Electrospun Nanofiber Membrane: An Efficient and Environmentally Friendly Material for the Removal of Metals and Dyes

Abstract

With the rapid development of nanotechnology, electrospun nanofiber membranes (ENM) application and preparation methods have attracted attention. With many advantages such as high specific surface area, obvious interconnected structure, and high porosity, ENM has been widely used in many fields, especially in water treatment, with more advantages. ENM solves the shortcomings of traditional means, such as low efficiency, high energy consumption, and difficulty in recycling, and it is suitable for recycling and treatment of industrial wastewater. This review begins with a description of electrospinning technology, describing the structure, preparation methods, and factors of common ENMs. At the same time, the removal of heavy metal ions and dyes by ENMs is introduced. The mechanism of ENM adsorption on heavy metal ions and dyes is chelation or electrostatic attraction, which has excellent adsorption and filtration ability for heavy metal ions and dyes, and the adsorption capacity of ENMs for heavy metal ions and dyes can be improved by increasing the metal chelation sites. Therefore, this technology and mechanism can be exploited to develop new, better, and more effective separation methods for the removal of harmful pollutants to cope with the gradually increasing water scarcity and pollution. Finally, it is hoped that this review will provide some guidance and direction for research on wastewater treatment and industrial production.

Keywords: electrospinning; metals and dyes; nanofiber membrane.

Figure 1

Preparation and structure of ENMs.

Figure 2

(a) SEM and TEM images of NFM at different voltages (the inset is the hole diameter distribution map). (b) SEM and TEM images of ENM at different flow rates (the inset is the pore diameter distribution map). Reprinted from ref. [39].

Figure 3

The effect of the distance from the tip to the collector on the ENM (a–e) at distances of 100 mm, 150 mm, 200 mm, 250 mm, and 300 mm, respectively. The bar scale in (a–e) is 10 μm and in (a′–e′) is 100 nm. Reprinted with permission from ref. [40]. Copyright 2019 Elsevier.

Figure 4

SEM images of NEM with different morphologies, (a) Core-shell structure; (b) Hollow structure; Reprinted with permission from ref. [44] Copyright 2017 Elsevier. (c) Porous structure; (d) Aligned structure; Reprinted with permission from ref. [34] Copyright 2020 Elsevier; (e,f) porous PAN micro/nanofiber membrane Reprinted with permission from ref. [43]. Copyright 2018 Elsevier.

Figure 5

(a) Pure PAN nanofiber; (b) PAN/Ppy nanofiber; (c) PAN/Ppy nanofiber; (d) SEM and TEM image of PAN/Ppy nanofiber membrane. Reprinted with permission from ref. [50]. Copyright 2013 Elsevier.

Figure 6

(a,b) SEM photos of CNF; (c,d) SEM photos of p-CNF; (e,f) the diameter distribution diagrams of CNF and p-CNF, respectively. Reprinted with permission from ref. [53]. Copyright 2019 Elsevier; (g) PAN; (h) porous PAN; (i) SEM and TEM images of porous PAN/GO nanofibers; (i–l) porous structure on the shell and core of porous PAN/GO nanofibers (inset: cross section membrane performance). Reprinted with permission from ref. [54]. Copyright 2020 Elsevier.

Figure 7

Effect of initial concentration of (a) Pb (II), (b) Cd (II), and (c) Cr (VI) ions on the adsorption of metal ions using PAN/chitosan/UiO-66-NH₂ nanofibrous adsorbent. Reprinted with permission from ref. [64]. Copyright 2019 Elsevier.

Figure 8

(a) The effect of the pH value of the Cr (VI) aqueous solution on the adsorption capacity of PAN/GO porous nanofibers; (b) zeta potential of porous PAN/GO nanofibers in aqueous solutions with different pH values; (c) The form of Cr (VI) at pH from stepwise from 1–10. Reprinted with permission from ref. [54]. Copyright 2020 Elsevier.

Figure 9

The effect of PAN/chitosan/UiO-66-NH₂ nanofiber layer thickness on the removal of (a) flux and (b) metal ions using PVDF/PAN/chitosan/UiO-66NH₂ nanofiber membrane, (c) permeation flux, and (d) removal efficiency of metal ions in the nanofiber membrane within 24 h. Reprinted with permission from ref. [64]. Copyright 2019 Elsevier; (e) regenerating metal on the PES/PVA/chitosan/A-Fe₃O₄-2 nanofiber membrane ion recovery rate; and (f) the influence of water flux. Reprinted with permission from ref. [100]. Copyright 2018 Elsevier.

Figure 10

(a) Schematic diagram of functionalized PAN nanofibers; (b) adsorption of functionalized nanofiber membranes. Reprinted with permission from ref. [105]. Copyright 2018 Elsevier; (c) synthesis of PDA@DCA–COOH film. Reprinted with permission from ref. [12]. Copyright 2020 Elsevier.