Filter membranes are an essential laboratory equipment that helps alleviate concerns about contaminated water sources. They are used in many important fields, with the main application being water treatment and microbiological technologies. Forget about traditional materials like sand, gravel, or clay—modern technology has introduced various types of filter membranes. These membranes are made from different materials but generally share high durability and efficiency. In this article, we will explore what filter membranes are and the common types available on the market.
Understanding the Concept of Filter Membranes
Image: Advantec filter membranes with high quality.
The concept of filter membranes dates back to the 18th century, but their use was limited and mostly confined to laboratories. Initially, they were used to test the safety of water when impurities were present. However, due to their unreliable performance, slow operation, and high costs, they were not widely used. It wasn't until the 1980s that large-scale use of membranes began with microfiltration and ultrafiltration technologies. Since then, many large companies and factories with experience in membrane production have emerged.
Simply put, a filter membrane is a thin, porous material capable of separating contaminants from water when pressure is applied. They are commonly used across a variety of industries, such as biotechnology, pharmaceuticals, dairy, food and beverages, as well as chemicals and petrochemicals.
Common Types of Filter Membranes in the Market
Image: Common types of filter membranes used in practice.
In practice, there are several ways to classify filter membranes, but the most common method is based on the size of the pore openings in the membrane. According to this classification, there are four main types: microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) membranes. These membranes vary in thickness, whether they are homogeneous or heterogeneous, and whether they are neutral or charged. Some are active, while others are passive. The following details will help you understand the most common types of filter membranes available on the market.
Microfiltration (MF) Membranes
Microfiltration membranes are capable of removing particles larger than 0.08–2 µm and operate within a pressure range of 7–100 kPa. These membranes are used to filter suspended solids, bacteria in water, proteins, and cell debris. They are also used in the final process for filtering fruit juices, milk, wine, beer, and sterile pharmaceutical products. This step serves as a pre-treatment before reverse osmosis and sterilization.
However, these microfiltration membranes typically operate at relatively low pressures, making them unsuitable for many customers. A recent improvement is the biological membrane reactor (MBR), which combines microfiltration and biological reactors for biological treatment.
Ultrafiltration (UF) Membranes
Image: Ultrafiltration membranes are capable of processing tertiary wastewater.
Ultrafiltration membranes can remove particles larger than 0.005–2 µm and operate within a pressure range of 70–700 kPa. This type of membrane is used in similar applications to microfiltration. Some ultrafiltration membranes can also remove high molecular weight dissolved compounds. Furthermore, they can eliminate viruses and certain endotoxins. Currently, ultrafiltration membranes are commonly used for oil filtration, fruit juice filtration, suspended solids, pharmaceuticals, and tertiary wastewater treatment.
Nanofiltration (NF) Membranes
Nanofiltration membranes, also known as “liquid” RO membranes, can remove particles smaller than 0.002 µm. They are used to remove selected dissolved components from wastewater. These membranes are mainly developed as a softening process, providing an alternative to chemical softening.
Likewise, nanofiltration can be used as a pre-treatment before direct reverse osmosis. Their main applications include:
- Reducing particles and microorganisms from RO membranes by removing turbidity and bacteria.
- Preventing expansion by removing hard ions.
- Reducing operational pressure in RO processes by reducing total dissolved solids (TDS).
Reverse Osmosis (RO) Membranes
Reverse osmosis membranes are typically used for desalination. They are commonly used to remove dissolved components from wastewater after advanced treatment with microfiltration. RO membranes exclude ions but require high pressure to produce deionized water (850–7000 kPa). With extremely small pore sizes (about 0.0001 microns), they are capable of removing all organic molecules and viruses. With many superior features, RO filter membranes are highly preferred for producing the purest water.
Conclusion
With the information provided above, Lab Cường Thịnh hopes to have answered the two most fundamental questions: What are filter membranes? And what are the most common types of filter membranes? Each type of membrane has its specific applications, so depending on your intended use, you can select the most suitable product. Please feel free to contact us via our website: labcuongthinh.vn or our hotline: 093.131.9988 for advice and support regarding filter membranes.
