Fabrication of interlayer-free silica-based membranes – effect of low calcination temperature using an organo-catalyst

Abstract

Communities in some wetland areas in South Kalimantan, Indonesia, find it difficult to access clean water because surface water is contaminated by saltwater intrusion, especially during the rainy season. Membrane technology provides a solution to this problem by removing the salt contained in the raw water. The membranes used are generally composed of a porous material – thin-film – medium that functions to separate particles with a specific molecular size from the solution. The purpose of this study is to synthesise and fabricate silica-based membranes using an organo-catalyst calcined at a low calcination temperature (200°C and 250°C) through rapid thermal processing. In order to fabricate these membranes, the sol–gel method was applied, using tetraethyl orthosilicate as the silica precursor and citric acid as an organo-catalyst (refluxed at 0°C and 50°C). The results show that all membranes prepared with the organo-catalyst produce mesoporous structures. The highest surface area and pore size achieved were 354 m2/g and 0.215 cm3/g, respectively, refluxed at 0°C. Furthermore, silica-based membranes calcined at 250°C showed lower silanol concentration compared with those calcined at 200°C. In addition, the organo-catalyst (citric acid) acts as a carbon source in the silica matrices and may increase the hydrostability of the silica networks.