Abstract:

The morphological structure and physicochemical properties of membrane materials are critical to the safety and stability of membrane filtration systems. The polyvinylidene fluoride (PVDF) modified hollow fiber membrane was used to investigate the effect of KMnO₄ on the surface morphology, hydrophobicity, mechanical strength, pure water flux and membrane fouling behavior at pH 5, 7 and 9, respectively. The results indicate that KMnO₄ destroys the modified and separated layers on the surface of PVDF membrane under different pH conditions, which leads to the evolution of different morphological structure, chemical composition, hydrophobicity and antipollution. Under acidic conditions, due to the oxidation of potassium permanganate, the CC of the PVDF membrane material is destroyed, and the hydroxyl group (OH) is introduced, then the aldehyde and ketone compounds are further oxidized. However, in the alkaline condition, the dehydrofluorination reaction took place on the membrane surface, resulting in the formation of carbonyl (CO). Membrane fouling experiments indicate that the change of physicochemical properties of membrane separation interface seriously affected the membrane fouling behavior. With the decrease of pH of KMnO₄ solution and the increase of contact time, the irreversible fouling of membrane surface became more and more serious. This study provides data references for the effect of pH changes on the morphology and properties of PVDF membrane materials in the pre-oxidation membrane filtration process.

Key words: membranes, oxidation, ultrafiltration, membrane property, potassium permanganate, pre-oxidation, pH, membrane fouling

摘要：

膜材料形貌结构和物化性能对膜过滤系统的安全和稳定至关重要。以聚偏氟乙烯(PVDF)改性中空纤维膜为研究对象，考察了预氧化剂高锰酸钾(KMnO₄)在pH分别为5、7、9条件下对膜材料表面形貌、亲疏水性、机械强度、纯水通量及膜污染行为的影响。结果表明，在不同pH条件下，KMnO₄对PVDF膜表面的改性层及分离层造成了破坏，导致了膜表面不同的形貌结构、化学成分、亲疏水性及抗污染性的演变。酸性条件下，由于高锰酸钾的氧化性，PVDF膜材料的CC遭到破坏，同时引入羟基(OH)，继续氧化生成了醛类和酮类化合物；而在碱性条件下，膜表面发生了脱氟化氢反应，生成了羰基(CO)。膜污染实验表明，膜分离界面的物化性质变化严重影响了膜污染行为。此研究为预氧化膜过滤工艺中pH的变化对PVDF膜材料形貌结构和性能的影响提供了数据参考。

关键词: 膜, 氧化, 超滤, 膜性能, 高锰酸钾, 预氧化, pH, 膜污染