Nanostructured ceramic membranes with tailored functionalization and geometry for virus filtration

• Applicant: Dr. Stephen Kroll
• Subject Area: Synthesis and Properties of Functional Materials
• Term: from 2011 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 197658935

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.

• DFG Programme: Research Grants