Nanofiltration (NF) membranes have been widely applied in wastewater treatment. However, their wider applications and further popularization are still hindered owing to severe membrane fouling and decreasing cleaning efficiency. In this study, Fenton/Fenton-like agents with a strong foulant degradation ability are prepared and selected, and their influence on the physicochemical properties of polyamide (PA) NF membranes and cleaning efficiency are systematically investigated. It is found that the secondary fouling caused by ferric hydroxide precipitates makes the conventional Fenton agent unsuitable for membrane cleaning. Then, a Fenton-like agent with magnetic Fe₃O₄ nanoparticles modified by γ-poly-glutamic acid (γ-PGA) and L-histidine (L-His) is prepared for membrane cleaning with a low concentration of hydrogen peroxide (<1 mM). Therein, the γ-PGA coating significantly inhibits the agglomeration of nanoparticles by improving their hydrophilicity/dispersibility and reduces their adsorption on the membrane as well as metal ion leaching. More importantly, the imidazole functional groups of L-histidine endow Fe₃O₄ nanoparticles with a higher affinity for hydrogen peroxide, thus ameliorating their catalytic activity for foulant degradation. Combining alkaline cleaning and Fenton-like catalysis cleaning, the stubborn pore fouling can be almost fully removed (100% and 95% for dead-end and cross-flow filtrations, respectively) because the alkali-induced pore swelling effect would enlarge the membrane pores and enhance the mass transfer of free radicals (˙O₂⁻ and ˙OH) into the pores and the release of oxidated foulants. Such a magnetic cleaning agent can be easily recovered and reused for green and sustainable membrane cleaning.

中文翻译：

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界面设计的磁性纳米粒子作为类芬顿催化剂用于聚酰胺纳滤膜的有效化学清洗

纳滤（NF）膜已广泛应用于废水处理。然而，由于严重的膜污染和降低的清洗效率，它们的更广泛应用和进一步推广仍然受到阻碍。在本研究中，制备和选择了具有强污垢降解能力的 Fenton/Fenton 类试剂，并系统地研究了它们对聚酰胺（PA）纳滤膜的理化性质和清洗效率的影响。研究发现，氢氧化铁沉淀引起的二次污染使传统的芬顿剂不适用于膜清洗。然后，用γ-聚_谷氨酸（ γ-PGA）和L-组氨酸（L-His) 用于使用低浓度过氧化氢 (<1 mM) 清洗膜。其中，γ-PGA涂层通过提高纳米粒子的亲水性/分散性并减少它们在膜上的吸附以及金属离子的浸出，显着抑制纳米粒子的团聚。更重要的是， L-组氨酸的咪唑官能团赋予了 Fe ₃ O ₄纳米颗粒对过氧化氢具有更高的亲和力，从而改善了它们对污垢降解的催化活性。结合碱清洗和类芬顿催化清洗，几乎可以完全去除顽固的孔污垢（死端过滤和错流过滤分别为 100% 和 95%），因为碱引起的孔膨胀效应会扩大膜孔并增强自由基（˙O ₂ ^-和˙OH）进入孔隙的质量传递和氧化污垢的释放。这种磁性清洗剂可以很容易地回收和重复使用，用于绿色和可持续的膜清洗。