Titanium Dioxide 1D Nanostructures as Photocatalysts for Degradation and Removal of Pollutants in Water

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article "Titanium dioxide 1D nanostructures as photocatalysts for degradaration and removal of pollutants in water" is quite interesting and the way it was written was very clear. I just recommend that figure 1B be adjusted. Another aspect to be considered would be a better approach to the degradation of target pollutants in the conclusion part of the text. I also recommend that the introduction mention the problems that target pollutants may cause to the environment.

 

Author Response

1. The article "Titanium dioxide 1D nanostructures as photocatalysts for degradaration and removal of pollutants in water" is quite interesting and the way it was written was very clear.

Thank you for the comment. We appreciate it.

2. I just recommend that figure 1B be adjusted. Another aspect to be considered would be a better approach to the degradation of target pollutants in the conclusion part of the text.

We apologize for the mistake. Figure 1B has been adjusted, and so Figures 1A and C by changing the crystalline structure instead of the number of the card.

3. I also recommend that the introduction mention the problems that target pollutants may cause to the environment.

Thanks for the suggestion. We have added in the introduction section a brief description of the consequences of the pollutants to aquatic organisms and humans in the lines 139-143  and 147-151 with two new references [28] and [31], respectively. We consider that other environmental issues have been described in lines 145-146.

Reviewer 2 Report

Comments and Suggestions for Authors 1. Does the study sufficiently highlight the novelty of TiO2 nanorods fabricated using the hydrothermal method? 2. Cite the following references: 10.3390/catal13010026; 10.1007/s42247-024-00646-9; 10.1016/j.mset.2023.10.005; 10.1016/j.chemosphere.2022.134731, etc. 3. Are the results of the photocatalytic activity tests, particularly for methyl orange, phenol, and 4-nitrophenol, clearly presented and effectively analyzed? 4. Is the impact of calcination at 400°C on the crystalline structure and surface area of TiO2 nanorods adequately explained? 5. Are the comparative advantages of N-P25-400 and N-TiO2-400 nanorods over sol-gel and commercial TiO2 clearly demonstrated? 6. Is the role of Ti³⁺ and sodium/hydrogen titanates in enhancing photocatalytic activity convincingly discussed? 7. Does the study provide sufficient justification for the use of the Kubelka-Munk equation to calculate the bandgap energy (Eg)?8. Are the morphological changes observed in nanorods post-calcination accurately described and linked to their photocatalytic properties? 9. Are the implications of these findings for large-scale applications in pollutant degradation adequately addressed? 10. Does the paper effectively balance the discussion of adsorption capacity and photocatalytic performance of the nanorods?

Author Response

1. Does the study sufficiently highlight the novelty of TiO2 nanorods fabricated using the hydrothermal method?

We appreciate the observation, since hydrothermal method is not new we emphasized the relevance of its low-cost and simplicity for obtaining materials in lines 116-118 of the revised version of the manuscript.

2. Cite the following references: 10.3390/catal13010026; 10.1007/s42247-024-00646-9; 10.1016/j.mset.2023.10.005; 10.1016/j.chemosphere.2022.134731, etc. 

We have revised the suggested refences and even though they are excellent literature, we have considered no to include them due to the following:

10.3390/catal13010026--refers to general properties of TiO₂ as photocatalysts, which we consider this is now a well-known topic and it is not the aim of the introduction.

10.1007/s42247-024-00646-9—describes the use of modified WO4/g-C3N4 materials for the degradation of MB, which are not comparable to TiO₂, instead we consider that the original cited literature related to different TiO₂ nanostructures is more suitable.

10.1016/j.mset.2023.10.005 -- is referred also to a nanocomposite made of graphene oxide and silver, which is not comparable to TiO₂.

10.1016/j.chemosphere.2022.134731- - is focused on the use of TiO₂ in the degradation of pharmaceutical drugs which is not the topic of the manuscript.

3. Are the results of the photocatalytic activity tests, particularly for methyl orange, phenol, and 4-nitrophenol, clearly presented and effectively analyzed? 

Thank you for asking. We have revised and considered that the obtained results have been suitable compared with corresponding literature from references 46, 48-53 as presented in lines 541-560.

4. Is the impact of calcination at 400°C on the crystalline structure and surface area of TiO2 nanorods adequately explained? 

The crystalline structure is dramatically affected by temperature. First, due to the alkaline conditions used for hydrothermal treatment and later for the calcination process. The detailed discussion can be found on lines 429-444.

5. Are the comparative advantages of N-P25-400 and N-TiO2-400 nanorods over sol-gel and commercial TiO2 clearly demonstrated?

In the discussion, the reviewers can find that the sol-gel method presented multifunctional properties. In order to highlight the advantages of this method, additional text has been added on lines 570-574.

6. Is the role of Ti³⁺ and sodium/hydrogen titanates in enhancing photocatalytic activity convincingly discussed? 

We appreciate the suggestion. Since the characterization performed for studying the obtained materials is limited, we speculate in the role of these species, based on the results from the structural characterization (XRD and Raman) and the surface composition (XPS) of the materials. We have improved the arguments given by adding the following lines  277-279,   467-471 and the new reference 46.

7. Does the study provide sufficient justification for the use of the Kubelka-Munk equation to calculate the bandgap energy (Eg)?

We appreciate the concern of the reviewer. In this sense, it has been accepted that despite there are other methods for measuring the band gap of semiconductors, the use of reflectance spectra and the Kubelka Munk are very good approximations for this purpose as demonstrated in reference 39.

 

8. Are the morphological changes observed in nanorods post-calcination accurately described and linked to their photocatalytic properties? 

We consider that no significant changes in morphology were observed. In this regard, the photocatalytic activity could be more related to differences in crystalline structure and impurities/defects because of the different staring materials used. This has been described in lines 568-575.

9. Are the implications of these findings for large-scale applications in pollutant degradation adequately addressed? 

We appreciate the suggestion. However, the purpose of the manuscript is to describe the potential use of 1D TiO₂ nanostructure for oxidation and reduction of some common pollutants at laboratory level. Large-scale applications will need additional experiments that were pointed out at the end of the discussion section.

 

10. Does the paper effectively balance the discussion of adsorption capacity and photocatalytic performance of the nanorods?

We have added some discussion related to the adsorption of the dye on lines 505-515.