In Situ Preparation Of MoS₂ Tubular Ceramic Membrane And Its Separation Performance

The two-dimensional（2D）materials with atomic thickness,micrometer size and nanoscale mass transfer channels have become the research hotspot of membrane separation layer materials.However,how to build a 2D material separation membrane with good uniformity,good stability and efficient transmission channel on the inorganic tubular ceramic substrate has become a research difficulty.Therefore,the main way to solve this problem is to develop the membrane preparation method.Firstly,molybdenum disulfide（MoS₂）tubular ceramic membrane was prepared on the tubular ceramic substrate by in-situ hydrothermal method.A 3D grid structure separation layer with inclined cross was constructed on the surface of the substrate,which reduced the transmission resistance of solvent in the membrane.Then,by adding alcohols with different number of hydroxyl groups into the precursor solution,MoS₂separation layers with different transport environments were constructed in suit on the surface of the substrate,which realized the regulation of the chemical properties,morphology and structure of the surface of the MoS₂tubular ceramic membrane,and further enhanced the permeability of the membrane.Firstly,in order to improve the operating stability of the membrane and the permeability of the solvent,the MoS₂tubular ceramic membranes were prepared on the alumina substrate by in situ hydrothermal method,and the membrane structure was regulated by controlling the concentration of the precursor solution.By means of X-ray powder diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM）,surface Zeta potential and other analytical methods,the microstructure and physicochemical properties of MoS₂tubular ceramic membrane were characterized,which indicated that a negatively charged MoS₂mass transfer environment with inclined cross 3D grid structure was constructed on the substrate.The MoS₂tubular ceramic membrane was used to remove dyes from organic solvents.The results showed that the constructed MoS₂mass transfer environment with tilt cross 3D grid structure improves the permeability of membrane to organic solvents and the separation performance of charged dyes.Under the conditions of precursor solution concentration of 2.2g·L^-1,hydrothermal time of 30h and hydrothermal temperature of 220℃,the separation performance of MoS₂tubular ceramic membrane for Evans blue（EB）in methanol was 403.1L·m^-2·h^-1·MPa^-1with a rejection of 98.1%.The membrane can operate stably for 80h in DMF.Secondly,alcohol with different hydroxyl groups,such as ethanol（ET）,ethylene glycol（EG）and glycerol（Gly）,was added to the precursor solution respectively,and the in-situ hydrothermal method was used to prepare MoS₂tubular ceramic membrane.The addition of alcohols with different hydroxyl groups can control the morphology and physical and chemical properties of MoS₂nanosheets and the surface of the membrane.The results of XRD,XPS,SEM,BET,AFM and contact angle show that the layer spacing,crystallinity,chemical composition,pore structure and micro morphology of MoS₂nanosheets were different from the unmodified MoS₂nanosheets;Compared with MoS₂tubular ceramic membrane,the surface morphology and wettability of MoS₂tubular ceramic membrane controlled by alcohol（alcohol@MoS₂tubular ceramic membrane）also changed,and the hydrophilicity of alcohol@MoS₂tubular ceramic membrane was improved.The alcohol@MoS₂tubular ceramic membrane was used to remove dyes from water or organic solvents respectively.The results showed that the addition of ET and EG can effectively improve the permeability of the membrane to water or organic solvents.The separation performance of ET@MoS₂,EG@MoS₂and Gly@MoS₂tubular ceramic membranes to EB in water was 593L·m^-2·h^-1·MPa^-1,418.8L·m^-2·h^-1·MPa^-1and81.3L·m^-2·h^-1·MPa^-1,respectively,and the rejection is greater than 98%.The flux of ET@MoS₂tubular ceramic membrane to methanol and DMF was437.5L·m^-2·h^-1·MPa^-1and 125.0L·m^-2·h^-1·MPa^-1,respectively,and the rejection of EB was 94.6%and 93.5%,respectively;the flux of EG@MoS₂tubular ceramic membrane to methanol and DMF was 281.3L·m^-2·h^-1·MPa^-1and164.8L·m^-2·h^-1·MPa^-1,respectively,the rejection of EB was about 94%.