Based On Monomer Design, A High-throughput And Anti-fouling Thin-layer Composite Polyamide Membrane Is Prepared

Thin-film composite polyamide?TFC PA?membranes are widely used in reverse osmosis?RO?/nanofiltration?NF?process for desalination and product concentration due to their excellent perm-selectivities and good quality of effluent.TFC PA membranes consist of a porous support layer and a dense polyamide?PA?active layer.The structure and properties of the PA active layer determine the selective separation and antifouling properties of the TFC membranes.Commercial TFC PA membranes are usually prepared by interfacial polymerization of m-phenylenediamine?MPD?or piperazine?PIP?as aqueous monomers with trimesoyl chloride?TMC?on a porous support layer.However,TFC PA membranes still suffer from the relatively low permeability and high fouling propensity.In this work,4-morpholine-m-phenylenediamine?MpMPD?monomer with a hydrophilic group and 4-piperazine-m-phenylenediamine?PMPD?monomer with both MPD and PIP molecular structure were synthesized by molecular design and used as the new monomers to tailor the hydrophilicity and cross-linking structure of PA active layer,and then the TFC PA membranes with high water flux and anti-fouling properties were fabricated.The major findings of this work are as follows:?1?Fabrication of high flux and anti-fouling TFC RO membranes using new monomer MpMPDHigh flux TFC PA reverse osmosis membrane?MpMPD membrane?was fabricated based on a new aqueous monomer MpMPD with a hydrophilic group through interfacial polymerization with TMC.Then the anti-fouling reverse osmosis membrane?MpMPD-PA membrane?was fabricated by zwitterionic modification of the membrane surface with reagent 3-BPA.The water permeability of the RO membrane MpMPD-PA was 1.7 L m^-2 h^-1 bar^-1,and the Na Cl rejection was 97.8%.In addition,the dynamic fouling experiments illustrated that the zwitterionic surface RO membrane possess excellent fouling resistance to protein bovine serum albumin?BSA?,polysaccharides sodium alginate?SA?,and surfactant sodium dodecyl sulfate?SDS?.Therefore,this work provides a simple and convenient way to fabricate novel zwitterionic surface RO membrane with high performance from the molecular level design.?2?Fabrication of high flux and anti-fouling TFC nanofiltration membranes using new monomer PMPDHigh flux TFC PA nanofiltration membrane?PMPD membrane?was fabricated based on a new triamine monomer PMPD possessing both PIP and MPD moieties through interfacial polymerization with TMC.Then the anti-fouling nanofiltration membrane?PMPD-PA membrane?was fabricated by zwitterionic modification of the membrane surface with reagent 3-BPA.Results show that the water permeability of the fabricated PMPD-PA nanofiltration membrane is 19.0 L m^-2 h^-1 bar^-1,the rejection of divalent salt Na₂SO₄ is 98.4%,and the rejection of monovalent salt Na Cl is 25.0%,and it also exhibited the stable water flux and salt rejection performance in long-term tests.Using BSA and SA as model pollutants,the flux decline and flux recovery ratio of the fabricated membrane were evaluated in the nanofiltration process.Results illustrate that the zwitterions modified PMPD-PA membrane exhibited a low flux decay rate and a high flux recovery ratio after the physical cleaning,compared with the PMPD membrane fabricated with the PMPD monomer.In this work,from the persepective of the monomer structure design,the novel aqueous monomers of MpMPD having a hydrophilic morpholine group and triamine PMPD having both PIP and MPD moieties were synthesized,and used to fabricate the TFC polyamide membrane with tailorable structure,perm-selectivity and anti-fouling performance.Our work provides some insights on the design of new monomers to develop the high performance thin film composite polyamide membranes.