Recent Patents on Chemical Engineering - Volume 4, Issue 2, 2011

Traditionally, ion exchange membranes (IEMs) are classified into anion exchange membranes (AEMs) and cation exchange membranes (CEMs) depending on the type of ionic groups attached to the membrane matrix. CEMs contains negatively charged groups such as -SO3-, -COO-, -PO32-, -PO3H-, - C6H4O-, etc., fixed to the membrane backbone and allow the passage of cations but reject anions; while AEMs contain positively charged groups such as -NH3+, -NRH2+, -NR2H+, -NR3+,-PR3+ , -SR2+, etc., fixed to the membrane backbone and allow the passage of anions but reject cations. The development of IEM-based process began in 1890 with the work of Ostwald who studied the properties of semipermeable membranes and discovered that a membrane can be impermeable for any electrolyte if it is impermeable either for its cation or its anion. Around 1940, interest in industrial applications led to the development of synthetic ion exchange membrane on the basis of phenol-formaldehyde-poly-condensation. Simultaneously, Meyer and strauss proposed an electrodialysis process in which AEMs and CEMs were arranged in alternating series to form many parallel solution compartments between two electrodes. Especially, with the development of stable, highly selective ion-exchange membrane of low electric resistance in 1950 by Juda and McRae of Ionics Inc., electrodialysis based on IEMs rapidly became an industrial process for demineralizing and concentrating electrolyte solutions. Since then, both IEMs and electrodialysis have been greatly improved and widely used in many fields. For example, in 1960s, first salt production from sea water was realized by Asahi Co. with monovalent ion permselective membranes in 1969, the invention of electrodiaylsis reversal (EDR) realized long-term run without salt precipitation or deposition on both membranes and electrodes in 1970s, a chemically stable cation exchange membrane based on sulfonated polytetra-fluorethylene was firstly developed by Dupont as Nafion® leading to a large scale use of this membrane in the chloralkali production industry and energy storage or conversion system (fuel cell). Simultaneously, a composition of cation exchange layer and an anion exchange layer into a bipolar membrane in 1976 by Chlanda et al. bring many novelties in electrodialysis applications today. Also, stimulated by the increasing demand in applications, many new types of IEMs were invented for the request with better selectivity, lower electrical resistance and improved thermal, chemical and mechanical properties. As an example, inorganic-organic ion exchange membranes were developed in the late 1990s by sol-gel for applications in severe conditions such as higher temperature and strongly oxidizing circumstances. IEMs is an “age-old” technology because it appeared more than 120 years ago; it is also an “emerging” technology with significant technical and commercial impact, because today IEMs and the related processes are receiving considerable attention and are successfully applied for desalination of sea and brackish water and for treating industrial effluents. They are efficient tools for the concentration or separation of food and pharmaceutical products containing ionic species and the manufacture of basic chemical products. The evolvement of IEMs not only makes the process cleaner and more energy-efficient but also recovers useful effluents that are now going to waste and thus makes the development of society sustainable. This may be the reason why more and more informative reviews including all the IEMs synthesis, IEMs applications, electro-catalytic membrane reactors, fuel cells based on IEMs, or bipolar membrane process and applications in environmental protection and in food industry have been published in the recent years. However, these reviews have been mainly based on the published journal papers. To understand the present patent states of ion-exchange membrane research, this special issue gives a summary of what has been accomplished in IEMs and the related processes from the point of view issued or applied patents. The issue contains ten papers so far, contributed by the selected researchers and professors in the corresponding fields. Paper 1 gives a substantial patent review on hybrid ion exchange membranes, which combine the advantages of inorganic and organic membranes and were recently developed and expected to be applied in harsh conditions, such as high temperature and strongly oxidizing circumstances. Paper 2 describes the patent status of ion exchange membranes and cation exchange membranes as protons or hydroxyl ions conductor for applications in fuel cells, respectively. Recently, sea water desalination has received much attention due to the comparatively low cost. But the limitation is due to the discarding of the concentrated effluents. The question arises how to simultaneously obtain both salts and pure water from the sea water? electrodialysis has been considered to be a promising tool. For this, ion exchange membranes with monovalent selectivity plays the role. So, paper 4 discusses such topic from the patent. Papers 5-9, respectively concentrate on the ion exchange membrane applications from both the processes such as elctrodialysis, electrodeionization (EDI), electrodialysis with bipolar membranes, adsorption and pervaporation and the fields such as chemical and environmental engineering, Agri-Food Sectors, etc. Another distinctive characteristic about ion exchange membrane technologies is integration flexibility, which is crucial to the realization of multiple functions needed for a specific complex industrial application. The last paper deals with such technique integrations and present the recent progress on electromembrane based integrations for industrial separations based on patents as well as some published articles. All the papers published in this special issue are invited ones. I appreciate the cooperation and active participation from all the authors, who, despite their extremely busy schedule of teaching and research (and even administration), found time to make this special issue a reality.

Organic-inorganic hybrid ion exchange membranes have been developing into a fascinating new field of research. The attractive characteristics of this kind of membranes are the improved chemical/mechanical/thermal stability, porosity, high adherence to different substrates, enhanced selectivity and/or permeability. In this article, we will focus on the recent patents concerning the preparations and applications of hybrid ion exchange membranes. Some related literature reports will also be introduced. The preparation methods mainly include sol-gel process, impregnation and mixing and surface grafting of inorganic substrates with silane. And the applications mainly comprise of diffusive dialysis (DD), fuel cells, microfiltration and ultrafiltration, and other separation processes. Through the patent and literature review, this article is intended to reveal the high level of diversity in the properties, the applications and the productions of the hybrid ion exchange membranes.

Recently, Alkaline Polymer Electrolyte Membrane Fuel Cells (APEMFCs) have been attracting worldwide attention mainly due to the prospect of using non-platinum-group metal catalysts. In addition, there is growing evidence that these fuel cells can operate with the presence of carbonate. This mini review will introduce the state-of-the-art in understanding of alkaline anion-exchange membranes (AAEMs) in solid alkaline fuel cells. Ionomers for membrane electrode assembly (MEA) fabrication and the chemistry of the carbonate and bicarbonate forms of the AAEMs are also discussed. Key references to the latest scientific literature and reviews are included, along with a brief overview of directly relevant patents.

Ion exchange membranes-based technology, as a non-hazardous technology in nature, is extending towards the newly emerging fuel cells beyond its successful application in various industrial processes, e.g. electrolysis, electrodialysis, diffusion dialysis, etc. Ever since the famous DuPont product Nafion®, a large number of cation exchange membranes for fuel cells application (known as proton exchange membranes) have been prepared to make fuel cells reliable, durable and feasible. Since most of commercial products originate directly from patents, it is of great importance, at the time when proton exchange membrane fuel cells are on the brink of commercialization, to make a special review focusing on proton exchange membranes reported in patents. To get a better understanding of the state of the art of proton exchange membranes from a viewpoint of patents, most relevant patents during the last decade are surveyed in this review and some critical comments on the tendency and prospect of proton exchange membranes are made.

Separation of ions with same charges but different valences using ion exchange membranes is not only desired for industrial requirements but also challenging for academic explorations. The aim of the present contribution was to review recent developments of cation exchange membranes with monovalent ion selectivity in several aspects, such as separation mechanisms, membrane-forming materials, manufacturing methods and its relevant applications reported in the open literatures, especially in the patents. And, the relevant advantages and disadvantages with respect to some cases were discussed and compared in detail. Furthermore, some future research directions in this field were also put forward tentatively.

A review of patents published between 2005 and beginning of 2011 on organic ion-exchange membranes and electro-membrane processes is given. The electro-membrane processes include classical electrodialysis (ED), ED with a bipolar membrane, metathesis ED, electro-electrodialysis, and electrolysis. The applications of ion-exchange membranes are diverse and can be divided into the following groups: desalination and purification, removal of harmful substances, recovery of valuable substances, regeneration of spent solutions, production of new compounds. The patents on reversed ED for electric energy production are also surveyed. A large number of patents published indicates that the efficiency and environmental friendliness of electro-membrane processes are widely recognized.

Pervaporation is a newly emerged separation process, known for its higher efficiency, lower energy consumption lower capital cost and so on. The main research field in pervaporation falls into three aspects: 1) the investigation of new membranes of good separation performance; 2) methods for manufacturing pervaporation membrane with high performance; 3) process modeling to find the bottleneck in the separation process. To date, lots of research papers are published and patents concerning the above mentioned research aspects have also been brought into the sight of those skilled in the art. As a branch membrane for pervaporation purpose, an ion exchange membrane, which is prepared from the charged polymers containing either anionic or cationic groups, has an important influence on the development of pervaporation. This paper thus discusses some valuable patents concerning the research of ion exchange membrane for pervaporation. Some basic processes using anionic membrane or cationic membrane, ways for the modification of charged polymers, manufacturing of pervaporation membrane and some insights of the mass transfer behavior are reviewed in this paper and finally a perspective conclusion is made.

Ion exchange membranes (IEMs) are the newly-developed technology for the separation of various species from mixed solutions. Among which, IEMs for the separation of substances by adsorption method have become attractive. This patents review is to summarize the recent and important patents on the preparations and potential applications of IEMs as adsorbents in various adsorptive separation fields. Two major parts are involved: (i) recent patents on the synthesis of organic IEMs and hybrid IEMs with different matrixes, (ii) recent patents on the potential applications of IEMs as adsorbents in industry via adsorptive separation, such as the adsorptive separation of heavy metal ions, biomedical species and natural organic matter (NOM). Especially, their applications for the adsorptive separation of heavy metal ions from contaminated water using hybrid ion exchange membranes (HIEMs) are highlighted. The present states and future perspective are also discussed.

The recent patents and progress of electrodeionization (EDI) in fields of water deionization and wastewater treatment are reviewed in the present paper. The discussion focuses on such major aspects: applied ion exchange media, inner configuration and operation manner of the EDI, integrated membrane processes based on EDI and new applications of the technology. As the newest outstanding technology for water deep desalting, EDI has been widely used for ultrapure water production in many industries and laboratories together with important improvements in recent years. Durative advancements have been achieved by inventors such as more even current distribution, higher contact efficiency between water and ion exchanger, more effective precipitation preventing and lower energy consumption. Besides, some improvements also have been achieved in other new fields in addition to pure water production. The application in water softening, seawater desalination and wastewater treatment were introduced for example. It is believed that the electromembrane process of EDI will play an important role in water desalting, wastewater reclamation and cleaner production of chemical engineering near future.

Electromembrane processes are considered to be one of the promising industrial applicable ones using an electrical potential as high energy-efficient processes. Their applications can be found in various fields such as water desalination, water and wastewater treatment, food industries, production of acids and bases, elimination of toxic components, regeneration of metal ions from industrial waste streams, ultra pure water production and etc. The electromembrane process integration with other processes has received more attention recently in the patents as well as published articles since it provides versatile tools for industrial separations, increasing process effectiveness by optimization of the utilization of electromembrane processes. A substantial number of industrial applications for the integration of electromembrane process can be found mainly in areas of chemical unit operations, pressure-driven membrane processes, and biochemical unit processes. This review presents the recent progress on electromembrane based integrations for industrial separations based on patents as well as some published articles. The patent search has been performed in different databases in which the patents can be searched and in most cases downloaded. The keywords such as “Electromembrane process, Integration, Separation, Purification, Electromembrane” were considered for the current patents on electromembrane based integrated/ hybrid processes.

Ion-exchange membranes (IEM) are used in the agri-food sector since the early 1950's. Their main applications are based on the demineralization of agri-food products or effluents. In these applications, anion- and cation-exchange membranes are stacked alternatively in an electrodialysis cell to produce two solutions, one concentrated and one impoverished in minerals. In this article we will focus on the recent patents published in the 5 last years and presenting the more recent uses and applications of ion-exchange membranes in this sector. These patents concerns mainly, the rectification of wine and grape juice, the production of salt and concentrated mineral solutions, the production of drinking water and functional drinking water, the demineralization of dairy and plants products, the production of sugar derivates, the bacterial decontamination of solution and the demineralization and purification of fermentation broth. These approaches will be discussed in terms of originality and novelty in comparison with current applications, as well as for their potential of application in the sector.

The patents annotated in this section have been selected from various patent databases. These recent patents are relevant to the articles published in this journal issue, categorized by medical imaging, bioinformatics, image processing, biomaterials, pharmaceutical drugs, bioengineering, medical devices, design, biological devices, biomechanics & diagnostic devices related to biomedical engineering....