magnetic, or electrical potential gradient. Nanofiltration and gas separation are two
commonly used membrane separation processes to employ dense membranes. On
the other hand, charged membranes consist of a charge (negative or positive) and
may be porous or dense depending upon the application. Again, the separation
mechanism is diffusion and selectivity based upon the charges present on the
membrane and feed particles. Electrodialysis is the most common example to use
charged membranes.
Microfiltration membrane separations are mainly used for separation, removal,
and concentration of cells and bacteria. Microfiltration membranes are being used for
retains cells and cell debris while allowing proteins and other small solutes to pass
into filtrate [4]. These are used for the removal of contaminants and particulates from
solutions in advance of chromatographic processing and for the clarification of
monoclonal antibody solutions. The microfiltration membranes are especially sterile
filtrations, and they do not concern the quality of the product or solutions. Sterile
membrane processes are the most important from an economical point of view
[7]. Ultrafiltration is extensively applied in biopharmaceutical industries to concentrate and diafilter biological particles, commonly proteins. The membrane selection
generally depends on the cleanability and compatibility. Ultrafiltration membranes
are typically used in cross-flow filtration devices. Membranes are used extensively
throughout the production, purification, and formulating biotechnological products.
Ultrafiltration membranes are used when there is requirement of high retention of
protein and other big size molecules (macromolecules) and used for highperformance tangential flow filtrations (HPTFF) [4]. Membrane chromatography
modules are the new technology in the field of pharmaceuticals. Membrane chromatography can be used for purification of products and materials, e.g., the separation of endotoxins from raw materials before using them in downstream processing.
The removal rates of these membranes depend on adsorptive and size-based retention mechanism [8]. Diafiltration and ultrafiltration are used for removal of thymidine and glycine. Virus filtrations used to protect cell cultures and introduction of
viral contaminants into medical raw materials [4].
Asymmetric membranes consist of two layers of different thickness, pore sizes,
and porosity [1]. The top layer is a dense membrane with thickness in the range of
0.1–0.5 μm. In contrast, the bottom layer consists of a porous membrane of thickness
in the range of 50–150 μm. The top dense layer offers selectivity, and strength is
given by the porous bottom layer [6, 9]. The bottom layer is kept porous so as to
reduce the flux resistance. The asymmetric membranes are named differently based
upon their constituents. For example, layers formed of two different materials are
known as composite membranes. Furthermore, the layers can be optimized independently based upon the requirements. Asymmetric membranes are the most
commonly used membranes in various membrane separation processes due to their
advantages of selectivity, productivity, and life span.
Furthermore, membrane processes are classified based upon their mechanism of
separation as reported in Table 1. The different categories are explained below.
4
R. Singh et al.
commonly used membrane separation processes to employ dense membranes. On
the other hand, charged membranes consist of a charge (negative or positive) and
may be porous or dense depending upon the application. Again, the separation
mechanism is diffusion and selectivity based upon the charges present on the
membrane and feed particles. Electrodialysis is the most common example to use
charged membranes.
Microfiltration membrane separations are mainly used for separation, removal,
and concentration of cells and bacteria. Microfiltration membranes are being used for
retains cells and cell debris while allowing proteins and other small solutes to pass
into filtrate [4]. These are used for the removal of contaminants and particulates from
solutions in advance of chromatographic processing and for the clarification of
monoclonal antibody solutions. The microfiltration membranes are especially sterile
filtrations, and they do not concern the quality of the product or solutions. Sterile
membrane processes are the most important from an economical point of view
[7]. Ultrafiltration is extensively applied in biopharmaceutical industries to concentrate and diafilter biological particles, commonly proteins. The membrane selection
generally depends on the cleanability and compatibility. Ultrafiltration membranes
are typically used in cross-flow filtration devices. Membranes are used extensively
throughout the production, purification, and formulating biotechnological products.
Ultrafiltration membranes are used when there is requirement of high retention of
protein and other big size molecules (macromolecules) and used for highperformance tangential flow filtrations (HPTFF) [4]. Membrane chromatography
modules are the new technology in the field of pharmaceuticals. Membrane chromatography can be used for purification of products and materials, e.g., the separation of endotoxins from raw materials before using them in downstream processing.
The removal rates of these membranes depend on adsorptive and size-based retention mechanism [8]. Diafiltration and ultrafiltration are used for removal of thymidine and glycine. Virus filtrations used to protect cell cultures and introduction of
viral contaminants into medical raw materials [4].
Asymmetric membranes consist of two layers of different thickness, pore sizes,
and porosity [1]. The top layer is a dense membrane with thickness in the range of
0.1–0.5 μm. In contrast, the bottom layer consists of a porous membrane of thickness
in the range of 50–150 μm. The top dense layer offers selectivity, and strength is
given by the porous bottom layer [6, 9]. The bottom layer is kept porous so as to
reduce the flux resistance. The asymmetric membranes are named differently based
upon their constituents. For example, layers formed of two different materials are
known as composite membranes. Furthermore, the layers can be optimized independently based upon the requirements. Asymmetric membranes are the most
commonly used membranes in various membrane separation processes due to their
advantages of selectivity, productivity, and life span.
Furthermore, membrane processes are classified based upon their mechanism of
separation as reported in Table 1. The different categories are explained below.
4
R. Singh et al.