重力驱动型纳米复合滤膜生物污染层结构调控与过滤效能

Membrane fouling, considering high input of energy and cost, has become a great obstacle for the development and application of membrane technology. Membrane fouling depends on the variable interactions between aqueous foulants and membrane surface, which can not be removed easily and completely. The project supported by new concept and theory attempts to approach and reach a stable permeate flux through the permeable biofouling layer atop membrane surface during the long-term gravity driven membrane process. First, functional monomers will be screened and selected to modify clay particles and three kinds of nanocomposite membranes with functional characteristics of superhydrophilicity, superhydrophobicity and charges will be prepared accordingly through the phase inversion technique, in which surface property and micro/nanostructures could be constructed. Second, irreversible fouling mechanisms reduced by well-decorated and construction of membrane surface property and micro/nanostructures will be explored through investigations of deposition, adsorption and accumulation behavior of aqueous organic matters on membrane surfaces. Then, heterogeneity structure development of biofouling layer modulated by well-decorated and construction of membrane surface property and micro/nanostructures will be concluded through investigations of adhesion, propagation and growth behavior of microbial organisms on membrane surfaces. Finally, the trade-off balance of stabilized flux and permeate quality of gravity driven nanocomposite membrane will be investigated and established. The project aims to provide important insights into mechanisms of irreversible fouling reducing and biofouling layer modulation through surface property and micro/nanostructures of gravity driven nanocomposite membrane, and further to guide the enhancements of flux stabilization and permeate quality.

膜污染导致高能耗、高成本，成为制约水处理膜技术发展与应用的主要限制因素。膜污染程度取决于污染物与膜表面相互作用强弱，未能完全清除。本研究拟利用重力驱动型滤膜生物污染层（生污层）的渗透性达到稳定通量，实现长期低能耗运行。首先，筛选功能单体对粘土改性，通过相转化法制备超亲水、超疏水、荷电性三种纳米复合滤膜，构建滤膜表面特性与微纳结构。其次，研究水中有机物在纳米复合滤膜表面的沉积、吸附、聚集行为，建立利用滤膜表面物化、微纳特性来减缓重力驱动过滤不可逆污染的机制。再次，研究水中微生物在纳米复合滤膜表面的粘附、生长行为，探索利用滤膜表面物化、微纳特性来调控生物污染层孔隙结构发展的规律。最后，研究纳米复合滤膜对稳定通量与出水水质平衡关系的影响，确立重力驱动型膜滤过程中二者关系。本研究旨在解析重力驱动型纳米复合滤膜表面特性与微纳结构对不可逆污染减缓、生污层结构调控的影响机制，改善稳定通量、出水水质。

膜污染导致高能耗、高成本，成为制约水处理膜技术发展与应用的主要限制因素。重力驱动型膜滤技术是解决膜污染难题的有效措施。本项目拟通过纳米材料掺杂制备纳米复合超滤膜，用于低能耗、低污染的重力驱动型超滤膜工艺，以达到低成本净水的目的。项目按申请书计划执，开展以下研究内容：（1）研究了亲水性聚乙二醇改性石墨烯/粘土掺杂聚偏氟乙烯超滤膜的制备、表征以及过滤效能；最大的孔隙率可达84.6%，平均孔径维持在4.8nm左右，水通量恢复率可以达90%以上。（2）利用醋酸纤维素（CA）、聚甲基丙烯酸酯（PMMA）两种高分子亲疏水特异性，在静电纺丝过程中制备具有抗污染特性的CA/PMMA凝胶膜，并研究其重力驱动油水分离效能；水通量可在17-1019 L/m2•h，油水分离效率高达90%以上，且具有良好的多次利用性。（3）基于环糊精的主客体识别对超滤膜进行双功能化改性，验证了其对抗有机污染、生物污染的效能；动态污染过程中改性膜的通量下降趋势分别减缓至35%和31%。（4）利用电化学阻抗谱的手段，对膜界面的电动特性进行系统研究，分析了膜本身、双电层和扩散边界层的厚度及电学特性，为重力驱动膜滤过程中的膜污染行为奠定了理论基础。（5）进行了重力驱动中空纤维超滤膜的长期运行，评估其在江水净化过程中的优势、规律与效能；稳定通量维持在1 ~10 L/m2•h。本研究解析了重力驱动型纳米复合滤膜表面特性与微纳结构对不可逆污染减缓、生污层结构调控的影响机制，为提高稳定通量、出水水质提供了理论指导。