Membrane technology is a generic term used for any separation process in which membranes are employed. A membrane can be defined as a physical barrier separating two phases and allowing a selective transportation of compounds from one phase to the other. The part that goes through the membrane is the permeate and the part that is rejected by the membrane is the retentate (Figure 1).
Figure 1. Membrane technology separation diagram.
Membrane technology can be applied for purposes such as:
- Water purification: undesired impurities are removed from the solution. For example: soft water production by the removal of calcium and magnesium cations.
- Concentration: required components are present at a low concentration and the solvent is removed. For example: fruit juice concentration by removing water.
- Fractionation: a mixture must be separated into two or more desired components. For example: milk fractionation in dairy industry.
Membranes can be classified depending on the compounds that membranes are capable of separating (Figure 2).
Figure 2. Pressure driven membranes.
In the laboratory of membrane technology the following equipments can be found:
- A laboratory-scale cross-flow stainless steel test unit for flat-sheet membranes. The system can be used as a microfiltration, ultrafiltration, nanofiltration or reverse osmosis.
- Spiral wound ultrafiltration and reverse osmosis membrane pilot plants that can be coupled and used in serie.