What is concentration polarization？
During the ultrafiltration process, due to the selective permeability of the membrane, the trapped solute components accumulate on the high-pressure side solution-membrane interface, so the solute concentration on the interface is higher than that of the main solution. This phenomenon is called concentration difference polarization. Concentration polarization has a great influence on the separation effect and process of pressure-driven membrane processes.
What are the hazards of concentration polarization?
1. Concentration polarization increases the solute concentration on the membrane surface, causing an increase in osmotic pressure, thereby reducing the driving force for mass transfer.
2. When the solute concentration on the membrane surface reaches its saturation concentration, a deposition or gel layer will be formed on the membrane surface, increasing the permeation resistance.
3. The formation of a deposited layer or a gel layer on the membrane surface will change the separation characteristics of the membrane.
4. When the organic solute reaches a certain concentration on the membrane surface, it may swell or dissolve the membrane and deteriorate its performance of the membrane.
5. Severe concentration polarization leads to crystal precipitation, blocking the flow channel and deteriorating operation.
How to solve the problem of concentration polarization
1. Strengthen the pretreatment of the feed.
2. Select the appropriate membrane module: module structure; adding turbulator; material and liquid transverse flow direction design; spiral flow.
3. Reasonable process design: pulse flow of material and liquid; increase flow rate.
4. Selection of suitable operating parameters: appropriately increase the temperature of the feed liquid to reduce the viscosity, increase the mass transfer coefficient, etc.