Fabrication and characterization of polyethersulfone nanocomposite membranes for the removal of endocrine disrupting micropollutants from wastewater. Mechanisms and performance

Abstract

The addition of small amounts of single walled carbon nanotubes (SWCNT) to polyethersulfone (PES) membranes improves the removal and adsorption of endocrine disrupting micropollutants (bisphenol A and nonylphenol). These small amounts of added SWCNT also reduce reversible and irreversible fouling. The isoelectric point of the SWCNT containing membranes decreases when the content of nanotubes increases with more negative charges at alkaline pH.Increasing nanotube loads into PES membranes makes them slightly more hydrophobous empowering the adsorption of bisphenol and nonylphenol, that are also hydrophobous, and making adsorption a key factor in the removal of these micropollutants. Moreover, the increasing voids generated by higher contents of SWCNT increase the adsorption surfaces. An increase in the transmembrane applied pressure decreases the removal and more steeply for the membranes containing more SWCNT most likely because high pressures increase sweeping and disturb adsorption on the inner surfaces.Higher porosities (or equivalently smaller effective membrane thickness), leading to higher water permeabilities, are also obtained for more loaded membranes. Too high SWCNT contents lead to a saturation and decrease of removal probably because high porosities lead to a decrease in adsorption due to both a decrease in the available surface and a clearing out due to convection through the membrane.