Mechanical based desalination

It can be seen from table I.l that differences in the size, vapour pressure, affinity, charge or chemical nature of molecules facilitate membrane separation. The number of possible separation principles, some of which are used in combination, distinguish this technique from other separation processes and also provide an indication of the number of situations in which membrane processes can be applied. It should be noted that competitive separation processes are not necessarily based on the same separation mechanism. This has already been demonstrated in the example given above on water desalination. However, this example did not indicate which of the separation processes mentioned is to be preferred. 

Membranes can be thought of as special types of films that provide specific end use characteristics. Membrane technology has replaced some conventional techniques for separation, concentration or purification [78]. Applications include desalination, dialysis, blood oxygenators, controlled release drug delivery systems and gas separation. Processing of polymer films and membranes is well known to affect the morphology, which in turn affects the physical and mechanical properties. As is true for all films, membrane separation properties are based on both the chemical composition and the structure resulting from the process. Membranes are produced in two major forms, as flat films and as porous hollow fibers, both of which will be discussed in this section. 

A good AEM should fulfill stringent mechanical, thermal, and chemical properties as mentioned in Section 11.2. Historically, the first AEM material was developed by researchers from the Toknyama Soda Company. They introduced quaternary ammonium groups to the divinylbenzene-cross-linked polychloropropene polymer matrix via trimethylamine. Since then, several membrane-associated companies explored various kinds of AEMs and pushed them to commercial market most of them were based on cross-linked polystyrene, polyvinyl alcohol, low (or high)-density polyethylene, and other aliphatic polymers through irradiation-grafting method. The primary objective of developing these materials was for applications in the fields such as electrodialysis, desalination, selective electrode, and waste acid recovery. However, they showed performance in AEM fuel cells far below practical... 

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