Review Reports - Reaction Mechanism and Process Control of Hydrogen Reduction of Ammonium Perrhenate

Round 1

Reviewer 1 Report

Below is the text of my comments, the figures for illustration with the text are in the attached document.

In brief, the analysis of the XPS spectra is scientifically not correct and must be seriously improved.

XPS analysis parameters: The fitting software was XPSPEAK. The spectral lines of the spin-orbit coupling are f 7/2 and f 5/2. The area ratio of the two peaks on the spectrum was 4f7/2: 4f5/2 =4: 3. The peak spacing was 2.4.eV? The line width of the weak peak at the high binding energy end was 1~4 eV wider than that at the low binding energy end.assuming this is what you mean, it would be clearer to write the 4f5/2 peak width was 1-4 eV wider than the 4f7/2 peak. However, a question is then why 1-4 eV and why not a fixed value. There is a lot of freedom in the fitting of these envelopes. And one should keep the proper physics. Please explain why? The positions of High BE and Low BE were determined, and the two points were joined as the background. To me this do=es not described well how the background was chosen. For instance, the backround is not a straight line nor an ever increasing or decreasing curve, it shows kind of bumps, see picture around 41 eV, why ? there should be a good reason for this, as such selection heavily influences quantitative number extracted. To get a good background the tail at the right right side of the spectrum (so beyond 51eV) should be much larger, as it is on the lower side: down to 32.5 eV.

It is also not clear whether background and peaks were fitted separately or simultaneously.

In essence, the description of how the fitting was done should be described more clearly.

Furthermore, the authors claim they have fixed the ratio 4f7/2 to 4f5/2 to 4:3. It is more than clear that whereas this is the case for the 700C spectrum below, this does not hold for the 600C spectrum. When the authors would disagree because the line-width were taken differently, then that is incorrect, the line-widths should be kept constant while fitting the series of spectra.

The same applies to various other spectra in the series, for instance the two spectra at 400C in A1 and A2: the 4f5/2 peak does not hjave the same relative intensity compared to the 4f7/2 peak.

This implies the numbers in the tables are not reliable. Moreover, it is not clear which intensity the authors have used to arrive at the numbers in Tables 2 and 3, this is not described.

The values in Tables 2 and 3 have two decimal places: this goes far beyond the accuracy and reliability of what can be retrieved from the analysis (fitting) of the spectra. These numbers should be reduced to max 3 relevant digits, e.g. 70.2 and for lower values 2 digits eg 2.7.

Comments for author File: Comments.pdf

Author Response

Please refer to the PDF attachment for the revised reply. Thank you for your professional review

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper describes a novel process for improving the particle size distribution uniformity and complete reduction reaction of ammonium perrhenate from raw material. While good work has been done, minor revision required to improve research outcomes.

Suggested English syntax changes in RED are made in the original manuscript attached, only for the first few pages. The authors need to get the whole manuscript re-edited.

Minor comments

1. Line 49-51: “Moreover, due to the low efficiency of mass transfer and heat transfer in the traditional process, the reduction of ammonium perrhenate is not perfect, but a second roasting at high temperature”

Suggested change: “Moreover, due to the low efficiency of mass and heat transfer in the traditional process, the reaction with hydrogen is not complete and the second reduction step at high temperature is required.

2. Fig. 1 Deoxidation is not the correct term used, Suggested change to reduction

3. Flow chart, figure 1, 2 and 11, should be improved.

4. Line 154, ammonium perrhenate is unnecessarily repeated.

5. Line 181 and 238, rhenium perrhenate and rhenium rhenate seem like typo? Is that supposed to be ammonium perrhenate to follow up the experiment?

6. Line 241, What is Figure A2?

Comments for author File: Comments.pdf

Author Response

Point 1: Suggested English syntax changes in RED are made in the original manuscript attached, only for the first few pages. The authors need to get the whole manuscript re-edited. Response 1: Thank you for your professional comments. We have revised our manuscript according to your comments.

Point 2: Line 49-51: “Moreover, due to the low efficiency of mass transfer and heat transfer in the traditional process, the reduction of ammonium perrhenate is not perfect, but a second roasting at high temperature”

Response 2: We have revised our manuscript according to your comments.

Point 3: Fig. 1 Deoxidation is not the correct term used, Suggested change to reduction.

Response 3: We have revised our manuscript according to your comments.

Point 4: Flow chart, figure 1, 2 and 11, should be improved.

Response 4: Thank you for your comments, we have improved figure 1, 2 and 11

Point 5: Line 154, ammonium perrhenate is unnecessarily repeated.

Response 5: According to your opinion, we have modified our language expression in the article.

Point 6: Line 181 and 238, rhenium perrhenate and rhenium rhenate seem like typo? Is that supposed to be ammonium perrhenate to follow up the experiment?

Response 6: Thank you for your careful review, they are typing errors. We have corrected them in the article.

Point 7: Line 241, What is Figure A2?

Response 7: Figure A2. X-ray photoelectron spectroscopy of the reduction products of ammonium perrhenate (D₅₀ was 81.05 µm, specific surface was 21.72 m²/kg) at different temperatures.

Figure 2 was in Appendix A.

The preparation of rhenium powder by hydrogen reduction of ammonium perrhenate is the only industrial production method. But reports on the process are scant, and the purpose of our research is to optimize the rhenium process which is the only industrial rhenium process. Our research is now in production and we believe our work will help our colleagues in rhenium metallurgy as well. Your comments are very important to our work. Thank you again for your comments.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper as its stands has several issues which need to be addressed before further consideration.

Sections 2.1 and 2.3 should be more clear the experimental section is incomplete, much more information should be given on each technique, this includes make and model of the spectrometers for example.

In terms of the XPS experimental section, information should be given on calibration point (was it the C1s line, if so what value was taken?). Excitation source, step size, pass energy etc should be included

The purity of the final Re should be reported – this can be achieved using XRF or EDX

Fig 4. This is the Perrhenate decomposition, the plot should be labelled more with the different reduction zones highlighted, the legend should be changed accordingly

XRD – Fig5, what powder diffraction databases were used for reference for each phase? The relative percentages of each phase could be determined and compared to the XPS surface phases (may expect percentages to be different)

XPS analysis, I’m surprised to see the work of Iqbal et al from 2017 (DOI: 10.1002/sia.6076) not included as this paper deals with reduction of XPS Re salts and how under XPS analysis the disproportionation occurs – I feel this should be included and reference to the analysis within the text.

For XPS reporting, only the Re 4f7/2 speak needs to be reported flor clarity and all XPS data plots should be reversed – i.e. low binding energy to the right hand side of the plot.

Fig6 (and table 2) – this reports wt% from XPS analysis. XPS analysis will give you at% not wt%, although the conversation can be made its fails to take in account particles size and dispersion effects for example so is not that reliable. It may be better to do a multi Y-axis plot showing in-situ XRD phase determined phase percentages vs surface fractions by XPS.

In terms of the XPS fitting (Appendix A), the FHWM of each peak doesn’t look to be correct, these should be fixed as is the area ratio, else the determined percentages will be wrong.

Author Response

Please refer to the PDF attachment for the revised reply. Thank you for your professional review

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I am happy to see the authors have improved the quantification by using the proper science for curve fitting the XPS data. They have noticed that this does change the values of their results, but now they are the correct results.

Author Response

Point 1: I am happy to see the authors have improved the quantification by using the proper science for curve fitting the XPS data. They have noticed that this does change the values of their results, but now they are the correct results.

Response 1: Thank you for your professional comments. Thank you for your recognition of our work. Wish you a happy life.

Reviewer 3 Report

I thnak the authors for making the changes and reanalysing their data accordingly, this makes fo r amuch better manuscript.

I would only now say that in the added section about XPS (lines 114 - 120 on page 3)

based should read base

2.4´10-8 pa - Units should be Pa, else conversion to mbar or Torr better despite SI convention. Should replace ' with x and -8 as superscript, ie.e 2.4x10^-8 Pa

Author Response

Point 1: I would only now say that in the added section about XPS (lines 114 - 120 on page 3)

based should read base

2.4´10-8 pa - Units should be Pa, else conversion to mbar or Torr better despite SI convention. Should replace ' with x and -8 as superscript, ie.e 2.4x10^-8 Pa

Response 1: We have revised the manuscript according to your suggestion. Your professional comments are very helpful to us. Thank you again for your comments