Fabrication Of Metakaolin Geopolymer-based Membranes And Their Application In Environmental-Protection

Geopolymer is an inorganic polymer with amorphous silicon oxide tetrahedron and aluminum oxide tetrahedron formed by condensation reaction of amorphous alumina or silica under activator conditions.Porous geopolymer is a kind of porous structure formed inside or outside the geopolymer by various pore-forming methods.Recently,plenty of research has been done on the preparation,characterization and application of porous geopolymers,and their applications are still to be developed.In this study,metakaolin-based porous geopolymer composite membranes were prepared by EVV modified metakaolin-based porous geopolymer.In this study,the porous structure can be obtained by controlling the amount of water without the use of additives and processing conditions.The structure of porous composite membrane was characterized by SEM,XRD and BET.The mechanical properties of the composite membranes were tested by universal press machine.The permeability of the membrane was investigated by water flux test.The rejection performance of composite membranes were investigated by filtration of artificial wastewater containing PEG,turbidity and dyes.In addition,the gradient porous membrane with porous structure was prepared by one-step molding with interfacial chemistry.The gradient structure of the porous membrane was characterized by SEM,XRD and mercury injection apparatus.The mechanical properties and permeability of the membrane were characterized by universal press machine and air flowmeter.The PM removal performance of the tube membrane was characterized by PM simulated filter and particle counter.The thermal stability and the PM loading capacity of the tube membrane was characterized by TG-DSC thermal analysis.Finally,the mechanism of PM removal by tube membrane was studied by SEM and EDS.The main findings are as follows:(1)EVV can be used to improve the mechanical properties of metakaolin-based geopolymer,mainly in toughness.The experimental results show that the compressive strength increases then decreases with the increase of EVV content in the geopolymer system in a certain range(0-2.5 wt%EVV).The bending strength increases with the increase of EVV content.The bending strength of geopolymer can be increased by about 50%with addition of 1.0 wt%EVV.(2)The gradient structure of porous geopolymer can be obtained by controlling the content of hydrogen peroxide,adding surfactant and controlling the hydrophobicity of the mold surface.In the metakaolin-based geopolymer system studied in this paper,the foamed porous geopolymer can be obtained with a compact surface on the smooth surface of mold,forming a gradient porous structure.(3)The porous geopolymer gradient tubular membrane has 67.6%porosity under the optimum conditions of 0.9 wt%hydrogen peroxide.PM filtration experiments showed that the tube membrane reached PM2.5 and PM 10 removal efficiency of 98.5%and 99.3%respectively and can be reused.