The Role of Nanofluids and Renewable Energy in the Development of Sustainable Desalination Systems: A Review

Round 1

Reviewer 1 Report

A very good and appropriate focus on nanofluids employment in desalination systems.

Author Response

Reviewer's Comment:

A very good and appropriate focus on nanofluids employment in desalination systems.

Response:

We appreciate your positive feedback and would like to thank you for positive feedback

Reviewer 2 Report

All the figures are copy-pasted from the literature. They are of poor resolution and quality. The authors should try to source the original files from the publishers. Some original tables and figures should be added as most of the discussions are based on simple compilation of the literature. Some original analysis is expected in a review article. Sustainability is mentioned several times in the article. However, it is unclear how the GO, MWCNT etc can be considered sustainable. The authors should elaborate on this point. Moreover, the faith of these nanomaterials in the nanofluids should also be discussed. The authors could mention the issue of plastic contamination. This is an increasingly important issue. For desalination it won’t be enough to remove salts but dissolved and degraded nanoplastics as well. At the top of page 4 and other paces the authors mention the role of nanotechnology for desalination. Some trending examples should be mentioned such as MCDI (DOIs 10.1021/acssuschemeng.9b02367, 10.1021/acsomega.8b01356), membrane distillation (DOIs 10.1016/j.memsci.2018.03.013, 10.1073/pnas.1701835114), membrane electrodialysis (DOIs 10.1039/C8TA09160A, 10.1016/j.memsci.2018.05.007). Use the IUPAC recommended x y^-1 format for the units throughout the manuscript, instead of the sometimes ambiguous x/y. Refrain from the unfounded statements such as “nanomembranes at present are far from the commercial production and application phase”. Figure 5 has no information content. Remove it from the review. Section 3.2 gives numerous examples about enhanced productivity expressed as a percentage. Give more in-depth discussions as it is unclear how these remarkable enhancements were achieved. What were the design considerations? The fundamental should be exaplained. What is the lifetime of the nanofluids? What happens with them when they reach the end of their lifetime? Spell out LCOW the first time it appears in the text. Lines 342 and 366 need to have references. At the end of the manuscript, a comprehensive table, comparing the different nanofluids, should be provided.

Author Response

Reviewer's Comments:

1. All the figures are copy-pasted from the literature. They are of poor resolution and quality. The authors should try to source the original files from the publishers

2. Some original tables and figures should be added as most of the discussions are based on simple compilation of the literature. Some original analysis is expected in a review article.

3. Sustainability is mentioned several times in the article. However, it is unclear how the GO, MWCNT etc can be considered sustainable. The authors should elaborate on this point. Moreover, the faith of these nanomaterials in the nanofluids should also be discussed.

4. The authors could mention the issue of plastic contamination. This is an increasingly important issue. For desalination it won’t be enough to remove salts but dissolved and degraded nanoplastics as well.

5. At the top of page 4 and other paces the authors mention the role of nanotechnology for desalination. Some trending examples should be mentioned such as MCDI (DOIs 10.1021/acssuschemeng.9b02367, 10.1021/acsomega.8b01356), membrane distillation (DOIs 10.1016/j.memsci.2018.03.013, 10.1073/pnas.1701835114), membrane electrodialysis (DOIs 10.1039/C8TA09160A, 10.1016/j.memsci.2018.05.007).

6. Use the IUPAC recommended x y^-1 format for the units throughout the manuscript, instead of the sometimes ambiguous x/y.

7. Refrain from the unfounded statements such as “nanomembranes at present are far from the commercial production and application phase”.

8. Figure 5 has no information content. Remove it from the review.

9. Section 3.2 gives numerous examples about enhanced productivity expressed as a percentage. Give more in-depth discussions as it is unclear how these remarkable enhancements were achieved. What were the design considerations? The fundamental should be exaplained.

10. What is the lifetime of the nanofluids? What happens with them when they reach the end of their lifetime?

11. Spell out LCOW the first time it appears in the text.

12. Lines 342 and 366 need to have references.

13. At the end of the manuscript, a comprehensive table, comparing the different nanofluids, should be provided. 

Responses:

We would like to thank you for pointing out the figures resolution. We have improved the quality of figures and have sourced figures from original files and we have also taken copyright permissions from the respective journals.  We have introduced some original research discussion from our experiments. Line 622 to 629 covers some original discussion for sustainable desalination.  We would like to thank you for pointing out this fact. Lines 598-615 covers up the discussion on role of nanofluids in sustainability of desaline systems.  We would like to thank you for the suggestion.We have added discussion on microplastics from lines 356-372. We have considered the research papers mentioned. However, we would like to point out that these papers are out of scope of the paper we have submitted as we focussed only on the nanofluids whereas these papers focusing on membrane based desalination.  We would like to thank you for bringing this fact in our knowledge. We have updated units as per IUPAC. Thank you for pointing out this mistake. We have added valid reference to justify the statement.  Thank you for the comment. We have reomved the figure 5 in the new version. We would like to thank you for the comment. We have added suitable disussion and experimental procedures in section 3.2 along with results. Thank you for pointing out this facet. We have added discussion on end of life details of nanofluids from lines 629-634. Thank you for pointing out this mistake. We have added LCOW spelling in the text at first place, it appeared. Thank you for pointing out the mistake. We have added valid references in both the lines.  Thank you for the suggestion. We have added table 7 comparing various nanofluids. 

Reviewer 3 Report

This paper presents the role of nanofluids and renewable energy in the development of sustainable desalination systems. The major advances in this field of nanotechnology for desalination are introduced. The following comments should be considered for this paper:

Line 12, please delete "),". Please check the English writing in the paper carefully before submission.  In Introduction, the authors should start to introduce status of water systems worldwide, not mention the situation in Qatar. The section should be reconstructed.  Most of the figures need to be improved for the quality of the figures. For example, in Figure 5, what is the subfigure of (a). How could you improve the efficiency of the sustainable desalination systems? More discussion should be added in the current paper. Please name the subfigures in Figure 3. In Table 4, are there only four processes for the post treatment? Or these methods are the common approaches that the researchers used? The effect of nanoparticle types should be discussed in the nanofluids sections. What is the effect of the nanoparticle physiochemical properties on the renewable desalination? The challenges and obstacles by using the renewable energy systems in the desalination process should be addressed.

Author Response

Reviewer's Comments:

1. This paper presents the role of nanofluids and renewable energy in the development of sustainable desalination systems. The major advances in this field of nanotechnology for desalination are introduced. The following comments should be considered for this paper:

2. Line 12, please delete "),".

3. Please check the English writing in the paper carefully before submission

4.  In Introduction, the authors should start to introduce status of water systems worldwide, not mention the situation in Qatar. The section should be reconstructed.

5. Most of the figures need to be improved for the quality of the figures. For example, in Figure 5, what is the subfigure of (a). 

6. How could you improve the efficiency of the sustainable desalination systems? More discussion should be added in the current paper. 

7. Please name the subfigures in Figure 3.

8. In Table 4, are there only four processes for the post treatment? Or these methods are the common approaches that the researchers used? 

9. The effect of nanoparticle types should be discussed in the nanofluids sections. What is the effect of the nanoparticle physiochemical properties on the renewable desalination?

10. The challenges and obstacles by using the renewable energy systems in the desalination process should be addressed. 

Responses:

We would like to thank you for the positive feedback on the paper. We have deleted the repeated symbols from line 12. Thank you for pointing out this facet. We have rechecked the english language with the help of Grammarly software and checked for grammar, punctuation, vocabulary, style and sentence structure.  Thank you for pointing out this aspect. We have rewritten the first part of the section with a global focus rather than Qatar or region specific details. Thank you for pointing out the figure quality issue. We have removed figure 5 from the paper and improved the quality of other images along with acquiring the copy right permission from the respective sources.  We have added discussion from lines 605-612 on the topic of efficiency enhancement in sustainable desalination systems. Moreover, the entire section 5, focuses on the similar discussion. However, we will be glad to accomodate any further suggestions.  Thank you. We have renamed both subfigures a and b.  Thank you. Table 4 points out the commonly used commercially available technologies for post treatment.  Thank you. We have described the effect of nanoparticles and their properties on renewable desalination. The discussion in from lines 596 to 605. Thank you. We have added discussion on obstacles of renewable energy integration from lines 586 to 595. 

Round 2

Reviewer 2 Report

The authors have taken into consideration all the comments provided. The manuscript improved and meets the requirements to be published.

Author Response

Reviewer's Comments: 

The authors have taken into consideration all the comments provided. The manuscript improved and meets the requirements to be published.

Response:

We would like to thank you for the positive feedback and valuable suggestions which helped us to improve the overall quality of manuscript. Thank You.

Reviewer 3 Report

Thanks for the authors‘ revisions. Before accepting the paper, the following comments should be addressed

The figure quality still needs improvements such as Figures 3 and 9. The possible mechanisms using nanofluids should be added (10.1016/j.renene.2017.11.031, 10.1016/j.ijheatmasstransfer.2016.11.074). In Fig. 5, what is the nanofluids concentration wt% or vol%?

Author Response

Thanks for the authors‘ revisions. Before accepting the paper, the following comments should be addressed

The figure quality still needs improvements such as Figures 3 and 9. The possible mechanisms using nanofluids should be added (10.1016/j.renene.2017.11.031, 10.1016/j.ijheatmasstransfer.2016.11.074). In Fig. 5, what is the nanofluids concentration wt% or vol%

Responses:

We would like to thank you for the positive feedback and valuable suggestions. We would like to request to kindly consider the following:

We have re worked the figures in the manuscript. Figure 9 was available in the source file in the similar resolution and hence the figure have been replaced with new figure from different source. Moreover, other figures have also been replaced with actual figures from original sources including            figure 3.  Thank you for the valuable suggestion. We have introduced discussion from these sources in lines 237-258.  Thank you for pointing out this aspect. In figure 5, X-axis is the weight concentration of the solution and Y-axis exhibits the productivity enhancement in %. Moreover, we have introduced a detailed discussion on figure 5 results from lines 280-290