Study On Preparation And Water Treatment Performance Of 2D Mica Nanosheets Membranes

Due to its unique atomic thickness and structure,2D materials show excellent properties different from traditional bulk materials,and are widely studied and applied in gas separation,seawater desalination,catalysis,energy conversion and storage and other fields.The layered channels between nanosheets can realized the rapid and selective transfer of molecules,which is expected to break the upper limit of the performance of traditional separation membrane,and has a great development prospect in the field of water treatment.2D mica nanosheets has been extensive used in electronics and chemical industry because of their atomic level flatness,high chemical inertness,electronics insulation and thermal stability.Due to the layered structure similar to graphene,good hydrophilicity and excellent stability,2D mica nanosheets also show great application potential in the field of membrane separation.In this study,nature ground mica was successfully peeled into 2D mica nanosheets by liquid-assisted ultrasonic method,and then the oil/water separation membrane and ultrafiltration membrane based on 2D mica nanosheets were prepared by pumping and blending phase separation respectively.The morphology,structure,properties and performance of the membrane were systematically explored.The specific research contents are as follows:Firstly,natural ground mica was used as raw material,through high temperature calcinations,acid and salt treatment,create an interlayer cation exchangeable mica activation performance,then the cationic surfactant CTAB is used to extend its layer spacing,finally further to make it stripping by means of ultrasonic assisted.The obtained material has a typical monolayer 2D structure with a size about 400 nm,and the thickness of the main layer is about 1 nm.Based on the analysis of TG,contact angle and FTIR,it was found that the 2D mica nanosheets exhibited good water dispersion,excellent hydrophilicity and high physical and chemical stability.Secondly,based on the advantages of 2D mica nanosheets such as low cost,high hydrophilicity,good layered structure,nanoscale size,high stability and so on.We used dopamine as an adhesive to deposit mica nanosheets on polyvinylidene fluoride(PVDF)substrate membrane by simple blending extraction and filtration method.The results of surface properties analysis show that the membrane has micro/nano surface roughness,good hydrophilicity and superhydrophobic properties,and very low adhesion to oil in water environment.The pure water flux reaches 750 L·m-2·h-1-bar-1,and the oil removal rate>99.9%.This study provides a new idea for the development of efficient oil-water separation materials and has potential application value in energy and environment fields.Thirdly,PVDF mixed matrix membrane was prepared by blending modification of PVDF membrane with mica nanosheets,and the influence of the addition of mica nanosheets on the performance of the mixed matrix membrane was explored.Scanning electron microscopy(SEM)and transmission electron microscopy(TEM)showed that the 2D mica nanosheets were uniformly dispersed in the membrane,and the addition of materials made the porosity of the mixed matrix membrane increase,and more fingerlike macropores were formed.The filtration experiment of mixed matrix membrane with 0.5%mica nanosheet was carried out,and it was found that the modified membrane flux could reach 546.49 L·m-2·h-1·bar-1.Compared with the original membrane,the water flux increased by 20.52%and the rejection rate of Evans blue remained above 98%,In addition,the recycling performance of the mixed matrix membrane was also investigated.The results showed that the recovery rate of the mixed matrix membrane was still more than 90%after three fouling cycles,and the existence of mica nanosheets improved the fouling resistance and flux of the membrane.To sum up,this study gives full play to the advantages of 2D mica nanosheets and applies them into water treatment membranes.The oil-water separation membrane with underwater superoleophobic properties and the 2D mica nanosheets mixed matrix membrane with excellent selective permeability and stain resistance,are designed respectively.The work provides a new idea for the preparation and application of 2D material membrane,and promotes the membrane water treatment technology to some extent.