Reversible swelling as a strategy in the development of smart membranes from electrospun polyvinyl alcohol nanofiber mats

Abstract

This work presents an electrospun nanofibrous membrane for water treatment, designed to reduce its pores through polymer swelling to retain contaminants, and after that, reopening them for easy cleaning. It consists of a polyvinyl alcohol (PVA) mat crosslinked with a natural agent to avoid water solubility but allow a high swelling of its nanofibers. Then, when the membrane is brought into contact with water, a transitory state occurs during which nanofibers increase their diameter 68%, closing the pores between them. For studying the swelling reversal effect, distilled water filtering was used observing a decrease in the permeate flow over time until a steady state is reached. This phenomenon is explained by the closure of pores, and it is described with a fouling model widely used in the literature. Thanks to this decrease in the pore size, the membrane achieves a rejection rate much higher than conventional PVA electrospun membranes, being capable to retain 20 nm nanoparticles with a rejection rate up to 99%. Swelling is reversible through a simple drying process, which allows reopening the pores and cleaning the fouling easily. Both the membrane and its use strategy extend the capacity of electrospun mats in a sustainable way.