The filtration includes two methods: positive pressure and negative pressure filtration. The two kinds of methods can both make the solvent and the solute of smaller molecules pass through the filtration membrane with certain pore size, while the solute of larger molecules cannot pass through, so as to dehydrate, desalinate and concentrate the macromolecule materials, which will intercept the bacteria and parasites in order to achieve the purpose of sterilization, bacteria collection or increase the detection rate.
According to the size of separated substances, the membrane filtration technology is divided into microfiltration (MF), ultrafiltration (UF), reverse osmosis (RO) and nanofiltration (NF), etc.
Most of the filter membranes are made of high molecular materials, including cellulose ester, regenerated cellulose, polyamide, polyvinyl alcohol derivative, polyacrylonitrile, polypropylene, polyethylene, polyvinyl chloride, acrylonitrile/vinyl chloride copolymer, polycarbonate, polytetrafluoroethylene, polyvinylidene fluoride, etc.
The pore size of the membrane is expressed in μm, mainly including 0.025, 0.03, 0.05, 0.08, 0.1, 0.22, 0.3, 0.45, 0.6, 0.8, 1.0, 2.0, 3.0, 5.0, etc.
The main components of the membrane are including flat membrane, foldable membrane, tubular membrane, roll-type, and hollow fiber.
Cellulose Ester Materials is a standard membrane filter, characterized in good pore-forming performance, good hydrophobicity, easy availability of materials and low cost. And the pore size specification of the membrane is of a wide variety. The temperature range of the film is very wide. It is suitable for resistant to acid and base, but not suitable for ketone, ester, strong acid and alkali liquid filtration.
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