Synthesis, Optimization, and Performance Demonstration of Electrospun Carbon Nanofiber–Carbon Nanotube Composite Sorbents for Point-of-Use Water Treatment

Abstract

We developed an electrospun carbon nanofiber-carbon nanotube (CNF-CNT) composite with optimal sorption capacity and material strength for point-of-use (POU) water treatment. Synthesis variables including integration of multiwalled carbon nanotubes (CNTs) and macroporosity (via sublimation of phthalic acid), relative humidity (20 and 40%), and stabilization temperature (250 and 280 °C) were used to control nanofiber diameter and surface area (from electron microscopy and BET isotherms, respectively), surface composition (from XPS), and strength (from AFM nanoindentation and tensile strength tests). Composites were then evaluated using kinetic, isotherm, and pH-edge sorption experiments with sulfamethoxazole (log Kow = 0.89) and atrazine (log Kow = 2.61), representative micropollutants chosen for their different polarities. Although CNFs alone were poor sorbents, integration of CNTs and macroporosity achieved uptake comparable to granular activated carbon. Through reactivity comparisons with CNT dispersions, we propose that increasing macroporosity exposes the embedded CNTs, thereby enabling their role as the primary sorbent in nanofiber composites. Because the highest capacity sorbents lacked sufficient strength, our optimal formulation (polyacrylonitrile 8 wt %, CNT 2 wt %, phthalic acid 2.4 wt %; 40% relative humidity; 280 °C stabilization) represents a compromise between strength and performance. This optimized sorbent was tested with a mixture of ten organic micropollutants at environmentally relevant concentrations in a gravity-fed, flow-through filtration system, where removal trends suggest that both hydrophobic and specific binding interactions contribute to micropollutant uptake. Collectively, this work highlights the promise of CNF-CNT filters (e.g., mechanical strength, ability to harness CNT sorption capacity), while also prioritizing areas for future research and development (e.g., improved removal of highly polar micropollutants, sensitivity to interfering cosolutes).

Emerging investigator series: development and application of polymeric electrospun nanofiber mats as equilibrium-passive sampler media for organic compounds

“…All ENMs were fabricated using a custom-built electrospinning apparatus described in our previous work (Figure S1). 20 Additional details of the polymers, the electrospinning apparatus and synthesis parameters are presented in the Electronic Supplementary Information (ESI).…”

Nanofiber-Based Materials for Persistent Organic Pollutants in Water Remediation by Adsorption

“…Nevertheless, the predominant efficiency of carbon and metal oxide adsorbent surfaces suggests that π-π electron and electrostatic interactions are the most efficient adsorption mechanisms towards selected pesticides, compared to hydrophobic interactions, which by comparison reached average performance when serving as the predominant mechanism at stake [29]. Furthermore, carbon nanofibers were reported to show adsorptive affinity for other contaminants, such as sulfamethoxazole, in a multi-contaminant flow through adsorption test, demonstrating the versatility of carbonaceous adsorbents towards organic molecules with unsaturated bonds such as aromatic rings [39]. Polystyrene molecular imprinted nanofibers showed limited performance against Atrazine and Chlorpyrifos (Table 4, N2 and Table 5, N1).…”

“…Molecular orientation of the contaminant is also considered to prevent size-exclusion effects when one molecule is already adsorbed along a pore wall, as highlighted by the performance comparison of Dieldrin and stereoisomer Endrin adsorption [73]. Adsorbent contact surface area ruled by the nanofiber average diameter impacted on the contaminant capture, with diameters below 150 nm yielding higher performance in the capture of Atrazine [39]. Higher surface specific areas led in general to higher adsorption capacities, provided there was contaminant diffusion along the surface pore channels.…”

Grown Carbon Nanotubes on Electrospun Carbon Nanofibers as a 3D Carbon Nanomaterial for High Energy Storage Performance

“…The production of CFs by electrospinning was established about 10 years ago and has gradually become popular due to their excellent properties. The limitations of the strength, porosity, wettability, conductivity, and surface area of pure CNFs hinder their use as reliable materials for different types of applications . CNFs can be easily obtained by electrospinning of a PAN solution under a specific condition and following carbonisation treatments .…”

“…CNTs are considered to be a promising sorbent in water treatments because both functionalised and non‐functionalised CNTs have been shown to be highly effective sorbents for aquatic pollutants . N‐doped CNTs proved to be better sorbents for π‐donor aromatic compounds ,. CNTs have a remarkable electrical capacitance >158 Fg −1 due to their large surface area and excellent electronic‐ionic conductivity .…”