In-Situ Synthesis Of Self-Supporting Faujasite Zeolite Membrane From Geopolymer And Its Application In Pervaporation

Geopolymer used natural mineral, waste residue and alkali activator as raw materials, is a new material similar to ceramics and cements. Because of its special silicon oxygen tetrahedron and tetrahedral three-dimensional network structure, Geopolymer have high compressive strength, good corrosion resistance, high temperature resistance and other advantages. So that, Geopolymers make up many properties that Portland cement and ceramic are difficult to achieve. So now, it is widely used in construction engineering, transport, packaging, nuclear waste disposal. In recent years, due to its widely raw material sources, low price, simple production process, energy-saving emission reduction. Geopolymer materials have attracted great interest from all over the world.Zeolite membrane as a kind of inorganic membrane materials, because of its good separation performance of high temperature resistance, corrosion resistance, become one of the important development direction of the inorganic membrane materials, This project prepared Na2O-3SiO2-A12O3geopolymer from metakaolin as raw material, used SEM、XRD、Universal pressure test machine to test the surface morphology and the crystallization of Na2O-3SiO2-Al2O3geopolymer and its in-situ FAU-type zeolite membrane; used permeation flux, separation factor to test the permeability of the zeolite membrane in ethanol-water system pervaporation;and explored the application of solution diffusion model in pervaporation process. The main conclusions are as follows:(1)Firsrtly, Using metakaolin and water glass as raw materials to prepare Na2O-3SiO2-Al2O3geopolymer, by hydrothermal synthesis method, to transform geopolymer into FAU-type zeolite membrane. The zeolite crystal size is between 500to600nm, the membrane is complete, continuous and compact. The optimum conditions for geopolymer and FAU-type zeolite membrane were determined:Curing temperature is50℃, Curing time is24h, Hydrothermal temperature is80℃, Hydrothermal time is15h. Then FAU-type zeolite membrane was used in pervaporation dehydration process of ethanol-water system, and further more determined the optimal operation parameters of pervaporation in ethanol water system:Operating pressure0.1MPa, Feed temperature is50℃,Feed composition (wt%)70%.(2)This project used XRD SEM, Universal test machine and other analysis methods to study the effects of curing temperature, curing time, hydrothermal temperature, hydrothermal time on the compressive strength of membrane material, surface morphology and crystallinity in the synthesis process;To study the effects of feed temperature and feed composition of flux of membrane and separation factor through pervaporation experiment and theoretical equation, The experimental result shows that:Curing time and curing temperature have a significant impact on the surface morphology and compression strength; Hydrothermal time and hydrothermal temperature have a significant impact on the surface density and the crystallinity of FAU-type zeolite membrane; FAU-type zeolite membrane permeation flux and separation factor can be optimal obtained by feed temperature and feed composition. Under the optimized conditions FAU-type zeolite membrane have high permeation flux and separation factor:Feed temperature50℃, Feeding composition of ethanol70%, The permeation flux and separation factor can reach1.41kg·hf·m-2and16.8.(3)This preject also analyzed the influence of feed composition on FAU-type zeolite membrane equilibrium solubility and equilibrium separation factor through the equilibrium solubility experiment. The result shows that:Flux and equilibrium solubility, pervaporation separation factor and the equilibrium separation factor have the same trend, Equilibrium separation factor determined the separation performance, Diffusion is the key of pervaporation process.