Preparation of new composite membranes for water desalination using electrodialysis

The use of polyethersulfone (PES), an excellent but highly hydrophobic thermoplastic, as a matrix material for ion-exchange membranes was investigated. To make PES ion-exchangeable, sulfonate groups were introduced to the polymer chains by sulfonation reaction with chlorosulfonic acid. The degree of sulfonation of sPES was estimated to be 21%. Preliminary experiments investigated the effect of polyethylene glycol (PEG) and Pluronic F127 as fillers to improve the hydrophilicity of the membranes. Moreover, a lab scale electrodialysis cell has been designed and set up to evaluate the performance of these novel membranes compared to the benchmark of commercial membranes. The results show promising properties of ion-exchange capacity, water uptake, conductivity and hydophilicity from blended membranes, comparable to commercial membranes, though the performance of the prepared membranes did not exceed the commercial one. Further characterization of the transport properties of ion-exchange membranes need to be investigated to be able to understand the effects of the fillers on the performance of the membranes in ED application

Formation mechanism of sPEEK hydrophilized PES supports for forward osmosis

International audiencePolyethersulfone/sulfonated polyetheretherketone (PES/sPEEK) supported osmotic thin film composite (TFC) membranes were fabricated with a focus on the optimization of the support layer of the TFC membrane by the phase inversion process. The polymer solution was cast directly on a glass substrate without any backing fabric to prepare the support layer. All resultant supports showed a fingerlike pore structure. The addition of a more hydrophilic polymer (sPEEK) to the polymer solution induced pores in the bottom layer of the support with average pore diameters ranging from 0.07 to 0.30 μm, which improved water flux. Bottom surface porosities were simply controlled by adjusting the polymer blend ratios. FO experiments were carried out in a high-throughput (HT) crossflow FO cell with DI water and a 0.5 M NaCl solution as feed and draw solution, respectively. TFC membranes with 5% sPEEK showed a water flux in PRO mode of 14.3 LMH and in FO mode of 6.2 LMH, which is superior to the commercial cellulose triacetate (CTA) and TFC membranes (HTI). In addition, a mechanism for the bottom layer formation was proposed. © 201

Review of nanomaterials-assisted ion exchange membranes for electromembrane desalination

In order to address the increasing demand for fresh water due to accelerated social and economic growth in the world, water treatment technologies, such as desalination, have been rapidly developed in attempts to safeguard water security. Electromembrane desalination processes, such as electrodialysis and membrane capacitive deionization, belong to a category of desalination technologies, which involve the removal of ions from ionic solutions with the use of electrically charged membranes termed ion exchange membranes. The challenges associated with ion exchange membranes have drawn the attention of many researchers, who have investigated various approaches to enhance their properties. The incorporation of nanomaterials is one of the popular approaches employed. Much research on nanomaterials incorporated ion exchange membranes was conducted for the purpose of fuel cell applications rather than electromembrane desalination. This review reports on the advances in nanomaterials incorporated ion exchange membranes applicable to desalination. The nanomaterials employed in ion exchange membranes fabrication include carbon nanotubes, graphene-based nanomaterials, silica, titanium (IV) oxide, aluminum oxide, zeolite, iron (II, III) oxide, zinc oxide, and silver. The aims of this article are to provide a snap shot of the current status of nanomaterials incorporation in ion exchange membranes, to assess the status of nanomaterials-facilitated ion exchange membranes research for electromembrane desalination, and to stimulate progress in this area