company news about Differdifference between positive penetration, reverse osmosis, nanofiltration?

Differdifference between positive penetration, reverse osmosis, nanofiltration?

Positive osmosis / reverse osmosis / nanofiltration

Human discovery and penetration has a history of more than 200 years. reverse osmosis research began in the 1950s. After more than 60 years of research, development and industrialization, reverse osmosis technology is increasingly mature, widely used for salt water desalination, pure water and ultra-pure water equipment, as well as concentrated purification and water reuse. nano filter research started in the mid-1970s and was commercialized by the mid-1980s. The main products are aromatic polyamide compound nano filter membrane and cellulose acetate asymmetric nanofilter membrane. Its aperture is somewhere between reverse osmosis and ultrafiltration. In contrast to other membrane processes, positive penetration is a spontaneous low energy consumption process that utilizes the differential penetration pressure of the solution on both sides of the membrane as a driving force to spontaneously move water molecules from the high chemical potential side to the low chemical potential side. Positive penetration has the advantages of low energy consumption, high water production rate and small pollution. It may be widely used in various fields, including sewage treatment and freshwater purification, desalination, food, medicine, pressure damping penetration power generation, etc.

01-reverse osmosis

This selective membrane, which passes one or several components in solution and the other cannot, is called a semipermeable membrane. When the pure solvent is separated from the solution (or a solution of different concentrations) by a semipermeable membrane, there is a spontaneous flow of the pure solvent through the membrane to the solution phase (or from a low concentration solution to a high concentration solution), a phenomenon called penetration (positive penetration). If an external pressure is added to the side of the solution (or the concentrated solution side) to hinder the solvent flow, the penetration rate will decrease, and when the pressure increases to stop the penetration completely, the tendency of penetration is balanced by the added pressure, which is called the osmotic pressure. Permemotic pressure is a property of the solution, independent of the membrane. If the pressure is further increased on the side of the solution, causing the solvent reverse osmosis flow, this phenomenon is habitually called "reverse (reverse) penetration".

02 Reverse osmosis membrane positive osmosis membrane filter membrane and membrane components

is mainly divided into two categories: one is cellulose acetate membrane, such as universal cellulose acetate-cellulose triacetate mixed asymmetric membrane and cellulose triacetate hollow fiber membrane; the other is aromatic polyamide membrane, such as universal aromatic polyamide composite membrane and aromatic polyamide hollow fiber membrane.

The shape of the membrane has sheet, tubular and hollow fibers. Plate and coil reverse osmosis device can be prepared with sheet film, tube reverse osmosis device with tube film, and hollow fiber reverse osmosis film. Current applications are roll reverse osmosis devices and hollow fiber reverse osmosis devices, and plate and tube reverse osmosis devices are only used for special concentration treatment occasions.

Na filter film and group devices are basically the same as reverse osmosis, in addition to inorganic Na filter film and corresponding group devices.

Positive osmotic membrane mainly includes two categories of cellulose acetate and polyamide thin-film membrane composite membrane, in addition to layer upon layer deposition of composite membrane bicortical membrane, biological bionic membrane and other new positive osmotic membrane.

03 Reverse osmosis filtration process and characteristics

Characteristics and application of the reverse osmosis process

Reverse osmosis is a high-efficiency and energy-saving technology. It is to separate the water (solvent) and ions (or small molecules) in the feed for the purpose of purification and enrichment. This process has no phase change, generally no heating, simple process, low energy consumption, easy operation and control, a wide range of applications. Due to the effect of osmotic pressure, it also requires strict control of scaling, pollution, pH and oxidant.
The main applications of reverse osmosis technology are seawater and salty water desalination, pure water and ultra-pure water preparation, industrial water treatment, drinking water purification, industrial liquid treatment and concentration of pharmaceutical, chemical and food products, and wastewater treatment.

Characteristics and application of the positive penetration process

The positive permeation process is driven by the solution penetration pressure difference on both sides of the semi-permeable membrane without providing applied pressure and thus has lower energy consumption compared to conventional separation techniques. In addition, because there is no external pressure or only a very low hydraulic pressure during the operation process, the tendency of membrane pollution is significantly reduced compared with the reverse osmosis process. There is also a concentrated differential polarization during the positive oscolation, substantially reducing the water flux in the FO mode due to the reduced net osmotic pressure difference.

Positive penetration technology can be applied to sewage treatment, fresh water purification, desalination, food, medicine, pressure damping penetration power generation and other fields.

Characteristics and application of the nano-filter process

The aperture of the nano-filter membrane is within the nanoscale, and some of them have a relatively different Donnan potential for different valent anions, its intercept molecular weight is in 100 magnitude, and there are significant differences for different valent anions, which can let the feed part or the vast majority of the unit valent inorganic salt through.

nanofiltration has unique advantages and obvious energy saving effect in water softening, grading of organic low molecules and desalting purification of organic matter.

04 Reverse osmosis and reverse osmosis positive penetration filter membrane assembly technology

reverse osmosis membrane group device technology

The reverse osmosis component is the smallest basic unit that the film assembled can be put into practical application and is the main component of the reverse osmosis device. Components can have different configurations and can be large or small to accommodate different scale devices and different applications.

Requirements for component design and production are as follows:

1. There is a good seal between the water inlet on the high pressure side of the membrane and the water production on the low pressure side.

1. The support of the membrane (sheet or tubular membrane) or the membrane itself (hollow fiber membrane) can withstand a high working pressure difference: prevent leakage between water intake and water production and between these liquids and the outside world, and avoid excessive pressure difference between water intake and water production.

1. The membrane flow channel is the key factor in design. According to the mechanical conditions of water and the membrane performance, optimize the parameters of rebinding process; have good flow state and reduce the differential polarisation to prevent accumulation and contamination of salt on the membrane surface.

1. High filling density for membrane replacement to reduce equipment cost and shall be prepared and assembled with high scale and high quality.

Technology of positive permeable membrane group devices

The positive osmosis membrane component is the smallest basic unit assembled into the positive osmosis membrane that can be put into practical engineering application, and is the core component of the positive osmosis device. However, because two solution circulation circuits of absorption and material must be configured in the positive permeability process, and the material to be treated is usually a highly polluted water body, the positive osmosis membrane assembly cannot completely copy the existing mature reverse osmosis membrane assembly design, which should be redesigned or targeted according to the characteristics of the positive permeability process.
According to the geometry of the membrane, the positive permeable membrane assembly is currently mainly divided into three basic forms: plate frame, roll and hollow fiber. Different types of membrane groups have their advantages and disadvantages, and their application field is related to the mode of operation (intermittent operation or continuous operation). The following focuses on the membrane component types, structural design and applicable fields currently used in the positive penetration process.

Filfilter group device technology

According on the geometry of the membrane, the commercialized nanofilter membrane components are also mainly in four basic forms: plate frame (PE), tube (T), roll (SW) and hollow fiber (HF). The design of nano-filter membrane assembly is similar to that of reverse osmosis membrane, and it is currently mainly coiled film assembly.