Abstract
The advancement in membrane technologies is driven by the development of membrane fabrication techniques and material studies. Nowadays, there are many fabrication techniques and materials available to produce membranes with characteristics that are ideal for specific applications. In this chapter, some fabrication methods are discussed for the three most widely used membrane types, i.e. the polymeric, ceramic, and metallic membranes. Each type of membrane possesses certain advantages and disadvantages attributed to the membrane structural properties as a result of the fabrication method. The choice of method and material are the two important aspects that determine membrane performance and efficiency. The membrane performance indicator is generally measured from the flux, rejection factor, and ability to withstand extreme chemical and physical conditions. Furthermore, the fabricated membranes are further assembled into a complete unit of membrane system called the membrane modules, namely tubular, plate-and-frame, spiral-wound, capillary, and hollow fibre.
TopIntroduction
Membrane fabrication is a sophisticated area in the membrane field comprising of various techniques that gives the different characteristics of the membrane. Most synthetic membranes are made from polymers, some incorporated ceramics, metals etc. to enhance the properties of the membrane for a specific application. In the scope of water and wastewater treatments, microfiltration, ultrafiltration, nanofiltration, reverse osmosis, and membrane distillation are the most widely used membrane technologies in these areas. Table 1 shows some examples of the fabrication methods and polymers used for the preparation of polymeric membranes for membrane-based water and wastewater treatment processes.
Table 1. Examples of fabrication methods and polymers used for the preparation of polymeric membranes widely used in water and wastewater treatments
| Membrane Technology | Fabrication Methods | Polymers Used in Fabrication Process | Average Membrane Pore Size |
| Microfiltration | • Phase inversion
• Stretching
• Track-etching | • Polyvinylidene fluoride (PVDF)
• Poly(tetrafluoroethylene) (PTFE)
• Polypropylene (PP)
• Polyethylene (PE)
• Polyethersulfone (PES)
• Polyetheretherketone (PEEK) | 0.1 – 10 µm |
| Ultrafiltration | • Phase inversion
• Solution wet-spinning | • Polyacrylonitrile (PAN)
• PES
• Polysulfone (PS)
• Polyethersulfone (PES)
• Poly(phthazine ether sulfone ketone) (PPESK)
• Poly(vinyl butyral)
• PVDF | 1 – 10 nm |
| Nanofiltration | • Interfacial polymerization
• Layer-by-layer deposition
• Phase inversion | • Polyamides
• Polysulfones
• Polyols
• Polyphenols | 1 – 10 nm |
| Reverse osmosis | • Phase inversion
• Solution casting | • Cellulose acetate/triacetate
• Aromatic polyamide
• Polypiperzine
• Polybenziimidazoline | 3 – 5 Ǻ |
| Membrane distillation | • Phase inversion
• Stretching
• Electrospinning | • PTFE
• PVDF | 0.1 – 1 µm |
Source: (Lalia et. al, 2013)
Key Terms in this Chapter
Fabrication Technique: Methods used to produce membrane which comprised of several steps which can be achieved through mechanical, chemical, or combination of both processes.
Configurations: Particular arrangement of membrane’s geometric module.
Membrane Material: Material or ‘ingredient’ used to produce membrane, which is primarily from the polymer (organic), ceramic (inorganic), metal (inorganic), or combinations of materials in the fabrication of composite membrane.
Membrane: A thin sheet of permselective barrier that separates two phases.
Ceramic: Solid material made from clay which is used to produce a thin sheet of the membrane by sintering at high temperature.
Module: A unit of membrane ‘cell' which are made from membranes, membrane housing compartment, an inlet(s) and outlet(s).
Metal: Solid material typically having the characteristics of hard, malleable, shiny, ductile, and good electrical and thermal conductivity, such as palladium, silver, gold etc.
Polymer: Chemical compound of large molecules formed by polymerization of repeating structural units known as the monomers.