The reverse osmosis membrane is the core element to realize reverse osmosis, and it is an artificial semipermeable membrane with certain characteristics made by simulating biological semipermeable membrane. Generally made of polymer materials. Such as cellulose acetate film, aromatic polyhydrazide film, aromatic polyamide film. The diameter of the surface pores is generally between 0.5 and 10 nm, and the permeability is related to the chemical structure of the membrane itself.
Principle
Reverse osmosis technology is a pressure-driven membrane separation technology, and the operating pressure is generally 1-10MPa. The retention component is 0.1-1 nm ions or small molecules. With the continuous development of membrane technology and the requirements of the energy crisis, people have carried out the development of ultra-low pressure reverse osmosis membranes, which can now be partially desalinated at a pressure of less than 1MPa.
The representative mass transfer mechanism of reverse osmosis membrane mainly includes dissolution-diffusion theory, preferential adsorption-capillary flow theory, hydrogen bond theory, Donnan equilibrium model and so on.
Types of reverse osmosis membranes
According to the type of membrane element, it can be divided into homogeneous membrane, non-paired membrane and composite membrane.
According to the characteristics of membrane elements, it can be divided into low pressure membrane, ultra-low pressure membrane, extremely ultra-low pressure membrane, low energy consumption membrane, ultra-low energy consumption membrane, high desalination rate membrane, ultra-high desalination membrane, high boron removal membrane, high flux membrane, anti- fouling membrane, etc.
According to the use of reverse osmosis membrane, it can also be divided into tap water membrane, brackish water membrane, seawater desalination membrane, semiconductor grade membrane, concentration separation membrane, thermal disinfection membrane, etc.
According to its raw materials, it can also be divided into cellulose acetate, polyamide, and composite membrane.
According to the size of the membrane element, it can be divided into small reverse osmosis membrane, 4040 membrane and 8040 membrane.
According to the structure, it can be divided into inorganic membrane, organic membrane and disc tube type.
Application
Desalination of seawater and brackish water to produce domestic water, softening of hard water to produce boiler water, and production of high-purity water. In recent years, the application of reverse osmosis technology in household water dispensers and direct drinking water supply systems has demonstrated its superiority.
In the pharmaceutical and food industries, it is used to concentrate medicinal liquids, fruit juices, coffee infusions, etc.
In printing and dyeing, food, papermaking and other industries, it is used to treat sewage, and to recycle useful substances in waste industries.
Preparation, purification and separation of certain products in chemical industry, metallurgy and pharmacy.
