Diclofenac sodium, as a typical deputation of non-steroidal anti-inflammatory drugs, is widely used in clinical treatment. Due to the heavy use, diclofenac sodium is commonly detected in water environment, and the removal of diclofenac sodium from wastewater is important for environmental protection. Notably, magnetic separation technology has become a novel performance in the removal of organic pollutants from wastewater in recent years. Herein, we engineered a lignin-based magnetic nanoparticle adsorbent (LMNA) by loading a magnetic core (Fe₃O₄) onto alkali lignin. This novel adsorbent has the advantage of green synthesis and low cost, making it an ideal material for wastewater treatment. Remarkably, the BET surface area of LMNA (739.2 m² g⁻¹) was higher than that of alkali lignin (2.2 m² g⁻¹). Adsorption batch experiments confirmed that the LMNA exhibited good adsorption performance to diclofenac sodium with a higher adsorption capacity of 106.4 mg g⁻¹. The adsorption kinetic data and isothermal were well fitted by the pseudo-second-order rate equation (R² = 0.980) and the Langmuir equation (R² = 0.991), respectively. Moreover, the reaction mechanisms between the diclofenac sodium and LMNA mainly related to the synergism of electrostatic attractions, π–π stacking interactions and hydrogen bonding interactions. Especially, the LMNA exhibited high magnetic saturation strength (10.5 emu g⁻¹) which made it easy to recycle, showing excellent reusability (4 cycles). Our work might introduce significant theoretical and experimental basis for realizing excellent adsorption of emerging organic pollutants from wastewater by the magnetic nanoparticle adsorbent.

Graphic Abstract

中文翻译：

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用于去除双氯芬酸钠的基于木质素的磁性纳米颗粒吸附剂：吸附行为和机理

双氯芬酸钠作为非甾体抗炎药的典型代表，在临床治疗中得到广泛应用。由于使用量大，水环境中普遍检测到双氯芬酸钠，去除废水中的双氯芬酸钠对环境保护具有重要意义。值得注意的是，磁分离技术近年来已成为去除废水中有机污染物的新表现。在此，我们通过将磁芯 (Fe ₃ O ₄ ) 加载到碱性木质素上，设计了基于木质素的磁性纳米颗粒吸附剂 (LMNA) 。这种新型吸附剂具有绿色合成、成本低等优点，是废水处理的理想材料。值得注意的是，LMNA 的 BET 表面积 (739.2 m ²  g ^-1) 高于碱木质素 (2.2 m ²  g ^-1 )。吸附批次实验证实，LMNA对双氯芬酸钠表现出良好的吸附性能，具有更高的吸附容量106.4 mg g ^-1。吸附动力学数据和等温数据分别符合拟二级速率方程 (R ²  = 0.980) 和朗缪尔方程 (R ²  = 0.991)。此外，双氯芬酸钠与LMNA之间的反应机制主要与静电引力、π-π堆积相互作用和氢键相互作用的协同作用有关。特别是，LMNA 表现出高磁饱和强度（10.5 emu g ^-1) 使其易于回收，显示出出色的可重复使用性（4 次循环）。我们的工作可能为实现磁性纳米颗粒吸附剂对废水中新兴有机污染物的优异吸附提供重要的理论和实验基础。

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