Synthesis And Study On Iron-Containing Ordered Mesoporous Silica Membrane Supported By Hollow Fiber

An iron-containing silica sol was prepared using Pluronic P123 as template, tetraethylorthosilicate as silica source and hydrated iron nitrite as precursor under acid condition by a one step sol-gel process. The iron-containing silica sol was assembled both on the outer and inner surface ofα-Al₂O₃ hollow fiber by the evaporation induced self assembly(EISA) processs. Their structures were characterized by small X-ray diffraction(SXRD), nitrogen adsorption isotherm, high-resolution transmission electron microscopy(HRTEM); the transformation during the heat treantment was characterized by FTIR, TG-DTA; and the supported membrane was characterized by scanning electron microscopy(SEM) and gas permeability test. The results show the unsupported membrane maintaining ordered mesoporous structure of an ordered 2-dimension hexagonal SBA-15 type can be synthesized by the iron-containing sol after an EISA processs; the iron species present as highly dispersed y- Fe₂O₃ nanocrystals in hexagonal walls; comparing to the pure silica mesoporous material, the iron containing material has higher surface area, larger pore volume, higher unit cell parameter, and decreased pore size. SEM images indicate that the membranes supported byα-Al₂O₃ hollow fiber are defect-free. Gas permeability test suggests that the membranes possess gas selectiveity. At the pressure difference of 0.10 MPa, the gas permeances of N₂ are 5.40×10^-6 mol/m²Â·s·Pa and 6.80×10^-6 mol/m²Â·s·Pa respectively for supported membranes on the outer surface deriving from the pure silica sol and iron-containing sol, and the separation factors of H₂/N₂ measured are 2.97 and 3.11 respectively. Based those above, the formation mechanism of the mesoporous silica membrane both on the outer and inner surface ofα-Al₂O₃ hollow fiber was discussed.