Study on Mechanism of Oxygen Oxidation Leaching with Low Acid for High Acid Consumption Sandstone Uranium Deposit
Round 1
Reviewer 1 Report
Study on mechanism of oxygen oxidation leaching with low acid for high acid consumption sandstone uranium deposit.
General comments: The manuscript was well written.
Abstract
· Line 10: The fact that this part ‘…he low acid plus oxygen leaching technology was proposed in the previous study.’ is in the abstract, it begs to be recast.
· Line 13: It should read ‘…low acid-oxygen leaching system…’
· Line 15 to 17: Which is which, oxidation of ferrous oxide by oxygen or oxidation of oxygen of ferrous oxide?
Problem statement
· Can Section 1 be amended from a problem statement to an introduction?
· Line 38: What causes the blokag when leaching is conducted in alkaline solution?
· Line 39: There is need to fix the sentence is ‘….leaching. n view of the…’ is hunging.
Analysis of ferrous oxidation mechanism
· I think this section needs to be renamed just as advised in the previous section.
· Line 54 to 57: It is important to state the condition at which the chemical reaction and constant for the equation in Table 1 are valid.
· The author rightly pointed out that it is better to have ferrous in the system than ferric which easily precipitates. In the text there are again talking about precipitation of ferrous (line 63). By the way, once you say ferrous then you can omit iron, we know that ferrous is Fe2+.
· Figure 2 and 3 need clarity. The author may think about having Fig. 1(a) and Fig. 1(b) for Figure 1. It is very difficult to understand the X-axis.
· Line 131: The authors need to state if the used oxygen was the enriched air and the per cent oxygen. If it was ozone then they need to state so.
Conclusion
· Conclusion point 1: There is no need to compare the oxidation power of hydrogen peroxide to that of oxygen unless it was ozone or enriched air used.
General questions
· Did the authors analyse the residues obtained when oxygen or hydrogen peroxide was used?
· What could be the difference on the surfaces of particles for different scenarios?
· Did the authors measure the oxidation potential of solutions? The control of oxygen can be challenging if there is no control of the potential.
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
Study on mechanism of oxygen oxidation leaching with low 2 acid for high acid consumption sandstone uranium deposit
1. Keywords: High acid consumption; In situ leaching of uranium; Dynamics; Coprecipitation 23
One of the keywords seems to be wrong . In metallurgy, we use kinetics, not dynamics, to describe processes. e.g kinetics of oxidation
2. From the perspective of thermodynamics, the stability of iron in aqueous solution 54 depends on the pH, potential and activity of the solution. The thermodynamics of iron 55
activity of what? and its activity in solution
3. The oxygen pressure during the experiment was set 131 at 0.5 MPa and 1.0 MPa respectively, and the oxidation of Fe(II) was compared with H2O2 132 as oxidant. 133
It is not stated how this pressure was achieved, i.e. closed leaching vessel or bubbling into the solution?
4. in fig. 2 and 3 as well 5 , 6 the unit of pressure Mpa was written incorrectly, it should be MPa (Pascal)
5. Fig.3. Oxidation of Fe(II) under different oxygen pressures
Question: in batch b Fig.3 Fig. 6 - 0.5MPa, only two measurements were made during 15 days at the beginning (day 1) and at the end (day 15)? Why such an approach in comparison to 5 measurements in the same cycle for a P=1 Mpa?
6. It can be seen from Fig.5 that when hydrogen peroxide is used as oxidant and the 193 reaction time is 1 day, the conversion rate of ferrous iron can reach more than 70% under 194
Figures should be separated/or at least signed as a and b
i.e. seen from Fig.5. b
7. 7. It can be seen from Fig.12 that under different oxygen pressures, the amount of Fe 262 precipitation increases with the increase of pH, and reaches the maximum at pH=3.5; 263
What if you test to higher pH, after all, the precipitation is still increasing, there is no plato?
8. Fig.13. Effect of different [Fe(II)] on iron precipitation. 282
Effect of Fe(II ) concentration and pH on iron ….
add pH
The question is whether it is precipitated total iron (2 and 3) or only divalent?
Then change:
Effect of concentration and pH on iron Fe(II ) precitipation
9. Fig.15. Variation of leaching rate with oxygen pressure and pH. 312
poorly matched, blurred something for part b (i.e.-right), superimposed axis markers, make scales inside the drawing or break it into two drawings.
Author Response
Dear reviewer,
Thank you for giving us the opportunity to submit a revised draft of the manuscript “Processes-2240960”. We appreciate the time and effort that you dedicated to providing feedback on our manuscript and are grateful for the insightful comments on and valuable improvements to our paper. We have incorporated all of the suggestions. Those changes are highlighted in the manuscript. The revisions were addressed point by point below in red font.
Point 1: Keywords: High acid consumption; In situ leaching of uranium; Dynamics; Coprecipitation 23 One of the keywords seems to be wrong . In metallurgy, we use kinetics, not dynamics, to describe processes. e.g kinetics of oxidation
Response 1: We have carefully reviewed Merriam-Webster's interpretation of these two words and believe that your suggestion is very accurate. This keyword has been modified in the article. Thank you for pointing this out.
Point 2: From the perspective of thermodynamics, the stability of iron in aqueous solution 54 depends on the pH, potential and activity of the solution. The thermodynamics of iron 55 activity of what? and its activity in solution
Response 2: We are grateful for the suggestion. The word“activity”here means the activity of iron in solution. We modified “activity of the solution” to “its activity in solution”in the article.
Point 3: The oxygen pressure during the experiment was set 131 at 0.5 MPa and 1.0 MPa respectively, and the oxidation of Fe(II) was compared with H2O2 132 as oxidant. 133
It is not stated how this pressure was achieved, i.e. closed leaching vessel or bubbling into the solution?
Response 3: The laboratory was carried out in a closed reactor, so the pressure was achieved closed leaching vessel. Thank you for your question, which we add that description in the article.
Point 4: in fig. 2 and 3 as well 5 , 6 the unit of pressure Mpa was written incorrectly, it should be MPa (Pascal)
Response 4: We were really sorry for our careless mistakes. Thank you for your reminder. As suggested, we have checked the figureses of the entire article and corrected the “Mpa” into “MPa”, these fig. 2 and 3 as well 5 , 6, 8, were corrected in this article.
Point 5: Fig.3. Oxidation of Fe(II) under different oxygen pressures
Question: in batch b Fig.3 Fig. 6 - 0.5MPa, only two measurements were made during 15 days at the beginning (day 1) and at the end (day 15)? Why such an approach in comparison to 5 measurements in the same cycle for a P=1 Mpa?
Response 5: We are grateful for the question. After comparing the results of multiple sets of experiments, we found that the most meaningful values for the analysis are the initial(1d) and final values(15d), so in the last set of conditional experiments, only the initial and final values were selected as references.
Point 6: It can be seen from Fig.5 that when hydrogen peroxide is used as oxidant and the 193 reaction time is 1 day, the conversion rate of ferrous iron can reach more than 70% under 194
Figures should be separated/or at least signed as a and b
i.e. seen from Fig.5. b
Response 6: We are grateful for the suggestion and fully agree with you. Fig.5 is separated as Fig.5. a and Fig.5. b. It is indeed much clearer after the change.
Point 7: It can be seen from Fig.12 that under different oxygen pressures, the amount of Fe 262 precipitation increases with the increase of pH, and reaches the maximum at pH=3.5; 263
What if you test to higher pH, after all, the precipitation is still increasing, there is no plato?
Response 7: Thank you fou the question. As we know, ferric ion would precipitation during pH of the solution is between 2.7--3.7, when pH of the solution achieves to 2.7 ,it began to precipitate. The precipitation is complete when the pH achieves to 3.7. So when we tried to rise the pH of the solution to 3.7, the iron in the solution precipitated rapidly and could not be detected for process analysis.
Point 8:. Fig.13. Effect of different [Fe(II)] on iron precipitation. 282. Effect of Fe(II ) concentration and pH on iron ….add pH
The question is whether it is precipitated total iron (2 and 3) or only divalent?
Then change:Effect of concentration and pH on iron Fe(II ) precitipation
Response 8: Under experimental conditions, ferric iron is converted into ferric iron, and then ferric iron precipitates. Fig.13. Effect of different [Fe(II)] on iron precipitation, which means effect of initial concentrations of ferrous and pH on iron precitipation. The title of Fig.13 changes to effect of concentration and pH on iron precitipation,which is more clearly.Thank you for your suggestion.
Point 9: Fig.15. Variation of leaching rate with oxygen pressure and pH. 312 poorly matched, blurred something for part b (i.e.-right), superimposed axis markers, make scales inside the drawing or break it into two drawings.
Response 9: Thanks for your suggestion.In order to have a clearer characterization figure, we divide Fig.15 into two pictures, namely Fig.15 and Fig.16. This part of the revision has already been reflected in the article.
Thank you again for your positive comments and valuable suggestions to improve the quality of our manuscript.
Best wishes for you!
Yours sincerely,
Ying Xu
February 23, 2023
Author Response File: Author Response.docx
