What is Crossflow Filtration?
Crossflow filtration is a process where product is separated through a porous membrane while the feed solution flows rapidly across the surface of the membrane.
Rapid crossflow causes turbulence at the surface of the membrane, which serves to keep the membrane from becoming plugged. As a result, a large volume of solution can be filtered in a short period of time.
Crossflow filtration is often referred to as tangential flow filtration because the feed solution flow is tangential to the surface of the membrane. The clarified solution is termed the filtrate or permeate. The concentrated solution that exits the membrane device is termed the concentrate.
Complete Filtration Resources Inc., offers four different types of filtration processes:
Micro-Filtration (MF)
Micro-Filtration is used primarily for solution clarification, bacteria removal and protein separation. The rejection properties of the membrane are very strongly related to operating variables such as system pH, ionic strength, hydrodynamics, permeate flux and also strongly dependent on fouling.
- 50,000 – .2 μm
- Feed—Water, Monovalent Ions, Multi-Valeant Ions, Sugars, Amino Acids, Proteins, Polysaccharides, Particulates, Colloids, Bacteria
- Concentrate—Particulates, Colloids, Bacteria
- Permeate—Water, Monovalent Ions, Multi-Valeant Ions, Sugars, Amino Acids, Proteins, Polysaccharides
Ultra-Filtration (UF)
Ultra-Filtration is used primarily to concentrate solutions of macromolecules such as proteins while permitting the removal of low molecular weight solutes. The rejection properties of the membrane are related to operating variables such as system pH, ionic strength, hydrodynamics, permeate flux and also strongly dependent on fouling.
- 3,000-300,000 Dalton MWCO
- Feed—Water, Monovalent Ions, Multi-Valeant Ions, Sugars, Amino Acids, Proteins, Polysaccharides, Particulates, Colloids, Bacteria
- Concentrate—Proteins, Polysaccharides, Particulates, Colloids, Bacteria
- Permeate—Water, Monovalent Ions, Multi-Valeant Ions, Sugars, Amino Acids
Nano-Filtration (NF)
Nano-Filtration functions as a loose or leaky RO membrane which permits water, univalent ions and small molecules like simple sugars to pass through. The rejection properties of the membrane are intimately related to operating variables such as system pH, ionic strength, hydrodynamics and permeate flux.
.1-10 Nanometer Pore Size
Feed—Water, Monovalent Ions, Multi-Valeant Ions, Sugars, Amino Acids, Proteins, Polysaccharides, Particulates, Colloids, Bacteria
Concentrate—Some Monovalent Ions, Multi-Valeant Ions, Sugars, Amino Acids, Proteins, Polysaccharides, Particulates, Colloids, Bacteria
Permeate—Water, Some Monovalent Ions
Reverse Osmosis (RO)
Reverse Osmosis uses a membrane which permits only water to pass through. Some small molecules with water like properties (such as ethyl alcohol) may also pass through. The rejection properties of the membrane are weakly related to operating variables such as system pH, ionic strength, hydrodynamics and permeate flux. Reverse Osmosis (RO) is almost always a concentration process.
- .1 nanometer Pore Size
- Feed—Water, Monovalent Ions, Multi-Valeant Ions, Sugars, Amino Acids, Proteins, Polysaccharides, Particulates, Colloids, Bacteria
- Concentrate—Monovalent Ions, Multi-Valeant Ions, Sugars, Amino Acids, Proteins, Polysaccharides, Particulates, Colloids, Bacteria
- Permeate—Water
Ceramics
Membrane Filtration Configurations
- Ceramic/Metallic
- Spiral Wound
- Tubular
- Hollow Fiber