PONE-D-23-10591TiO2 NPs-immobilized Silica Granules: New Insight for Nano Catalyst Fixation for Hydrogen Generation and Sustained Wastewater TreatmentPLOS ONE

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: N/A

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The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: No

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Manuscript ID: PONE-D-23-10591

Title: TiO2 NPs-immobilized Silica Granules: New Insight for Nano Catalyst Fixation for

Hydrogen Generation and Sustained Wastewater Treatment

In this manuscript, the authors desribe a novel method for immobilizing R25 nanoparticles on silica granules using hydrothermal treatment and calcination was introduced for heterogeneous catalytic processes. The resulting composite showed good performance in removing methylene blue dye and improved photocatalytic activity for hydrogen generation from sewage wastewaters under direct sunlight. The topic of the paper is interesting but the manuscript contains information and some propositions that are not well-justified. Furthermore, additional experiments are required to evaluate the catalytic performance of the as-prepared material. Therefore, the paper cannot be accepted for publication in its present form and major revision is needed. Some suggestions were listed as follows:

1. Abstract and introduction sections should be concisely rewritten to emphasize and highlight the results and urgency of this work.

2. In this work, the authors used a hydrothermal process for fabricating materials, so the hydrothermal method should be introduced, and some previous studies (such as https://doi.org/10.1016/j.ijhydene.2018.09.174, https://doi.org/10.1166/jnn.2018.15719) should be mentioned as examples for advantages of the hydrothermal route.

3. The authors investigated the effect of temperature (140, 150, 170, and 185 oC) on the formations of the catalysts by the hydrothermal routes, so the authors should be showed the change of behaviors of catalysts according to the temperatures. Why the authors did not investigate the effect of reaction time, which is a vital factor in fabricating the materials?

4. The particle size of TiO2 before and after also should be confirmed by its effect on the catalytic performance. In addition, can the author control the TiO2 structure?

5. In photocatalysis applications, the band gap, and surface area are important parameters to improve the photocatalytic efficiency, so the authors should be determined such values of the as-made catalysts.

6. The photocatalytic mechanism of the as-obtained photocatalysts should be mentioned. Some references such as https://doi.org/10.1021/acs.jpcc.0c03590; https://doi.org/10.1002/ceat.202200388 should be mentioned when discussing the photocatalytic mechanism.

7. Did the authors investigate the reusability of the catalyst for the photocatalytic degradation of dyes?

8. Some typos of English in the whole manuscript should be re-checked and improved.

Reviewer #2: The article entitled “TiO2 NPs-immobilized Silica Granules: New Insight for Nano Catalyst Fixation for Hydrogen Generation and Sustained Wastewater Treatment has significant scientific value.

In this work,. a novel approach for immobilizing R25 NPs on the surface of silica granules using hydrothermal treatment followed by calcination process. Due to the privileged characteristics of the subcritical water, during the hydrothermal treatment process, the utilized R25 NPs were partially dissolved and precipitated on the surface of the silica granules. Calcination at high temperature (700oC) resulted in improving the attachment forces. The structure of the newly proposed composite was approved by 2D and 3D optical microscope images, XRD and EDX analyses. The functionalized silica granules were used in the form of a packed bed for continuous removal of methylene blue dye. The results indicated that the TiO2:sand ratio has a considerable effect on the shape of the dye removal breakthrough curve as the exhaustion point, corresponding to ~ 95% removal, was 12.3, 17.4 and 21.3 min for 1:20, 1:10 and 1:5 metal oxides ratio, respectively. Moreover, due to inhibition of the electrons/holes recombination process, the calcination treatment distinctly improves the photo catalytic activity of the introduced coated silica. Furthermore, the modified silica granules could be exploited as a photocatalyst for hydrogen generation from sewage wastewaters under direct sunlight with a good rate; 75×10-3 mmol/s. Interestingly, after the ease separation of the used granules, the performance was not affected. Based on the obtained results, the 170 oC is the optimum hydrothermal treatment temperature . My comments listed below may help the authors further improve their work:

1. The authors can explain a bit about the adsorption effect using nanomaterials in the introduction part. Authors are suggested to enhance the discussion on adsorption kinetics and consider the following papers for the same:

https://doi.org/10.1016/j.matlet.2022.131716

https://doi.org/10.1016/j.surfin.2022.102182

https://doi.org/10.1007/s11356-022-20743-8

2. Authors need to improve the highlights as they are very generic and don’t exactly include the main points of their original work.

3. The novelty aspects of this research paper need to be further modified and compared with the already present research (if any) to further enhance the overall impact.

4. How the reusability of catalyst can be assured?. Please refer for some of the papers for a better explanation.

https://doi.org/10.1016/j.ijbiomac.2022.11.241

https://doi.org/10.1016/j.matlet.2022.131716

https://doi.org/10.1007/s11356-022-20743-8.

DOI: 10.1016/j.jmst.2021.01.051

5. The paper in its current state has so many typos, technical and formatting related errors. There are certain space, grammar, and English related errors in the manuscript which are significantly ignored. Authors are suggested to proofread the manuscript thoroughly and eliminate the errors such as subscripts, superscripts, uniformity in presentation (Fig.Xa&b/Fig.X a and b).

5. Have authors tested it under light just to see effect of photocatalysis

Reviewer #3: Please check typographical all the whole manuscripts. The author should rewrite the manuscript more concisely and succinctly, focusing on the obtained research results instead of rambling the textbook knowledge.

1. Introduction:

It should be shorter and more concise

2. Experimental part

It is not recommended to include basic knowledge from the textbook such as COD and BOD analysis procedures in the scientific article

3. The sections Results and discussion

Please focus on results and discussions in this section, do not include basic knowledge

There is no need to write too much about the concept, such as the concept of supercritical water.

It is not necessary to state the advantages and disadvantages and the purposes of the characterization of the produced catalyst analysis (EDX, XRD)

Fig 1 should be in section 2 Experimental part.

Table 1 should be used footnote for “Where COD is chemical oxygen demand, BOD is the biological oxygen demand, TSS is the total soluble suspended solids, TDS is the total dissolved solids, VSS is volatile suspended solids, total P is the total phosphorus, total N is the total nitrogen and Alk is the total alkalinity.” Paragraph.

Fig 4 should be added the legend

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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Submitted filename: Manuscript ID_PONE-D-23-10591.docx

TiO2 NPs-immobilized Silica Granules: New Insight for Nano Catalyst Fixation for Hydrogen Generation and Sustained Wastewater Treatment

PONE-D-23-10591R1

Dear Dr. Barakat,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Van-Huy Nguyen, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Manuscript ID: PONE-D-23-10591_R1

Title: TiO2 NPs-immobilized Silica Granules: New Insight for Nano Catalyst Fixation for

Hydrogen Generation and Sustained Wastewater Treatment

The authors addressed all reviewer comments, providing a comprehensive point-by-point response to every concern raised. Consequently, the manuscript is now eligible for acceptance in PLOS ONE.

Reviewer #2: (No Response)

Reviewer #3: The revision has been improved well. However, recheck some typos of English in the whole manuscript before publishing.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

Reviewer #3: Yes: Lan Anh Phan Thi

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