Layer-by-layer Assembly Of Aquaporinz Incorporated Biomimetic Membranes For Water Purification

Seawater desalination is one of the effective ways to solve the shortage of water resources, while the membrane separation technology is the most efficient and economical way to realize seawater desalination. The design of high performance membrane is the foundation and core of membrane technology. We currently reach a consensus that preparing new composite membrane can reduce energy consumption effectively and achieve efficient and convenient water purification technology. It is also the direction of future development in membrane material research field. The aquaporin, which has extremely strong water permeability and single-choice permeability, is an ideal channel of water molecules. Formed through wrapping water channel proteins in the membrane of the bilayer and spreading in nanofiltration membrane, the new type of bionic composite membrane is able to overcome the traditional polymer composite membrane’s "trade-off effect". The essay presents the method of preparing for the bionic composite phospholipid membranes with aquaporin, which unites vesicle fusion with covalent bond combination. Furthermore, the membrane’s structure and performance are also characterized and tested.In this paper, we fabricated a biomimetic nanofiltration (NF) membrane by immobilizing the AqpZ incorporated supported lipid bilayer (SLB) on a layer-by-layer (LbL) complex polyelectrolytes membrane to achieve excellent permeability and salt rejection, accompanied with a considerable high stability. The polyelectrolytes membranes were prepared by LbL assembly of poly(ethyleneimine) (PEI) with positive charges and poly(sodium 4-styrenesulfonate) (PSS) with negative charges on a porous hydrolyzed polyacrylonitrile (H-PAN) substrate alternately. Aquaporin Z (AqpZ) incorporated DOPC/DOTAP vesicles with positive charges were deposited on the H-PAN/PEI/PSS polyelectrolytes membrane surface. The resultant biomimetic membrane provided high flux of 22 L·m-2·h-1 (LMH), excellent MgCl2 rejection of-97% and NaCl rejection of ～75% under the operation pressure of 0.4 MPa. Due to the attractive electrostatic interaction between SLB and polyelectrolytes membrane, the biomimetic membrane showed satisfactory stability and durability. It exhibited stable NF flux and rejection for at least 36h. Moreover, the AqpZ containing biomimetic membrane was immersed in a 0.24 mM (CMC) Triton X-100 solution for 5 min. The flux and rejection were slightly influenced by the Triton X-100 treatment. The current investigation demonstrated that the AqpZ incorporated biomimetic membranes fabricated by LbL method led to excellent separation performances and robust structures to withstand a high operation pressure within a relatively long operation time.We also designed a forward osmosis membrane using layer-by-layer method, The experiment inspects the influence on the structure and performance of the compound membranes, which are formed with different kinds of polymer, different layers and different concentration of AQP solution. And they are characterized by the contact angle, attenuated total reflection infrared, Atomic force microscope, the water flux and rejection. With the increase of the protein concentration, the performance of membranes becomes better. In this experiment, a kind of forward osmosis (FO) compound phospholipid membranes of high separation efficiency is obtained. It provides a preliminary work and preparation for the research of the new FO membranes.