The adsorption behavior of tetracycline (TC) on Fe-N-modified rice straw biochar (Fe-N-RSBC) was systematically investigated to elucidate the underlying mechanisms governing pollutant removal. The enhanced performance of Fe-N-RSBC stems from its unique physicochemical properties, including high surface area (606.62 m²/g), developed mesoporous structure, abundant functional groups, and magnetic characteristics. These features collectively contribute to a highly efficient adsorption process. Adsorption kinetics revealed rapid uptake within the first 60 minutes, with equilibrium reached at approximately 360 minutes. The pseudo-second-order model provided the best fit (R² = 0.9939), indicating that chemisorption is the dominant mechanism, involving active site binding rather than physical diffusion alone.
Isotherm studies demonstrated that TC adsorption followed the Langmuir model, suggesting monolayer coverage on homogeneous surfaces. The maximum adsorption capacity of Fe-N-RSBC reached 156 mg/g, significantly surpassing RSBC (29 mg/g), N-RSBC (19 mg/g), and Fe-RSBC (82 mg/g). The favorable adsorption process was further confirmed by RL values below 1 across all samples. pH variation experiments showed that Fe-N-RSBC maintained over 90% removal efficiency in the pH range of 3.0–11.0, with optimal performance between pH 5.0 and 9.0. This stability arises from the combination of electrostatic attraction and other non-electrostatic interactions, as the point of zero charge (pHPZC) of Fe-N-RSBC was 1.BRCA1 Antibody site 90, resulting in a positively charged surface at neutral pH, which favors interaction with anionic TC species.
Co-existing ions such as Na⁺, K⁺, Ca²⁺, and Mg²⁺ had minimal impact on TC removal, indicating good selectivity and resistance to interference. However, Cu²⁺ exhibited a complex influence: at low concentrations (10 mg/L), it slightly reduced removal efficiency due to competition for adsorption sites; at higher levels (50 mg/L), it enhanced TC removal possibly through ternary complex formation with TC and biochar surfaces. FTIR and XPS analyses after adsorption confirmed key mechanisms: peak shifts in –OH (3440 → 3430 cm⁻¹), C=O (1099 → 1102 cm⁻¹), and Si–O–Si (468 → 464 cm⁻¹) indicated hydrogen bonding formation. The appearance of new peaks at 1560, 1505, and 1400 cm⁻¹, along with changes in Fe–O and C–N signals, supported surface complexation and π–π stacking interactions.Gas6 Antibody Epigenetics Raman spectroscopy showed a decreased ID/IG ratio after TC adsorption, confirming increased graphitic order and stronger π–π interactions.PMID:35115300
In summary, the primary mechanisms responsible for TC removal by Fe-N-RSBC are pore filling (particularly in mesopores), hydrogen bonding, surface complexation with Fe–O sites, and π–π stacking between aromatic rings. Electrostatic forces play a secondary role. The integration of multiple mechanisms enables high adsorption capacity, fast kinetics, and excellent reusability. After three cycles, Fe-N-RSBC retained 76.65% of its initial adsorption capacity, with HCl regeneration proving effective. This study demonstrates that Fe-N-RSBC is a robust, multifunctional adsorbent capable of efficiently removing tetracycline from aqueous environments, offering a viable solution for antibiotic pollution control in real-world water treatment applications.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com