Fabrication of an aquaporin-based forward osmosis membrane through covalent bonding of a lipid bilayer to a microporous support†
AquaporinZ (AqpZ)-containing, planar, biomimetic membranes hold great application potential in water purification and seawater desalination, due to the excellent permeability and selectivity of AqpZ. However, there remain many challenges for the production of robust and defect-free supported lipid bilayer (SLB) biomimetic membranes. By forming amide bonds between the lipid bilayer and microporous substrate, we fabricated an AqpZ-incorporated SLB forward osmosis (FO) membrane, with a large area of 36 cm2. With deionized water and 2 mol L−1 MgCl2 draw solution, the AqpZ-incorporated biomimetic membrane exhibited a water flux of ∼19.2 L m−2 h−1 (LMH) and a reverse solute flux of ∼3.2 g m−2 h−1 (gMH). When positively charged phospholipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) was blended in the 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) bilayer, a higher flux (∼23.1 LMH) could be reached accompanied by a constant reverse salt flux of 3.1 gMH, due to more AqpZ being embedded in the mixed bilayer. From the nanofiltration (NF) test, the water permeability (A) could reach 6.31 LMH per bar with a relatively low solute permeability (B) of 1.7 LMH for the AqpZ-DOPE/DOTAP SLB membrane. When rinsed with a 0.24 mmol L−1 TritonX-100 (TX-100) surfactant solution, water flux and reverse salt flux of the biomimetic membrane with covalent bonds only slightly increased, whereas the membrane without covalent bonds showed a significant increase in both water flux and reverse salt flux after TX-100 treatment. This paper presented an effective method for the preparation of biomimetic FO membranes with good separation performance as well as excellent stability and durability.