The Preparation Of Modified Composite Membrane Based On GO

Membrane separation technology has good separation,purification,refining and concentration functions,and has the characteristics of low energy consumption,environmental protection,simple and easy filtration process.Therefore,membrane separationtechnologyisnowwidelyusedinfood,medicineandwater treatment.Conventional water treatment membranes such as cellulose acetate?CA?ultrafiltration membranes,polyethersulfone?PES?membranes,etc.,have problems such as low water flux,poor mechanical strength,and weak anti-pollution performance during separationtesting,whichlargelyaffecttheperformanceoftheseparation membrane.Nanomaterials such as graphene oxide?GO?have excellent physical and chemical properties,good hydrophilicity,environmental protection and other advantages,and have good research and application prospects in separation membrane modification.In this paper,graphite flakes,concentrated sulfuric acid?H₂SO₄?,concentrated nitric acid?H₃PO₄?,potassium permanganate?KMnO₄?and hydrogen peroxide?H₂O₂?were used as raw materials to prepare partially oxidized graphite oxide?GO?by modified Hummers method.The obtained product was characterized by infrared spectroscopy?FT-IR?and X-ray diffraction?XRD?,The results show that the obtained product has a large number of oxygen-containing functional groups,and the interlamellar spacing is about 0.834 nm,which is determined as the target product.GO was used as a surface modifier,and GO was coated onto the surface of CA base film by means of auxiliary pressure vacuum self-assembly.The GO/CA separation membrane was successfully prepared.Infrared?AT-IR?spectroscopy,Raman spectroscopy were performed on the GO/CA separation membrane,and the flux,rejection and anti-fouling properties of the separation membrane were tested.The results show that GO as a modifier enhances the hydrophilicity of the surface of CA membrane.With the increase of GO content,the pure water flux of GO/CA separation membrane increases first and then decreases.When GO content is 0.3 mg,the pure water flux is the highest,reaching at 96 L/m²·h,and the rejection of CaCl₂ is about 82%.When the GO content increases again,the pure water flux gradually decreases because the surface coverage is excessive,which increases the mass transfer resistance of the water molecules.At the same time,the anti-fouling performance of GO/CA membrane prepared with GO added amount of 0.3 mg is more than 10%higher than that of CA membrane.When operating within 120 h,the flux recovery rate of pure water can be stabilized above 70%,which is much better than the CA membrane.The GO was mixed with ethylenediamine?EDA?,and the modified CA membrane was added with trimesoyl chloride?TMC?to prepare a novel GO-PA/CA modified membrane.The modified membrane was characterized by infrared spectroscopy?AT-IR?,scanning electron microscopy?SEM?and X-ray diffraction?XRD?,and its separation performance and anti-fouling performance were tested.The results show that after the introduction of the polyamide?PA?layer,GO can be attached to the surface of the membrane by covalent bond,the membrane structure is more stable than the GO/CA membrane,and the performance of various aspects is also improved.With the increase of GO concentration,the surface of GO-PA/CA membrane is smoother,which improves the anti-fouling performance of the modified membrane;At the same time,increasing the concentration of GO can enhance the hydrophilicity of the membrane and increase the pure water flux;the negative charge intensity on the surface of the membrane will also increase,so that the rejection rate will increase.The excessive increase of the GO concentration will lead to an increase in the thickness of the membrane,and the mass transfer resistance of the water molecules will also increase.After protein contamination of the modified membrane,the retention of the salt solution decreased significantly,but with the increase of GO concentration,the retention of CaCl₂,NaCl and Cu?NO₃?₂ increased significantly,indicating that the addition of GO is beneficial to the anti-fouling performance of the membrane;at the same time,the flux recovery rate diagram also shows that after the introduction of PA,the stability of the modified membrane is greatly improved compared to the previous one.