Construction Of Layered Membrane With Two-dimensional Materials Used For Molecule Sieving

Organic solvent nanofiltration?OSN?is a new type of membrane separation technology that applies the nanofiltration process to the organic phase.It can separate organic mixtures at the molecular level by pressure driving.The efficient and environmentally friendly treatment and recycling of the liquid is very important.How to build a high-performance separation membrane is a problem that researchers are paying close attention to.Both the two-dimensional material membrane and the metal-organic framework?MOF?membrane can separate the solution at the molecular or ionic level,but there are still some problems in the research process.The first is that the graphene oxide membranes prepared in the same way in different research work do not follow the trade-off effect in the separation application;the second is that the MOF membrane preparation process in most research work is cumbersome and not easy to operate and implement.Therefore,how to construct a membrane with high separation performance in a relatively simple method is necessary to promote the development of the separation membrane field.In this paper,two-dimensional materials and MOF materials were used as research objects.Two different configurations of hierarchical separation membrane were prepared by a simple vacuum filtration method to achieve efficient separation of dye molecules in solvents.The main contents of the study were as follows:?1?By using the difference in the separation performance of the membrane due to the difference in the lateral diameter of graphene oxide,the two types of graphene oxide with a diameter difference of one order of magnitude are assembled in three different modes.These models were assembled by vacuum suction filtration.The influence of different assembly modes on nanofiltration performance was investigated.The results showed that when the mode was micro-sized GO-nano-sized GO-substrate,it had the best nanofiltration performance.When the mass ratio of micro-sized GO and nano-sized GO is 1:5,the thickness of the non-defective membrane was only 10 nm.The separation performance of the membrane was the best under the conditions,and the rejection of Methylene Blue,Evans Blue,Rhodamine B and Basic Fuchsin?dissolved in water and iso-propanol respectively?were all higher than 90%,while the permeance was maintained at 100 L·m^-2·bar^-1·h^-1.This research proposed a way to stack different separation layers based on the difference in GO sheets,lateral diameter,which is of great significance for the preparation of other two-dimensional material membranes.?2?Although the MOF membrane had great application prospects in the field of separation,its preparation process was usually cumbersome and requires difficult reaction conditions.At the same time,the durability of the membrane was poor,and it was difficult to apply it to actual industrial production.In response to this problem,the author proposed to combine molybdenum disulfide?Mo S₂?nanosheets with Zn BTC or Co-MOF-74 to prepare membranes by the method of simple vacuum filtration.Mo S₂ nanosheets were mainly used as support materials in the membrane,and the separation performance of the membrane was mainly provided by the pore structure of Zn BTC or Co-MOF-74.By adjusting the mass ratio between Mo S₂ nanosheets and Zn BTC?or Co-MOF-74?,a layered membrane with good nanofiltration performance in organic solvents was obtained.For dye molecules larger than the pore size of Zn BTC?or Co-MOF-74?,it had a 100%rejection rate and a high permeance of 400 L·m^-2·bar^-1·h^-1.This part of the research proposed an innovative method for preparing separation membranes with MOF as the main separation layer by a simple method,which had reference significance for other materials and separation applications.