Preparation And Separation Performance Research Of Aminated Graphene Oxide Nanofiltration Membrane

Graphene oxide（GO）has a great potential in improving the separation performance of membrane owing to its two-dimensional structure.The selective separation of dyes and inorganic salts can be achieved by adjusting the lamellar spacing of GO,which can realize the recovery of dyes and inorganic salts respectively.GO nanofiltration membrane exists swelling and re-dissolution phenomena when running in water environment.In addition,GO has the problems of compact sheet stacking and easy agglomeration,which seriously limits its application of nanofiltration membrane.In this study,dendritic hyperbranched polyamide-amine was used to aminated GO to prepare aminated graphene oxide（GO-NH₂）.Based on GO-NH₂,two novel nanofiltration membranes used for dye separation and salt separation in water treatment were further prepared to improve their separation performance for target pollutants.In this paper,dendritic hyperbranched polyamide-amine as an amino agent was used to modify GO to prepare GO-NH₂,firstly.By using co-deposition method,GO-NH₂ was uniformly deposited on the surface of polyethersulfone ultrafiltration membrane to prepare GO-NH₂ loose nanofiltration membrane.The effect of GO-NH₂ addition amount on the separation performance of nanofiltration membrane was studied and analyzed.FT-IR,FE-SEM and AFM was used to study the loose nanofiltration membrane.Results showed that the separation layer became looser,the hydrophilicity increased.Performance test showed that and the permeation flux of the loose nanofiltration membrane increased significantly when GO-NH₂ existed.When the addition amount of GO-NH₂ was 0.5 mg m L^-1,the pure water flux reached 201.2±10 L m^-2 h^-1,which was 20.12%higher than that of the blank sample.The rejection rates of reactive blue 19 and direct orange S reached 96.5%and 89.8%respectively.After five circulating flux tests,the flux recovery rate reached 94.3%,increased by 9.0%.The permeation flux decreased by only 4%after 120 hours’long-term operation.This is because the introduction of nano sheet material of GO-NH₂ ensured the existence of two-dimensional nano channels in the separation layer,which increased the structural stability of the loose nanofiltration membrane,and reduced the resistance of water molecules through the nanofiltration membrane.Further,piperazine and trimesoyl chloride were used as react monomers to prepare the GO-NH₂/PA composite nanofiltration membrane by interfacial polymerization on the surface of the GO-NH₂ loose nanofiltration membrane,which was used for desalination treatment process.The effect of GO-NH₂ addition amount on the separation performance of composite nanofiltration membrane was investigated.Mechanism analysis conjectured that the GO-NH₂existed in the composite nanofiltration membrane as an intermediate layer,which made piperazine react with benzoyl chloride on the surface of the loose nanofiltration membrane,which significantly improved the permeation flux of the composite nanofiltration membrane.The inorganic salt rejection test showed that the surface of the composite nanofiltration membrane was negatively charged,which mainly depended on electrostatic repulsion to reject the inorganic salt ions.When the addition amount of GO-NH₂ was 0.5 mg m L^-1,the permeation flux reached 85.7±4.3 L m^-2 h^-1,increased by 94.3%compared with the blank sample.The rejection rate of Na₂SO₄ was 96.5%,increased by 9%,and the flux recovery rate reached 98.0%,increased by 11.63%.After 120 hours’long-term operation test,the rejection rate of Na₂SO₄could still reached 94.62%,showing an excellent operation stability.