Polymeric Electrospun Nanofiber Composites as Fast Equilibrium Passive Samplers: Integration of Surface Functionalities and Porosity to Improve Organic Chemical Uptake

Abstract

Despite advances in passive sampling technologies, challenges persist in improving the selectivity, sensitivity, and response time. This study presents the fabrication and evaluation of electrospun nanofiber mats (ENMs) embedded with carbon nanotubes (CNTs), with and without surfactant modifications, as fast equilibrium passive sampling materials. We investigated the sorption and desorption behaviors of four common surface water contaminants: atrazine, metolachlor, diuron, and 2,4-dichlorophenoxyacetic acid (2,4-D). We demonstrated that ENMs modified with the cationic surfactant tetrabutyl ammonium bromide (TBAB) exhibited higher sorption than their unmodified PAN/CNT counterparts for all species, including anionic 2,4-D, for which uptake increased by up to 45-fold. ENMs modified with sodium dodecyl sulfate (SDS), a leachable porogen, exhibited greater surface area and improved sorption of atrazine, metolachlor, and diuron, resulting in an 8- to 40-fold increase in uptake. Across formulations, sorption to CNT-containing ENMs was largely reversible, with stronger, more irreversible binding at higher CNT wt %. The optimal formulation of PAN/10 wt % COOH-CNT/20 wt % SDS exhibited rapid, reversible sorption of atrazine, with 96% desorption after 48 h and fast equilibrium in response to changing solution concentrations. Field deployment in an agriculturally impacted creek showed good agreement with grab samples for atrazine (with ENM-derived concentrations within 5–40% of grab sample-derived concentrations) but overestimated metolachlor concentrations (with ENM-derived concentrations up to 500% greater than grab sample-derived concentrations), which we attribute to metolachlor's greater hydrophobicity, resulting in more irreversible binding to CNTs. Although further refinement is needed, these findings highlight the potential of ENM-CNT composites as novel materials for use as fast equilibrium passive samplers, especially for atrazine, and underscore the importance of tailoring the ENM composition to target specific micropollutants.