Relationship between pore size and filtration rate

Explain the relationship between pore size and filtration rate? | Yahoo Answers

relationship between pore size and filtration rate

These techniques are based on a well-known relationship between a size of a pore and the associated pressure drop necessary to evacuate a. MF (microfiltration) – Pore size generally spans micron to 1 micron, the relation between the gas permeation rate and the TMP, pore size. i don't know if this has greater meaning than what i am thinking, but pores are " holes" traditionally, and filtration is a means of sifting in a sense.

Describe one way in which osmosis is similar to simple diffusion and one way in which it is different. Osmosis is similar to simple diffusion in that it is a passive diffusion and moves down the concentration gradient.

It is different because Osmosis takes place when there is a difference in concentration gradient across a selectively permeable membrane.

Classification of membranes according to pore size - OnlineMBR

Solutes are sometimes measured in milliosmoles. Water moves though most membranes easily and moves when there is a change in water concentration between two sides of membrane; meaning that water is chasing the concentration gradient. The conditions were 9 mM albumin in the left beaker and 10 mM glucose in the right beaker with the MWCO membrane in place. The osmotic pressure for both was L.

Even with a high osmotic pressure albumin was still unable to pass though the MWCO membrane. We predicted that with a higher osmotic pressure both would diffuse though the membrane, but glucose was the one molecule that was able to diffuse through the membrane. Explain in your own words why increasing the pore size increased the filtration rate.

relationship between pore size and filtration rate

Use an analogy to support your statement. By increasing the pore size in the membrane the filtration rate increased because more molecules were able to diffuse though the larger pres faster than smaller pores.

relationship between pore size and filtration rate

Our prediction was that the rate of filtration would increase because the pores were larger, allowing more molecules to pass the pores. In the kidneys, the membrane pores are larger which allows glucose and urea to pass though the pores. Which solute did not appear in the filtrate using any of the membranes?

Measuring these characteristics allows prediction of the performance of the filtration media arising from these properties. Pore size distribution curve describing amount of through pores of different sizes present Measurement of Through Pores in Filtration Media A number of methods are routinely used in the development and product control activities associated with the manufacture of filtration media.

Microscopy provides a direct assessment of the pore structures present in the media, but each image is localized; therefore, obtaining a representative assessment of the entire material can be quite time consuming. Performance, or challenge, tests provide a direct assessment of the media performance but are also very labor and time intensive. For some time now, both Bubble Point Tests and Capillary Flow Porometry have been used to assess the through pores present in filtration media.

These techniques are based on a well-known relationship between a size of a pore and the associated pressure drop necessary to evacuate a wetted fluid from that pore. The Washburn Equation based on the Young-Laplace Equation defines the relationship between this pressure drop and the size of the capillary, or pore, as follows: Knowing how the fluid wets the material, the surface tension of the fluid, and an estimate of the pore geometry provide the ability to correlate pressure and pore size.

These techniques are simple, fast, and accurate assessments of through pores in filtration media, and therefore ideally suited for both research and product control purposes. A Bubble Point Test involves covering a sample of filtration media with a fluid, classically water or isopropyl alcohol. An air stream is fed to the membrane from the opposite side and slowly pressurized. The pressure of the air stream is increased until the largest through pore present expels its fluid and allows air to flow through the membrane, which is observed in the fluid as an air bubble.

The size of the largest through pore defines the size of the largest particle, which will pass through the membrane. This test is also useful in understanding whether or not there are unforeseen defects in the membrane. This test has been used for product control purposes due to its speed and consistency in assessing the maximum pore size.

In addition, automated instruments greatly reduce the amount of uncertainty in the measurement compared with manually operated versions. Unfortunately, the amount of information this simple test provides is fairly limited. In practice there are an infinite number of membrane pore structures with the same maximum pore size, which exhibit vastly different filtration performance and flow through characteristics.

To understand how many through pores of different sizes are present in a filtration medium an assessment of the pore size distribution must be made. Rejection efficiencies of small organics without charge such as methanol, ethanol, propanol, acetone, etc.

Explain the relationship between pore size and filtration rate?

A few theoretical models exist to describe the phenomena and are described here. Classification of membrane filtration as a function of molecular weight cut off and pore size Koch Membrane Systems.

relationship between pore size and filtration rate

MF and UF typically run at low pressure, e. The following diagram shows the solutes that are rejected by each membrane. As discussed hereregardless of the membrane pore size, actual solute sizes rejected by MF and UF are approximately same since the cake layer formed on membrane surface acts as a dynamic membrane in actual filtration process.

However, tiny molecules with low molecular weight perhaps less than a few tens of thousand Dalton can be better rejected by UF than by MF regardless of the existence of dynamic membrane. NF branes and RO membranes are used to remove trace organic molecules and ions in water filtration. RO membranes reject mono-valent ions at It is noteworthy that NF and RO are not solely rely on the size exclusion mechanism, but also rely on the solution-diffusion mechanism that essentially affected by how easily the solutes can dissolve in the membrane material.

Since low-molecular-weight charge-neutral solvents, such as methanol, ethanol, acetone, etc.