Stucture Design Of A GO/CNT Composite Membrane For HA Ang The Anti-fouling Permance

Membrane separation technology,as one of the most potential technologies in the field of water treatment in recent years,has many advantages including low energy consumption,no secondary pollution,flexible and convenient operation and environmental friendliness.Membrane can be divided into organic membrane and inorganic membrane according to the membrane material.Organic membrane is processed from organic polymer materials.The structure of conventional polymer membrane is composed of porous support layer and dense separation layer.The adsorption and deposition of foulants on the surface of conventional polymer membrane or in membrane pores will lead to serious membrane pollution.In this project,a carbon nanomaterial composite membrane with reverse structure design（with upper sparse and lower dense structure）is prepared by using the positive pressure filtration device.The upper loose carbon material structure is carbon nanotubes（CNT）layer,and the lower dense structure is Graphene Oxide（GO）layer.The pollution receiving performance and the antifouling ability of the carbon nanomaterial composite membrane is improved by the pre-adsorption and pre-filtration of the upper CNT and the interception of the dense GO layer.Furthermore,Polydopamine（PDA）was used to non-covalent modified CNT,and the antifouling ability of GO/CNT composite membrane was further improved by strengthen the hydrophilicity and pollution receiving performance of PDA/CNT layer.The results about the preparation method and characterization of GO/CNT composite membrane showed that CNT and GO can be stably loaded on the membrane surface with the optimal GO dosage of 0.03mg.The analysis results showed that GO has rich oxygen-containing functional groups,which made the prepared GO membrane have good hydrophilicity.The experimental results show that the composite membrane is superior to other membranes in the removal of HA and its antifouling performance with the increase of p H value of solution,the removal effect of HA becomes worse and the antifouling performance is better.With the increase of Ca²⁺concentration in the solution,the removal effect of GO/CNT composite membrane becomes better,and the antifouling performance is less affected by the ionic strength.With the increase of the concentration of Na⁺in the solution,the HA removal rate of GO/CNT composite membrane becomes worse,and the antifouling performance is less affected by the ionic strength.The experimental results show that under neutral conditions,the removal rate and anti pollution performance of the composite membrane are better than those of the base membrane,single-layer CNT membrane and single-layer GO membrane.The increase of p H value and Na⁺concentration will enhance the electrostatic repulsion between HA and the membrane,so as to reduce the removal rate of the composite membrane;The concentration of Ca²⁺has little effect on the removal rate of the composite membrane.The antifouling performance of the composite membrane is better in the presence of Ca²⁺and is less affected by other solution environment.The PDA@CNT membrane and the GO/PDA@CNT menbrane were prepared with non-covalent modification of CNT by PDA.The appearance of N element in the XPS spectrum and the new peak caused by-C-N bond prove that PDA has successfully modified CNT.The contact angle results showed that the hydrophilicity of CNT film modified by PDA is significantly improved,and the contact angle is reduced from 110°to 70°,indicating that a large number of hydrophilic functional groups,such as phenolic hydroxyl and imine,could be introduced into the outer wall of CNT after the non-covalent modification of PDA.Therefore,the antifouling performance of the membrane is improved.Taking HA as the model pollutant,the removal and antifouling experiment of composite membrane are carried out.The experimental results show that the GO/PDA@CNT composite membrane has the best removal effect on HA,and the removal rate is 68%after 4 h.The upper PDA@CNT layer plays an adsorption and interception role on HA,and the HA that is not adsorbed can be further intercepted and removed by the GO dense layer,thus improving the HA removal rate of the composite membrane The change results of specific flux in membrane filtration experiment show that compared with the base membrane,the modified membrane can effectively alleviate membrane pollution.Among them,the specific flux curve of GO/PDA@CNT composite membrane decreases slowly in the membrane filtration process,and the specific flux value after 2h is 0.73,which has the best effect in alleviating membrane pollution.