Cellulose acetate membranes are used in cold sterilization and ultrafiltration procedures due to their ability to allow water passage while preventing salt permeation. They are composed of cellulose and acetyl groups and have an asymmetrical structure. They are useful for filtering organic compounds and holding proteins for recovery, but are limited in their ability to withstand extreme pH levels and imaging techniques. They were once used as films but tend to degrade when exposed to acids or extreme heat.
Cellulose acetate membranes are film layers of an ester, composed of the cellulose of the plant fiber and a variable number of acetyl groups. These membranes allow the passage of water and prevent salts from permeating them, therefore they are used in cold sterilization and ultrafiltration procedures. Cellulose is a chain of linked glucose molecules and acetyl groups are small structures of carbon, hydrogen and oxygen molecules. These membranes are described as asymmetrical, because they have a dense skin on their surface with a more porous layer underneath. Both the leather and the support are composed of chemically identical cellulose acetate, even if their external structure and appearance are different.
Generally, cellulose acetate membranes are composed of a fibrous cellulose polymer, with each cellulose molecule bonded to two or three acetyl groups from a source such as acetic acid. These membranes might have only diacetyl or triacetyl groups bonded to the cellulose, or they might have a mixture of the two. After the cellulose and acetic acid have been combined, along with a catalyst such as sulfuric acid, the resulting film is then placed in a water bath, which washes off the excess acetic acid and creates the asymmetrical layers in the membrane. Although cellulose acetate membranes are inexpensive to manufacture and can easily filter chlorinated water, unlike other types of membranes, they are limited in their ability to withstand extreme hydrogen (pH) levels.
In addition to effectively filtering salts, cellulose acetate membranes do not bind organic molecules easily and are quite strong, so they are an excellent choice for filtering organic compounds such as proteins and enzymes in a laboratory setting. The strength of these membranes makes them useful for holding proteins for recovery during experiments or processes where these substrates need to be recovered which is why they are used as food analysis products and environmental monitoring products. The properties of cellulose acetate membranes can be limiting in laboratory techniques requiring imaging, however, because the porous underside of cellulose acetate tends to absorb liquid and become transparent. This means it can be difficult to determine how well these membranes adhere to other surfaces or to substrates such as proteins.
The transparency and strength of cellulose acetate membranes are two qualities that led to their use as films in the 1930s. These membranes, however, tend to degrade when exposed to acids or extreme heat, leading to unusable films. For this reason cellulose acetate is no longer a common film component, but has continued to be used in ultrafiltration.
Protect your devices with Threat Protection by NordVPN
