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<p>Corn stalk-based biochar particles (C-B) were synthesized using polyvinyl alcohol as a binder. Oxidative modification was subsequently applied to the biochar particles through treatments with potassium permanganate (KMnO<sub>4</sub>) and hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>), yielding modified biochar particles (C-BC-XT). The adsorption performance of these modified biochar particles toward oxytetracycline hydrochloride (OTC) in aqueous solutions was systematically evaluated. Structural and surface properties were characterized via scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FT-IR). Key results demonstrated that C-BC-900 (pyrolyzed at 900℃) exhibited an 81% higher adsorption efficiency compared to C-BC-700 (pyrolyzed at 700℃). Under 900℃ carbonization conditions, H<sub>2</sub>O<sub>2</sub>- and KMnO<sub>4</sub>-modified biochar particles achieved 40% and 70% enhancements in OTC adsorption capacity, respectively, relative to unmodified biochar. Surface characterization revealed that oxidative modification significantly increased porosity and introduced oxygen-containing functional groups (e.g., hydroxyl [-OH] and carboxyl [-COOH]), which facilitated hydrogen bonding and coordination interactions with OTC molecules. Optimal adsorption occurred under acidic conditions (pH 3), with a maximum adsorption capacity of 35.63&#xa0;mg·g<sup>−1</sup>.Adsorption kinetics followed both pseudo-first-order and pseudo-second-order models, while equilibrium data were well-fitted by Langmuir and Freundlich isotherms. The Langmuir model indicated a maximum adsorption capacity of 21.79&#xa0;mg·g<sup>−1</sup> for C-BC-XT at 308&#xa0;K, suggesting a dual adsorption mechanism: monolayer adsorption on homogeneous surface sites and multilayer adsorption within heterogeneous pore structures.Thermodynamic analysis revealed a positive enthalpy change (ΔH = 43.01&#xa0;kJ/mol) and negative Gibbs free energy values (ΔG &lt; 0), confirming the spontaneous and endothermic nature of the adsorption process. The positive entropy change (ΔS = 0.1553&#xa0;J/(mol·K)) indicated increased system disorder during adsorption. Notably, elevated temperatures enhanced adsorption efficiency, aligning with the endothermic characteristics. These findings highlight the critical role of oxidative modification in optimizing biochar's pore structure and surface chemistry for effective antibiotic contaminant remediation.</p>

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Adsorption of Oxytetracycline Hydrochloride by Oxidatively Modified Biochar Particles: Performance and Mechanism

  • 期刊论文

  • 发表日期：

    2025年11月25日

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  • Rong Chen,
  • Jianlin Zhou,
  • Lingling Wang,
  • Weiyin Liu,
  • Zeyu Dai,
  • Zhang Chen,
  • Guoliang Chen,
  • Zhixian Li

摘要

Corn stalk-based biochar particles (C-B) were synthesized using polyvinyl alcohol as a binder. Oxidative modification was subsequently applied to the biochar particles through treatments with potassium permanganate (KMnO4) and hydrogen peroxide (H2O2), yielding modified biochar particles (C-BC-XT). The adsorption performance of these modified biochar particles toward oxytetracycline hydrochloride (OTC) in aqueous solutions was systematically evaluated. Structural and surface properties were characterized via scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FT-IR). Key results demonstrated that C-BC-900 (pyrolyzed at 900℃) exhibited an 81% higher adsorption efficiency compared to C-BC-700 (pyrolyzed at 700℃). Under 900℃ carbonization conditions, H2O2- and KMnO4-modified biochar particles achieved 40% and 70% enhancements in OTC adsorption capacity, respectively, relative to unmodified biochar. Surface characterization revealed that oxidative modification significantly increased porosity and introduced oxygen-containing functional groups (e.g., hydroxyl [-OH] and carboxyl [-COOH]), which facilitated hydrogen bonding and coordination interactions with OTC molecules. Optimal adsorption occurred under acidic conditions (pH 3), with a maximum adsorption capacity of 35.63 mg·g−1.Adsorption kinetics followed both pseudo-first-order and pseudo-second-order models, while equilibrium data were well-fitted by Langmuir and Freundlich isotherms. The Langmuir model indicated a maximum adsorption capacity of 21.79 mg·g−1 for C-BC-XT at 308 K, suggesting a dual adsorption mechanism: monolayer adsorption on homogeneous surface sites and multilayer adsorption within heterogeneous pore structures.Thermodynamic analysis revealed a positive enthalpy change (ΔH = 43.01 kJ/mol) and negative Gibbs free energy values (ΔG < 0), confirming the spontaneous and endothermic nature of the adsorption process. The positive entropy change (ΔS = 0.1553 J/(mol·K)) indicated increased system disorder during adsorption. Notably, elevated temperatures enhanced adsorption efficiency, aligning with the endothermic characteristics. These findings highlight the critical role of oxidative modification in optimizing biochar's pore structure and surface chemistry for effective antibiotic contaminant remediation.