Relationship between the addition of carbon nanotubes and cut-off of ultrafiltration membranes and their effect on retention of microcontaminants

The addition of nanotubes changes the surface properties of the membrane – it affects the charge on the membrane surface, the contact angle, the porosity of the membrane, and thus its effectiveness on the retention of contaminants in water. Depending on the purpose for which the membrane is to be used, as well as the compounds to be retained, various modifications of nanotubes are used – their functionalization with strong acids cause functional groups such as carboxyls, hydroxyls, amines, or amides to appear on the surface of the membrane. In this paper, single-walled carbon nanotubes with carboxyl groups were used with high-purity, large surface area, single-walled nanotubes to test their properties in the removal of microcontaminants. In this work, the participation of nano-tubes in the membrane matrix was combined with surface properties and cut-off measurements of the membrane. However, due to the addition of carbon nanotubes, the adsorption was improved; it also resulted in changes to the hydrophilicity of the membrane, porosity, and charge on its surface. Four substances were used in the study: caffeine, bisphenol A, carbamazepine, and endosulfan.