PVDF-Based Piezo-Catalytic Membranes-A Net-Zero Emission Approach towards Textile Wastewater Purification

Abstract

Among the various water purification techniques, advancements in membrane technology, with better fabrication and analysis, are receiving the most research attention. The piezo-catalytic degradation of water pollutants is an emerging area of research in water purification technology. This review article focuses on piezoelectric polyvinylidene difluoride (PVDF) polymer-based membranes and their nanocomposites for textile wastewater remediation. At the beginning of this article, the classification of piezoelectric materials is discussed. Among the various membrane-forming polymers, PVDF is a piezoelectric polymer discussed in detail due to its exceptional piezoelectric properties. Polyvinylidene difluoride can show excellent piezoelectric properties in the beta phase. Therefore, various methods of β-phase enhancement within the PVDF polymer and various factors that have a critical impact on its piezo-catalytic activity are briefly explained. This review article also highlights the major aspects of piezoelectric membranes in the context of dye degradation and a net-zero approach. The β-phase of the PVDF piezoelectric material generates an electron-hole pair through external vibrations. The possibility of piezo-catalytic dye degradation via mechanical vibrations and the subsequent capture of the resulting CO₂ and H₂ gases open up the possibility of achieving the net-zero goal.

Keywords: PVDF; degradation; net-zero emissions; piezo-catalysis; piezoelectric materials; reactive oxygen species (ROS).

Figure 1

Piezoelectric material under external vibration with separate electron e⁻ and hole h⁺; this separation results in the formation of reactive radicals and causes piezo-catalytic dye degradation.

Figure 2

Piezo-catalytic degradation by carbon-based nanocomposites.

Figure 3

(a) α-phase PVDF and (b) β-phase PVDF transformation.

Figure 4

SEM images of (a) pristine and (b) composite PVDF membranes. (c,d) Piezo-catalytic degradation of dyes by PVDF composite films.

Figure 5

PVDF-based textiles as piezoelectric materials [90]. (a) PVDF NFs on top of PET fabric to obtain a highly flexible, tailorable, breathable, and washable fabric, designed by slicing two PET materials in half and placing a conductive fabric between them. (b) A piezoelectric and triboelectric hybrid nanogenerator (PTHNG) fabricated entirely of nanofibers by electrospinning PVDF and silk fibroin nanofibers on conductive textiles. (c) A piezoelectric nanogenerator with ZnO nanowires and a PVDF polymer as a piezoelectric layer. (d) A triaxial braided PVDF yarn harvester made by braiding nylon yarns and coated with a conductive and piezoelectric PVDF melt. (e) An elastic core with a piezoelectric polymer PVDF on a helical structural fiber-based PENG. This image is a modified version of an image from an article originally published in the Journal of Advanced Materials by Kai Dong et al.

Figure 6

Different methods to enhance electroactive phase of PVDF for better piezocatalytic properties and improved dye degradation. (i) Poling. (ii) Electrospining. (iii) Spin coating. (iv) Solvent casting. (v) Phase transition method. (vi) Addition of nanofillers.

Figure 7

Schematic diagram of PVDF polarization: (a) before poling process, (b) during poling process.

Figure 8

(a) Direct poling of polymer. (b) Corona poling setup.

Figure 9

Mechanism of heterojunction formation in PVDF by addition of nanofillers. (a) PVDF matrix. (b) Nanofillers. (c) Formation of the beta phase in PVDF.

Figure 10

Piezo-degradation of pollutants by generation of reactive oxygen species. This image is a modified version of various images from articles published in the Journal of Cleaner Production by Qing Nie et al., the Journal of the American Chemical Society by Gurpreet Singh et al., and the Journal of Hazardous Materials by Srikanta Karmaker et al.

Figure 11

Schematic diagrams of generation of reactive oxygen species (ROS) by ultrasonication and catalytic degradation of dye. This image is modified from an article related to piezo-catalysis from the Journal of Nano Energy by Biswajoy Baghchi et al., a Journal of Chemistry article by Rao Akshatha et al., a Journal of Materials Chemistry and Physics article by Sakthivel Jayaraman et al., and a Journal of Molecular Structure article written by Muhammad Farooq Khan.

Figure 12

Piezo-atalysis for degradation of organic dyes and production of CO₂ and H₂ as fuel. This image is modified from an article by Bian yang et al., from the Journal of Material Chemistry.