四环素在不同聚集形态水铁矿上的吸附与解吸
- Adsorption and Desorption of Tetracycline on Ferrihydrite in Different Aggregate States
- 基金项目：国家自然科学基金（NO.42277228，NO.42077337）；广东省科技计划项目（2024B1212050009）
- 摘要：水铁矿作为土壤中活跃的铁（氢）氧化物，其在复杂土壤环境中的聚集形态影响着四环素（TTC）的迁移转化行为。本研究模拟干湿交替（风干）和冻融（冷干）的土壤环境，制备具有不同聚集形态的水铁矿，考察其对TTC的吸附解吸行为。结果表明，新鲜沉淀的水铁矿呈凝胶状，孔隙结构明显；风干和冷干后结构致密，比表面积减小，粒径增大。三种形态的水铁矿对TTC均表现出非线性吸附和解吸滞后现象。吸附容量与比表面积呈正比，凝胶状水铁矿的最大吸附容量最高（680 mg·g-1）。TTC通过静电吸引、氢键和化学络合作用与水铁矿结合，C=O和-N(CH3)2为主要络合位点，而-CONH2和苯环C=C仅与凝胶和风干状水铁矿结合。凝胶状水铁矿因高反应活性导致结构中的Fe(Ⅲ)还原为Fe(Ⅱ)，TTC发生化学键断裂和结构重排。在土壤铁循环中，凝胶状水铁矿通过高比表面积和孔隙结构有效固定并催化转化TTC；而在干湿交替及冻融环境中的水铁矿固定能力下降，增加TTC淋溶或径流进入地下水的风险。因此，评估铁氢氧化物对TTC环境风险的影响需考虑土壤条件的差异。
- Abstract：Ferrihydrite, an active iron (hydr)oxide in soils, could influence the migration and transformation of tetracycline (TTC) via its aggregate states in complex soil environments. In this study, we prepared the ferrihydrite with different aggregate states through wet-dry cycles (air-drying) and freeze-thaw cycles (freeze-drying), and investigated the adsorption-desorption behaviors of TTC on their surface. Fresh precipitated ferrihydrite exhibited a gel-like structure with noticeable porosity, whereas air-dried and freeze-dried ferrihydrites became more compact, showing reduced specific surface areas with larger particle size. The adsorption and desorption of TTC on the three state minerals exhibited nonlinear. The adsorption capacity was directly propotional to the specific surface area, the maximum adsorption capacities were the highest for gel-like ferrihydrite (680.3 mg·g-1).TTC could be uptaken with ferrihydrite through electrostatic attraction, hydrogen bonding, and chemical complexation, with C=O and -N(CH?)? serving as primary binding sites. Additionally, -CONH? and benzene ring C=C specifically bound to gel-like and air-dried ferrihydrites. The high reactivity of gel-like ferrihydrite not only resulted in the reduction of Fe(III) to Fe(II) but also led to the bond cleavage and structural rearrangement of TTC. In the soil iron cycle, the effective immobilization and catalytic transformation of TTC by gel-like ferrihydrite is facilitated by its high specific surface area and pore structure. However, the immobilization capacity of ferrihydrite is significantly reduced under alternating dry-wet and freeze-thaw conditions, thereby increasing the risk of TTC leaching or runoff into groundwater. Therefore, assessing the environmental risks of TTC associated with iron (hydr)oxides requires considering variations under different soil conditions.
