Gas Hydrate-Based Heavy Metal Ion Removal from Industrial Wastewater: A Review
Hongwei Bai
Round 1
Reviewer 1 Report
This review is interesting, however there are big room for improvement.
a) The logical structure is unclear, and did not protrude the significance of Gas hydrate based heavy metal removal, while a broad range is summarized.
b) The tile is not appropriate to cover the main point or highlight its key findings.
c) More works should be put on the mentioned gas hydrate method, its advantages on heavy metal removal in comparison with others
d) practically, is it possible for the method to be used for heavy metal removal for real application? Typical engineering cases should be studied to show its meaningful points
e) Reference citation should be well rephrased to cite those articles really matters.
Author Response
Reviewer 1:
This review is interesting, however there are big room for improvement.
- The logical structure is unclear, and did not protrude the significance of Gas hydrate based heavy metal removal, while a broad range is summarized.
Significance of gas hydrate metal removal is listed in section 2.4
- The tile is not appropriate to cover the main point or highlight its key findings.
This title signifies how the novel gas hydrate mechanism can be used in removal of heavy metals from wastewater and also this review gives a brief overview of the conventional technologies used in desalinating water with their advantages and limitations and covers the mechanism of gas hydrate technology in removing metal ions with key findings highlighted.
- More works should be put on the mentioned gas hydrate method, its advantages on heavy metal removal in comparison with others
As suggested by reviewer Table 3 covers the merits and demerits of conventional technologies and Table 4 relates to the key findings in metal’s removal by the conventional technologies and Table 5 covers the comparison and advantages of hydrate-based technology over the conventional methods.
- practically, is it possible for the method to be used for heavy metal removal for real application? Typical engineering cases should be studied to show its meaningful points
Yes, this method is possible for real application as at present its still under investigation at lab scale. In this review key findings in removing heavy metals from seawater /aqueous solutions is highlighted with focus on removal efficiency, water recovery, enrichment factor and yield using gas hydrate method. As such the gas hydrate technology is not yet commercialized yet so at present there are no case studies available to present.
- Reference citation should be well rephrased to cite those articles really matters.
Corrected as suggested by reviewers
Author Response File: 
Author Response.docx
Reviewer 2 Report
The work is average but may be improved by the inclusion of the following suggestions. The main text in this manuscript is collection of literature and its presentation. It is lacking the novelty. A great deal of language polishing is needed. The abstract and conclusion should be concise. The presentation of novelty is required. It will be better if the authors include ne section on the application of metal ions removal at industrial or large scale. The challenges should be highlighted. Most importantly, the future perspectives area so need. The quality of figures need to be improved. The references are lacking specially the most recent one. It will be better if the following refs will be cited.
Conventional treatment methods like adsorption, membrane, chemical precipitation, 45 and electrochemical techniques are used to eliminate heavy metals from inorganic effluent.
Photochemistry and Photobiology 94 (5), 935-941 (2018); Int. J. Biol. Macromol 132, 244-253 (2019); TrAC Trends in Analytical Chemistry 129, 115921 (2020).
Author Response
Reviewer 2:
Comments and Suggestions for Authors
The work is average but may be improved by the inclusion of the following suggestions. The main text in this manuscript is collection of literature and its presentation.
- A great deal of language polishing is needed
Language is proof read
- It will be better if the authors include ne section on the application of metal ions removal at industrial or large scale
Application of heavy metal removal by various conventional technologies is listed in table 4 and also the comparison of conventional technology with novel technology is represented in table 5.
- The challenges should be highlighted.
As suggested by the reviewer the limitations of gas hydrate technology is added under section 3.8
- It will be better if the authors include ne section on the application of metal ions removal at industrial or large scale. The challenges should be highlighted. Most importantly, the future perspectives area so need
As suggested by reviewer heavy metals in wastewater (Table 1) and their toxicological effects on human health (Table 2) and limitations (section 3.8) and opportunities of gas hydrate-based desalination. Future prospective are listed in opportunities section 3.9
- The quality of figures needs to be improved.
As suggested by reviewer’s the quality of figures is improved.
- The references are lacking specially the most recent one. It will be better if the following refs will be cited.
As suggested by reviewer recent references are updated in red colour text.
- It will be better if the following refs will be cited- Photochemistry and Photobiology 94 (5), 935-941 (2018); J. Biol. Macromol 132, 244-253 (2019); TrAC Trends in Analytical Chemistry 129, 115921 (2020)
We thank the reviewer for the comment and the sources provided. As suggested by reviewer the following references are cited
Author Response File: Author Response.docx
Reviewer 3 Report
This article reviews the latest advances, benefits, and drawbacks of several heavy
metal removal treatment systems for industrial wastewater in detail. The
conventional physiochemical techniques used in heavy metal removal processes
with their advantages and limitations are evaluated. A particular focus is given to
innovative gas hydrate-based separation of heavy metals from industrial effluents.
The paper is well-written, and the manuscript will make a good addition to the
relevant literature and the research is timely. However, as there are many things to
be implemented, so, my decision is ‘Major revision’ with the following comments.
1. Please check the document for grammatical errors and typos.
2. In the study, most of the paragraphs are too long, which can make the
reader lose focus. Please make short paragraphs and improve the
organization of the work.
3. Critical analysis is an important aspect of survey papers. However, in
this work, critical analysis is missing. Please add a critical analysis
section.
4. Future research direction is also missing in the study.
5. Please provide a section “Research motivation”.
6. All references should be in a uniform format. Please double-check it.
7. Provide a comparative analysis table for various heavy metal Ion
Removal methods for clear understanding of the readers.
8. The introduction section is too short, please improve it.
9. The literature review needs to be improved by adding more recent work.
As for now, very old references are used.
10. Figure 1, is one of the critical component of the research work, however,
the figure is not mentioned in the work and is not thoroughly discussed.
Author Response
Reviewer 3:
Comments and Suggestions for Authors
This article reviews the latest advances, benefits, and drawbacks of several heavy
metal removal treatment systems for industrial wastewater in detail. The
conventional physiochemical techniques used in heavy metal removal processes
with their advantages and limitations are evaluated. A particular focus is given to
innovative gas hydrate-based separation of heavy metals from industrial effluents.
The paper is well-written, and the manuscript will make a good addition to the
relevant literature and the research is timely. However, as there are many things to be implemented, so, my decision is ‘Major revision’ with the following comments.
- Please check the document for grammatical errors and typos.
As suggested by the reviewer proof read the document
- In the study, most of the paragraphs are too long, which can make the reader lose focus. Please make short paragraphs and improve the organization of the work.
As suggested by the reviewer organization of work is improved
- Critical analysis is an important aspect of survey papers. However, in this work, critical analysis is missing. Please add a critical analysis section.
Various reactor designs and their limitations are addressed and also various researchers findings with their challenges in removing of heavy metals is listed and comparison of conventional technologies with hydrate based technology along with limitations and opportunities or future prospects. All changes are made in red colour text.
- Future research direction is also missing in the study.
As suggested by reviewer Opportunities section 3.9 is added from lines 951-976
- Please provide a section “Research motivation”.
As suggested by the reviewer we included from lines 951-976
- All references should be in a uniform format. Please double-check it.
As suggested by reviewer all references are adjusted to their normal format
- Provide a comparative analysis table for various heavy metal Ion Removal methods for clear understanding of the readers.
As suggested by reviewer table 4 is added for clear understanding based on technology and metal removal and also a comparative study between conventional methods and hydrate technology is also listed in table 5.
- The introduction section is too short, please improve it.
As suggested by reviewer improved the introduction. Changes are made in red colour text.
- The literature review needs to be improved by adding more recent work. As for now, very old references are used.
As suggested by the reviewer updated recent work. Changes are made in red colour
10. Figure 1, is one of the critical components of the research work, however, the figure is not mentioned in the work and is not thoroughly discussed.
As suggested by the reviewer discussion on Figure 1 is added.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Accepted
Reviewer 3 Report
Authors have significantly improved the paper.
I do not have more comments.
