Binding characterization of sulfonamide antibiotics and polycyclic aromatic hydrocarbons to micelles using semi-equilibrium dialysis (SED) and 1H NMR spectroscopy

Abstract

Micellar enhanced ultrafiltration (MEUF) has been shown to be an effective removal technique for a variety of trace contaminants in wastewater, especially for low molecular weight organic contaminants. In MEUF, contaminants first partition into surfactant micelles prior to removal by ultrafiltration, where the contaminants are below the molecular weight cut-off of the ultrafiltration membrane but the micelles are above the cut-off. To predict the removal efficiency of MEUF, it is important to measure of extent to which a species will bind to a micelle as well as to develop an understanding of the dynamics of the binding interactions. Herein, we report micellar binding constants for a series of sulfonamide antibiotics (sulfadoxine, sulfathiazole, sulfamethoxazole, sulfamerazine, sulfadiazine, sulfamethazine, sulfacetamide, sulfaguanidine, and sulfanilamide) with CTABr micelles, as determined using semi-equilibrium dialysis and 1H NMR methods. We also report the binding constant measurements for polycyclic aromatic hydrocarbons (PAHs), including phenanthrene, naphthalene, pyrene and fluorene, to several micelle types. Unlike the antibiotics, where charge-charge interactions determined binding to CTABr micelles, the neutral PAHs show strong binding with micelles because of hydrophobic interactions. Our results enabled us to develop a relationship between binding constant (Log KB) and Log KOW for both charged and neutral compounds, which will be useful for predicting MEUF performance for removal of organic micro contaminants from wastewater.