Extraction of Lanthanides(III) from Nitric Acid Solutions with N,N′-dimethyl-N,N′-dicyclohexyldiglycolamide into Bis(trifluoromethylsulfonyl)imide-Based Ionic Liquids and Their Mixtures with Molecular Organic Diluents

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript presents the extraction of rare earths from nitrate medium by DMDCHDGA in IL. The reaction of the extractant and IL was also studied. And the stoichiometry of the extracted complexes is determined. The document is well prepared. However, it is suggested to add the significance of the study on the reaction and extraction of IL on the point of decreasing the loss of IL which can reduce the organic contaminant. There is a mistake, i.e., the sentence in Line 413 is not correct. It might mean that the complex formed by the reaction of IL and nitrate ions has higher hydrophobicity than IL itself so that Tf2N- ions moved into the aqueous solution. Please check all the text.

 

Author Response

Reply to Reviewer #1 Comments

 

 

Reviewer #1:

This manuscript presents the extraction of rare earths from nitrate medium by DMDCHDGA in IL. The reaction of the extractant and IL was also studied. And the stoichiometry of the extracted complexes is determined. The document is well prepared. However, it is suggested to add the significance of the study on the reaction and extraction of IL on the point of decreasing the loss of IL which can reduce the organic contaminant. There is a mistake, i.e., the sentence in Line 413 is not correct. It might mean that the complex formed by the reaction of IL and nitrate ions has higher hydrophobicity than IL itself so that Tf2N- ions moved into the aqueous solution. Please check all the text.

 

Authors reply:

 “The significance of the study on the reaction and extraction of IL on the point of decreasing the loss of IL which can reduce the organic contaminant”.

This is added in Conclusions.

Authors reply:

 

the sentence in Line 413 is not correct.

This sentence has been corrected.

 

Thanks to the Reviewer for helpful comments!

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript reports extraction of lanthanides(III) from nitric acid solutions using ionic liquids. The topic is interesting. If the following issues are solved completely, this work might be positively considered for publication.

 

Comment (1): In the introduction, clarify your innovation points and need to be rewritten.

 

Comment (2): Standardize and unify the format of each formula and give the references of every equation in the manuscript.

 

Comment (3): Unified font format and size, line size, subheading position, etc. for all images. Clearly define the title of each group of images, as well as the small images within each group. Don't use unprocessed original test images.

 

Comment (4): Please rewrite the conclusion as it was not addressed in any future scope of this work. The shortcomings of ionic liquids and deep eutectic solvents should be mentioned in the revised and the future recommendations.

 “The low viscosity and high volatility of ionic liquids and deep eutectic solvents at high temperatures pose significant safety and environmental pressures. Thus, it is necessary that the applications of ultrasound and microwave to treat a mixture of ionic liquids and deep eutectic solvents can greatly enhance the leaching efficiency of valuable metals from industrial end-of-life wastes, which can be attributed to the increase in the penetration of ionic liquids and deep eutectic solvents [1-3]”.

[1] Review of Ultrasound-Assisted Recycling and Utilization of Cathode Materials from Spent Lithium-Ion Batteries: State-of-the-Art and Outlook

[2] Recycling Lithium and Cobalt from Libs Using Microwave-Assisted Deep Eutectic Solvent Leaching Technology at Low-Temperature.

[3]

 

Comment (5): Grammatical corrections in the manuscript should be needed.

Author Response

Reply to Reviewer #2 Comments

 

 

Reviewer #2:

The manuscript reports extraction of lanthanides(III) from nitric acid solutions using ionic liquids. The topic is interesting. If the following issues are solved completely, this work might be positively considered for publication.

Comment (1): In the introduction, clarify your innovation points and need to be rewritten.

Authors reply:

 

Thanks to the Reviewer for the overall positive assessment of our work.

 

In accordance with the Reviewer's comment, the Introduction section has been partially rewritten in the new version of the manuscript. Innovative points arising from our work are formulated in the Conclusions.

 

Reviewer #2:

Comment (2): Standardize and unify the format of each formula and give the references of every equation in the manuscript.

 

Authors reply:

 

In the new version of the manuscript, all formulas are written in a single format.

 

Reviewer #2:

Comment (3): Unified font format and size, line size, subheading position, etc. for all images. Clearly define the title of each group of images, as well as the small images within each group. Don't use unprocessed original test images.

Authors reply:

 

We have tried to comply with all the fair provisions of this remark in the new version of the manuscript.

 

Reviewer #2:

Comment (4): Please rewrite the conclusion as it was not addressed in any future scope of this work. The shortcomings of ionic liquids and deep eutectic solvents should be mentioned in the revised and the future recommendations.

 “The low viscosity and high volatility of ionic liquids and deep eutectic solvents at high temperatures pose significant safety and environmental pressures. Thus, it is necessary that the applications of ultrasound and microwave to treat a mixture of ionic liquids and deep eutectic solvents can greatly enhance the leaching efficiency of valuable metals from industrial end-of-life wastes, which can be attributed to the increase in the penetration of ionic liquids and deep eutectic solvents [1-3]”.

[1] Review of Ultrasound-Assisted Recycling and Utilization of Cathode Materials from Spent Lithium-Ion Batteries: State-of-the-Art and Outlook

[2] Recycling Lithium and Cobalt from Libs Using Microwave-Assisted Deep Eutectic Solvent Leaching Technology at Low-Temperature.

[3]

Authors reply:

 

The conclusion has been corrected.

 

Reviewer #2:

Comment (5): Grammatical corrections in the manuscript should be needed.

Authors reply:

 

In accordance with the Reviewer's comment, the new version of the manuscript was read and edited by a native English speaker.

 

 

 

Thanks to the Reviewer for helpful comments!

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Ionic liquid extraction and separation of metal elements is a very interesting field, and your research content is also very interesting. However, the entire article needs revisions. especially the formatting is very messy.

 

Page 1 Line 2-5 FK1: Checked their names and affiliated institutions, there should be no problem.

Page 2 Line 65-67: There are significant formatting issues with the article, with the font size fluctuating between large and small, which is very unsightly.

Page 2 Line 637 figure 18、figure20、figure21: I fully understand that Pm is unnecessary in this image, but drawing it in this way will interrupt the continuity of the image and make people confused. Suggest connecting the image line segments directly and add an explanation next to the image that there is no Pm.

 

Page 28 Line761 FK2: I'm very sorry, I'm unable to answer this question.

Author Response

Reply to Reviewer #3 Comments

 

 

Reviewer #3:

Ionic liquid extraction and separation of metal elements is a very interesting field, and your research content is also very interesting. However, the entire article needs revisions. especially the formatting is very messy.

 

Authors reply:

Thanks for the note. The formatting has been standardized in the new version of the manuscript.

 

Reviewer #3:

Page 1 Line 2-5 FK1: Checked their names and affiliated institutions, there should be no problem.

Authors reply:

We have checked our names and affiliated institutions.

 

Reviewer #3:

Page 2 Line 65-67: There are significant formatting issues with the article, with the font size fluctuating between large and small, which is very unsightly.

Authors reply:

As already written above, the new text is formatted in accordance with the standards of the MDPI publishing house.

 

Reviewer #3:

Page 2 Line 637 figure 18、figure20、figure21: I fully understand that Pm is unnecessary in this image, but drawing it in this way will interrupt the continuity of the image and make people confused. Suggest connecting the image line segments directly and add an explanation next to the image that there is no Pm.

Authors reply:

We would like to leave Figures 18, 20, 21 as they are presented. Such an image is often used in the literature to characterize the extraction of Ln(III) in the lanthanide series. In particular, it allows us to estimate the presence of the tetrad effect in the system. The designation of the symbols La … Lu on the X-axis corresponds to the atomic numbers (57 … 71). Direct connection of the points for Nd and Sm disrupts the course of the logD_Ln – Z dependence.

Reviewer #3:

Page 28 Line761 FK2: I'm very sorry, I'm unable to answer this question.

Authors reply:

In the new version, we have clarified the wording of the Acknowledgments.

 

Thanks to the Reviewer for helpful comments!

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

In this paper, the extraction of REEs with novel unsymmetrical TODGA, DMDCHDGA, in combination with IL is studied in detail. Significant improvement of the extraction efficiency and intra-group selectivity are presented. Thus, this is essentially publishable in the journal as a scientific paper. However, there are some minor points.

(1)  L35, L36, L91, L749: The authors defined rare earth elements as REEs in the beginning of the paper (L33). Thus, throughout the paper, this abbreviation should be applied; that is, “rare earth elements” on these lines should be “REEs”.

(2)  L114: “bis(trifluoromethanesulfonul)” should be “bis(trifluoromethanesulfonyl)”.

(3)  L150-153: This sentence is difficult to understand.

(4)  L154: “The residue was added 80 ml of diluted (1:2) HCl” would be “The residue was added to 80 ml of deiluted (1:2) HCl”.

(5)  L172: “was consistently dissolved” should be “were consistently dissolved”.

(6)  L180: “The concentration” should be “The concentrations”.

(7)  L181: “was determined” should be “were determined”.

(8)  L192: “were presented in in the initial aqueous phase” should be “were present in the initial aqueous phase”.

(9)  L198: “aliquots of each phase were” should be “aliquots of each phase was”.

(10)               L272: Please use English throughout the manuscript.

(11)               L305, etc. “cm-1” : “-1” of “cm-1” should be superscript.

(12)               L340-341: Comparison of the two values should be done based on the same basis; on logarithm or antilogarithm.

(13)               L394: “the concentration of HNO3” should be “the concentration of the acid”.

(14)               L476: “DLn/(IL)” should be “DLn(IL)”.

(15)               Figure 12: The sequence of REEs is in contradiction to other experimental data. The tendency is that heavier REE shows higher DLn. But in Fig. 12, the tendency is opposite. Please check it.

(16)               Figure 13: Please describe the name of nitrate salt used to change [NO3-].

(17)               L529: “[Tf2N]” should be “[NO3-]”.

(18)                L554-555: “are coordinate to Ln(III) ions” should be “are coordinated to a Ln(III) ion”.

(19)               L674: “[C4mim][Tf2N] [C4mim][Tf2N]” should be “[C4mim][Tf2N]”.

Comments on the Quality of English Language

As I wrote above, careless mistakes in English are often seen in this manuscript. It is necessary to carefully check English before re-submission.

Author Response

Reply to Reviewer #4 Comments

 

 

Reviewer #4:

In this paper, the extraction of REEs with novel unsymmetrical TODGA, DMDCHDGA, in combination with IL is studied in detail. Significant improvement of the extraction efficiency and intra-group selectivity are presented. Thus, this is essentially publishable in the journal as a scientific paper. However, there are some minor points.

 

Authors reply:

Thanks to the Reviewer for the overall positive assessment of our work!  

 

Reviewer #4:

(1)  L35, L36, L91, L749: The authors defined rare earth elements as REEs in the beginning of the paper (L33). Thus, throughout the paper, this abbreviation should be applied; that is, “rare earth elements” on these lines should be “REEs”.

 

Authors reply:

The remark is fair. The indicated replacements have been made.

 

Reviewer #4:

(2)  L114: “bis(trifluoromethanesulfonul)” should be “bis(trifluoromethanesulfonyl)”.

 

Authors reply:

The remark is fair. The indicated replacements have been made.

 

Reviewer #4:

(3)  L150-153: This sentence is difficult to understand.

 

Authors reply:

corrected

 

Reviewer #4:

(4)  L154: “The residue was added 80 ml of diluted (1:2) HCl” would be “The residue was added to 80 ml of deiluted (1:2) HCl”.

Authors reply:

corrected

 

Reviewer #4:

(5)  L172: “was consistently dissolved” should be “were consistently dissolved”.

Authors reply:

corrected

 

Reviewer #4:

(6)  L180: “The concentration” should be “The concentrations”.

Authors reply:

corrected

 

Reviewer #4:

(7)  L181: “was determined” should be “were determined”.

Authors reply:

corrected

 

Reviewer #4:

(8)  L192: “were presented in in the initial aqueous phase” should be “were present in the initial aqueous phase”.

Authors reply:

corrected

 

Reviewer #4:

(9)  L198: “aliquots of each phase were” should be “aliquots of each phase was”.

Authors reply:

corrected

 

Reviewer #4:

(10)               L272: Please use English throughout the manuscript.

Authors reply:

corrected

 

Reviewer #4:

(11)               L305, etc. “cm-1” : “-1” of “cm-1” should be superscript.

Authors reply:

corrected

 

Reviewer #4:

(12)               L340-341: Comparison of the two values should be done based on the same basis; on logarithm or antilogarithm.

Authors reply:

corrected

 

Reviewer #4:

(13)               L394: “the concentration of HNO3” should be “the concentration of the acid”.

Authors reply:

corrected

 

Reviewer #4:

(14)               L476: “DLn/(IL)” should be “DLn(IL)”.

Authors reply:

corrected

 

Reviewer #4:

(15)               Figure 12: The sequence of REEs is in contradiction to other experimental data. The tendency is that heavier REE shows higher DLn. But in Fig. 12, the tendency is opposite. Please check it.

 

Authors reply:

corrected

 

Reviewer #4:

(16)               Figure 13: Please describe the name of nitrate salt used to change [NO3-].

Authors reply:

corrected

 

 

Reviewer #4:

(17)               L529: “[Tf2N]” should be “[NO3-]”.

Authors reply:

corrected

 

Reviewer #4:

(18)                L554-555: “are coordinate to Ln(III) ions” should be “are coordinated to a Ln(III) ion”.

Authors reply:

corrected

 

Reviewer #4:

(19)               L674: “[C4mim][Tf2N] [C4mim][Tf2N]” should be “[C4mim][Tf2N]”..

Authors reply:

corrected

 

 

Reviewer #4:

Comments on the Quality of English Language

As I wrote above, careless mistakes in English are often seen in this manuscript. It is necessary to carefully check English before re-submission.

Authors reply:

The comment is fair. In accordance with the Reviewer's comment, the new version of the manuscript was read and edited by a native English speaker.

 

 

 

 

Thanks to the Reviewer for helpful comments!

 

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

The manuscript is well-structured and the conducted study is discussed in the context of existing literature. I only suggest to standardize the formatting of the text since the different font sized and a word in Russian script irritated me slightly.

Author Response

Reply to Reviewer #5 Comments

 

 

Reviewer #5:

The manuscript is well-structured and the conducted study is discussed in the context of existing literature. I only suggest to standardize the formatting of the text since the different font sized and a word in Russian script irritated me slightly.

 

Authors reply:

 

Thanks to the Reviewer for the overall positive assessment of our work!

 

In accordance with the Reviewer's comment, the word in Russian script has been removed from the new version of the manuscript and the "formatting of the text" has been carried out in accordance with the rules of the MDPI publishing house. The new version of the manuscript was read and edited by a native English speaker.

 

 

Thanks to the Reviewer for helpful comments!

 

Author Response File: Author Response.pdf