Membrane, Semipermeable

Name:
Membrane, Semipermeable
Detailed information:
A microporous structure, either natural or synthetic, that acts as a highly efficient filter in the range of molecular dimensions, allowing passage of ions, water, and other solvents and very small molecules, but is almost impermeable to macromolecules (proteins) and colloidal particles. The thickness is about 100 Å, the pore diameter is from 8 Å for the walls of tissue cells to 100 Å or more for manufactured membranes. Plant cell wall membranes are proteinaceous substances that function in natural osmosis. Membranes of cellophane, collodion, asbestos fiber, etc., are used in such industrial operations as waste-liquor recovery, desalination, and electrolysis; processing whey proteins, biomedical research; gas separations, e.g., adjusting carbon monoxide/hydrogen ratios for ammonia production from synthesis gas; metal extraction and recovery.See Osmosis; Dialysis.