Preparation And Properties Of Hyperbranched Polyamide-Amine Modified Polyethersulfone Loose Nanofiltration Membrane

Loose nanofiltration membranes have attracted extensive attention due to their selective separation performance and high flux.They are characterized by large permeation flux and can selectively separate dyes and inorganic salts.Hyperbranched polyamide amine（HPAMAM）is a kind of macro molecular polymer.Its molecular structure is rich in branching,and there are large cavities in the molecule,so it is a good modified materially.In this paper,HPAMAM modified polyether sulfone nanofiltration membrane was prepared by interfacial polymerization of commercial hyperbranched polyamide-amine as aqueous monomer with trimesoyl chloride（TMC）.Firstly,using polyethersulfone（PES）ultrafiltration membrane as the base membrane,it was proved by ATR-FTIR,XPS,SEM,AFM and other characterization methods that HPAMAM-TMC loose nanofiltration membrane was successfully prepared,and dispersed particles were observed on the surface of the membrane structure,the surface of the separation layer of the nanofiltration membrane is relatively smooth,and with the increase of the addition amount,the nanofiltration layer tends to be flat,and the hydrophilicity of the modified nanofiltration membrane has been significantly improved.The separation performance test showed that the loose nanofiltration membrane has a typical interception order of negatively charged nanofiltration membranes Na₂SO₄>Mg SO₄>Mg Cl₂>Na Cl,and the interception capacity increases significantly with the increase of the concentration of the aqueous phase.HPAMAM has a large molecular structure,and the presence of cavities in its branched molecular chains improves the flux of the nanofiltration membrane.The loose nanofiltration membrane prepared has a high retention rate to dye chrome black T（EBT）,methyl blue（MYB）,Congo red（CR）,and Victoria blue B（VBB）,while the Na Cl retention rate is low.The prepared loose nanofiltration membrane sample M-0.03 has a 99.01%retention rate for chrome black T and a Na Cl retention rate of only 3.69%.The results show that the purified water flux can reach260.5 L m^-2 h^-1 under 0.4 MPa pressure,which enables rapid salt dye separation under low pressure.The results showed that the membrane surface exhibited significant anti-pollution performance after dye interception.The anti-organic pollution tests were carried out on the membrane samples.The recovery rates of M-0.05 and M-0.2 were 81.65%and 94.59%,respectively.The results showed that the prepared loose nanofiltration membrane had good anti-organic pollution performance.The prepared loose nanofiltration membrane samples have molecular weight cut-offs of 5630 Da,3018 Da,1275 Da,804 Da and good long-term stability.The permeation flux remained above 85%of the initial values after long-term running tests.This study provides a scheme for preparing a loose nanofiltration membrane with anti-pollution performance and fast operation under low pressure for salt-dye separation system.On this basis,using HPAMAM and piperazine（PIP）together as the aqueous phase reaction monomer,and TMC as the organic phase monomer,HPAMAM/PIP-TMC nanofiltration was prepared on the polyethersulfone base membrane by interfacial polymerization modification method.The effects of interfacial polymerization conditions and the change of the ratio of HPAMAM and PIP in the aqueous monomer on the preparation of nanofiltration membranes were discussed.The occurrence of interfacial polymerization was proved by ATR-FTIR and XPS characterization methods.The surface contact angle and microstructure characterization of the membrane showed that the introduction of HPAMAM improved the hydrophilicity of the nanofiltration membrane and reduced the surface roughness of the nanofiltration membrane.The separation performance test found that with the increase of the proportion of HPAMAM,the pure water flux of the nanofiltration membrane increased,and the interception capacity of inorganic salts decreased.The sample M-1:1 has a rejection rate of 95.8%for Congo red and96.1%for methylene blue,and a pure water flux of 70.5 L m^-2 h^-1 at 0.4 MPa.Adjust the ratio of monomers in the water phase The final nanofiltration membranes have molecular weight cut-offs of 1224 Da,1443 Da,and 1583 Da,which basically belong to the range of molecular weight cut-offs of loose nanofiltration membranes.It proves that nanofiltration membranes with different cut-off capabilities can also be prepared by adjusting the ratio of monomers in the aqueous phase.The nanofiltration membrane showed good anti-protein pollution ability,and the flux recovery rate reached 98.37%.After long-term stable operation test,the flux still reached 54 L m^-2 h^-1,showing good operation stability.