Nanostructured ceramic membranes with tailored functionalization and geometry for virus filtration

本研究的目的是制备一种具有定制功能和特殊几何形状的高性能和高效的病毒过滤器。在本项目的范围内，基于氧化钇稳定的氧化锆（YSZ）的陶瓷毛细管膜通过挤出制备。为了调节膜的颗粒间孔径，使用具有不同初级粒度的初始YSZ粉末，其中增加的YSZ粒度导致增加的膜孔径。利用初级粒径在约30-600 nm范围内的YSZ颗粒分别产生平均孔径在上中孔（30-50 nm）和下大孔（50-500 nm）范围内的膜，提供超滤膜和微滤膜。根据膜的颗粒间孔径的增加，在病毒过滤期间渗透通量显著增加。为了实现高的病毒截留效率，必须确保至少4的对数减少值（LRV > 4），这对应于99.99%的病毒减少。基于由膜孔介导的这种物理屏障，开发了方便的膜功能化策略，以确保在膜表面上的电荷依赖性病毒吸附。病毒的等电点（IEP）在pH值约为3.5至7的范围内，因此，在中性pH值条件下，受污染的水样中的病毒带负电荷。因此，病毒可以被IEP> 7的带正电荷的膜吸附。为了生成正电性膜，首先通过羟基化接着氨基硅烷化来活化处于烧结状态的惰性陶瓷膜。基于这样的氨基官能化和带正电荷的过滤器表面，提供了再生病毒过滤器，并且饱和的过滤器元件可以通过pH变化和随后的洗涤（吸附-洗脱方法）容易地清洁。除了官能化的毛细管膜之外，通过挤出制造用于病毒过滤的膜，其显示出以曲折形和螺旋形取向形式的特殊几何形状。与传统的线性毛细管膜相比，曲折形和螺旋形膜可以基于陶瓷基质的给定节距（每单位长度的绕组）和弯曲（分别为曲折宽度和螺旋直径）在毛细管的内部通道中产生湍流。由于产生的湍流，在病毒过滤期间可以减少孔堵塞和膜污染。

The aim of this research project is to fabricate a high-performance and highly efficient ceramic filter with tailored functionalization and special geometry for virus filtration.Within the scope of this project, ceramic capillary membranes based on yttria-stabilized zirconia (YSZ) are fabricated by extrusion. To adjust the interparticle pore size of the membrane, initial YSZ powders with different primary particle size are used where increased YSZ particle sizes lead to increased membrane pore sizes. The utilization of YSZ particles with primary particle sizes in the range between ~30-600 nm results in membranes with average pore sizes in the upper mesoporous (30-50 nm) and lower macroporous range (50-500 nm), respectively, providing ultra- and microfiltration membranes. In accordance with an increase of the interparticle pore size of the membrane, the permeate flux is significantly increased during virus filtration. To realize a high virus-retention efficiency, a log reduction value of at least 4 (LRV > 4) has to be ensured which corresponds to a virus reduction of 99.99 %.Based on this physical barrier mediated by the membrane pores, convenient membrane fuctionalization strategies are developed to ensure a charge-dependent virus adsorption on the membrane surface. Isoelectric points (IEPs) of viruses are found in the pH range from around 3.5 to 7 and therefore, viruses are negatively charged in contaminated water samples at neutral pH conditions. Consequently, viruses can be adsorbed by positively charged membranes featuring IEPs > 7. For generation of electropositive membranes the inert ceramic membranes in the sintered state are firstly activated by hydroxylation followed by an aminosilanization. Based on such amino-functionalized and positively charged filter surfaces, a regenerative virus filter is provided and saturated filter elements can easily be cleaned by pH-shift and subsequent washing (adsorption-elution method).In addition to the functionalized capillary membranes, membranes for virus filtration showing a special geometry in form of a meander-shaped and helical-shaped orientation are fabricated by extrusion. Compared to conventional linear capillary membranes, meander- and helical-shaped membranes can generate turbulent flows in the inner channel of the capillary based on given pitch (windings per unit length) and bending (meander width and helix diameter, respectively) of the ceramic matrix. Because of the resulting turbulence, pore clogging and membrane fouling can be reduced during virus filtration.