Influence of Non-Ionic Surfactant and Silver on the Photocatalytic Activity of TiO₂ Films for Degradation of Dyes in Distilled and Tap Water

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript, " Enhanced photocatalytic degradation of Malachite Green and 2 Methylene Blue using non-ionic surfactant in pure and silver photo-fixed TiO2 films", presents the photocatalytic decomposition of Malachite Green and Methylene Blue under ultraviolet and visible illumination with supported catalysts composed of PEG and Ag/TiO2. The catalyst seems interesting; however, it requires further characterizations and more data, especially concerning adsorption tests, photolytic tests, and even tests with the material in suspension. The use of dyes as model pollutants is also no longer well-regarded. I suggest using other model contaminants. Methylene Blue has issues, especially under visible radiation. The photocatalytic assays are very simplistic; there is no variation in variables such as pH, nor is the concentration of the catalyst during the tests known. As such, the article cannot be accepted in its current form.

1.      The text is mostly well-written and grammatically correct; however, there are some minor grammar errors. I suggest an overall review of the English.

2.      The summary needs to be rewritten.

3.      "The glasses were dipped in both TiO2 suspensions (containing PEG 2000 and PEG 4000) at room temperature using the dip-coating technique" (L103) - What were the coating conditions? Dipping and withdrawal speeds, immersion time in the solution...?

4.      You had an area of 35 cm² to cover, what was the catalyst/solution ratio?

5.      "In our earlier work, we successfully degraded organic dyes and photo-fixed powder ZnO and TiO2 (only with PEG 4000) films with silver ions using the chemical photodeposition technique [25, 26]." (L117) - This sentence can be removed, as it does not add value in its current placement.

6.      "The results indicate that when compared to the TP2 sample, the film made using the higher molecular weight surfactant has a larger and more developed specific surface area." (L172) - This cannot be stated with a difference of only 3 m²/g.

7.      "...are anticipated to exhibit the highest photocatalytic activity, while the pure TP2 and TP4 films have a lower efficiency. Thus, one can expect that the photocatalytic properties of catalysts are dependent on these properties." (L176) - This can be removed, it is not necessary to state expectations in a work with results. It would be more appropriate to discuss the results and the possible reasons why Ag10-2 showed a larger specific surface area.

8.      The XRD graphs need to be redone; they are overlapping and too noisy.

9.      The caption for Figure 5 needs to be rewritten.

10.  A diagram of the photocatalytic reactor would be useful. How is the catalyst arranged in the reactor? Is there reflective radiation on all sides of the plate?

11.  In line 240, you mention the mineralization of the compounds. However, this is not supported by TOC or analysis of intermediaries; I suggest changing it to only removal.

12.  In studies involving the degradation of dyes, especially MB, it is necessary to include the reaction mechanisms, as the use of MB, especially under visible light, is problematic.

13.  There are missing photolytic tests for dye removal. Many of them have removal just by photolysis.

14.  Analyses of the adsorption of dyes on the catalysts are missing. Photocatalysis is a mechanism that involves the adsorption of molecules into the pores. Adsorption tests should be performed.

15.  It would be more iterative to insert the linearity constants from Table 3 next to the legends in the graphs of Figures 5 and 6.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

1.      The text is mostly well-written and grammatically correct; however, there are some minor grammar errors. I suggest an overall review of the English.

Author Response

The manuscript: " Influence of non-ionic surfactant and silver on the photocatalytic activity of TiO2 films for degradation of dyes in distilled and tap water "

by Dobrina Ivanova, Elisaveta Mladenova, Nina Kaneva

Manuscript ID: applsci-2997124

We thank you very much to the Reviewer for the valuable marks, comments, and suggestions, supporting the presentation of our work. We accepted all the recommendations and corrected our paper properly following the suggestions the Reviewer gave in the same sequence.

We hope you find the revised manuscript suitable for publication in Applied Sciences. We look forward to hearing from you in due course. The new changes in the paper text are pointed out in blue color. Please, see our comments below.

Response to Reviewer 1:

The manuscript, "Enhanced photocatalytic degradation of Malachite Green and 2 Methylene Blue using non-ionic surfactant in pure and silver photo-fixed TiO2 films", presents the photocatalytic decomposition of Malachite Green and Methylene Blue under ultraviolet and visible illumination with supported catalysts composed of PEG and Ag/TiO2. The catalyst seems interesting; however, it requires further characterizations and more data, especially concerning adsorption tests, photolytic tests, and even tests with the material in suspension. The use of dyes as model pollutants is also no longer well-regarded. I suggest using other model contaminants. Methylene Blue has issues, especially under visible radiation. The photocatalytic assays are very simplistic; there is no variation in variables such as pH, nor is the concentration of the catalyst during the tests known. As such, the article cannot be accepted in its current form.

We successfully use and degrade other pollutants in our previous articles - dyes and drugs. But in this work, we have chosen these two dyes because they are comparable in structure. Applied Sciences has a requirement that the article be 4000 words from abstract to conclusion, for this reason, we cannot include all these tests and experiments, as recommended. Despite the limitation, we additionally performed newly eighteen photocatalytic experiments to evaluate the behavior of our catalysts for the degradation of dyes in distilled and drinking water, which have different pH. TOC analyzes were also performed after these new sixteen photocatalytic experiments. Catalyst concentration cannot be considered and discussed because we are working with films, not powders. For this reason, we have changed the title of our article: “Influence of non-ionic surfactant and silver on the photocatalytic activity of TiO2 films for degradation of dyes in distilled and tap water”

1. The text is mostly well-written and grammatically correct; however, there are some minor grammar errors. I suggest an overall review of the English.

The paper has been revised by a native English speaker. The English language throughout the article has been corrected. The new changes in the paper text are pointed out in blue color.

2. The summary needs to be rewritten.

We changed the Abstract, as you recommended.: “Here in, we demonstrate the impact of surfactant molecular weights (PEG 2000 and PEG 4000) on the photocatalytic activity of TiO2 films, deposited via dip-coating from a PEG-stabilized suspension and silver-functionalized photo-fixation of Ag+ under UV illumination. The photo-catalytic activity of pure and Ag/TiO2 films is assessed in the aqueous-phase degradation of Malachite Green and Methylene Blue in distilled and tap water under UV and visible illumination. The results indicate positive effect of both the higher molecular weight non-ionic surfactant and Ag-functionalization yield higher photocatalytic efficiency. Notably, films photo-fixed with 10−2 M Ag+ show the highest degradation percentages in all experimental condition. A direct correlation between the concentration of Ag+ ions and the enhancement of the photocatalytic activity is re-vealed: Pure TiO2 < Ag, 10−4/TiO2 < Ag, 10−3/TiO2 < Ag, 10−2/TiO2. Flame Atomic Absorption Spec-trometry is used to study the Ag+ leeching from the Ag/TiO2 films. Structural properties of the nanostructures were investigated through Scanning electron microscopy, Brunauer-Emmett-Teller analysis, Energy-Dispersive X-ray spectroscopy, and X-ray diffraction. Additionally, after three cycles of operation, Ag, 10-2/TiO2 (PEG 4000) films can maintain their photocatalytic activity, sug-gesting a potential application in the treatment of dye wastewater.”

3. "The glasses were dipped in both TiO2 suspensions (containing PEG 2000 and PEG 4000) at room temperature using the dip-coating technique" (L103) - What were the coating conditions? Dipping and withdrawal speeds, immersion time in the solution...?

We added in the text: “The glass slide substrates were coated employing a dip-coating technique, performed at room temperature at a withdrawal rate of 0.9 cm/min.”

There is no immersion time, we immerse the glass substrate and immediately withdraw it. Hence the article does not write residence time in the precursor solution.

4. You had an area of 35 cm² to cover, what was the catalyst/solution ratio?

35 cm² is the surface of the glass substrates, which is covered by the dip-coating technique (dipping and withdrawal), not the ratio between catalyst/solution. The ratio (catalyst/solution) is around 36.5 mg/120 ml. In the text, we added the amount of dipping catalyst on the glass substrate.

5. "In our earlier work, we successfully degraded organic dyes and photo-fixed powder ZnO and TiO2 (only with PEG 4000) films with silver ions using the chemical photodeposition technique [25, 26]." (L117) - This sentence can be removed, as it does not add value in its current placement.

We completely agree with the reviewer, we deleted the sentence.

6. "The results indicate that when compared to the TP2 sample, the film made using the higher molecular weight surfactant has a larger and more developed specific surface area." (L172) - This cannot be stated with a difference of only 3 m²/g.

We agree with the reviewer, the difference is very small. For this reason, we have deleted this sentence.

7. "...are anticipated to exhibit the highest photocatalytic activity, while the pure TP2 and TP4 films have a lower efficiency. Thus, one can expect that the photocatalytic properties of catalysts are dependent on these properties." (L176) - This can be removed, it is not necessary to state expectations in a work with results. It would be more appropriate to discuss the results and the possible reasons why Ag10-2 showed a larger specific surface area.

We completely agree with the reviewer, we deleted the sentence: 

8. The XRD graphs need to be redone; they are overlapping and too noisy.

We redid XRD graphs, as recommended.

9. The caption for Figure 5 needs to be rewritten.

      We changed the caption of Figure 5 and Figure 6. After the new research and added figures, Figures 5 and 6 became Figures 6 and 7.

10. A diagram of the photocatalytic reactor would be useful. How is the catalyst arranged in the reactor? Is there reflective radiation on all sides of the plate?

We understand that such a diagram would be useful, but the article becomes too many figures (11 figures). The catalyst (glass substrate) is located under the reactor lamp and the light illuminates the entire surface.

11. In line 240, you mention the mineralization of the compounds. However, this is not supported by TOC or analysis of intermediaries; I suggest changing it to only removal.

We provide TOC analysis at the end of photocatalytic process for the degradation of Malachite Green and Methylene Blue, as recommended. We added new figure in our article for the TOC analysis (Figure 11).

Discussion is added to the text:” The TOC percentages for dye mineralization in tap and distilled water are determined (Figure 11). In tap water, TP4 showed higher TOC conversion rates compared to TP2 for both MG and MB, while in distilled water, similar trends are observed. The introduction of Ag+ into TiO2 increased the TOC conversion rates, with higher rates observed for films with higher concentrations of silver and surfactant molecular mass. However, comparing TOC analysis to UV-vis spectroscopy revealed lower values, indicating the involvement of complex intermediate steps and products in the dye breakdown process [33, 34]. These intermediate products, upon interaction with with OH• produced during photocatalysis, exhibit unique oxidation potentials.”

 

 

12. In studies involving the degradation of dyes, especially MB, it is necessary to include the reaction mechanisms, as the use of MB, especially under visible light, is problematic.

We agree with the reviewer. In our previous article (N. Kaneva, A. Bojinova, K. Papazova, D. Dimitrov, I. Svinyarov, M. Bogdanov, Effect of thickness on the photocatalytic properties of ZnO thin films, Bulgarian Chemical Communications, 47, 1, 395–401, 2015.) we have commented on the reaction mechanism of the two dyes in the presence of zinc oxide. We assume that in the case of a titanium dioxide catalyst, the mechanism will be similar.

13. There are missing photolytic tests for dye removal. Many of them have removal just by photolysis.

                  We conducted additional experiments related to photolytic tests for the degradation of dyes in the absence of a catalyst. We added new figure in the article – Figure 5. Photolysis rates for MG and MB in absence of a photocatalyst.

Discussed is added to the text: “The photocatalytic efficiencies of TiO2 powder films with surfactants of two different molecular weights are assessed under UV and visible light for decomposinge Malachite green and Methylene blue. As visible light is known to cause photolysis in colored dyes, a control experiment was carried to estimate the dye removal rates in absence of a photocatalyst. The results are shown in Figure 5 for both MB and MG, indicating an upwards of 13.2% Malachite green lost due to photolysis within 4 hours, and a higher rate of 18% for Methylene blue, which is known to act as a photosensitizer and thus more prone to photolysis.”

14. Analyses of the adsorption of dyes on the catalysts are missing. Photocatalysis is a mechanism that involves the adsorption of molecules into the pores. Adsorption tests should be performed.

We agree with the reviewer that photocatalysis is a mechanism that involves the adsorption of molecules into pores. Adsorption tests were performed on all experiments (15 min) before turning on the irradiation lamp and starting the photocatalytic process. Approximately 3% adsorption is observed. We forgot to include this information in the article: “Additionally, a dark-phase adsorption experiment was carried for the pristine, cat-alysts. No discernable difference was observed between MB and MG where in both cases the decrease in concentration was ~3% of the initial 10 ppm.”

15. It would be more iterative to insert the linearity constants from Table 3 next to the legends in the graphs of Figures 5 and 6.

We inserted the rate constants from Table 3 in the graphs of Figures 5 and 6. Table 3 is removed. After the new research and added figures, Figures 5 and 6 became Figures 6 and 7.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This work reports the fabrication of TiO2 films with silver for the photodegradation of malachite green. The authors reported the characterization of the films (and some techniques as powders, which is not certainly adequate) and provided relatively good efficiencies. However, this topic is widely reported and previously investigated. This work does not provide any new information in the area. Also, the activity analysis fails to provide blank or statistical experiments. Generally, the glass tended to absorb dye molecules, which hides the actual activity of the films. Also, the authors does not provide any analysis of the reaction mechanism or absorption spectra to monitoring the degradation of the pollutant. Thus, I dont recommend its publication.

Comments on the Quality of English Language

The English grammar should be revised by a professional service.

Author Response

We have completely revised our paper by conducting additional photocatalytic experiments on the degradation of dyes in tap water, TOC analyses, as well as photolytic tests of the two pollutants. We have added data related to adsorption.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors in this study provide a very interesting novel facet toward the enhancement in photocatalysis of doped titania. The influence of the nature and molecular size of polyglycols on activity opens the door to many new interesting facets for the future of titanium dioxide. The data and outcomes are well supported by detailed analysis and the article is well structured and written in a clear style and presentation. useful supportive references are critically integrated within the discussion.

Author Response

We thank you very much to the Reviewer for the gorgeous marks and comments on our article.

Reviewer 4 Report

Comments and Suggestions for Authors

The proposed paper represents a nice contribution to photocatalytic chemistry and can be accepted as such after revision. Specific comments:

 

Is the method of preparing the material based on a previous work or is it the original contribution of the author?

The schematic illustration of the work is not of sufficient quality and should be improved.

Did the authors examine the effect of a parameter such as starting pH or analyte concentration?

Testing the effectiveness of the material in real water (rainwater or some other surface water) would be a significant contribution to the work.

In the conclusion, the authors could specify further plans regarding the development of this area and the application of materials.

Author Response

The manuscript: " Influence of non-ionic surfactant and silver on the photocatalytic activity of TiO2 films for degradation of dyes in distilled and tap water "

by Dobrina Ivanova, Elisaveta Mladenova, Nina Kaneva

Manuscript ID: applsci-2997124

We thank you very much to the Reviewer for the valuable marks, comments, and suggestions, supporting the presentation of our work. We accepted all the recommendations and corrected our paper properly following the suggestions the Reviewer gave in the same sequence.

We hope you find the revised manuscript suitable for publication in Applied Sciences. We look forward to hearing from you in due course. The new changes in the paper text are pointed out in blue color. Please, see our comments below.

Response to Reviewer 4:

The proposed paper represents a nice contribution to photocatalytic chemistry and can be accepted as such after revision. Specific comments:

 Is the method of preparing the material based on a previous work or is it the original contribution of the author?

In our previous two studies - Ivanova, D.; Mladenova, R.; Kolev, H.; Kaneva, N. Effect of Ultraviolet Illumination on the Fixation of Silver Ions on Zinc Oxide Films and their Photocatalytic Efficiency. Catalysts 2023, 13, 1121.; Kaneva, N.; Bojinova, A.; Papazova, K. Enhanced Removal of Organic Dyes Using Co-Catalytic Ag-Modified ZnO and TiO₂ Sol-Gel Photocatalysts, Catalysts 2023, 13, 245., we synthesize sol-gel thin films (ZnO, TiO2) using the following reagents – 2-methoxyethanol, monoethanolamine, zinc acetate dehydrate, titanium isopropoxide. The method of photofixation and the method of modification with silver ions is the same.

In the present paper, we modify with silver ions films prepared from commercial TiO₂ powder for the first time. We believe that this fabrication strategy is much faster and cost-effective. We used for the first time two non-ionic surfactant with different molecular mass. The degradation of Malachite Green and Methylene Blue in tap and distilled water is also a novelty in this study. All these effects have not previously been taken into account.

The schematic illustration of the work is not of sufficient quality and should be improved.

Figure 1 (the schematic process) is improved, as recommended.

Did the authors examine the effect of a parameter such as starting pH or analyte concentration?

We would like to thank the reviewer for the question. 

The purpose of these experiments was to investigate the optimal concentration of the co-catalyst, the non-ionic surfactant with different molecular mass (PEG 2000 and PEG 4000) and waters (distilled and tap) to achieve enhancement of the photocatalytic degradation of Malachite Green and Methylene Blue. Follow-up works are associated with a study of the initial pH concentration and analyte concentration. All these things are future experiments.

Testing the effectiveness of the material in real water (rainwater or some other surface water) would be a significant contribution to the work.

We completely agree with the reviewer. Therefore, we conducted eight more experiments related to the degradation of dyes in tap water. We added new figure in article – Figure 10. Degradation of the dyes in distilled and tap waters under UV illumination. 

In the conclusion, the authors could specify further plans regarding the development of this area and the application of materials.

We changed the conclusion: “In conclusion, TiO2 films produced via a dip-coating method with the addition of surfactants (PEG2000 and PEG4000) showed enhanced photocatalytic activity when Ag+ was photo-fixed under UV light. Films with higher concentrations of silver and surfactant molecular mass demonstrated the highest percentages of dye degradation under light exposure. The system's improved photocatalytic efficiency and the beneficial effects of Ag+ make it a promising option for pollutant (dye or pharmaceutical drug) degradation, contributing to the development of efficient and environmentally friendly wastewater treatment techniques under ultraviolet and sunlight.”

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors effectively addressed most of the concerns, and the quality of the article has improved. That said, there are still some points that need to be resolved for the article to be published.

• Although it is not prohibited, it is uncommon to use first-person pronouns (I/we) in scientific articles. Generally, sentences containing these pronouns are replaced with phrases like 'this study describes' and similar terms. I suggest revising the abstract again.
• Regarding the coating technique, five immersions were performed. What was the time interval between the immersions? I ask this because, typically, this technique requires a waiting period for dripping.

• On line 205, correct the TiO2.
• The caption for Figure 5 can be revised. If it is a photolytic process, it is not necessary to mention that it is in the absence of a catalyst.
• I am not satisfied with the response to Question 14 regarding the adsorption period. At least one long-duration adsorption test is necessary to verify equilibrium. (At least the same duration as the photocatalytic test to determine the influence of each process)
• Regarding Figures 6 and 7 and the constants, I may have expressed myself poorly in the last question. It would be better if the constants were placed next to their respective legends. Like this
  
   

 

Comments for author File: Comments.pdf

Author Response

The manuscript: " Influence of non-ionic surfactant and silver on the photocatalytic activity of TiO2 films for degradation of dyes in distilled and tap water "

by Dobrina Ivanova, Elisaveta Mladenova, Nina Kaneva

Manuscript ID: applsci-2997124

We hope you find the revised manuscript is already suitable for publication in Applied Sciences. We look forward to hearing from you in due course. The new changes in the paper text are pointed out in green color. Please, see our comments below.

Response to Reviewer 1:

The authors effectively addressed most of the concerns, and the quality of the article has improved. That said, there are still some points that need to be resolved for the article to be published.

• Although it is not prohibited, it is uncommon to use first-person pronouns (I/we) in scientific articles. Generally, sentences containing these pronouns are replaced with phrases like 'this study describes' and similar terms. I suggest revising the abstract again.

We deleted the first-person pronoun (I/we) and replaced them with 'this study describes', as recommended.

 

• Regarding the coating technique, five immersions were performed. What was the time interval between the immersions? I ask this because, typically, this technique requires a waiting period for dripping.

The interval between the individual immersions is 2 minutes until the film is dried at 100C. This is described-"After each coating cycle the samples were dried at 100°C for 2 minutes and finally annealed for one hour at 500°C to burn off organic material. "

 

• On line 205, correct the TiO2.

We corrected.

 

• The caption for Figure 5 can be revised. If it is a photolytic process, it is not necessary to mention that it is in the absence of a catalyst.

We agree with the reviewer, the caption to Figure 5 has been corrected: “Figure 5. Photolysis rates for MG and MB.”

 

• I am not satisfied with the response to Question 14 regarding the adsorption period. At least one long-duration adsorption test is necessary to verify equilibrium. (At least the same duration as the photocatalytic test to determine the influence of each process)

We made four new experiments related to the adsorption tests. Adsorption processes are carried out with both dyes using the pure catalyst (TP2; TP4): “Additionally, a dark phase adsorption experiment with both dyes is carried out for the pristine catalysts (TP2, TP4). The decrease in the concentration of dyes in both cases is ~15% of the initial 10 ppm. The data from adsorption and photolysis are included in Figures 6 and 7.”

• Regarding Figures 6 and 7 and the constants, I may have expressed myself poorly in the last question. It would be better if the constants were placed next to their respective legends. Like this

We placed rate constants next to their respective legends, as recommended. In this way, the figures became more orderly.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The authors attended all the reviewers comments. Thus, I recommend to accept after minor suggestions:

1) Figure 1. It could be a good option to include the evolution of the TiO2 film in this schema (real pictures).

2) Include why the strain decreased after Ag addition.

3) Figure 5. Include in the same graph the results of photolysis and the photocatalytic activity of films. To compare the results. Note: The change of C/Co (not the kinetical analysis).

4) Improve the quality of Figure 8.

5) In my opinion, that form of present the stability of films is not the adequate. Include graphs such as:   

https://bitly.cx/E8P 

https://bitly.cx/LgZqZ

6) Compare your results with recent works (or powder systems). Highlight your contribution.

7) Include literature about PEG effect on the synthesis of films:  https://doi.org/10.1016/j.ceramint.2014.04.052

8) Compare with other type of immobilization, e.g., https://doi.org/10.1016/j.ceramint.2021.06.100 https://doi.org/10.1016/j.conbuildmat.2021.126205 https://doi.org/10.1016/j.conbuildmat.2023.134804

https://doi.org/10.1007/s12649-023-02309-y

9) Revise sub and super scripts in all the document.

Comments on the Quality of English Language

Moderate revisions should be included in the following revision.

Author Response

The manuscript: " Influence of non-ionic surfactant and silver on the photocatalytic activity of TiO2 films for degradation of dyes in distilled and tap water "

by Dobrina Ivanova, Elisaveta Mladenova, Nina Kaneva

Manuscript ID: applsci-2997124

We hope you find the revised manuscript is already suitable for publication in Applied Sciences. We look forward to hearing from you in due course. The new changes in the paper text are pointed out in green color. Please, see our comments below.

Response to Reviewer 2:

The authors attended all the reviewers comments. Thus, I recommend to accept after minor suggestions:

• Figure 1. It could be a good option to include the evolution of the TiO2 film in this schema (real pictures).

As recommended, we included real images of pure and silver-modified TiO₂ films in Figure 1.

 

• Include why the strain decreased after Ag addition.

We added in the article the reason for the reduced particle size of films modified with silver, supported by a literary source: “The reduced particle size in Ag/TiO₂ films may be attributed to the effect of electron confinement, which prevents surface Plasmon resonance from interacting with light. Tsivadze A. et al.'s explanation of this phenomenon can be linked to electronic barrier sets for Ag with tiny sizes [33]. The slight reduction in crystal size is consistent with XRD analysis.”

 

3) Figure 5. Include in the same graph the results of photolysis and the photocatalytic activity of films. To compare the results. Note: The change of C/Co (not the kinetical analysis).

We included the results of photolysis, adsorption, and the photocatalytic efficiency of films in Figures 6 and 7.  We agree with the reviewer because that's really how the results compare.

4) Improve the quality of Figure 8.

We improved of the quality of the figure.

5) In my opinion, that form of present the stability of films is not the adequate. Include graphs such as:  

https://bitly.cx/E8P    https://bitly.cx/LgZqZ

There are many authors in the literature who present the stability of their catalysts in exactly this way. We have borrowed from them the idea of presenting the data from the catalytic experiments. Your way of presenting is different and interesting. We promise to study and implement it in our next article.

 

6) Compare your results with recent works (or powder systems). Highlight your contribution.

We compared our previous results with present data, as recommended. The explanation is given in the materials and methods: “In our previous three studies [29-31], we synthesize sol-gel and powder films (ZnO, TiO₂). The method of photo-fixation and the method of modification with silver ions is the same. In these two papers, we degrade the organic dyes (Malachite Green, Methylene Blue) and drug (Paracetamol) in the presence of ultraviolet and visible light for 4 hours. In the present paper, we modify with silver ions films prepared from commercial TiO₂ powder. This strategy is more effective because the pollutants are decomposed for a shorter period of time.”

7) Include literature about PEG effect on the synthesis of films:  https://doi.org/10.1016/j.ceramint.2014.04.052

We included literature in the introduction and in references:

24. Luévano-Hipólito, E.; Martínez-de la Cruz, A.; Yu, Q.; Brouwers, H. Precipitation synthesis of WO3 for NOx removal using PEG as template. Ceram. Int. 2014, 40, 12123-12128.

8) Compare with other type of immobilization, e.g.,

https://doi.org/10.1016/j.ceramint.2021.06.100

https://doi.org/10.1016/j.conbuildmat.2021.126205 https://doi.org/10.1016/j.conbuildmat.2023.134804

https://doi.org/10.1007/s12649-023-02309-y

We included literature in the introduction and in references:

“The high activity of photocatalysts has rendered them attractive materials for pollutant removal and recycling waste substances in the environment [1-4].”

1. Vega-Mendoza, M.; Luévano-Hipólito, E.; Torres-Martínez, L. Design and fabrication of photocatalytic coatings with α/β-Bi2O3 and recycled-fly ash for environmental remediation and solar fuel generation. Ceram. Int. 2021, 47, 26907-26918.
2. Luévano-Hipólito,E.; Torres-Martínez, L.; Vega-Mendoza, M.; Treviño-Garza, M.; Vázquez-Guillén, J.; Báez González, J.; Rodríguez-Padilla, C. Photocatalytic performance of alkali-activated materials functionalized with β-Bi2O3/Bi2O2CO3 heterostructures for environmental remediation. Constr. Build. Mater. 2022, 320, 126205.
3. Rodríguez-Alfaro, L.; Torres-Martínez, L.; Treviño-Garza, M.; Vázquez-Guillén, J.; Rodríguez-Padilla, C.; Luévano-Hipólito, E. Design and fabrication of photocatalytic magnesium oxychloride cement with improved moisture stability: A step towards sustainable construction. Constr. Build. Mater. 2024, 414, 134804.
4. E. Luévano-Hipólito, E.; Torres-Martínez, L.; Rodríguez-González, E. Recycling Waste Materials to Fabricate Solar-Driven Self-Cleaning Geopolymers. Waste Biomass Valorization 2024, 15, 2833–2843.

9) Revise sub and super scripts in all the documents.

We revised sub and super scripts in all figures, and text in our article.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have made the necessary changes; however, there is still a small detail to be corrected before the article can be accepted.

• In the materials and methods section, the paragraph between lines 114 and 120 was added. The English of this paragraph needs to be revised, as well as its coherence. Are there three studies (refs 29, 30, and 31) or two? Additionally, it was included in a section that does not align well with the rest of the text. I suggest including comparisons with these previous works in the results section.

Author Response

There are three of our previous articles. In haste, we wrote two instead of three in the article. We rewrote this comparison part and moved it to the Results and Discussion section, 3.2. Photocatalytic evoluation:"

Sol-gel (ZnO, TiO₂) and powder (ZnO) films were created in our three earlier studies [34–36]. Both the silver ion modification method and the photo-fixation method are the same. For four hours, we break down the medication (paracetamol) and organic dyes (malachite green and methylene blue) in these three publications when exposed to UV and visible light. Using surfactants with two distinct molecular weights, we photo-fixed silver ions onto films from commercial TiO₂ powder in this paper. Due to the pollutants' shorter 3-hour half-lives under UV and visible light, this approach is more successful. The contaminants are malachite green and methylene blue. " 

We have renumbered all the literature.