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membrane

A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Biological membranes include cell membranes (outer coverings of cells or organelles that allow passage of certain constituents); nuclear membranes, which cover a cell nucleus; and tissue membranes, such as mucosae and serosae. Synthetic membranes are made by humans for use in laboratories and industry (such as chemical plants).
This concept of a membrane has been known since the eighteenth century but was used little outside of the laboratory until the end of World War II. Drinking water supplies in Europe had been compromised by the war and membrane filters were used to test for water safety. However, due to the lack of reliability, slow operation, reduced selectivity and elevated costs, membranes were not widely exploited. The first use of membranes on a large scale was with micro-filtration and ultra-filtration technologies. Since the 1980s, these separation processes, along with electrodialysis, are employed in large plants and, today, several experienced companies serve the market.The degree of selectivity of a membrane depends on the membrane pore size. Depending on the pore size, they can be classified as microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) membranes. Membranes can also be of various thickness, with homogeneous or heterogeneous structure. Membranes can be neutral or charged, and particle transport can be active or passive. The latter can be facilitated by pressure, concentration, chemical or electrical gradients of the membrane process. Membranes can be generally classified into synthetic membranes and biological membranes.

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  1. L

    Is a polythene membrane necessary between biscuit mix and floor boards?

    Hi! I am looking for some feedback regarding the use of a polythene membrane between my UFH in drymix and the CaberDek floor above. We have no such thing installed, is it essential? I have only seen it suggested once as a recommendation on a website. The floor is: 200mm celotex, osb, pipes...
  2. P

    HepvO and Wirquin 90mm Slim Shower Waste (Waterless Membrane) question

    I'm in the process of revamping a bathroom. At the moment it contains a toilet, basin and bath with an overhead shower. The basin and toilet share a common waste pipe which feeds into the soil stack behind the toilet. The soil stack is internal and boxed behind a stud wall in a corner and has...
  3. gassafe

    Ancient shanks siphon repair

    Anyone tried repairing one of these old relics... Is it just a regular membrane inside? I cant replace for a regular as it has a really weird connection on to the pan, plus 2' plus siphoning pan!
  4. B

    Toilet siphon

    Alright guys? i don't really do any plumbing work but a friend has asked me to look at his toilet as you have to pump the handle a few times to get a decent flush. So in guessing the siphon membrane has failed. my question is though, how do you size the siphon? Just measure the height of the...
  5. T

    waterproof membrane

    Hello anyone recommend a good waterproof membrane? I have battened a wall and fixed plasterboard to it im wanting a decent but cheap membrane to put behind the plasterboard any ideas?
  6. S

    damp proof membrane behind radiators?

    ive came across a problem as the house i had removed radiators from to let the customer redecorate, found rising damp in the walls. the company have stripped the plaster and put up a membrane to stop the damp coming through, they are in the middle of plastering over the membrane but they are...
  7. G

    Coated membrane diffusers

    We are a pulp and paper mill that has used practically every aeration technology available on the market. Each one seemed to have a problem in one facet or another. It wasn’t until we tried SSI’s PTFE coated membrane diffusers that our problems were solved. No more severe fouling, rapid increase...
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