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Membrane Filtration 101: Flow Rate

When working with a filtration application understanding the filtration flow rate of your membrane filter is important for the accuracy and integrity of your work. But how do you know what the flow rate of a membrane filter is? Different membrane filters have different flow rates and it’s important to know the flow rate of the membrane you’re working with. 

What is Flow Rate?

Flow rate is the rate at which liquid or gas can pass through the membrane filter. This is important to know so that you and your team can determine the speed at which filtration will take place. 

What Factors Affect Flow Rate?

A few different factors in your membrane filter will affect filtration flow rate. 

  • Thickness
  • Porosity
  • Pore Architecture 

How your membrane filter is made will contribute to these factors, as will what material is used for your membrane filter. Knowing what flow rate would work best for your application is important knowing the speed at which the filtration process will happen. But how can you know what the flow rate of a membrane filter is? 

Determining the Filtration Flow Rate of a Membrane Filter

Filtration flow rate can be determined by testing the speed of the flow rate with a proper liquid. As “water-loving” filters, hydrophilic filters are tested with water. As “water-hating” filters, hydrophobic filters are tested with alcohol. A membrane used for air filtration can be filtered with dry air or dry nitrogen. 

Testing with Liquid Filtration 

Testing with liquid filtration can be done using the following method:

  1. Place the membrane filter in the filter holder. 
  2. Add the volume of the liquid needed to the membrane. 
  3. Use a vacuum to pull the liquid through the filter. 

It is important to note that water or alcohol may not be the best liquids to use for testing. Factoring in the viscosity of the liquid is also important when working with serums, blood, or any other thicker liquids.

Testing With Gas Filtration 

Testing with gas or air filtration is a slightly more complicated method and several other factors must be considered. 

  • Sterility 

Sterility is important to consider in filtration flow rate of gasses because hydrophobic membrane filters and hydrophilic membrane filters retain bacterial material differently. Knowing the exact membrane filter needed is absolutely necessary.

  • Pore Size 

A membrane with a larger pore size would be used in a more general application allowing for a faster flow rate. 

Any and all changes to the environment where testing is done has to be considered. Even a slight variation in pressure could throw results off. 

The Tools You Need

Here at Tisch Scientific we have a wide variety of membrane filters for your every use and a friendly customer service team to answer all of your questions and a helpful guide for choosing membrane filtration material so you can choose the best membrane for your application. 

  • Capsule Filters

Our capsule filters are extremely durable and easily transportable. Membrane filters are often fragile and could require extreme caution in handling, but our capsule filters are protected making them easier and safer to handle. 

  • Syringe Filters

Our syringe filters are available in a variety of diameters, materials, and non sterile vs sterile options to give you and your team as much variety as possible 

  • Disk Filters

A disk filter is a great alternative to a syringe filter when dealing with a higher volume of test material. 

  • Membrane Roll Stock 

We have a wide variety of membrane roll stock that can cut to you and your team’s precise measurements. 

Whatever the ideal filtration flow rate of your project is, we have a membrane filter to serve you and your team’s purposes. 

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