Simultaneous Removal of Arsenate and Fluoride Using Magnesium-Based Adsorbents

Round 1

Reviewer 1 Report

Thank you for inviting me to review this manuscript. The manuscript afforded Simultaneous Removal of Arsenate and Fluoride Using Magne-sium-Based Adsorbents. However, there are following some issues that need to be considered to be published in this journal. Here are some concerns:

1. The title of Figure 1 need be checked.

2. Why not have dynamics of Arsenate and Fluoride?

3. Is the adsorption simultaneous or interfered with? It's not clear.

4. Is the production of magnesium fluoride a precipitation mechanism? It needs more proofs.

5. What is the adsorption mechanism by using magne-sium-based adsorbents? Too little mechanistic research.

6. The references should be checked again. Such as, 2019, 694, Ecosystems and Society, 2021, 101246.

It can be checked again.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

I think this work is well done, and any major changes is nor requared but the area of this research is overlap with work [https://doi.org/10.3390/su15021179]. Authors should be provide a short comment about this. 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

In proposed manuscript authors examined different Mg-based sorbents for removal of As(V) and F ions. In the introductory part, the authors gave an overview of previous research dealing with this issue and highlighted the novelties that their study provides. However, the experimental study requires corrections before potential publication.

1. Add more specific conclusions from the study in the abstract.

2. I suggest the authors supplement their manuscript with SEM analysis of the material before and after adsorption.

3. Are standard deviations available for the results?

4. In figures 1 and 2, change the colors of the points in order to see more clearly the dependence on concentration.

5. The results should be supplemented with interpretations related to the influence of Mg-type on the obtained result.

6. Compare the obtained results with the available literature.

7. In general, the adsorption study should be supplemented by the influence of contact time, etc. I suggest you look at the following publications for this: https://doi.org/10.2166/aqua.2023.012 - which you mentoined 

and

https://doi.org/10.1016/j.molliq.2023.121424

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Summary: In this study, the authors investigate use of Mg-based adsorbents namely, MgO, Mg(OH)2, and MgCO3 to simultaneously remove As(V), and fluoride (F) from contaminated water. Measuring the effect of pH and the amount of adsorbent per volume of solution are both important in determining the feasibility of an adsorbent material. Comparing different Mg species contributes to the scholarship and would be of interest to the readers.

Overall thoughts: The authors have done detailed work regarding use of Mg based adsorbents for water treatment. The fitting of experimental data into Langmuir and Freundlich models and using that to draw conclusions is creditable.

Comments/Questions:

1. In the introduction section the authors focus mainly on other works with Mg based adsorbents and do not discuss other ways or other adsorbent materials used for removing As(V) and F. 

2. How does the cost of Mg compare to other inorganic/organic adsorbents? Or what makes Mg based adsorbents more lucrative for this application over other adsorbents.

3. The authors have not provided enough background for why As and F need to be removed simultaneously. More specifically, is there any correlation between the presence of both of these species in the same effluent stream.

4. What prompted the authors to use MgO at such low WAD0/V levels compared to MgOH or MgCO3. Clear explanation of this choice and may be references to similar work previously done need to be provided

5. Providing XRD patterns for MgOH and MgCO3 adsorbents would really add depth and make the XRD section complete.

6. XRD patterns for Mg-arsenate and Mg-F salts would help make the arguments around the mechanism of ion adsorption even stronger.

7. The discussion doesn’t provide any explanation on why the MgO and MgOH fit the Freundlich model so poorly.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Authors corrected their manuscript, so now it can be considered for publication.

Author Response

We are very grateful for your acceptance of our revised manuscript.

Your suggestions and comments have greatly improved our manuscript.

Thank you so much.

Sincerely,

Hajime Sugita