Photocatalytic Degradation of Methylene Blue Dye from Wastewater by Using Doped Zinc Oxide Nanoparticles

Round 1

Reviewer 1 Report

Manuscript ID: water-2410214

Shreya Modi, Virendra Kumar Yadav and co-authors reported “Photocatalytic Degradation of Methylene Blue Dye from Wastewater by Using Doped Zinc Oxide Nanoparticles". Although the topic is interesting but some important aspects were not performed.

1.      Abstract is not coherent. Should be revised.

2.      Line no. 17 & 26 having same wording as meaning, actively it should be enough only for one time.

3.      Abstract should be consisting of some SEM, TEM resulting values to show Nano particles properties with altering dopants.

4.      As line no. 28&29 showing ideal conditions for exposure to solar radiation but in abstract degradation mentioned for both so optimum under UV should be included.

5.      All over introduction is about only composition of material and its properties, there is no literature for other dyes removing techniques and materials. Also advreese effects of methylene blue should be briefly described in introduction. Following articles might be helpful for guidance, information and citation, Chemical Physics Letters 805 (2022) 139939, Catalysts 2023 13 813, Applied Clay Science 190 (2020) 105564, doi:10.1080/03067319.2021.1998471 

6.      Fig. 1 scheme of something misprint; it should be consisting of clear data. Similar the case with Fig.2. should replace with proper one

7.      Fig.15 is not captioned correctly, it should be corrected relevant to graph

8.      Fig.13 presentation should be in line graph to understand concentration factor clearly not in scattered. Fitting lines should be drawn in graphs of all models

9.      In Fig.14 correct Methylene as Methylene blue. Alos check whole manuscript. There are lot of such mistake in manuscript

10.  In set figures of Fig.9 are not readable. Should replace with better resolution figures

11.  pH effect is confusing. There is very less decrease in % degradation at low pH in comparison to high pH. Why?. What is pH_ZPC of catalysts? Should be calculated.

12.  Differences under both UV light and solar lamp should be clear to understand conflicting point about degradation phenomena

13.  FTIR should be performed after degradation to check functionalities difference

14.  XRD graph is not showing any difference b/w all three types of ZnONPs. How it possible? Some additional peaks and different in peaks intensities might be there.

15.  Which method and solvents were used for the regeneration of catalyst for recycling experiment?

16.  There is not mentioned captioned for figs that data is about UV or solar degradation

17.  A lot of changings are required for betterment in figs as well as written data for worth of manuscript

18.   language, spelling and formatting errors are present in whole manuscript. Should be carefully revised

Language, spelling and formatting errors are present in whole manuscript. Should be carefully revised

Author Response

Shreya Modi, Virendra Kumar Yadav and co-authors reported “Photocatalytic Degradation of Methylene Blue Dye from Wastewater by Using Doped Zinc Oxide Nanoparticles". Although the topic is interesting but some important aspects were not performed.

1. Abstract is not coherent. Should be revised.

A/R: Thank you for this valuable comment and suggestion. The authors have now revised the abstract in the revised version of the manuscript.

2. Line no. 17 & 26 having same wording as meaning, actively it should be enough only for one time.

A/R: Thank you for pointing out this mistake. The authors have now rectified the mistake in the revised manuscript as suggested by the reviewer.

3. Abstract should be consisting of some SEM, TEM resulting values to show Nano particles properties with altering dopants.

A/R: Thank you for this valuable comment and suggestion. The authors have now modified the abstract including the results of SEM, and TEM in the revised manuscript.

4. As line no. 28&29 showing ideal conditions for exposure to solar radiation but in abstract degradation mentioned for both so optimum under UV should be included.

A/R: Thank you for this valuable comment and suggestion. The authors have now modified the abstract accordingly. The authors have found optimum degradation under solar light for doped NPs.

5. All over introduction is about only composition of material and its properties, there is no literature for other dyes removing techniques and materials. Also adverse effects of methylene blue should be briefly described in introduction. Following articles might be helpful for guidance, information and citation, Chemical Physics Letters 805 (2022) 139939, Catalysts 2023 13 813, Applied Clay Science 190 (2020) 105564, doi:10.1080/03067319.2021.1998471 

A/R: Thank you for this valuable comment and suggestion. The authors have now added the adverse effects of methylene blue in the introduction in addition to all three suggested papers.

 

6. 1 scheme of something misprint; it should be consisting of clear data. Similar the case with Fig.2. should replace with proper one

A/R: Thank you for pointing out this mistake. The authors have now corrected Figure 1 as suggested by the reviewer.

7. 15 is not captioned correctly, it should be corrected relevant to graph

A/R: Thank you for pointing out this mistake. The authors have now rectified the caption for Figure 15 as suggested by the reviewer in the revised manuscript.

8. 13 presentation should be in line graph to understand concentration factor clearly not in scattered. Fitting lines should be drawn in graphs of all models

A/R: Thank you for pointing out this mistake. Due to technical errors, the authors missed the Excel file for this data.

9. In Fig.14 correct Methylene as Methylene blue. Alos check whole manuscript. There are lot of such mistake in manuscript

A/R: Thank you for pointing out this mistake. The authors have now rectified the mistake in the revised manuscript as suggested by the reviewer.

10. In set figures of Fig.9 are not readable. Should replace with better resolution figures

A/R: Thank you for pointing out this mistake. The authors have now improved the quality of the image in the revised manuscript.

11. pH effect is confusing. There is very less decrease in % degradation at low pH in comparison to high pH. Why?. What is pH_ZPC of catalysts? Should be calculated.

A/R: Thank you for this valuable comment and suggestion. As MB is having a positive charge, it might be due to at a high pH, negatively charged OH- ions on the surface of doped ZnO attracted MB dye molecules. The authors have added results as per the values they have received.

12. Differences under both UV light and solar lamp should be clear to understand conflicting point about degradation phenomena

A/R: Thank you for this valuable comment and suggestion. The authors have used direct sunlight and a Philips UV-A lamp during the study.

13. FTIR should be performed after degradation to check the functionalities difference

A/R: Thank you for this valuable comment and suggestion. The authors have now added the FTIR graph after degradation also in the revised manuscript as suggested by the reviewer. It has been observed from the below figure that all the peaks corresponding to MB dye have disappeared after the photocatalytic degradation shown in Fig.14 in the revised manuscript.

 

14. XRD graph is not showing any difference b/w all three types of ZnONPs. How it possible? Some additional peaks and different in peaks intensities might be there.

A/R: Thank you for this valuable comment and suggestion. The authors have used a very low concentration of dopant and proper doping was carried out. Even though the authors didn’t find new peaks but authors have now provided a summarized Table for XRD presented below in the revised manuscript in the XRD section.

 

2 Theta degree	hkl	FWHM	D-value	Size (nm)	Lattice strain
ZnO NPs
31.5	100	0.501	2.83	17.22	0.0077
34.18	002	0.313	2.61	27.75	0.0044
36.03	101	0.496	2.48	17.6	0.0066
47.34	102	0.456	1.91	19.88	0.0045
56.41	110	0.498	1.62	18.91	0.004
62.68	103	0.5	1.48	18.84	0.0041
66.21	112	0.47	1.38	21.28	0.0031
ZnO-W
31.8	100	0.467	2.8114	18.48	0.0072
34.44	002	0.272	2.6018	31.95	0.0038
36.28	101	0.486	2.4738	17.97	0.0065
47.33	102	0.614	1.1989	14.76	0.0061
56.6	110	0.567	1.6248	17.49	0.0042
62.85	103	0.589	1.6248	16.5	0.0042
ZnO-Sb
31.74	100	0.817	2.8163	10.55	0.0125
34.43	102	0.556	2.6026	15.63	0.0078
36.23	101	0.772	2.4770	11.30	0.0103
47.55	102	0.811	1.9105	11.18	0.008
56.59	110	0.813	1.8248	11.59	0.0066
62.88	103	0.713	1.4786	13.64	0.0051
67.99	112	0.513	1.3787	12.11	0.0072

 

15. Which method and solvents were used for the regeneration of catalyst for recycling experiment?

A/R: Thank you for this comment. Here the authors have used double distilled water as a solvent for studying the regeneration of catalyst for recycling experiment.

16. There is not mentioned captioned for figs that data is about UV or solar degradation

A/R: Thank you for this comment. Authors have written in the text but not mentioned in the Figure caption. Now it has been added in the caption i.e. under solar light irradiation

17. A lot of changings are required for betterment in figs as well as written data for worth of manuscript

A/R: Thank you for this valuable comment and suggestion. The authors have now rectified and modified all the figures, Tables and their captions in the revised manuscript a suggested by the reviewer.

18. language, spelling and formatting errors are present in whole manuscript. Should be carefully revised

A/R: Thank you for this valuable comment and suggestion. The authors have now thoroughly edited the manuscript in terms of English editing, spelling and grammar.

Author Response File: Author Response.pdf

Reviewer 2 Report

The content of the manuscript is well explained and the materials are very well characterized. The only fixes I recommend are:

- Elimination of figures 1 and 2, because they do not provide new information or clarify the contents previously explained in the text. Also, these figures are of poor quality.

- Figures 8 should be replaced by those corresponding to the Kuberlka-Munk adjustment to obtain the band gap values.

- The authors should expand the information regarding the content of figures 13, explaining what each one is in the footer. It's not understood.

 

Author Response

The content of the manuscript is well explained and the materials are very well characterized. The only fixes I recommend are:

1. Elimination of figures 1 and 2, because they do not provide new information or clarify the contents previously explained in the text. Also, these figures are of poor quality.

A/R: Thank you for this valuable comment and suggestion. The other 4 reviewers have asked to rectify these two figures so can’t be eliminated. Now the authors have modified the diagram and rectified all the errors in the revised manuscript.

2. Figures 8 should be replaced by those corresponding to the Kuberlka-Munk adjustment to obtain the band gap values.

A/R: Thank you for this valuable comment and suggestion. The authors are mainly from a biological background and don’t have expertise in physics or material science background so unable to incorporate this in the revised manuscript. 

3. The authors should expand the information regarding the content of Figure 13, explaining what each one is in the footer. It's not understood.

A/R: Thank you for this valuable comment and suggestion. The authors have now expanded the Fig.13 content in the revised manuscript as suggested by the reviewer. Moreover, the detail is also given in Table 3.

Reviewer 3 Report

Reviewer comment.

 

In the reviewer's opinion, the manuscript cannot be published in its current form. The most urgent points are that the analysis is not done correctly and the list of references needs to be improved. Nevertheless, I am convinced that the ZnO particles themselves are interesting, even if the quality of the manuscript needs to be improved.

 

Spezific comments

-       -        List of references could be improved.

 

A number of illustrations (Fig.1,…) are incorrectly converted and could not be evaluated.

-        Histogram: Counting and measuring 25 particles is not nearly enough(is without statistical relevance). What about aspect ratio (measuring the narrowest and widest diameter for all, This is very important for your particles)? Take a look at the correct procedure as shown in Figure S14 (DOI: 10.1039/c5nr00850f)

-        Figure 9: Quality is poor.

-        “solar irradiation.” Without further information, the information is unfortunately useless. (conditions, how was the experiment performed, used filters (like glass), inside, outside (position: longitude …, latitude …, altitude … m, clouds?), data from an optical radiometer with known and defined parameters would be greatà Reduced total hemispherical radiation on a horizontal surface H(t) - D(t) and diffuse sky radiation D(t).) In this way it is even possible to calibrate optical detectors by solar radiation.

-        UV = no information !! (light source, intensity, W/cm² on the sample, ….)

-        What about the photo decomposition of the ZnO material in water?

-        WO3 does not dissolve during the preparation? Could it be possible that the small signals in the XRD are form the WO3. How large are these WO3 nanoparticles ? Do you have some kind of ZnO composite material? This is a critical point, how can it dope if it is not soluble? Check that the composition is OK in the context of your EDX measurements. Can you do locally resolved measurements?

-        You should mention and cite the Photo-Kolbe reaction (an oxidation of an organic acid followed by fragmentation (CO 2 release) (or -COH, C=O, COOH) which is known for ZnO NPs. In line 436 you mention mineralization but this is the only hind.

-        FTIR: concentrations of particles are too high. The signal is saturated.

-        Please perform a Scherer Analysis of the XRD diffraction patterns, analyse the aspect ratio (direction of growth).

-        Comparing TEM and XRD the non-spherical particles seems to be the one with W?! Overall you should use the same experimental procedure for the undoped particles. I guess that the amine influence the aspect ratio.

-        Clearly state that you did not use waste water (model system of MB dissolved in water). Wastewater sound like a real field test.

-        Figure 13+15 Add information concerning a,b,c,d,e,… (Are the measurements under sunlight carried out at least simultaneously?!)

-        I guess Figure 15 a contains the blank measurement, the MB without catalyst under illumination ?

-        Effect of surface charge on the ZnO NP, determination of point of zero charge (zeta potential), e.g. in the above mentioned reference.

-        TOC analysis is not explained.

good

Author Response

In the reviewer's opinion, the manuscript cannot be published in its current form. The most urgent points are that the analysis is not done correctly and the list of references needs to be improved. Nevertheless, I am convinced that the ZnO particles themselves are interesting, even if the quality of the manuscript needs to be improved.

 

Specific comments

1. List of references could be improved.

 A/R: Thank you for this valuable comment and suggestion. The authors have now improved the references in the revised manuscript as suggested by the reviewer.

2. A number of illustrations (Fig.1,…) are incorrectly converted and could not be evaluated.

 Histogram: Counting and measuring 25 particles is not nearly enough(is without statistical relevance). What about aspect ratio (measuring the narrowest and widest diameter for all, This is very important for your particles)? Take a look at the correct procedure as shown in Figure S14 (DOI: 10.1039/c5nr00850f)

A/R: Thank you for this valuable comment and suggestion. The authors have now improved all such Figures in the revised manuscript. The authors have followed a similar method for the preparation of histograms for TEM.

 

2. Figure 9: Quality is poor.

A/R: Thank you for this valuable comment and suggestion. The authors have now improved the references in the revised manuscript as suggested by the reviewer.

-        “solar irradiation.” Without further information, the information is unfortunately useless. (conditions, how was the experiment performed, used filters (like glass), inside, outside (position: longitude …, latitude …, altitude … m, clouds?), data from an optical radiometer with known and defined parameters would be greatà Reduced total hemispherical radiation on a horizontal surface H(t) - D(t) and diffuse sky radiation D(t).) In this way, it is even possible to calibrate optical detectors by solar radiation.

Ans: Thank you for this valuable comment and suggestion. The authors have run experiments under a direct sunlight environment.

-        UV = no information !! (light source, intensity, W/cm² on the sample, ….)

A/R: Thank you for this valuable comment and suggestion. The authors have used 2 No. of Philips UV A light (6 W), Germany which is mentioned now in the revised manuscript as suggested by the reviewer.

-        What about the photo decomposition of the ZnO material in water?

A/R: Thank you for this valuable comment and suggestion. The authors have not assessed the photodecomposition of the ZnO material in water.

-        WO3 does not dissolve during the preparation? Could it be possible that the small signals in the XRD are form the WO3. How large are these WO3 nanoparticles ? Do you have some kind of ZnO composite material? This is a critical point, how can it dope if it is not soluble? Check that the composition is OK in the context of your EDX measurements. Can you do locally resolved measurements?

A/R: Thank you for this valuable comment and suggestion. The authors have used a very minimal concentration of WO3 followed by vigorous stirring conditions so we didn’t check for the same.

-        You should mention and cite the Photo-Kolbe reaction (an oxidation of an organic acid followed by fragmentation (CO 2 release) (or -COH, C=O, COOH) which is known for ZnO NPs. In line 436 you mention mineralization but this is the only hind.

-        FTIR: concentrations of particles are too high. The signal is saturated.

A/R: Thank you for this valuable comment. The authors agree with the reviewer’s comment.

-        Please perform a Scherer Analysis of the XRD diffraction patterns, analyse the aspect ratio (direction of growth).

A/R: Thank you for this valuable comment and suggestion. The authors have calculated the same in the revised manuscript as suggested by the reviewer.

-        Comparing TEM and XRD the non-spherical particles seems to be the one with W?! Overall you should use the same experimental procedure for the undoped particles. I guess that the amine influence the aspect ratio.

A/R: Thank you for this valuable comment. The authors agree with the reviewer’s comment -        Clearly state that you did not use waste water (model system of MB dissolved in water). Wastewater sound like a real field test.

A/R: Thank you for this valuable comment and suggestion. The authors have prepared different concentrations of MB dye (10, 25, and 50 ppm) in distilled water.

-        Figure 13+15 Add information concerning a,b,c,d,e,… (Are the measurements under sunlight carried out at least simultaneously?!)

A/R: Thank you for this valuable comment and suggestion. The authors have added proper captions in the said figure in the revised manuscript as suggested by the reviewer.

-        I guess Figure 15 a contains the blank measurement, the MB without catalyst under illumination?

A/R: No

-        Effect of surface charge on the ZnO NP, determination of point of zero charge (zeta potential), e.g. in the above mentioned reference.

A/R: Thank you for this valuable comment and suggestion. The authors have not studied zeta potential for this experiment as it is not one of the objectives during material synthesis and characterization.

-        TOC analysis is not explained.

A/R: Thank you for pointing out this mistake. The authors have now explained the TOC analysis in the revised manuscript as suggested by the reviewer.

 

Reviewer 4 Report

This manuscript reported two kinds of doped ZnO NPs to realize photocatalytic degradation for wastewater remediation. However, some important issues should be solved before it can be accepted. Detailed comments are listed as follows.

 1. The figure 1 should be revised. Some words are covered. Moreover, this schematic figure is not attractive.

2. Some words in figure 2 are also covered.

3. The “Zinc” in “3. Characterization of pristine and doped Zinc oxide nanoparticles” should be revised.

4. What is the figure in page 9?

5. The figure 6 should be checked more, such as some dimension mark in figure 6e, the "1" and "-" in figure 6c can be deleted.

6. The EDS spectra were used to detected W and Sb elements. However, the XPS characterization can be more precise.

7. The figure 14 is suggested to be adjusted. It has been out of shape.

8. There are many results in figure 15, however, all of them were not discussed in the manuscript. Moreover, what do all these figures refer to should be explained more.

9. The references in this manuscript are too old. Some works focusing on the wastewater remediation published in recent years can be read and may be added, such as Environmental Research, 2022, 214, 113936, Mater. Horiz., 2022,9, 2496-2517, Environmental Research, 2022, 214 113955, Mater. Horiz., 2023,10, 1020-1029.

The quality of English can be accpeted.

Author Response

This manuscript reported two kinds of doped ZnO NPs to realize photocatalytic degradation for wastewater remediation. However, some important issues should be solved before it can be accepted. Detailed comments are listed as follows.

1. The figure 1 should be revised. Some words are covered. Moreover, this schematic figure is not attractive.

A/R: Thank you for this valuable comment and suggestion. The authors have now improved Figure 1 in the revised manuscript as suggested by the reviewer.

2. Some words in figure 2 are also covered.

A/R: Thank you for this valuable comment and suggestion. The authors have now improved Figure 2 in the revised manuscript as suggested by the reviewer.

 

3. The “Zinc” in “3. Characterization of pristine and doped Zinc oxide nanoparticles” should be revised.

A/R: Thank you for pointing out this mistake. The authors have now rectified the mistake in the revised manuscript as suggested by the reviewer.

4. What is the figure in page 9?

A/R: Thank you for this valuable comment and suggestion. Fig.9 is porosity by N2 adsorption isotherm. Earlier it was blurred now it is improved in the revised version of the manuscript as suggested by the reviewer.

5. The figure 6 should be checked more, such as some dimension mark in figure 6e, the "1" and "-" in figure 6c can be deleted.

A/R: Thank you for this valuable comment and suggestion. Since the images are provided by the technician, from the outsourced facilities so it is not possible to edit them for us. So, the dimension from Fig.6e cannot be removed. Thank you for pointing out the error in Fig.6c, which has been rectified by the authors in the revised manuscript.

6. The EDS spectra were used to detected W and Sb elements. However, the XPS characterization can be more precise.

A/R: Thank you for this valuable suggestion. XPS is available at very limited places and too has a long queue. Moreover, it is a very expensive technique and authors can’t afford its analysis. Already authors have spent a lot on the characterization from their side. So, we will surely do XPS in the future.

7. The figure 14 is suggested to be adjusted. It has been out of shape.

A/R: Thank you for this valuable suggestion. The authors have now improved the quality and adjusted Figure 14 in the revised manuscript as suggested by the reviewer.

8. There are many results in figure 15, however, all of them were not discussed in the manuscript. Moreover, what do all these figures refer to should be explained more.

A/R: Thank you for pointing out this mistake. The authors have now explained all the individual Figures of Fig.15 now 16 in the revised manuscript as suggested by the reviewer.

9. The references in this manuscript are too old. Some works focusing on the wastewater remediation published in recent years can be read and may be added, such as Environmental Research, 2022, 214, 113936, Mater. Horiz., 2022,9, 2496-2517, Environmental Research, 2022, 214 113955, Mater. Horiz., 2023,10, 1020-1029.

A/R: Thank you for this valuable comment and suggestion. The authors have now added recent references in the revised manuscript as suggested by the reviewer. Moreover, the authors have also added the suggested references in the revised manuscript.

Reviewer 5 Report

In the current version, the article appears as a very rough draft that is quite difficult to read. Due to errors and oversights, it is hard to understand many aspects of the work. Most of the illustrations have issues. In Figures 1 and 2, part of the text in the Text Box is displayed incorrectly. Figure 5 is split between pages and distorted. Figure 9 is of low quality and also distorted in proportion. A portion of the text is missing in Figure 14. The labels in Figure 6(e) are unreadable due to their small size. Captions for images and tables are incomplete; they should be readable independently from the text. The text in the article is also incomplete. In particular, in the "Materials" section (Tungsten oxide (WO3) (Renkem, Gujarat, India), ammonium solution (NH4OH) 105 (Renkem, Gujarat, India), sodium hydroxide or NaOH (SRL, Gujarat, India); antimony 106 chloride (SbCl2) (Renkem, Gujarat, India); Zinc nitrate or Zn(NO3)2 (Renkem, Gujarat, In-107 dia)), the starting components are listed, but there are no explanations about what was synthesized from them (presumably). The reference list is not prepared in accordance with the journal's format. I do not see the possibility of publishing the work in its current form. I recommend fixing the illustrations, supplementing the text, and resubmitting the work.

Additional recommendations to authors: 

1. Some information is mentioned without a citation (e.g., "A team led by Celik 2020" and "Sinornate et al., 2021").

2. Unclear objectives: The objectives of the study are not clearly stated until the end of the introduction. It would be more effective to present the objectives earlier, so readers can better understand the context and goals of the research. 

Additionally, the context of the novelty of this work is not entirely clear. This should be emphasized more clearly in the introduction. A more distinct comparison with the existing literature is needed, as ZnO is a well-studied material.

 

The text is incomplete. Captions for pictures and tables are incomplete. Some sentences (for example, in the section "Materials") are incomplete, which also interferes with reading.

Author Response

In the current version, the article appears as a very rough draft that is quite difficult to read. Due to errors and oversights, it is hard to understand many aspects of the work. Most of the illustrations have issues.

 In Figures 1 and 2, part of the text in the Text Box is displayed incorrectly.

A/R: Thank you for pointing out this mistake. The authors have now corrected the mistake related to both the figures in the revised manuscript as suggested by the reviewer.

 

Figure 5 is split between pages and distorted.

A/R: Thank you for pointing out this mistake. The authors have now corrected the mistake related to Figure 5 in the revised manuscript as suggested by the reviewer

Figure 9 is of low quality and also distorted in proportion.

A/R: Thank you for pointing out this mistake. The authors have now provided Figure 9 of higher resolution in the revised manuscript as suggested by the reviewer.

A portion of the text is missing in Figure 14.

A/R: Thank you for pointing out this mistake. The authors have now corrected the mistake related to Figure 14 in the revised manuscript as suggested by the reviewer.

The labels in Figure 6(e) are unreadable due to their small size.

A/R: Thank you for pointing out this mistake. The authors would like to say that the scaling and diameter of the nanomaterial are being done by the TEM operator and machine itself, so it cannot be changed. Any changes in this will come under image manipulation. So, please bear with us.  

Captions for images and tables are incomplete; they should be readable independently from the text.

A/R: Thank you for pointing out this mistake. The authors have now corrected the mistake related to the captions of Figures and Tables in the revised manuscript as suggested by the reviewer.

The text in the article is also incomplete. In particular, in the "Materials" section (Tungsten oxide (WO3) (Renkem, Gujarat, India), ammonium solution (NH4OH) 105 (Renkem, Gujarat, India), sodium hydroxide or NaOH (SRL, Gujarat, India); antimony 106 chloride (SbCl2) (Renkem, Gujarat, India); Zinc nitrate or Zn(NO3)2 (Renkem, Gujarat, In-107 dia)), the starting components are listed, but there are no explanations about what was synthesized from them (presumably).

A/R: Thank you for pointing out this mistake. After publishing 120 papers I have never got this comment related to chemicals and their use for synthesis in materials itself. Methodology clearly explains the use of chemicals which we can’t provide in the materials section.

Authors welcome any support for such published paper preferably from the reviewer. Thank you for the suggestion.

The reference list is not prepared in accordance with the journal's format. I do not see the possibility of publishing the work in its current form. I recommend fixing the illustrations, supplementing the text, and resubmitting the work.

A/R: Thank you for this valuable comment and suggestion. The authors have now modified the references as per the journals in MDPI format.

Additional recommendations to authors: 

1. Some information is mentioned without a citation (e.g., "A team led by Celik 2020" and "Sinornate et al., 2021").

A/R: Thank you for pointing out this mistake. The former citation was missing now it has bee added while the later one was already there.

2. Unclear objectives: The objectives of the study are not clearly stated until the end of the introduction. It would be more effective to present the objectives earlier, so readers can better understand the context and goals of the research. 

A/R: Thank you for this valuable comment and suggestion. The authors have now modified the objective in order to make it clearer as suggested by the reviewer in the revised manuscript.

Additionally, the context of the novelty of this work is not entirely clear. This should be emphasized more clearly in the introduction. A more distinct comparison with the existing literature is needed, as ZnO is a well-studied material.

A/R: Thank you for this valuable comment and suggestion. The authors have now modified the novelty section in the introduction of the revised manuscript.

Round 2

Reviewer 1 Report

Accept in present form

Minor editing required

Author Response

Accept in present form

Minor editing required

A/R: Thank you for accepting our manuscript. The authors have now rectified all the errors related to English in the revised manuscript as suggested by the reviewer.

Reviewer 3 Report

The quality of the manuscript was significantly improved after the reviewer's comments and the comments of the previous reviewers were taken into account. I especially love the table. The manuscript can be accepted after minor revisions.

Nevertheless, they should include information about the position on the Earth's surface (your university is located near the equator, which increases the solar radiation enormously), clear sky conditions (I believe that the sun is always shining) and the time of measurement. With the help of the zenith of the sun, the illuminance can be calculated. A simple procedure is presented in M. Schmitt, F. Heib, About the possibility of calibrating optical detectors by solar radiation, RSC Advances, 4, 17639–17647 (2014). You used calibrated data from pyrometers, if your experiments were done not very far from the highest zenith of the sun I think you can assume the maximum radiant power of the sun on the surface of the earth (ASTMG173, direct and circular in the range of 900 W/m2 for the full wavelength range).

2^nd point you should also add,name and cite the Photo-Kolbe reaction equation [10]. h_VB+ + dye à CO2 + outher degration products  

 

 

 

Author Response

The quality of the manuscript was significantly improved after the reviewer's comments and the comments of the previous reviewers were taken into account. I especially love the table. The manuscript can be accepted after minor revisions.

1. Nevertheless, they should include information about the position on the Earth's surface (your university is located near the equator, which increases the solar radiation enormously), clear sky conditions (I believe that the sun is always shining) and the time of measurement. With the help of the zenith of the sun, the illuminance can be calculated. A simple procedure is presented in M. Schmitt, F. Heib, About the possibility of calibrating optical detectors by solar radiation, RSC Advances, 4, 17639–17647 (2014). You used calibrated data from pyrometers, if your experiments were done not very far from the highest zenith of the sun I think you can assume the maximum radiant power of the sun on the surface of the earth (ASTMG173, direct and circular in the range of 900 W/m2 for the full wavelength range).

 

 

A/R: Thank you for this valuable comment and suggestion. The authors have now added an Earth’s surface map in the revised manuscript as suggested by the reviewer. The authors also took help from the provided paper.

 

2. 2^ndpoint you should also add,name and cite the Photo-Kolbe reaction equation [10]. h_VB+ + dye à CO2 + outher degration products  
3. A/R: Thank you for this valuable comment and suggestion. The authors have now added and cited the Photo-Kolbe reaction equation [10]. h_VB++ dye à CO2 + other degradation products in the revised manuscript as suggested by the reviewer.

Reviewer 4 Report

No other comments.

Author Response

No other comments.

Thank you for accepting our manuscript.

Reviewer 5 Report

The text has been improved, there are still problems with the quality of the pictures and their proportions. The manuscript can be accepted, but I recommend that the editorial department pay special attention to the technical quality of the article. At the moment it is still insufficient.

I don't see serious issues.

Author Response

The text has been improved, there are still problems with the quality of the pictures and their proportions. The manuscript can be accepted, but I recommend that the editorial department pay special attention to the technical quality of the article. At the moment it is still insufficient.

A/R: Thank you for this valuable comment and for accepting our manuscript. The authors have now redrawn the BET figure in the revised manuscript as suggested by the reviewer.