Photocatalytic Degradation and Adsorptive Removal of Emerging Organic Pesticides Using Metal Oxide and Their Composites: Recent Trends and Future Perspectives
, Eman F. H. Alzaimoor 1, Suad Rashdan 1, Amina A. Abdalhafith 2 and Ayman H. Kamel 1,3,*
Round 1
Reviewer 1 Report
The manuscript entitled “Metal Oxide Nanomaterials and Their Composites as Effective Adsorbents and Photocatalysts for Organic Pesticides Removal” by Kamel et al summarized various metal oxides and functionalized metal oxide nanomaterials including cobalt oxide, copper oxide, zinc oxide, iron oxide, titanium oxide, magnesium oxide, cerium oxide, aluminum oxide, and others for the removal of pesticides by adsorption and photocatalytic degradation. In my opinion, this is a significant topic and suitable for publication in Sustainability. As a review, there are some issues that need to be addressed.
1. It is recommended to add the selected chemical structure formulas of the classical pesticides in Tables 1&2.
2. It is recommended to add a discussion of the toxicity of metal oxide nanomaterials, especially in comparison to pesticides.
3. I note that the authors have cited a number of metal oxide/metal organic framework composites, in fact the potential of metal oxide/covalent organic framework composites cannot be ignored, and suggest adding relevant discussions and citations(Molecules 2022, 27, 8002).
Author Response
- It is recommended to add the selected chemical structure formulas of the classical pesticides in Tables 1&2.
The structures of common pesticides including Pyrethroids, Organophosphates, Carbamates and Organochlorines have been included in Figure. 15 following Table 1. Also, all the structures for the pesticides included in Tables 2 have been included as well.
It is recommended to add a discussion of the toxicity of metal oxide nanomaterials, especially in comparison to pesticides.
Pointed out in page 3, lines 105-108.
I note that the authors have cited a number of metal oxide/metal organic framework composites, in fact the potential of metal oxide/covalent organic framework composites cannot be ignored and suggest adding relevant discussions and citations (Molecules 2022, 27, 8002).
A highlight has been made on metal oxides/metal organic frameworks in the introduction, and the suggested reference has been added. Kindly check reference 34.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In this review, the authors summarize the research progress of metal oxide based nanomaterials in adsorption and photocatalytic removal of organic pesticides removal. However, this article is not well structured and does not highlight unique perspectives; there is only a general presentation of the published literature. After reading this manuscript, the reader cannot be inspired and it is difficult to get a quick overview of the field. Therefore, I recommend that it should not be considered for acceptance until a major revision has been completed.
The abstract needs to be rewritten. The current form does not convey the intent of the article. It should address the current research on the removal of pesticides by metal oxide nanomaterials, which specific problem the authors have addressed, and what conclusions they have finally reached.
In the Introduction section, the description of the hazards of persistent organic chemicals is too much and is not the focus of the article. More information should be given about how to remove them by photocatalysis and adsorption.
There is no logical connection between the third and fourth paragraphs. I do think that the description of nanomaterials in the fourth paragraph is redundant.
More information on the properties of metal oxide nanomaterials should be added to this section so that the reader can easily understand the advantages of this material for treating pesticides.
There are detailed descriptions of the structure and properties of various Metal Oxide in the text, but these are not linked to the manifestation of photocatalysis and adsorption ability, and this needs to be added and adjusted.
Adsorption and photocatalysis are two completely different modes of action, so why are they discussed together in this article? Is it that metal oxides rely on these two modalities alone to treat pesticides? What are the characteristics of the efficiency of each of these two methods that should be given specifically.
In Challenges and Outlook, the author's points should be based on the content of the text, such as the recycling of secondary waste, and the introduction of each metal oxide nanomaterial should be supplemented with further treatment issues after they have been utilized.
The Conclusions need to be rewritten, because in their current form they do not appear to be a carefully argued view of the author. Instead, it is more like a summary of the article.
Author Response
In this review, the authors summarize the research progress of metal oxide-based nanomaterials in adsorption and photocatalytic removal of organic pesticides removal. However, this article is not well structured and does not highlight unique perspectives; there is only a general presentation of the published literature. After reading this manuscript, the reader cannot be inspired, and it is difficult to get a quick overview of the field. Therefore, I recommend that it should not be considered for acceptance until a major revision has been completed.
- The abstract needs to be rewritten. The current form does not convey the intent of the article. It should address the current research on the removal of pesticides by metal oxide nanomaterials, which specific problem the authors have addressed, and what conclusions they have finally reached.
The abstract is re-written as requested from the reviewer. All Changes are highlighted with a red color.
- In the Introduction section, the description of the hazards of persistent organic chemicals is too much and is not the focus of the article. More information should be given about how to remove them by photocatalysis and adsorption.
The introduction has been modified to focus on the scope of the review. The suggested approach has been taken into consideration. Please view the modifications in the introduction. Description of POPs have been reduced and more light was carried out on photocatalysis and adsorption.
- There is no logical connection between the third and fourth paragraphs. I do think that the description of nanomaterials in the fourth paragraph is redundant.
The introduction has been modified to be more cohesive, interconnected, and organized. The suggested approach has been taken into consideration. Please view the modifications in the introduction.
- More information on the properties of metal oxide nanomaterials should be added to this section so that the reader can easily understand the advantages of this material for treating pesticides.
Properties of metal oxides have been added and discussed substantially in the introduction as recommended. Please view the modifications in the introduction.
- There are detailed descriptions of the structure and properties of various Metal Oxide in the text, but these are not linked to the manifestation of photocatalysis and adsorption ability, and this needs to be added and adjusted.
These are pointed out in sections 4. & Section 5. Table 3 is added. Figure 15 shows a schematic diagram for pesticide photodegradation mechanism using metal oxides nanoparticles and their composites.
- Adsorption and photocatalysis are two completely different modes of action, so why are they discussed together in this article? Is it that metal oxides rely on these two modalities alone to treat pesticides? What are the characteristics of the efficiency of each of these two methods that should be given specifically.
Adsorption is an easy, popular, and accessible method of treatment. However, the generation of secondary products is a rising issue that is seldomly addressed. Photocatalytic degradation solves this issue by mineralizing the toxicant, but compromises with the need of oxygen as an oxidant and has a more complex operation. Metal oxides do not necessarily rely on those two modalities to treat pesticides, however, to achieve a good efficient photodegradation rate, high adsorption of the photocatalyst towards the pollutant is required. Kindly refer to the introduction section where this issue has been discussed.
- In Challenges and Outlook, the author's points should be based on the content of the text, such as the recycling of secondary waste, and the introduction of each metal oxide nanomaterial should be supplemented with further treatment issues after they have been utilized.
Challenges and outlook have been rewritten to be more interrelated with the outcome of the review. Kindly refer to the Challenges and outlook section.
- The Conclusions need to be rewritten, because in their current form they do not appear to be a carefully argued view of the author. Instead, it is more like a summary of the article.
Conclusion has been rewritten as recommended, the suggested approach has been taken into consideration. Please view the modifications in the conclusion section.
Author Response File: Author Response.docx
Reviewer 3 Report
Comments for author File: 
Comments.pdf
Author Response
The manuscript is written properly and should be accept after minor changes.
- The heading “types of metal oxides” seems to be inappropriate use proper heading as if you discuss types of metal oxides it should cover vast family of metal oxides for examples perovskites, spinals etc.
It is changed into “Nanoarchitectures of Metal Oxides and oxide perovskites”.
Add references corresponding to these metal oxides. “Metal oxides nanoparticles including ferric oxides, cobalt oxides, copper oxides, zinc oxides, titanium oxides, magnesium oxides, cerium oxide, aluminum oxides and other metal oxides have shown promising removal and degradation results towards pollutants including heavy metals and POPs”.
For copper-based nanoparticles add Ascorbic acid assisted synthesis, characterization and catalytic application of copper nanoparticles.
https://doi.org/10.1021/acs.energyfuels.2c03396
Include discussion regarding photocatalytic degradation of pollutants using following paper.
https://doi.org/10.1002/slct.202201800
As recommended, new references have been added in the introduction for metal oxides. The suggested references have been also included in the discussion of the review as well.
- Proper formatting needed to be done for example in Fe3O4@nSiO2 @mSiO2, Zincblende in line number 167 subscripting is needed.
Format has been modified.
- Specify the application of MgO in solar applications as it have large band gap has been discussed so it may be confusing
As recommended, the application was specified for MgO in lines 269,270.
- In titanium oxide authors mentioned control of morphology it should be discussed in detail.
Further discussion has been added on the controlled morphology of titanium oxide in line 233 – 244.
- Also, the application and mechanism of photocatalytic removal of organic molecules should be included.
The detailed mechanism of the photocatalytic degradation of pesticides is explained extensively in section 5. The mechanism of photocatalytic removal of organic molecules is carried out in a similar fashion and is noted in the text. “The mechanism of photocatalytic degradation starts when the photocatalyst is irradiated under UV or visible light that has energy equal or greater than its band gap [1]. The detailed mechanism of the reaction is shown in Eq.(3) to Eq.(9). Notably, photocatalytic degradation of organic molecules is carried out in a similar manner [2].
- Authors should also mention the scope of the review and disadvantages associated with the different adsorption processes involved in different mental oxides.
Please refer to the end of the introduction section for the scope of the review. The advantages and disadvantages of the adsorption processes have been included in Table 3.
- Future perspective should be also included before conclusion section. Also, authors should conclude comparison between adsorption and photocatalytic degradation properties of metal oxides.
Challenges and outlook are included before the conclusion section, kindly refer to it. The comparison between adsorption and photocatalytic degradation is inserted in the introduction section.
- Strategies used to enhance the photocatalytic and adsorption properties of metal oxides should be discussed. Like effect of doping, heterostructure development, composite development etc. take following example as the model paper to discuss: https://doi.org/10.1166/jnn.2020.17516
The strategies have been added as recommended. Please refer to line 91 – 99 in the introduction.
Author Response File: Author Response.docx
Reviewer 4 Report
The manuscript "Metal Oxide Nanomaterials and Their Composites as Effective Adsorbents and Photocatalysts for Organic Pesticides Removal" deals with the use of metal oxides for the photocatalytic removal of pesticides. It is an interesting review. However, some key points need to be reviewed as follows:
1) Figure 4 need to be amended since its description does not correspond to the order of the crystalline structures.
2) Section 2. It is suggested to add a comparative table for the mentioned metallic oxides giving their advantages and disadvantages as well as their main functionalization chemical groups.
3) Section 2. Please provide a deep and fundamental discussion about the effect of the crystalline structure on the photocatalytic/sorption performance of the different metallic oxides.
4) Section 4. It is suggested to discuss with deeper and fundamental aspects the advantages of certain functionalization /doping strategies and not just present the compilation of different works as a Table.
Author Response
1) Figure 4 need to be amended since its description does not correspond to the order of the crystalline structures.
The order of crystalline structures has been fixed in Figure 4.
2) Section 2. It is suggested to add a comparative table for the mentioned metallic oxides giving their advantages and disadvantages as well as their main functionalization chemical groups.
Section 2.10. is added
3) Section 2. Please provide a deep and fundamental discussion about the effect of the crystalline structure on the photocatalytic/sorption performance of the different metallic oxides.
Section 2.10, lines 371-392.
4) Section 4. It is suggested to discuss with deeper and fundamental aspects the advantages of certain functionalization /doping strategies and not just present the compilation of different works as a Table.
Tables 3 & 4 Clearly explain all characteristics and performances for the MO and their composites towards the photocatalytic/sorption processes. If we discuss the compilation of these works deeper and in details, the number of pages may increase to 100. So, we mentioned all of these characteristics in tables.
Author Response File: Author Response.docx
Reviewer 5 Report
I reviewed your manuscript “Metal Oxide Nanomaterials and Their Composites as Effective Adsorbents and Photocatalysts for Organic Pesticides Removal” very judiciously. The work carried out in the manuscript is very interesting and seems scientifically logical. The authors have added good technical value and knowledge to remove the pesticides. it needs to make some changes in the manuscript properly. Therefore, I would like to recommend this article for "Minor Revision".
The title is not interesting. It should be meaningful and attractive.
Arrange the keywords in alphabet order (A-Z)
1. Introduction
The author should made comparison between their photocatalysts and already reported photocatalysts like hexaferrites materials and MOFs etc. The author should also read the research articles related to the wastewater purification, chemical physics letters 805, (2022), 139939, 431–440, New J. Chem., 2022,46, 19848
Author Response
I reviewed your manuscript “Metal Oxide Nanomaterials and Their Composites as Effective Adsorbents and Photocatalysts for Organic Pesticides Removal” very judiciously. The work carried out in the manuscript is very interesting and seems scientifically logical. The authors have added good technical value and knowledge to remove the pesticides. it needs to make some changes in the manuscript properly. Therefore, I would like to recommend this article for "Minor Revision".
- The title is not interesting. It should be meaningful and attractive.
Done. The title becomes” Photocatalytic Degradation and Adsorptive Removal of Emerging Organic Pesticides Using Metal Oxide and Their Composites: Recent Trends and Future Perspectives.”
- Arrange the keywords in alphabet order (A-Z)
The keywords have been arranged in alphabetic order.
- Introduction
The author should made comparison between their photocatalysts and already reported photocatalysts like hexaferrites materials and MOFs etc. The author should also read the research articles related to the wastewater purification, chemical physics letters 805, (2022), 13 9939, 431–440, New J. Chem., 2022,46, 19848
The feedback is much appreciated. The suggested research articles related to wastewater purification has been added as citations in the introduction section.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
This revised manuscript can be considered for acceptance in its current form.
The copyright acquisition description of the figure cited from the published article should be consistent.
Author Response
Reviewer’s Comments, Second Round
Reviewer #2
This revised manuscript can be considered for acceptance in its current form.
The copyright acquisition description of the figure cited from the published article should be consistent.
This issue has been fixed. Thank you for your time.
Reviewer #4
Thank you for attending the observations.
Thank you for your time.
Note for Editor
All copyrights and permissions have been attached in this document. Only figure 6 has been removed, and accordingly all the figures numbering has been fixed.
Copyrights and permissions
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Author Response File: Author Response.docx
Reviewer 4 Report
Thank you for attending the observations
Author Response
Reviewer’s Comments, Second Round
Reviewer #2
This revised manuscript can be considered for acceptance in its current form.
The copyright acquisition description of the figure cited from the published article should be consistent.
This issue has been fixed. Thank you for your time.
Reviewer #4
Thank you for attending the observations.
Thank you for your time.
Note for Editor
All copyrights and permissions have been attached in this document. Only figure 6 has been removed, and accordingly all the figures numbering has been fixed.
Author Response File: Author Response.docx
