8/7/2020 9:33:22 PM

Manufacturing Membranes with Eastman™ Cellulose Acetate

Membrane Filtration

Membrane filtration is the process of separating one material from another by use of a semi-permeable membrane.  It is used everyday in many critical applications including water treatment, beverage clarification, natural gas separation, HVAC, and countless others.  The membranes used in filtration must provide a balance of durability, efficiency, and efficacy; therefore, choosing the proper material for the membrane poses a unique challenge.

Choosing Membrane Materials


There are a variety of different polymers that can be used for the manufacture of membranes including polyamides, fluorinated polymers like PVDF, polysulfones, and cellulosic derivatives like cellulose acetate.  The properties of these polymers vary and the intended use of the membrane should be carefully considered when choosing a membrane material.  The table below lists polymers used to make membranes and compares important properties for membrane performance, efficiency, and durability.

 

Why Use Eastman™ Cellulose Acetate


In comparing the materials above we can see that cellulose derivatives have an advantage over the others in terms of cost and oxidant resistance.  Another important attribute to note is that cellulose derivatives are hydrophilic.  This allows for better contact with aqueous feed streams and provides increased resistance to fouling.  In addtition, cellulose acetate can withstand harsh cleaning envrionments that polymers like PVDF cannot.  It is for these reasons that cellulose acetate is used for membrane filtration applications where fouling is a concern.  Cellulose acetate also has an inherent selectivity for CO2 and CH4.  This is why it is still the leading polymer for spiral wound and hollow-fiber membrane modules used in natural gas filtration.  In addition, all Eastman™ membrane materials are available with FDA approval for food contact in food and beverage processing operations making them an ideal choice for RO and FO membranes used to clarify or concentrate beverages like juice, milk, beer, and wine.  See the table below for available Eastman™ membrane material grades of cellulose acetate.

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