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This is a type of membrane filtration that separates molecules whose size is in the range of 0.0005-0.001µm. Lactose and some amino acids fall into this range, and some monovalent ions, such as sodium and potassium, pass through the pores of the membranes. The operating pressure used in nanofiltration ranges from 1 to 3 MPa. Nanofiltration membranes are designed to separate water and some minerals. As a result of thickening, a concentrate (retentate) and permeate (water containing minerals and salts) are obtained. Most often, thickening at the nanofiltration plant is carried out up to 18% -20% of solids, due to maximum economic efficiency. Moreover, the water obtained as nanofiltration – permeate can be purified at a reverse osmosis plant and used for technological needs.
Thus, if the whey is thickened by means of a nanofiltration unit, a partial demineralization of the concentrate occurs. Therefore, in some cases (salt whey processing) nanofiltration can be highly efficient and cost effective.
Whey processed through nanofiltration can be used for further production of dry powder.

Main application of nanofiltration
Typically, nanofiltration is used in cases where proteins, amino acids, sugar and other particles need to be removed from the solution, leaving only salt molecules in the filtrate:
• partial demineralization and thickening of sweet and sour whey;
• partial demineralization of whey protein concentrate in the production of baby food, as a pre-treatment, before electrodialysis;
• partial demineralization of milk;
• partial demineralization of permeate after ultrafiltration;
• desalination of sea water;
• process water recovery.