Review Reports - Biowaste Valorization to Produce Advance Carbon Material-Hydrochar for Potential Application of Cr (VI) and Cd (II) Adsorption in Wastewater: A Review

Round 1

Reviewer 1 Report

The following report is based on my review of the manuscript entitled “Biowaste valorization to produce advance carbon material – hydrochar for potential application of Cr (VI) and Cd (II) ad-sorption in wastewater: research trends”, with manuscript number “water-1990173”. The manuscript fits within the scope of “water” and is also interesting. However, the following shortcomings have been pointed out and need to be addressed properly for further improvement of the manuscript. They are:

1- Line 10: It is suggested to rephrase the first sentence of the abstract.

2- Line 11 should be rephrased as “Biowaste valorization to produce hydrochar as an advanced material is regarded as a promising carbon neutrality technology for biomass waste recycling and utilization.

3- Line 21-24 should be rephrased as “The review develops a better understanding of Cr (VI) and Cd (II) adsorption by hydrochar in wastewater, making an innovative perspective for the improvement and large-scale application of hydrochar as an advanced carbon material as well as biowaste utilization.

4- The graphical abstract and Table of content should be removed from the main body of the manuscript. It is suggested to submit the graphical abstract in a separate file to the editor.

5- The sequence of the introduction section is not appropriate. It should be improved. The introduction is too lengthy and should be reduced, highlighting only important points.

6- Most paragraphs in the entire manuscript are too lengthy. Kindly consider at least 4 and at most 9 sentences in each paragraph. It is suggested to revise all through the manuscript.

7- The novelty and practical applicability of this study should be highlighted more in the introduction section. The introduction section could be improved. Author should refer to these articles and several others from reputable journals to enrich and enhance the introduction section of the manuscript. Hence, they should be cited appropriately. These are:

· Water 2021, 13(7), 999 https://doi.org/10.3390/w13070999;

· IJRPH 2021, 18(15), 7949 https://doi.org/10.3390/ijerph18157949;

· https://doi.org/10.1016/j.asej.2020.02.004;

· https://doi.org/10.1155/2022/3590462;

· https://doi.org/10.1016/j.asej.2020.06.016;

· 10.1109/ICOTEN52080.2021.9493473

8- Authors tried to present the structure of the article at the end of the introduction. However, it is not well structured. Kindly improve on that. The novelty of the work alongside the objectives should be highlighted more in the last paragraph of the introduction section.

9- The methodology adopted for the review was not highlighted. Thus, it is strongly suggested to create a section describing the methodology adopted, how referenced articles were sourced and from where. The methodology should be more specific and systematized with references to support it.

10- Figure 2 and 3 should be moved to the methodology section, when created.

11- Figure 5 should be redrawn. The quality is a bit poor. Kindly improve on the resolution

12- A remark column should be added to Table 2. This is to explain findings from the referenced article.

13- List of abbreviation should be provided in the manuscript since there are so many abbreviations.

14- A section should be provided separately for “Future perspectives”.

15- The conclusion should be a separate section. The present conclusion is too much and lacks some basic components. It must be re-written in a well-structured manner. It is suggested to re-organize the conclusion section much better to cover a summary of the problem(s), objectives methodology, findings, and recommendation(s).

Finally, the manuscript should be modified according to above said comments and be thoroughly reviewed again before accepting it for publication.

Author Response

Thank you for the positive feedback.

However, the following shortcomings have been pointed out and need to be addressed properly for further improvement of the manuscript.

As suggested by the esteemed reviewer, we paid a lot of attention and thoroughly and carefully revised and updated the manuscript as mentioned below point by point.

Line 10: It is suggested to rephrase the first sentence of the abstract.

Thank you; we have rephrased the first sentence of the abstract. Please see Line 10.

Line 11 should be rephrased as “Biowaste valorization to produce hydrochar as an advanced material is regarded as a promising carbon neutrality technology for biomass waste recycling and utilization.”

Thank you; in accordance with your comments, we have revised it to a more appropriate formulation. (Line 12-13)

Line 21-24 should be rephrased as “The review develops a better understanding of Cr (VI) and Cd (II) adsorption by hydrochar in wastewater, making an innovative perspective for the improvement and large-scale application of hydrochar as an advanced carbon material as well as biowaste utilization.”

Thank you; in accordance with your comments, we have revised it. (Line 24-26)

The graphical abstract and Table of content should be removed from the main body of the manuscript. It is suggested to submit the graphical abstract in a separate file to the editor.

Thank you; we have redrawn the graphical abstract; we have also removed the section on the table of contents.

The sequence of the introduction section is not appropriate. It should be improved. The introduction is too lengthy and should be reduced, highlighting only important points.

Thank you; we have streamlined the introductory section and made the relevant sequential and logical adjustments.

Most paragraphs in the entire manuscript are too lengthy. Kindly consider at least 4 and at most 9 sentences in each paragraph. It is suggested to revise all through the manuscript.

Thank you; we have restructured the entire manuscript by cutting out sections of each paragraph and reorganizing the layout.

The novelty and practical applicability of this study should be highlighted more in the introduction section. The introduction section could be improved. Author should refer to these articles and several others from reputable journals to enrich and enhance the introduction section of the manuscript. Hence, they should be cited appropriately. These are:

Water 2021, 13(7), 999 https://doi.org/10.3390/w13070999;

IJRPH 2021, 18(15), 7949 https://doi.org/10.3390/ijerph18157949;

https://doi.org/10.1016/j.asej.2020.02.004;

https://doi.org/10.1155/2022/3590462;

https://doi.org/10.1016/j.asej.2020.06.016;

10.1109/ICOTEN52080.2021.9493473.

Thank you; we have focused more on our innovation and research aims in the introduction section; Thank you for the relevant research literature, which we have read carefully and cited in its entirety. They are: Reference 56、Reference 57、Reference 65、Reference 66、Reference 107、Reference 110.

Authors tried to present the structure of the article at the end of the introduction. However, it is not well structured. Kindly improve on that. The novelty of the work alongside the objectives should be highlighted more in the last paragraph of the introduction section.

Thank you; we have revised the content and structure of the introductory section and clarified the purpose and innovation of the study.

The methodology adopted for the review was not highlighted. Thus, it is strongly suggested to create a section describing the methodology adopted, how referenced articles were sourced and from where. The methodology should be more specific and systematized with references to support it.

Thank you; we have reworked the structure of the article and created a section for data sources.

Figure 2 and 3 should be moved to the methodology section, when created.

Thank you; we have created the data sources section with two graphs incorporated into the content.

Figure 5 should be redrawn. The quality is a bit poor. Kindly improve on the resolution.

Thank you; we have re-uploaded the images in higher quality and resolution.

A remark column should be added to Table 2. This is to explain findings from the referenced article.

Thank you; we have re-structured the articles and grouped them according to the issues found in each article.

List of abbreviation should be provided in the manuscript since there are so many abbreviations.

Thank you; we have explained the first occurrence of the acronym and reduced the subsequent acronyms in the article.

A section should be provided separately for “Future perspectives”.

Thank you; following the comments, we have re-planned the final structure and listed a new section, the “Future perspectives” section.

The conclusion should be a separate section. The present conclusion is too much and lacks some basic components. It must be re-written in a well-structured manner. It is suggested to re-organize the conclusion section much better to cover a summary of the problem(s), objectives methodology, findings, and recommendation(s).

Thank you; we have re-summarized and revised the conclusion section to make it more concise and structured.

Finally, the manuscript should be modified according to above said comments and be thoroughly reviewed again before accepting it for publication.

Thank you so much for your kind suggestion.

Reviewer 2 Report

This review intends to describe the biowaste valorization process for producing advance carbon material- hydrochar for potential application of Cr(VI) and Cd(II) adsorption in wastewater. The authors illustrated on detail the application of hydrochar in the adsorption of Cr(VI) and Cd(II) with different level (low and high adsorption capacity) but I suggest revising these paragraphs because they appear too long. The addition of figure and/scheme could improved the quality of the manuscript.

The introduction paragraph is also too long and lacking in reporting the description of the main goals .

Author Response

This review intends to describe the biowaste valorization process for producing advance carbon material- hydroch ar for potential application of Cr(VI) and Cd(II) adsorption in wastewater. The authors illustrated on detail the application of hydrochar in the adsorption of Cr(VI) and Cd(II) with different level (low and high adsorption capacity) but I suggest revising these paragraphs because they appear too long. The addition of figure and/scheme could improved the quality of the manuscript.

Thank you; we have revised the overall structure of the article in terms of content and the quality of the images in order to have a better presentation of the content. The structure is clearer, the paragraphs are more concise, the order and logic is stronger, the purpose is clearer and the pictures are of better quality. Thank you very much for your comments.

The introduction paragraph is also too long and lacking in reporting the description of the main goals.

Thank you; we have made significant changes to the introductory section and have made our research aims and methodology clearer.

Reviewer 3 Report

This paper covers different technical and scientific aspects of the treatment of biomass wastes using hydrochar-based valorization. The paper provides a comprehensive review on production and application of hydrochar to remove some cationic pollutants from wastewaters. Moreover, effects of some key operating factors have been summarized and important features in involved mechanisms have been well presented. The paper can be suggested for publication after some minor technical modification since it can contribute to the current knowledge of the issue:

1. Authors may rethink about the title. It is somehow misleading. Using key words such as “review” and/or removing Cr and Cd from the title would be useful.

2. Please refresh the keywords and use more representative ones.

3. Graphical abstract is not representative. Please redraw a more suitable one.

4. What is the meaning of Fig. 1?

5. Figs. 2 and 3 are not necessary. Please remove them.

6. Fig. 4 is of low quality. Please use a larger one with higher quality.

7. Table 7, the name of strain must be in italic form.

Good luck,

Author Response

Thank you for the positive feedback.

The paper can be suggested for publication after some minor technical modification since it can contribute to the current knowledge of the issue:

As suggested by the esteemed reviewer, we paid a lot of attention and thoroughly and carefully revised and updated the manuscript as mentioned below point by point.

Authors may rethink about the title. It is somehow misleading. Using key words such as “review” and/or removing Cr and Cd from the title would be useful.

Thank you; we recognized the problem with the title and added the word “Review” to the title.

Please refresh the keywords and use more representative ones.

Thank you; we have reworked and refocused the keywords.

Graphical abstract is not representative. Please redraw a more suitable one.

Thank you; we have redrawn an abstract map to better highlight the research content of the article.

What is the meaning of Fig. 1?

Thank you; we have used diagrams to better explain the origin of biochar, simple reaction steps and product forms to make the text clearer and easier to understand.

2 and 3 are not necessary. Please remove them.

Thank you; we have reset the structure of the article, added a section on data sources and explained the meaning of the two figures better.

4 is of low quality. Please use a larger one with higher quality.

Thank you; we have made the images sharper and made them a little bigger so that the reader can see them more clearly.

Table 7, the name of strain must be in italic form.

Thank you; we have set it in italics and we will pay more attention to this in the future.

Round 2

Reviewer 1 Report

The authors have significantly improved the manuscript