Pore Fouling in Azo-Dye-Functionalization Membranes*

The textile dye industry is one of the largest polluters of freshwater on Earth, contributing to the nearly 2.8 x 10⁵ tons of synthetic textile dyes discharged into the environment annually. While this specific type of pollution occurs in specific areas around the World, the effects are of global concern. Recent research shows that polycarbonate filters functionalized with anionic azo dyes have the potential to enhance dye rejection, leaving nearly completely decolorized water after filtration in specific instances. This process, referred to as azo-dye-functionalization, provides an elegant solution to water pollution by textile dyes, demonstrating that the textile dyes, hence the contaminants themselves, are part of the solution. By using data for an anionic direct dye series at 1000µM and models that already exist in literature, this work aims to understand and highlight the pore fouling that occurs at the polycarbonate surface during the functionalization process. By keeping the charge of the dyes fixed, the dependency of charge is eliminated, allowing for the examination of structure and functional end groups effect on pore fouling. To test for functionalization, direct red 28 and direct red 81 were cycled from low concentration to high concentration and back. Both showed hysteresis (changes) in the data as the concentration was increased and then decreased, with direct red 28 having larger hysteresis than direct red 81. In the end, this research paves the way for the overall goal of water purification of textile dyes and other charged contaminants.