest Al3⁺ uptake was observed at 30 °C (24.47 mg/g) and pH 7 (33.52 mg/g). After adsorption, RHAC contained Al atomic percentage of 1.10%, equivalent to 21.03 mg Al3⁺ per gram, as shown by EDX. Isotherm analysis with four models (Langmuir, Freundlich, Temkin, and Koble-Corrigan) showed the Freundlich model best fit (R2 = 0.9841), indicating multilayer Al3⁺ coverage on RHAC. The Langmuir maximum capacity (Qm) was 42.92 mg/g, while the heterogeneity factor (nF) was 1.62, which indicated favorable adsorption. The adsorption kinetics followed the pseudo-first-order (PFO) model and was limited by film diffusion. Adsorption of Al3⁺ onto RHAC was exothermic, spontaneous, and governed by physisorption, as revealed by the thermodynamic study.