Electrospun 3D Curly Electret Nanofiber Air Filters for Particulate Pollutants

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The templete should be respected. A numerous  spelling mistakes are in hole article.

1. The PVDF acronim should be explained.

2. Line 20 What means electret performance? 

3. How the relative humidity was determined?

4. How the fiber diameter was mesured?

5. The FTIR spectra it is not consistent with the explanation in the text. In the figure 5 at 876 cm-1 is mentioned C-C, in the text is mentioned C-H. Also, at 836 cm-1 and also at 1071. Is mandatory to to check the vibrations and connections.

6. In the P formula is not H.

7. How h was mesured? There is no explanation of the measurement methods.

8. The results are not corellated with method' description.

 

Author Response

Thank you very much for taking the time to review this manuscript. The following is my reply. The article revised according to the suggestion is in the attachment, and the revised part of the article has been highlighted.

1. Polyvinylidene fluoride powder (PVDF, Mw = 500 000) was purchased from Arkema.
2. An electret material possesses a permanent electrical dipole moment. Dielectrics with permanent polarizations which are able to create a strong external electric field for a long time are called electrets. Electrostatic forces contribute to particle filtration, especially in respirators and masks made of electret fibers. Fibers with electret effect will have electrostatic adsorption. Generally speaking, the stronger the electret effect, the better the electrostatic adsorption effect.
3. The relative humidity in the process of electrospinning is measured by a temperature and humidity tester.
4. The fiber diameter distribution was estimated by the statistical analysis of 200 fibers randomly selected using an image analysis software(ImageJ).
5. Figure 5. show FTIR spectra of different nanofiber membranes are shown respectively. At 1401cm^-1, there is the stretching vibration absorption peak of CH2.At 1274 cm−1 and 1177 cm−1 to the symmetrical and asymmetrical stretching of CF2. which is the main peak in PVDF and represents the fluoride part in PVDF. At 1071cm^-1, the vibration of CF2 indicates a special bending vibration of fluoride groups. 876cm⁻¹ to one of the characteristic peaks of PVDF; the peak at 836cm^-1 is the bending vibration absorption peak of the CH bond. Ti-O stretching vibration: A new broad characteristic absorption peak appears in the range of 500-800 cm^-1, which may appear as one or more peaks. The tensile vibration of O-Ti-O bond in doped TiO₂ is the main reason for the appearance of additional peaks and peak shifts. It shows that TiO₂ NPS was successfully compounded into PVDF nanofibers.
6. In the p formula, it is h.
7. h represents the thickness of the membrane, that was obtained based on the SEM images of side views.
8. In this article, 3D curly nanofibers were prepared by electrostatic spinning in a high humidity environment above 95RH%. Compared with the densely packed nanofiber membrane prepared in a normal humidity environment, the 3D curly nanofibers formed a highly fluffy nanofiber membrane, and its filter pressure drop decreased significantly. A suitable quantity of TiO₂ NPs was incorporated as an electret reinforcement to fabricate a highly voluminous 3D curly PVDF/TiO₂ nanofiber membrane. The element distribution, functional groups and element content on the surface of the fiber membrane were analyzed by EDS, FTIR and XRD, which showed that TiO₂ NPs had been successfully compounded on PVDF fiber. It provides some basic research for PVDF/TiO₂ composite fiber membrane. The doping of a small amount of TiO₂ NPs has no obvious influence on the 3D curly fluffy structure. The addition of electret particle TiO₂ NPs obviously enhances the electrostatic adsorption of fiber membrane, greatly improves the electrostatic effect in the process of fiber membrane filtration, and improves the filtration efficiency of 3D curly nanofiber membrane. The filtration efficiency of H-P/T2 fiber membrane with TiO₂ NPs addition amount of 0.5wt% is about 99.197%, and the pressure drop is about 49.83Pa.

This study provides a new idea for the preparation of air filtration materials with high efficiency and low resistance by combining high fluffy 3D curly structure with TiO₂ with excellent electret effect. In addition, PVDF and TiO₂ materials themselves have other excellent properties, and they can continue to develop multi-functions by using the 3D curly fluffy structure and other properties of materials in the future.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The work is interesting. The aim of this study is to show the effect of adding TiO2 nanoparticles on the performance of fiber membranes. The work is well written and structured. The results are well presented and the conclusions are based on the results obtained.

I feel that with some minor corrections, the work could be accepted for publication.

 

Many words appear together in the text, spaces need to be added, especially after periods.

The results shown in figure 3 are difficult to see. This figure could be improved and the explanation and text of the legend could be expanded.

The size of the TiO2 crystalline particles could be obtained from the XRD results.

  The conclusions state that XPS analyses were carried out, please check this. If they were carried out, it would be advisable to include the spectra in the work, especially in the Ti spectral region.

Author Response

Thank you very much for taking the time to review this manuscript. The following is my reply. The article revised according to the suggestion is in the attachment, and the revised part of the article has been highlighted.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The paper could be published.