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

TL;DR

Researchers developed electrospun nanofiber composites that can quickly and effectively sample organic pollutants in water, with some formulations showing up to 45-fold better uptake.

Contribution

The study introduces electrospun nanofiber composites with tailored surface and porosity features for enhanced and rapid passive sampling of water contaminants.

Findings

CNT-containing ENMs showed higher sorption of contaminants like atrazine and 2,4-D compared to unmodified materials.

Surfactant-modified ENMs increased uptake of specific pollutants by up to 40-fold.

Field tests showed good agreement with grab samples for atrazine but overestimated metolachlor due to stronger binding.

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.

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