Zirconium-containing mesoporous silica Zr-MCM-48 for alkali resistant filtration membranes

Zirconium-containing mesoporous silica (Zr-MCM-48) membranes were synthesized on a porous alumina support from an aqueous solution containing tetraethylorthosilicate (TEOS), zirconium propoxide (ZrPr) and cetyltrimethylammonium bromide (C16TAB). The Zr-MCM-48 membranes show high resistance in alkaline solutions at pH 9–12 although the structure of the pure silica MCM-48 membranes collapsed even at pH 10. Zirconium species is considered to present near the pore surface of MCM-48 because the reactivity of ZrPr with surfactant (C16TAB) molecules is much higher than TEOS in the starting solution. Zr-MCM-48 shows more stable in alkaline solutions than Ti-containing MCM-48 (Ti-MCM-48). The gas permeation and permporometry measurements suggest that there are no large pinholes and cracks in the Zr-MCM-48 membranes. From permporometry the average pore size of the Zr-MCM-48 membrane is estimated to be 2.5 nm. The filtration of polyethylene glycol (PEG) in water shows that the membranes has molecular weight cutoff (MWCO) of about 3800 u. The corresponding molecular size is 2.3 nm. The sharp increase in the rejection of PEG with increase in molecular weight shows narrow pore size distribution of the membrane. These results show that Zr-MCM-48 membranes have great potential for nanofiltration and ultrafiltration with high performance.