Abstract: Iron and nitrogen co-doped modified biochar (K2FeO4@NSBC) was prepared by a one-step pyrolysis method using loofah sponge as the carbon source, sodium bicarbonate as the activator, potassium ferrate and urea as the iron and nitrogen sources, respectively. The adsorption performances and mechanisms of K2FeO4@NSBC for bisphenol A (BPA) from water were studied. Under the conditions of a K2FeO4∶NaHCO3∶CH4N2O∶loofah sponge (mass ratio) of 0.1∶0.5∶0.5∶1 and pyrolysis temperature of 800℃, the prepared K2FeO4@NSBC exhibited a large specific surface area (864.83 m2/g) and pore volume (0.54 cm3/g). The adsorption equilibrium capacity (312.58 mg/g) of K2FeO4@NSBC for BPA at 298 K was much higher than that of the original biochar (7.00 mg/g). The influence of solution pH and exogenous organic matter (humic acid) on BPA removal was found to be minimal, indicating that K2FeO4@NSBC can effectively adsorb BPA across a range of environmental conditions. However, the presence of exogenous CO_3^(2-) ions in the solution significantly inhibited BPA removal. The adsorption of BPA by K2FeO4@NSBC followed a pseudo-second-order kinetic model, and the Sips model described the adsorption equilibrium well, suggesting that the adsorption process was governed not only by surface adsorption but also by a heterogeneous distribution of adsorption sites. Additionally, the adsorption process was spontaneous, endothermic, and disorder-enhancing. K2FeO4@NSBC exhibited excellent regeneration and reuse performance, maintaining high BPA removal efficiency after multiple cycles. The main mechanisms for BPA removal by K2FeO4@NSBC were pore filling, hydrophobic interactions, and π-π interactions, with the incorporation of Fe and N playing important roles in the adsorption process. The Fe component could contribute to the formation of active sites, while the N doping could increase the surface charge and improve the interaction between the biochar and BPA molecules. This research provides an environmentally friendly and economically feasible solution for the removal of BPA from water using biochar. The excellent adsorption capacity, stability, and reusability of K2FeO4@NSBC make it a promising candidate for practical applications in water treatment.

Key words: biochar, iron and nitrogen co-doping, sodium bicarbonate, adsorption, bisphenol A, density functional theory

摘要： 本工作以丝瓜络为碳源，碳酸氢钠为活化剂，高铁酸钾和尿素作为铁源和氮源，采用一步热解法制备了铁氮共掺杂生物炭(K2FeO4@NSBC)，并研究了其对水中双酚A (BPA)的吸附去除性能与作用机制。在K2FeO4∶NaHCO3∶CH4N2O∶丝瓜络为0.1∶0.5∶0.5∶1 (质量比)、热解温度为800℃条件下，制备的K2FeO4@NSBC具有较大的比表面积(864.83 m2/g)和孔隙体积(0.54 cm3/g)。在298 K条件下，其对BPA的吸附平衡容量(312.58 mg/g)远高于原始生物炭(7.00 mg/g)。溶液pH与外源有机物腐殖酸对K2FeO4@NSBC吸附去除BPA的影响较小，外源离子CO_3^(2-)对BPA的去除有明显抑制作用。K2FeO4@NSBC对BPA的吸附过程遵循拟二级动力学模型，Sips模型能很好地描述其吸附平衡，且该吸附是一种自发、吸热且无序性增强的过程。K2FeO4@NSBC具有良好的再生和回用性能。孔隙填充、疏水作用和π-π相互作用是K2FeO4@NSBC去除BPA的主要机制，同时Fe和N元素的引入在吸附过程也起到了重要作用。本研究为生物炭去除水中BPA提供了兼具环境友好性与经济可行性的解决方案。

关键词: 生物炭, 铁氮共掺杂, 碳酸氢钠, 吸附, 双酚A, 密度泛函理论