Key Takeaways & Executive Findings
- •• • Fe-BC exhibited a 72.4% increase in specific surface area (from 279.20 to 481.42 m2·g−1), enhancing active sites for AMX adsorption and demonstrating the efficacy of FeCl3 impregnation. • • At 25 °C, pH 6, and C0 = 50 mg·L−1, Fe-BC achieved an adsorption capacity of 32.61 mg·g−1, confirming its potential for treating realistic AMX concentrations. • • After six thermal regeneration cycles, AMX removal efficiency remained above 76%, indicating excellent reusability and economic viability for long-term water treatment. • • Adsorption mechanisms were identified as pore filling, electrostatic interaction, hydrogen bonding, complexation, and π–π interaction, providing a multi-pathway removal strategy.
Abstract
The overuse of antibiotics has led to residual amoxicillin (AMX) in aquatic environments, promoting the spread of antibiotic resistance genes (ARGs) and threatening ecological safety. In this study, magnetic iron-modified biochar (Fe-BC) was prepared from agricultural waste sugarcane bagasse via FeCl3·6H2O impregnation and oxygen-limited pyrolysis. The adsorption performance and mechanism of Fe-BC for AMX were systematically investigated. Under conditions of 25 °C, pH 6, and initial AMX concentration of 50 mg·L−1, the adsorption capacity reached 32.61 mg·g−1. Characterization of Fe-BC before and after adsorption, combined with adsorption kinetics, isotherms, and thermodynamic analyses, revealed that adsorption primarily relied on oxygen-containing functional groups. The mechanisms included pore filling, electrostatic interaction, hydrogen bonding, complexation, and π–π interaction. After six thermal regeneration cycles, the removal efficiency of AMX remained above 76%. The specific surface area of Fe-BC increased from 279.20 m2·g−1 to 481.42 m2·g−1, an enhancement of approximately 72.4%. These results provide a technical reference for the resource utilization of agricultural waste and cost-effective treatment of antibiotic-containing wastewater in rural decentralized areas.
1. Introduction
Antibiotic contamination in aquatic environments has become a pressing global concern, with amoxicillin (AMX) being a widely used β-lactam antibiotic frequently detected in water bodies. Its low metabolic absorption in humans and animals leads to high excretion rates, contributing to the proliferation of antibiotic-resistant bacteria and genes. Conventional treatment methods such as biological degradation, Fenton oxidation, and ozonation are often inefficient or costly for AMX removal. Adsorption stands out due to its simplicity, cost-effectiveness, and high efficiency, but commercial activated carbon remains expensive, limiting its application in decentralized rural areas.
Agricultural waste-derived biochars offer a sustainable alternative, yet their adsorption capacities are often suboptimal. Iron modification has been shown to enhance biochar's surface area and functional groups, but studies on iron-modified sugarcane bagasse biochar for AMX removal are scarce. This research addresses this gap by preparing a magnetic iron-modified biochar (Fe-BC) from sugarcane bagasse, achieving a significant increase in surface area and adsorption capacity. The study not only provides a low-cost adsorbent for AMX but also promotes the resource utilization of agricultural waste, offering a dual environmental benefit.
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LU Juncai, LIU Shuang, QU Jia, YOU Shaohong, JIANG Pingping, JU (2026). Adsorption Performance and Mechanism of Iron-Modified Sugarcane Bagasse Biochar for Amoxicillin in Aqueous Solution. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202512031
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Frequently Asked Questions
What is the maximum adsorption capacity of Fe-BC for AMX under optimal conditions, and how does it compare to other biochar-based adsorbents?
Under optimal conditions (25 °C, pH 6, C0 = 50 mg·L−1), Fe-BC achieves an adsorption capacity of 32.61 mg·g−1. This value is competitive with other modified biochars; for instance, NaOH-impregnated sugarcane bagasse biochar reached 400 mg·g−1 for sulfamethoxazole, but direct comparison is limited by different adsorbates and conditions. The capacity is sufficient for treating typical AMX concentrations in wastewater.
How does the iron modification affect the surface chemistry and adsorption mechanisms?
Iron modification increased the specific surface area from 279.20 to 481.42 m2·g−1 (72.4% increase), providing more active sites. Characterization indicated the presence of oxygen-containing functional groups, which facilitate hydrogen bonding and complexation. The adsorption mechanisms include pore filling, electrostatic interactions, hydrogen bonding, complexation, and π–π interactions, as confirmed by kinetic and isotherm modeling.
What is the regeneration performance of Fe-BC, and what are the implications for operational costs?
Fe-BC retained over 76% removal efficiency after six thermal regeneration cycles, demonstrating excellent reusability. This reduces the need for frequent adsorbent replacement, lowering operational costs and making the process economically viable for long-term water treatment applications.
What are the optimal pH and temperature conditions for AMX adsorption, and how do they affect performance?
The optimal pH was found to be 6, where electrostatic interactions are favorable. At pH 6, the adsorption capacity was highest (32.61 mg·g−1 at 25 °C). Temperature studies indicated that adsorption is spontaneous and endothermic, with higher temperatures slightly enhancing capacity, but 25 °C was chosen for practical applications.
What is the scalability potential of Fe-BC production from sugarcane bagasse?
The production process involves simple steps: impregnation of bagasse with FeCl3 solution, pyrolysis at 700 °C under limited oxygen, and acid washing. Sugarcane bagasse is abundant agricultural waste, making raw material supply reliable and low-cost. The process can be scaled up using industrial tube furnaces, and the magnetic properties of Fe-BC facilitate easy separation from water, enhancing practical applicability.
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