13.11. ULTRAFILTRATION MEMBRANE PROCESSES
Ultrafiltration is a membrane process that is quite similar to reverse osmosis. It is a pressure-driven process where the solvent and, when present, small solute molecules pass through the membrane and are collected as a permeate. Larger solute molecules do not pass through the membrane and are recovered in a concentrated solution. The solutes or molecules to be separated generally have molecular weights greater than 500 and up to 1 000 000 or more, such as macromolecules of proteins, polymers, and starches as well as colloidal dispersions of clays, latex particles, and microorganisms.
Unlike reverse osmosis, ultrafiltration membranes are too porous to be used for desalting. The rejection ...