Ultrafiltration is a pressure film separation technology, that is, under a certain pressure, so that small molecules solute and solvent through a certain pore size of the special film, leaving the macromolecule solute can not pass, stay on the side of the membrane, so that Macromolecules have been partially purified.
The key to ultrafiltration is membrane. The membrane has a variety of different types and specifications that can be selected according to the needs of the work. The early membranes are isotropic homogeneous membranes, which are commonly used as microporous films, with pore diameters of typically 0.05 mm and 0.025 mm. In recent years, some anisotropic asymmetric ultrafiltration membranes have been produced, in which an anisotropic diffusion film is composed of a very thin, porous "skin layer" having a certain pore size (about 0.1 mm to 1.0 mm thick) , And a relatively thick (about 1mm) more permeable, as a support for the "sponge layer" composition. The skin layer determines the selectivity of the membrane, while the sponge layer increases the mechanical strength. As the skin layer is very thin, so efficient, good permeability, large flow, and is not easy to be blocked by the solute flow rate. Commonly used membranes are generally made from a mixture of acetate fibers or nitrocellulose or a mixture of both. In recent years, non-fibrous anisotropic films such as polysulfone films, polysulfone amide films and polyacrylonitrile films have been developed to meet the need for sterilization in the pharmaceutical and food industries. The membranes are stable at pH 1 to 14 and can function normally at 90 ° C. Ultrafiltration membrane is usually relatively stable, if used properly, can be used continuously for 1 to 2 years. Not available, can be immersed in 1% formaldehyde solution or 0.2% NaN3 preservation. The basic performance indicators of the ultrafiltration membrane are: water flux [cm3 / (cm2 • h)]; rejection rate (expressed as%); chemical and physical stability (including mechanical strength) and so on.
1. The RO unit is temporarily shut down (no more than three days) and must be flushed with a safety filter for 30 minutes every day to ensure that the RO assembly is filled with filtered water.
2. RO devices such as long-term shutdown (more than three days), should be 1% formaldehyde solution, filled with RO components, and then close all the valves, and check once a month. Summer, control the ambient temperature to mildew, winter antifreeze, if necessary, add 10-20% glycerol.
3. Save the best water with reverse osmosis fresh water, formaldehyde application of chemical reagents products.
4. When the reverse osmosis system consisting of the composite membrane is to be suspended for more than one week, the system should be soaked with 1% NaHSO3 solution to prevent bacteria from propagating on the membrane surface.