Fabrication of PRO & FO aquaporin membranes
WP2 will focus on developing PRO and FO biomimetic aquaporin membranes5 for use with hypersaline concentrations in PRO and in anaerobic SMBRs. In the membranes water selective aquaporin proteins are stabilized in a polyamide matrix which is immobilized onto the surface of membrane support substrates (both flat sheet and hollow fiber geometries) through interfacial polymerization. Through this process the substrate is functionalized with an aquaporin active layer, which boosts membrane performance as a result of the high Water transport capacity and water selectivity of the aquaporin proteins.
Specifically WP2 will focus on how to:
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stabilize the matrix material for use with hypersaline and high pressure gradients in PRO where the goal is to ensure stable PRO operation at >16 bar transmembrane applied pressure and >200 bar osmotic pressure difference;
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stabilize the matrix material for use in FO SMBRs with high levels of feed SS.
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optimize aquaporin protein loading (e.g. by increasing vesicle affinity to the matrix material) in order to obtain high-flux membranes where the goal is to have a specific water permeability coefficient >1.5 L/(m2·bar·hr);
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optimize the performance of the support structure, in particular to minimize the solute resistivity via minimizing the structure parameter S=t3/ where t is the support thickness, is the tortuosity, and is the porosity. Here we will focus on casting finger-like hydrophilic structures where the goal is to obtain S values <200 μm while preserving stability and robustness. A starting point will be classical polysulfone supports prepared from nonsolvent-induced phase inversion with non-woven polyester backing where the pristine polysulfone will be rendered more hydrophilic (e.g. by covalently conjugating with polyvinylpyrrolidone (PVP) groups) in order to avoid dewetted zones and to ensure optimal coupling to the aquaporin-containing matrix material.