Y(III) Ion Migration in AlF3–(Li,Na)F–Y2O3 Molten Salt
Round 1
Reviewer 1 Report
the sample of AlF3–(Li, Na)F with Y(III) ions was electrolysis at 900-1000oC for 1 H. Over 1000oC, did the migration number of Y(III) ions will be increas?
Author Response
Thank you very much for your valuable comments. We have made corresponding adjustments and explanations.
(1) The sample of AlF3–(Li, Na)F with Y(III) ions was electrolysis at 900-1000oC for 1 H. Over 1000oC, did the migration number of Y(III) ions will be increases?
Response: In this work, the experimental results show that the migration number of Y(III) ions increases with temperature from 0.70 to 0.80 almost linearly in the temperature range of 900–1000 °C, and the experiment of measuring the migration number of the system above 1000 ℃ was not carried out, therefore, there is no experiment data to analyze the change law of the migration number of the system above 1000 ℃, but according to the general experience and concept, it can be predicted that with the increase of temperature, the self-diffusion coefficient of current carrying ions in the system will increase and the conductivity of the system will also increase in a specific high temperature range. Therefore, The migration number of Y (III) ions will also increase, but not necessarily linearly.
Reviewer 2 Report
The manuscript titled “Y(III) Ion Migration in AlF3–(Li,Na)F–Y2O3 Molten Salt” by Tingting Hao et al. described the Y(III) ion migration in the above system using the HITTROF method and simulated by COMSO (?) software. The authors have shown how the migration number of Y(III) ion is varied by changing the temperature, current density, and molar ratio of (Li, Na)F/AlF3. The lack of the present research is authors didn’t compare the migration number value with any other rare earth elements or any standard molten salt and didn’t comment on the importance of studying the Y(III) ion migration of different temperatures, current density, and the molar ratio of (Li, Na)F/AlF3. The manuscripts can be published in the Applied Sciences journal after the major revision. The comments are given below.
- In page 1, line 13, “the flow field and electric field was established using the COMSO system” what is COMSO system? What are the parameters used for the calculation?
- In page 2, line 36, “Previously, the authors of this article has prepared an Al–Cu…..[7]”. The authors' names were not found in the given reference no 7. Authors should recheck.
- In page 2, line 52, “has been adopted by many researchers. In this study, three slots…….” Authors should establish this statement with valid reference/s.
- Can authors comment on the structure of the Y(III) ion inside the molten salt as Y2O3 is covalent in nature.
- In page 6, line 225,” ..the radius of these ions is small,….” What is the radius of the ions here?
- In Figure 4, the Y axis is labeled as “Particle migration number”. Authors should clear which particle they are talking about?
- In page 6, line 230. “This reaction produces active complexed Y(III) ions in the melt and increases their migration number”- Authors didn’t mention the structure of the complex with Y(III) and how the migration number will increase after forming the complex with Y(III).
- Authors should show the error bar in Fig 4.
- The labels are missing in Fig 3.
- In page 5, line 203, “the diffusion rate of active complex Y(III) ions in the system…..” What is the diffusion rate and what is the “precipitation potential”? How did the authors find the value of precipitation potential in the present system?
- Authors should cite the references from reputed international journals as most of the journals are not available for reviewers.
Author Response
Response to Reviewer 2 Comments
Thank you very much for your valuable comments. We have made corresponding adjustments and explanations.
(1) In page 1, line 13, “the flow field and electric field was established using the COMSO system” what is COMSO system? What are the parameters used for the calculation?
Response: The flow field and electric field was established using the COMSOL system and corresponding modifications have been made in the revised draft. The calculated meshing parameters are supplemented in section 3.1.1.
(2)In page 2, line 36, “Previously, the authors of this article has prepared an Al–Cu…..[7]”. The authors' names were not found in the given reference no 7. Authors should recheck.
Response: The corresponding references[7] are supplemented.
(3)In page 2, line 52, “has been adopted by many researchers. In this study, three slots…….” Authors should establish this statement with valid reference/s.
Response: References [14], [15], [16] are supplemented in the revised manuscript.
(4)Can authors comment on the structure of the Y(III) ion inside the molten salt as Y2O3 is covalent in nature.
Response: The ion migration number is only one of the physical and chemical properties of the melt under specific conditions, and the ion structure and composition of the system are determined by its chemical bond, therefore, the inappropriate expression on page 2 and line 6 of the paper is deleted.
(5)In page 6, line 225,” ..the radius of these ions is small,….” What is the radius of the ions here?
Response: The ion here refers to F-ion, which has been modified in the revised manuscript.
(6)In Figure 4, the Y axis is labeled as “Particle migration number”. Authors should clear which particle they are talking about?
Response: It should be the Y (III) ion migration number, which is modified in Figure 4.
(7)In page 6, line 230. “This reaction produces active complexed Y(III) ions in the melt and increases their migration number”- Authors didn’t mention the structure of the complex with Y(III) and how the migration number will increase after forming the complex with Y(III).
Response: In page 6, line 230 to 233. T The reason why the electric transfer number of Y (III) ions changes with the molar ratio of (Li, Na)F/AlF3 is unclear, so it is modified in the revised draft.
(8)Authors should show the error bar in Fig 4.
Response: In the revised manuscript, the error in Figure 4 is modified.
(9)The labels are missing in Fig 3.
Response: In the revised manuscript, the error in Figure 3 is modified.
(10)In page 5, line 203, “the diffusion rate of active complex Y(III) ions in the system…..” What is the diffusion rate and what is the “precipitation potential”? How did the authors find the value of precipitation potential in the present system?
Response: In page 5, line 203 to 206. The discussion that the migration number of Y (III) ions increases with temperature is not clear enough, so it is revised in the revised manuscript.
(11)Authors should cite the references from reputed international journals as most of the journals are not available for reviewers.
Response: The references are comprehensively supplemented and amended in the revised manuscript.
Reviewer 3 Report
The parameter of ion migration number is an important data to predicate the conductivity which significantly affects electrolysis efficiency and product quality.This manuscript attempts to measure the Y(III) species migration in AlF3–(Li,Na)F–Y2O3 molten salt. The language is readable. I have a few questions and suggestions as follow,
1,Line 74-77, 230; different font sizes
2,Line 147; a figure(not mentioned in the manuscript) about cell voltage unexpectedly inserted in the text.
3, All the Figures; Chinese texts are presented in X and Y Axis; Please don't cover with a textbox, modify it directly in the origin software.
4,Wrong reference 10, no information about Hittorf method is described in it.
5, line 105-107, the authors mentions liquid cathode, where is it in your experiment?
6, Please present more details about the calculation of ion migration number in section 2.1, which is important and convenient for new readers to understand your work.
7, Please give more details about the apparatus, for example, you must collect the total charge Q of the electrolysis test, In addition, sampling process for ICP which is very important the evaluate the quality of your results, also need to present clearly.
8, Please explain, why (Li,Na)F/AlF3 molar ratio of 2.5 is the inflection point in Figure 4?
Author Response
Response to Reviewer 3 Comments
Thank you very much for your valuable comments. We have made corresponding adjustments and explanations.
(1)Line 74-77, 230; different font sizes
Response: The font sizes has been modified in the revised manuscript.
(2)Line 147; a figure(not mentioned in the manuscript) about cell voltage unexpectedly inserted in the text.
Response: The following formula (7) should be inserted here.
(3)All the Figures; Chinese texts are presented in X and Y Axis; Please don't cover with a textbox, modify it directly in the origin software.
Response: All drawings have been modified in the revised manuscript.
(4)Wrong reference 10, no information about Hittorf method is described in it.
Response: Reference 10 was replaced in the revised manuscript as follows.
- Vink, Hans. A new modified Hittorf method for the determination of transport numbers in polyelectrolyte solutions[J]. Journal of the Chemical Society Faraday Transactions, 1984, 80(5):1297-1304.[CrossRef]
(5) line 105-107, the authors mentions liquid cathode, where is it in your experiment?
Response: The statement here is wrong. It should be the cathode, not the liquid cathode. It has been modified in the revised draft.
(6) Please present more details about the calculation of ion migration number in section 2.1, which is important and convenient for new readers to understand your work.
Response: The details of migration calculation in Section 2.1 are supplemented.
(7)Please give more details about the apparatus, for example, you must collect the total charge Q of the electrolysis test, In addition, sampling process for ICP which is very important the evaluate the quality of your results, also need to present clearly.
Response: Section 2.2 is revised again, and the details of the experimental equipment are given.
(8)Please explain, why (Li,Na)F/AlF3 molar ratio of 2.5 is the inflection point in Figure 4?
Response: In Page 6, lines 226 to 230. The law that the electric transfer number of Y (III) ions changes with the molar ratio of (Li, Na)F/AlF3 is restated.
Round 2
Reviewer 2 Report
The authors have answered most of the comments and revised the manuscript accordingly, however, a few comments are not replied to adequately. I would ask the authors to revisit comments no. 4, 5, 7, 8, and 10 and reply again before the revised manuscript would be recommended for the Applied Science.
Author Response
Response to Reviewer 2 Comments
Thank you very much for your valuable comments. We have made corresponding adjustments and explanations. The comments no. 4, 5, 7, 8, and 10 have been revisited and reply again as follows.
(1) Comment 4: Can authors comment on the structure of the Y(III) ion inside the molten salt as Y2O3 is covalent in nature.
Response:
It should be pointed out here that the dissolution of Y2O3 in (Li, Na)F-AlF3 system is a complex process with both physical and chemical dissolution. Its chemical dissolution is mainly the competitive oxidation of F in molten salt system and O in Y2O3. In fact, the author of the article has been conducting quantum chemical analysis of Y2O3, and the results of electron density and localization function (ELF) are shown in the figure below, It can be seen that Yb2O3 molecule is asymmetric, and O2 atom between two Yb atoms has more negative charge. The ELF values between Y-O are very low (ELF is close to 0), and the Y-O bond is not covalent.
(2) Comment 5 and 7:
In page 6, line 225,” ..the radius of these ions is small,….” What is the radius of the ions here?
In page 6, line 230. “This reaction produces active complexed Y(III) ions in the melt and increases their migration number”- Authors didn’t mention the structure of the complex with Y(III) and how the migration number will increase after forming the complex with Y(III).
Response:
For Comment 5 and 7, the relevant parts of the paper are sorted and modified, and the key points are as follows:
(1) When the molar ratio of system (Li, Na)F/AlF3 is lower than 2.5, with the increase of system (Li, Na) F ratio, the free fluorine ions in the system mainly fluorinate with Y2O3 in the system, the number of active Y(III) ions in the system increases, and the share of conductivity increases. At the same time, the number of Li+,Na+,F- ions in the system also increases, and the share of conductivity also increases. The comprehensive effect is that the electric transfer number of Y(III) ions does not change significantly;
(2) When the molar ratio of system (Li, Na) F/AlF3 is higher than 2.5, with the further increase of system (Li,Na)F ratio, the number of activeY(III) ions in the system reaches saturation, Li+,Na+,F-ions in the system become the main carrier of current, the proportion of activeY(III) ions participating in conductivity decreases, and the number of electric transfer decreases approximately linearly.
(3) The radius of Li+,Na+,F-ions is smaller than that of Y (III) ions, and the electromigration rate is higher.
(3) Comment 8:Authors should show the error bar in Fig 4.
Response: The error bar in Figure 4 is modified in the revised manuscript 2.
(4) Comment 10: In page 5, line 203, “the diffusion rate of active complex Y(III) ions in the system…..” What is the diffusion rate and what is the “precipitation potential”? How did the authors find the value of precipitation potential in the present system?
Response:
Diffusion rate refers to the mass transfer rate of Y (III) ions. With the increase of the temperature of the system, the average kinetic energy and self diffusion coefficient of Y (III) ions will increase, which will eventually increase the mass transfer rate of Y (III) ions. At the same time, the conductivity of the system will increase, and the electric transfer number of Y (III) ions will also increase.
Precipitation potential refers to the reduction potential of Y (III) ions. With the increase of temperature, the theoretical decomposition voltage of Y2O3 will also decrease, that is, the reduction potential of Y (III) ions moves forward, and the electroreduction reaction is easier to carry out, resulting in the increase of electromigration number of Y (III) ions.
Author Response File: 
Author Response.docx
Reviewer 3 Report
Please see it in the attach file
Comments for author File: Comments.doc
Author Response
Response to Reviewer 3 Comments
Thank you very much for your valuable comments. We have made corresponding adjustments and explanations. The details of the revisions to the manuscript( ID: applsci-1538903) and responses to the referees’ comments as as follows.
(1)Line 178-180, The wrong format of formula 7 has been edited and inserted again in revised manuscript 2.
(2) The English of the full text was polished and improved by Editage before submission, and the revised manuscript (Round 2) has also been polished and improved again.
Author Response File: Author Response.docx
