Microporous Silica Based Membranes for Desalination

Abstract

Abstract:This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.

Mesoporous TiO 2 based membranes for water desalination and brine processing

“…This was attributed to an ion exchange mechanism between the saline water and the ions in the zeolite crystal [6]. Pure silica membranes are also known to be hydrothermally unstable, and several strategies have been pursued to improve their stability by embedding carbonised surfactant or triblock copolymers or metal oxides in the silica matrix and by synthesizing hybrid organosilicas [7]. As shown in Table 1, all these microporous inorganic membranes generally deliver high salt rejection at improved water fluxes of values up 11.5 kg m -2 h -1 depending upon the testing conditions.…”

Desalination techniques — A review of the opportunities for desalination in agriculture

“…If the membrane is simply a support structure that allows a meniscus to form on the feed side and plays no role in the separation, then the process is MD. If the membrane actively participates in the separation process then the process is PV [14,34].…”

Plasma treatment of hydrophobic sub-layers to prepare uniform multi-layered films and high-performance gas separation membranes

“…One of the most important applications is gas separation such as H 2 purification, CO 2 capture or O 2 enrichment [6][7][8]. In general, porous silica membranes are prepared by coating silica sols on a hydrophilic intermediate layer (␥-alumina, SiO 2 -ZrO 2 or TiO 2 ), followed by drying and calcination [6][7][8][9][10]. However, when water vapor is present in the separation processes, this can affect gas separation performance of membranes [11,12].…”