Membrane separations

Membrane separations

Processes for separating mixtures by using thin barriers (membranes) between two mis-cible fluids. A suitable driving force across the membrane, for example concentration or pressure differential, leads to the preferential transport of one or more feed components.

Membrane separation processes are classified under different categories depending on the materials to be separated and the driving force applied: (1) In ultrafiltration, liquids and low-molecular-weight dissolved species pass through porous membranes while colloidal particles and macromolecules are rejected. The driving force is a pressure difference. (2) In dialysis, low-molecular-weight solutes and ions pass through while colloidal particles and solutes with molecular weights greater than 1000 are rejected under the conditions of a concentration difference across the membrane. (3) In electrodialysis, ions pass through the membrane in preference to all other species, due to a voltage difference. (4) In reverse osmosis, virtually all dissolved and suspended materials are rejected and the permeate is a liquid, typically water. (5) For gas and liquid separations, unequal rates of transport can be obtained through nonporous membranes by means of a solution and diffusion mechanism. Pervaporation is a special case of this separation where the feed is in the liquid phase while the permeate, typically drawn under subatmospheric conditions, is in the vapor phase. (6) In facilitated transport, separation is achieved by reversible chemical reaction in the membrane. High selectivity and permeation rate may be obtained because of the reaction scheme. Liquid membranes are used for this type of separation.

References in periodicals archive ?
Elimelech's research interests include engineered osmosis for sustainable production of water and power; environmental applications and implications of nanomaterials; membrane separations for desalination and water reuse; and water and sanitation in developing countries.
The overall impact applies beyond the project we will be able to increase the control of membrane separations used worldwide, helping industries including food, water, healthcare and chemicals.
Several particular types of processes receive their own chapters, including evaporative separations, extraction and leaching, absorption and adsorption, solid-liquid separation, particulate removal, membrane separations, and crystallization.
Zydney, "Membrane separations in biotechnology," Current Opinion in Biotechnology, vol.
Today, Permionics has the most extensive range of membranes to suit various industrial requirements becoming a "one-stop solution" for membrane separations.
Membrane separations are classified by pore size and by the separation driving force.
Membrane separations are used in a wide range of industrial processes to separate biological macromolecules, colloids, ions, solvents and gases.
Among the topics are ion exchange chromatography, affinity ligands from chemical and biological combinatorial libraries, membrane separations, conventional isoelectric focusing in gel slabs and capillaries and immobilized pH gradients, capillary electrophoretic separations, and high throughput screening techniques in protein purification.
Coverage encompasses advances in catalysis, chemistry, and processes for steam reforming and catalytic partial oxidation of gaseous and liquid fuels, as well as processes for gasification of solid fuels for the production, separation, and purification of hydrogen and syngas, including water-gas-shift, pressure swing adsorption, membrane separations, and desulfurization technologies.
GE Healthcare Membrane Separations, Westborough, MA www.ge.com or call 508-475-2012
Preterm labor complicated three other cases, and 11 patients demonstrated chorioamniotic membrane separations that eventually led to premature rupture of membranes.
The current $1.7-billion membrane separations market is expected to increase at an [average annual growth rate (AAGR)] of 8.9 percent to reach about $2.6 billion in 2008."

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