High-Strength TiO₂/TPU Fibers via Electrospinning Machine

Reserach background 

Industrial dye wastewater, a major contributor to water pollution, is marked by large volumes, high levels of organic pollutants, high alkalinity, and poor quality. Triphenylmethane dyes like rhodamine B (RhB), widely used in industrial dyeing due to their favorable properties, pose significant threats as they are highly toxic, carcinogenic, and hard to degrade. Photocatalysis, a technology harnessing solar energy for environmental remediation and energy conversion, has gained attention for its low energy consumption, high efficiency, and absence of secondary pollution. However, nanostructured photocatalysts used in liquid - phase systems suffer from activity loss, nanoparticle - induced secondary contamination, and challenges in recovery and separation. To address these, immobilizing nanostructured catalysts on suitable supports, such as composite fibers and fabrics made from organic polymers, has become a research focus. Thermoplastic polyurethane (TPU), with its elasticity, wear resistance, processability, and solvent resistance, is an ideal support. Previous studies combined commercial titanium dioxide (P25) and TPU to create composite fibers, but these faced issues like decreased activity and a need to balance catalytic activity and mechanical strength for large - scale industrial applications.

Abstract

Integrating nanostructured photocatalysts into polymer matrices is crucial for the practical application of fiber - based photocatalytic composite textiles. In this study, highly durable TiO 2/TPU composite fibers with high TiO 2 content (>30 wt.%) were prepared via wet spinning using 1D electrospun TiO 2 nanofibers (TNFs). Thanks to the fiber reinforcement principle, these composite fibers outperformed pure TPU fibers in mechanical properties. The TNF/TPU composite fibers with a 1:2 ratio showed remarkable degradation efficiency for rhodamine B (RhB). The orientation of 1D TNFs and the strong interface between TNF and TPU matrices not only enhanced load sharing and transfer but also improved photogenerated charge transfer efficiency, resulting in high strength and photocatalytic activity. The hollow and porous structures of the composite fibers increased TNF exposure, facilitating photocatalytic degradation. Notably, when the RhB concentration exceeded 15 ppm, the TNF/TPU composite fibers had a higher degradation efficiency than TNF powder. Thus, TNF/TPU composite fiber - based textiles, with high photocatalytic activity and strength, hold promise in solving the separation and recovery problems of nanostructured catalysts in practical wastewater treatment.

a Schematic illustration of the preparation process of the TNF/TPU composite fiber: Step 1: Electro-spinning process; Step 2: Wet-spinning dispersion process; Step 3: Wet-spinning process. b FE-SEM images and diameter distribution of TNFs powder. c FE-SEM images of TNF/TPU composite fiber with different weight ratios of TNFs: TPU (1-5, 1-3, 1-2 and 1-1.5).

Main Research Content

Preparation and Characterization of TNF/TPU Composite Fibers: TNFs were synthesized by electrospinning and combined with TPU through wet spinning to obtain TNF/TPU composite fibers with different mass ratios. The structure, morphology, optical properties, and mechanical properties of the composite fibers were characterized using SEM, XRD, UV - Vis spectroscopy, and tensile tests. The results showed that the TNF/TPU composite fibers had a porous and hollow structure, and with the increase of TNF content, the fiber diameter and Young's modulus increased, while the tensile strain decreased. The 1 - 3 TNF/TPU composite fibers had the highest tensile strength, and the 1 - 2 TNF/TPU composite fibers had excellent comprehensive properties.

a XRD patterns, b UV-Vis absorption spectra of TNFs powder and TNF/TPU composite fiber. c stress-strain curves, d Tensile strength, e tensile strain and f toughness of TNF/TPU composite fiber. g–i SEM images of different TiO2/TPU composite fiber.

Photocatalytic Performance of TNF/TPU Fiber - Based Textiles: The composite fibers were woven into textiles, and their photocatalytic performance was evaluated by degrading RhB in an aqueous solution under light irradiation. The results indicated that the adsorption and photocatalytic degradation ability of the TNF/TPU composite fibers improved with the increase of TNF content, and the 1 - 2 TNF/TPU composite fibers had the best degradation effect, achieving a 99.47% removal rate of RhB in 270 minutes. The stability of the composite fibers in photocatalytic experiments and the influence of RhB solution concentration were also studied. It was found that when the RhB concentration exceeded 15 ppm, the TNF/TPU composite fibers had a higher degradation efficiency than TNF powder, and the 1 - 2 TNF/TPU composite fibers maintained a degradation efficiency of about 99% after five cycles.

a Time profiles and b First-order reaction kinetics in the presence of TNF/TPU composite fiber. c–f Compared photocatalytic performances of 1-2 TNF/TPU composite fiber and TNFs powder in different RhB concentrations. g Time profiles in the repeated cycles in the presence of 1-2 TNF/TPU composite fiber. h Proposed mechanism of TNF/TPU composite fiber-based textiles for RhB photodegradation.

Photocatalytic Mechanism of TNF/TPU Fiber - Based Textiles: A possible photocatalytic mechanism was proposed. Under light irradiation, excited electrons and holes were generated on the surface of TNFs in the composite fibers, which degraded organic pollutants. The 1D TNFs not only enhanced the fiber strength but also improved the photogenerated charge transfer efficiency. The hollow and porous structures of the composite fibers increased the exposure of TNFs, promoting the degradation of RhB.

Conclusions

The TNF/TPU composite fibers prepared in this study exhibited higher mechanical properties compared to pure TPU fibers and 1 - 5 P25/TPU composite fibers, along with enhanced photocatalytic activity. The 1 - 2 TNF/TPU composite fibers demonstrated the best photocatalytic performance, achieving over 99% removal of RhB in 270 minutes. In the five - cycle test, the textile could be easily retrieved from wastewater, showing high photocatalytic performance and stability. At higher RhB concentrations, the textile outperformed TNF powder in degradation performance, offering a solution to the challenges of recovering and separating nanostructured photocatalysts from wastewater. However, for large - scale industrial wastewater treatment applications, further research is required, including large - scale preparation of composite fibers to improve photocatalytic performance, design of large - scale photocatalytic textile reactors and investigation of their long - term operation effects, and in - depth exploration of charge transfer mechanisms in composite fiber - based textiles.

Electrospinning Nanofibers Article Source: 

https://doi.org/10.1038/s41545-024-00390-x