Page 328 - Biosystems Engineering

Bioseparation Pr ocesses 305

9.3.9 Membrane Technology
In membrane separation, the membrane used may be a solid matrix.
A liquid may also act as a separation barrier between two phases or
mediums where transport occurs using the solution–diffusion mech-
anism. The advantages of the process are as follows:
1. Operation of the process is easy.
2. It replaces the conventional process and provides clean
technology.
3. The process can recover high-value product with appreciable
energy savings.
4. There is a possibility of modifying the design at any time.
5. This process is more easier to separate without heat treatment,
for example, separation of alcohol from water than chemical
process.
6. Separation of amino acids can be done due to like electro-
static charge, hydrophobicity, molecular size, or solubility.
7. Membrane technology can be utilized for the immobilization of
the enzymes in enzyme emulsions. This can be done by immo-
bilizing the enzyme systems in liquid surfactant membrane
emulsions. Enzyme emulsions have a broad field of applica-
tions in cell-free fermentation broth, to preselect the desired
substrate for enzymatic reaction in the complex mixture.
8. Membrane technology specially liquid membrane can be used
in gas-separation techniques. High selectivity is also achieved
due to extraordinary solubility of certain gases in liquids.
Disadvantages of the process are as follows:

1. The membrane process is expensive due to the high cost of
the membrane.
2. Membrane fouling is a common problem in the separation
process.
3. There is an upper solid limit in the membrane separation
process.

Ultrafiltration Membrane
This is a pressure-driven process (Fig. 9.9) in which water and
low-molecular-weight components can pass through the membrane,
whereas particles, colloids, and macromolecules are retained. Ultra-
filtration pore ratings range approximately from 1000 to 500,000 Du.
Thus, filtration makes the membrane more permeable than nano-
filtration. In ultrafiltrated milk, lactose and minerals pass in a
50 percent separation ratio; for example, in the retention there will be