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<p>This study evaluates the potential of corncob-derived hydrochar (CHC), both unmodified and modified with potassium ferrate (K₂FeO₄), as an adsorbent for methylene blue (MB) removal from aqueous solutions. Hydrothermal carbonization (HTC) was employed to transform raw corncob into a porous hydrochar, resulting in a significantly increased surface area and greater availability of binding sites, as evidenced by scanning electron microscopy (SEM) analysis. While the original hydrochar demonstrated some MB adsorption capabilities due to the presence of polar functional groups indicated by Fourier transform infrared (FT-IR), subsequent modification with K₂FeO₄ substantially enhanced its adsorption capacity. This improvement is attributed to a combination of factors, including an increased negative surface charge, a higher concentration of hydroxyl groups (indicated by FT-IR), and the introduction of amorphous iron oxides onto the hydrochar surface as confirmed by X-ray diffraction (XRD). These modifications facilitate various adsorption mechanisms, such as hydrogen bonding, electrostatic interactions, ion exchange, and surface complexation. Single-factor experiments identified optimal adsorption conditions as a pH of 8, an adsorbent dosage of 0.15&#xa0;g, an initial MB concentration of 50&#xa0;mg/L, and a contact time of 2&#xa0;h. The adsorption process was best described by the Langmuir isotherm model and followed pseudo-second-order kinetics. After three regeneration cycles, the modified CHC retained an MB adsorption rate exceeding 76%. The MB adsorption performance of the modified hydrochar was comparable to that of activated carbon derived from citrus peels, highlighting its potential as an effective and sustainable alternative.</p>

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Adsorption behavior and mechanistic insights of potassium ferrate-modified corncob hydrochar for methylene blue removal: implications for carbon-based adsorbents

  • 期刊论文

  • 发表日期：

    2025年2月18日

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  • Qin-Qin Li,
  • Ao Sun,
  • Xiao-Chun Tian,
  • Cheng-Yu Wang,
  • Wang-Ze Xiao,
  • Jin-Long Xu,
  • Kang-Le Ding

摘要

This study evaluates the potential of corncob-derived hydrochar (CHC), both unmodified and modified with potassium ferrate (K₂FeO₄), as an adsorbent for methylene blue (MB) removal from aqueous solutions. Hydrothermal carbonization (HTC) was employed to transform raw corncob into a porous hydrochar, resulting in a significantly increased surface area and greater availability of binding sites, as evidenced by scanning electron microscopy (SEM) analysis. While the original hydrochar demonstrated some MB adsorption capabilities due to the presence of polar functional groups indicated by Fourier transform infrared (FT-IR), subsequent modification with K₂FeO₄ substantially enhanced its adsorption capacity. This improvement is attributed to a combination of factors, including an increased negative surface charge, a higher concentration of hydroxyl groups (indicated by FT-IR), and the introduction of amorphous iron oxides onto the hydrochar surface as confirmed by X-ray diffraction (XRD). These modifications facilitate various adsorption mechanisms, such as hydrogen bonding, electrostatic interactions, ion exchange, and surface complexation. Single-factor experiments identified optimal adsorption conditions as a pH of 8, an adsorbent dosage of 0.15 g, an initial MB concentration of 50 mg/L, and a contact time of 2 h. The adsorption process was best described by the Langmuir isotherm model and followed pseudo-second-order kinetics. After three regeneration cycles, the modified CHC retained an MB adsorption rate exceeding 76%. The MB adsorption performance of the modified hydrochar was comparable to that of activated carbon derived from citrus peels, highlighting its potential as an effective and sustainable alternative.