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Pervaporation Membranes

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Pervaporation Membranes
Most membranes work as a barrier or filter preventing unwanted elements from travelling through and separating the contaminant from the target. There are several types of membranes with various pore sizes (micro filtration, ultra filtration and nano filtration) that will block particles the size of sand to bacteria. These membranes are usually made of either ceramic or polymer materials. These filter-like membranes fall under the definition of Porous Membranes where separation is determined by pore size and particle (molecule) size.

Pervaporation membranes are non porous and used for separating liquid from liquid mixtures. It enables solvent mixtures to be separated without using any third substance or entrainer. Azeotropes can be broken effectively and economically irrespective of vapor-liquid equilibriums. Molecules with high affinity are attracted by the membrane layer and are diffused through the membrane while molecules with low affinity are retained. For example hydrophilic membranes have high affinity to water molecules and so allow water to diffuse through the membrane while preventing other molecules from doing so while a hydrophobic membrane will do the opposite. The membrane separates mixtures at the molecular level, separating and driving similar type molecules in a vapor phase into one tank while redirecting the other portion of the liquid mixture back to the original tank or a third tank.

KmX pervaporation membranes are made from a blend of polymers and reinforced materials that can withstand the harshest of compounds including ketones, alkalis and acids. The membranes ability to select certain molecules and reject others is achieved mainly through polarity differences and a combination of the polymer properties and vacuum application. These and other forces permit the separation and high purification of the target component(s) to take place.

There are three classes of membranes within the pervaporation family:

  1. Hydrophilic membranes (view graphic) are used to remove water from a chemical or mixture of chemicals ... Learn more

  2. Hydrophobic membranes (view graphic) are used to separate Volatile Organic Compounds from a body of water ... Learn more

  3. Organophilic membranes (view graphic) reject certain chemical molecules while having an affinity for others and are used to separate mixtures with two or more chemicals.

These membranes come in both flat sheet and hollow fiber (view photo) configurations. Flat sheet is the configuration of choice when processing harsher chemicals, while hollow fiber membranes provide significantly lower cost of manufacture and assembly and therefore open up the opportunity to economically and effectively recover lower valued spent chemical mixtures.



Click to enlarge   Hollow Fibre Membranes





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