Introduction
Flux and transmembrane pressure (TMP) are two of the most critical parameters in membrane filtration. They determine filtration speed, efficiency and filter lifetime. Understanding the relationship between flux and TMP helps users optimize filtration processes and avoid membrane fouling.
1. What Is Flux?
Flux is the rate at which liquid passes through the membrane surface. It is usually expressed as flow per unit area.
- High flux = faster filtration
- Low flux = slower filtration or fouling occurring
- Flux depends on pressure, membrane properties and liquid characteristics
2. What Is Transmembrane Pressure (TMP)?
TMP refers to the pressure difference across the membrane. It is the driving force that pushes fluid through membrane pores.
- TMP increases when resistance rises
- High TMP may indicate fouling or clogging
- TMP must stay within filter’s operating limits
3. Relationship Between Flux and TMP
In an ideal clean membrane, flux increases proportionally with pressure. However, in real filtration applications, fouling changes this relationship over time.
| Filtration Stage | Flux Behavior | TMP Behavior |
|---|---|---|
| Initial Clean Stage | Flux increases linearly with pressure | Low and stable |
| Intermediate Stage | Flux gradually decreases | TMP slowly increases |
| Fouled Stage | Flux no longer increases even with higher pressure | TMP rises sharply |
4. Causes of Flux Decline
Flux decline occurs when resistance builds up on or inside the membrane.
- Cake Layer Formation: Particles accumulate on the surface.
- Pore Blocking: Solids or colloids enter and obstruct pores.
- Adsorption: Proteins or polymers attach to membrane material.
- Gel Layer Build-Up: High-viscosity materials form a dense layer.
5. How to Optimize Flux and TMP
Proper process design helps maintain stable flux and ideal TMP.
- Use prefiltration to reduce particle load.
- Operate at the recommended pressure range.
- Choose low-protein-binding membranes for biological fluids.
- Increase membrane surface area to lower pressure drop.
- Perform flushing or cleaning when TMP rises.
6. Importance in Different Industries
Flux and TMP control is essential in the following applications:
- Pharmaceuticals: Sterile filtration and protein solutions.
- Food & Beverage: Juice clarification and microbial reduction.
- Chemical Processing: High-viscosity fluid filtration.
- Water Treatment: Ultrafiltration and microfiltration systems.
Conclusion
Understanding flux and transmembrane pressure is essential for achieving efficient and stable membrane filtration. Proper control of TMP and optimization of filtration conditions help prevent fouling, reduce costs and improve overall process performance.
Purchase Suggestion
We supply a full range of membrane filter cartridges and capsules designed for stable flux and controlled TMP performance. Contact our technical team to select the right solution for your process.