The cross-flow filtration membrane technology is used to physically separate from an aqueous solution even extremely small soluble substances (ions, molecules), whose size is measurable in nm (nanometers).
The degree of filtration depends on many factors:
Ultrafiltration membranes are true porous membranes, capable of retaining medium molecular weight organic substances (in the range of 1,000-500,000 D - from narrow ultrafiltration up to the microfiltration thresholds).