Changes in temperature do affect the effectiveness of filter membranes. The effect of temperature on filtration membrane performance depends on the specific membrane material and the nature of the filtration process. Several factors contribute to this effect:
1. The effect of thermal expansion and contraction. When the temperature changes, the filter material will expand and contract with heat, which may change the pore size distribution, thereby changing the filtration efficiency. For example, an increase in temperature can cause the pores to expand, allowing more particles to pass through, which can lead to a decrease in filter efficiency. Also, when the temperature is lowered, the pore size shrinks, the loss of the filter becomes larger, and the effect of the filter is also affected.
For example, among all membranes, the temperature range of PTFE film is from minus 190 degrees to 250 degrees, and its melting point is 327 degrees. The cooking temperature of the general induction cooker is only 130 to 240 degrees, so the temperature change of the PTFE membrane material is the most stable among all the membranes.
2. Fluid viscosity differences caused by temperature changes, temperature changes will change the viscosity of the filtered fluid. As the temperature increases, the viscosity of the fluid generally decreases, which causes the flow rate through the membrane to increase. This affects the separation efficiency and overall performance of the filtration process.
As far as the filter membrane of nylon material is concerned, ordinary PA nylon can withstand a temperature of 90-120 degrees, and can withstand a temperature of 150 degrees under the condition of adding glass fiber. The highest performance of high-temperature resistant nylon can reach more than 200 degrees. For the membrane, it is necessary to combine the material selection of nylon according to the demand.
3. The generation of membrane fouling, temperature will affect the speed of membrane fouling, when particles, molecules or organisms accumulate on or in the membrane, membrane fouling occurs, which hinders the flow and reduces the filter efficiency. Higher temperatures can increase the rate of fouling by promoting the growth of microorganisms or increasing the solubility of certain foulants. High temperature will accumulate salts or other particles in the liquid, forming stubborn dirt.
4. Changes in chemical stability caused by excessive temperature. Some filter membrane materials may be more sensitive to temperature changes than others, and their chemical stability will be affected. For example, high temperatures can cause some polymers to degrade, resulting in loss of mechanical strength and reduced filtration performance.
5. Diffusion and convection rate. Changes in temperature will affect the diffusion and convection rate of particles and molecules in the fluid, thereby affecting the separation efficiency of the membrane.
Through the above comprehensive analysis, the specific influence of temperature on the filtration membrane depends on factors such as membrane material, fluid characteristics and the nature of the particles to be filtered. Therefore, it is crucial to consider the expected operating temperature range of the filter membrane and select a suitable membrane material that will maintain its performance within this range.
Citation
1. Zhang, X., Zhao, Y., Chen, V., & Chen, G. (2018). Membrane fouling control in ultrafiltration: A review. Journal of Membrane Science, 549, 101-114.
2. Sodaeizadeh, H., Gohari, R. J., & Ranaei, M. (2014). Effects of temperature on performance of microfiltration membrane in treatment of oily wastewater. Journal of Environmental Health Science and Engineering, 12(1), 104.
3. Ahmad, A. L., Low, S. C., & Ooi, B. S. (2006). Effect of temperature on performance of nanofiltration membrane for treatment of oily wastewater. Journal of Membrane Science, 276(1-2), 152-160.
3. The generation of membrane fouling, temperature will affect the speed of membrane fouling, when particles, molecules or organisms accumulate on or in the membrane, membrane fouling occurs, which hinders the flow and reduces the filter efficiency. Higher temperatures can increase the rate of fouling by promoting the growth of microorganisms or increasing the solubility of certain foulants. High temperature will accumulate salts or other particles in the liquid, forming stubborn dirt.