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

Synthesis and electrochemical behavior of ceramic cation-exchange membranes based on zirconium phosphate

Cation-exchange membranes made exclusively from ceramic materials have been synthesized by means of the impregnation of microporous ceramic supports with zirconium phosphate. Changes in the pore size distribution and total pore volume of the supports were provoked by the addition of starch as pore former in the fabrication procedure. This allowed the production of supports with increased effective electrical conductivities and with larger pores available for the zirconium phosphate deposition. An improved functionality for the exchange of cations was given to the ceramic membranes by means of their impregnation with the active particles of zirconium phosphate. The ion-exchange properties of the membranes were increased with further impregnation cycles and the resulting current voltage curves showed a similar shape to that typical of commercial polymeric ion-exchange membranes. The production of ionexchange membranes with increased chemical and radiation stability will broaden their applicability for the treatment of specific industrial waste waters, which are very aggressive for the current commercial ion-exchange membranes.Manuel-Cesar Marti-Calatayud wants to express his gratitude to Universitat Politecnica de Valencia for a postgraduate grant (Ref. 2010-12). S. Sales would like to express her gratitude to Ministerio de Ciencia e Investigacion (Spain) for a postgraduate grant (AP2009-4409). This work was supported by Ministerio de Ciencia e Innovacion (Spain) with the project numbers CTQ2008-06750-C02-01/PPQ and CTQ2008-06750-C02-02/PPQ.Martí Calatayud, MC.; García Gabaldón, M.; Pérez-Herranz, V.; Sales, S.; Mestre, S. (2013). Synthesis and electrochemical behavior of ceramic cation-exchange membranes based on zirconium phosphate. Ceramics International. 39(4):4045-4054. https://doi.org/10.1016/j.ceramint.2012.10.255S4045405439

Forward osmosis research trends in desalination and wastewater treatment: A review of research trends over the past decade

Issues of water scarcity and water security have driven the rapid development of various technologies to ensure water sustainability. The forward osmosis (FO) membrane process has been widely recognized as one of the more promising technologies to play an important role in alleviating the issues of water sustainability. Extensive research has been carried out worldwide to explore the potential of FO in desalination, water and wastewater treatment and reclamation. It is of the utmost importance to understand the topics of interest and research trends to further advance the development of FO process technology. In this study, a bibliometric analysis based on the Scopus database was carried out to identify and understand the global research trends of FO process based on 6 main analyses: basic growth trends, journals, countries, institutions, authors, and keywords. A total of 1462 article published between 1967-2018 were extracted from Scopus and used as the raw data for bibliometric analysis using VOSviewer software. The total number of FO articles has sharply increased since 2009 and stabilized at around 250 publications in the past three years. FO research started to diversify after the appearance of commercial FO membranes with improved characteristics, enabling the researchers to employ them for various application studies. Keywords analysis showed that the main directions of FO research could be categorized into three clusters: application of FO, membrane fouling study, and FO membrane synthesis. These bibliometric results provide a valuable reference and information on current research directions of FO for researchers and industry practitioners

Novel Organic-Inorganic Nanocomposite Membranes for Electrodialysis Application in Water Recovery

Water shortage has become one of the major global concerns and has led to great efforts towards the search and utilization of an alternative water supply such as from abundant salt rich brackish water and sea water. Desalination by membrane separation process becomes an important technology for global population by producing fresh water out of saline water. Membrane is the key element in the membrane separation processes that determines to a large extent the performance, process efficiency, energy consumption and water production cost of the desalination. Up to date, the majority of existing commercial membranes is polymer based membranes which still require further modifications to achieve high desalination efficiency and low energy consumption. The key target of this work is to synthesize a new class of ion-exchange membranes applicable for electrodialysis desalination process by utilizing a new concept of composite membrane design. Organic-inorganic composite membranes have recently gained increasing attention due to their hybrid functionalities derived from organic and inorganic phases that may offer a variety of important applications. Fortunately, the composite design concept can provide enormous opportunities to control membrane structure and properties by simply tuning material components, compositions, and functionalities. Introducing metal oxide nanoparticles into the polymer matrix is expected to improve conductivity and transport properties of the polymer membranes while still keeping favorable mechanical and thermal stability. Polyethersulfone (PES), an inexpensive and high performance polymer with excellent mechanical, thermal and chemical stability, was selected as a main organic matrix in this work. The PES was first chemically modified by sulfonation reaction to introduce charged functional groups into polymer backbones to form sulfonated polyethersulfone (sPES) for use as ion-exchangeable polymer matrix. High surface area mesoporous silica was also chemically modified with sulfonate groups and used as an inorganic filler. A series of composite membranes containing sPES and sulfonated mesoporous silica (SS) have been prepared via a number of membrane preparation techniques. Systematic material synthesis and characterizations have been applied to elucidate the crucial links among synthesis conditions, membrane structure and properties and their desalination performance. It is well-known that the properties and performance of the membranes depends highly on their structure which in turn is affected by membrane preparation conditions. In the first part of this work, the relationship among membrane fabrication condition, membrane structure and property is the main focus for establishing an optimized membrane preparation procedure. The membranes prepared by different phase inversion techniques offered different structures and distinct properties. The preparation conditions in the ternary system of solvent/nonsolvent/polymer in the phase inversion were carefully investigated. It was found that the combination of two commonly-used phase inversion techniques, namely wet and dry phase inversion, was an effective tool for preparing membranes with adjustable structure, pore size and porosity. The structure and porosity of the prepared sPES membranes can be easily controlled by tuning ageing periods of membrane formation in the steps of dry and wet phase inversions. The properties of polymer matrix membrane are further improved by incorporating surface functionalized mesoporous silica. In the second part of this thesis, the influence of inorganic fillers with different sizes and shapes on the membrane structure and properties was investigated. It was found that by incorporating small amount of inorganic additive, the membrane properties such as water content, conductivity, and transport number were significantly enhanced while the membranes still maintain their mechanical and thermal stabilities. The desalination results by a custom-designed lab-scale electrodialysis (ED) cell of the composite membranes also exhibited good performances with high current efficiency over 80%, which is compatible to a benchmark membrane (FKE, FumaTech). The newly developed membranes can thus be considered as excellent candidates for ion-exchange membranes in desalination application. The findings from this project will generate a suite of new knowledge that underpins both fundamental understanding of membrane design and their applications in ED desalination. The outcomes are expected to lead to the development of new alternative composite ion-exchange membranes which may open up cost-effective and less energy consumption desalination application

MCM-41/PVA Composite as a Separator for Zinc–Air Batteries

Membrane separators are one of the critical components in zinc–air batteries (ZABs). In the control of mass transfer, and hence, electrochemical reaction, membrane separators have an important role to play. This work addresses the issue of battery performance in a ZAB via a new composite membrane separator based on polyvinyl alcohol (PVA). To enhance the electrolyte uptake and ionic conductivity, mesoporous Mobil Composition of Matter No. 41 (MCM-41) is incorporated as a filler in the membrane while maintaining its integrity. The presence of MCM-41 is seen to reduce the number of cycles of secondary ZABs due to the uninvited drawbacks of increased zincate crossover and reduced triple phase boundary at the air cathode, which is pivotal for oxygen reduction reaction. Overall, results suggest that the application of the MCM-41/PVA composite has the potential for use as a separator in high-capacity primary ZABs

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

Worth their salt

Researchers are making efforts to desalination of saline water or sea water to produce potable water due to increasing demand for potable water. The federal government of Australia invested $1.6 billion to develop Western Corridor Recycled Water project to recycle water for power stations, industry, and residential purpose. Desalination can be done by using electrodialysis, membrane distillation, solar desalination, or capacitive deionization. Electrodialysis process involves the removal of salt ions by the membrane from the solution, while reverse osmosis process uses water-permeable membranes. Researchers are developing a new electrodialysis membranes by using functional nanomaterials and polymer nanocomposites. Electrodialysis technology can control the quantity of ions being removed from the solutions that make this technology a suitable substitute of the reverse osmosis process