Nanofiltration membrane is also called low pressure reverse osmosis membrane, the Japanese scholar had toshio otani of nanofiltration membrane separation principle has carried on the concrete definition: operating pressure 1.50 mPa, or less intercept molecular weight 200 ~ 1000, NaCl withholding rate is 90% or less of the membrane can be thought of as nanofiltration membrane.
Nanofiltration membrane separation technology has been separated from the reverse osmosis technology, become the independence between ultrafiltration and reverse osmosis technology of separation technology, has been widely used desalination, ultrapure water production, food industry, environmental protection, and many other fields, and become an important branch of water treatment technology.
The principle of nanofiltration.
Dissolution and diffusion principle: permeate dissolved in the membrane, and gradient diffusion along its impetus, formed on the surface of nanofiltration membrane phase, the chemical equilibrium between the transfer form is: energy concentration o mobility = o impetus, makes a substance must overcome osmotic pressure through the membrane.
Electricity effect, nanofiltration membrane and the electrolyte ion, forming electrostatic interactions between different electrolyte salt ion charge intensity, causing membrane for interception of ion rate difference, in containing the different valence ion multiple system, due to the south (DONNAN) effect, makes the membrane with different ion selectivity is different, the proportion of different ions through the membrane is not the same.