Preparation, Characterization and Performance of Templated Silica Membranes in Non-Osmotic Desalination

Abstract

Abstract:In this work we investigate the potential of a polyethylene glycol-polypropylene glycol-polyethylene glycol, tri-block copolymer as a template for a hybrid carbon/silica membrane for use in the non-osmotic desalination of seawater. Silica samples were loaded with varying amounts of tri-block copolymer and calcined in a vacuum to carbonize the template and trap it within the silica matrix. The resultant xerogels were analyzed with FTIR, Thermogravimetric analysis (TGA) and N 2 sorption techniques, wherein it was determined that template loadings of 10 and 20% produced silica networks with enhanced pore volumes and appropriately sized pores for desalination. Membranes were created via two different routes and tested with feed concentrations of 3, 10 and 35 ppk of NaCl at room temperature employing a transmembrane pressure drop of <1 atm. All membranes demonstrated a salt rejection capacity of >85% (in most cases >95%) and fluxes higher than 1.6 kg m −2 h −1 . Furthermore, the carbonized templated membranes displayed equal or improved performance compared to similarly prepared non-templated silica membranes,

The Preparation and Characterization of Geopolymer Based Inorganic Membranes

“…The PWF of geopolymer inorganic membranes. The trends of geopolymer inorganic membranes' PWF (pure water flux) [9], water-glass's modulus and H 2 O/Na 2 O ratio could be judged from Fig. 3, there was a certain regularity: under identical H 2 O/Na 2 O ratio, PWF reduced along with the increase of modulus; Under the same modulus, PWF increased along with the H 2 O/Na 2 O ratio's augment.…”

Microporous Silica Based Membranes for Desalination

“…However, this long term testing successfully demonstrated the improved hydro-stability of CoOxSi membranes at several temperature points and feed concentrations. In the only other studies reported thus far, Duke et al reported stable performance over 5 h of the CTMSS (Ionic 6) membrane [19]; and Ladewig et al showed stable performance over 12 h, suggesting the benefit of the carbonized templating method to improve the hydro-stability of amorphous silica membranes [68]. …”

“…However, the water vapour pressure change as a function of the salt concentration at constant temperature is not large enough to justify the large reduction of flux as reported by several groups in Table 1. For instance, in the case of carbonized template CTMSS (ionic C6), experiment was conducted at a fixed temperature of 20 °C [68]. Indeed, water flux was reduced by more than half (56%) by increasing the feed concentration from 0.3 wt % to 3.5 wt %.…”

“…However, if the concentration of ionic surfactants is too high they form micelles [67] which drastically limits the possibility of using the sol-gel to dip coat substrates. In order to increase the carbon content in the silica framework, Ladewig et al [68] proposed the use of a non-ionic surfactant such as a tri-block copolymer like polyethylene glycol-polypropylene glycol-polyethylene glycol (PEG-PPG-PEG), a high molecular weight polymer. Silica samples were mixed with 1-20 wt % PEG-PPG-PEG, and increasing the loading of the tri-block copolymer to 10 wt % effectively doubled the pore volume and surface area compared to pure silica, whilst still maintaining microporosity.…”