超滤膜对纳米级絮凝初始颗粒调控的响应机制

Ultrafiltration performance can be improved dramatically by adding coagulant prior to membrane in drinking water treatment. However, on the one hand, coagulant helps decrease the membrane fouling caused by natural organic matter(NOM); on the other hand, flocs which are formed in flocculation process probably aggravate membrane fouling to a certain extent. Until now, few researchers have evaluated the fouling mechanisms during this process from a microscopic point of view. Therefore, this project will discuss how the ultrafiltration membrane will behave in response to structural variations of cake layer on the membrane surface. Also, it will explore the relationships between the property of cake layer and nano-scale flocculated primary particles and their connection modes, and how the relationships will affect the ultrafiltration performance. The micromorphology and aggregation of primary particles will be analyzed by Mastersizer 2000,electron microscopy , CCD camera, etc. Then the size and surface property of primary particles will be adjusted by adding oxidant, flocculation aid, adsorbent and different species of ions to improve the structure of cake layer and reduce the accumulation of NOM on membrane pores in order to alleviate membrane fouling. This project firstly focuses on the mechanisms of membrane fouling in this system at nano-scale. It may provide theoretical basis for enhancing organic substance removal by ultrafiltration and decreasing fouling rate in the case of coagulation pretreatment, and building an optimized ultrafiltration process for drinking water purification.

饮用水处理中，预投絮凝剂可显著提高超滤膜的净水效能。然而，在降低天然有机物导致膜污染的同时，絮凝剂水解形成的絮体又可能在一定程度上造成膜污染。目前，该过程中的膜污染微观机制尚不清晰。为此，本项目将深入研究超滤膜对其表面滤饼层结构组成变化的动态响应，阐明滤饼层演变过程与组成絮体的纳米级絮凝颗粒特性的作用机制，探讨该机制对膜滤净水效能产生的影响。通过电子显微镜、激光粒度检测仪及CCD 摄像技术等分析手段，考察纳米级絮凝初始颗粒的微观特性及其凝聚过程，并利用氧化剂、助凝剂、吸附剂与不同离子对絮凝初始颗粒的形态尺寸、粘结方式、表面有机物解吸等进行调控，以改善滤饼层的微观结构，减少有机物在膜孔表面的沉积，从而降低超滤膜污染。本项目首次在纳米级微观层面上展开对该系统膜污染的机理研究，为絮凝预处理强化超滤膜截留有机物、减缓膜污染速率、构建最优化超滤净水工艺提供有力的理论依据。

全球水资源短缺和水污染严重的问题日益突出，研究和开发高效节能的水处理技术显得尤为必要。饮用水处理中，预投絮凝剂可显著提高超滤膜的净水效能。然而，在降低天然有机物导致膜污染的同时，絮凝剂水解形成的絮体又可能在一定程度上造成膜污染。目前，该过程中的膜污染微观机制尚不清晰。为此，本项目将深入研究超滤膜对其表面滤饼层结构组成变化的动态响应，阐明滤饼层演变过程与组成絮体的纳米级絮凝颗粒特性的作用机制，探讨该机制对膜滤净水效能产生的影响。本项目通过多种分析手段，考察纳米级絮凝初始颗粒的微观特性及其凝聚过程，并利用氧化剂（如锰酸钾）、助凝剂（如聚丙烯酰胺）、吸附剂（如羟基氧化铝纳米颗粒、碳纳米纤维）对絮凝初始颗粒的形态尺寸、粘结方式、表面有机物解吸等进行调控，以改善滤饼层的微观结构，减少有机物在膜孔表面的沉积，从而降低超滤膜污染。本项目首次在纳米级微观层面上展开对该系统膜污染的机理研究，为絮凝预处理强化超滤膜截留有机物、减缓膜污染速率、构建最优化超滤净水工艺提供有力的理论依据。本基金的研究内容为采用超滤技术的水厂提供了新型预处理技术的相关机理分析和技术参考，从而达到延长膜的使用寿命、提高出水水质的目的。