Effect of Lead in Antimony and Tin Dissolution from Recycled Lead–Acid Battery Dross in Hydrobromic Acid Solution
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsEffect of Lead in Antimony and Tin Recovery from Recycled Lead Acid Battery Dross in Hydrobromic Acid Solution is very interesting paper in nonferrous extractive metallurgy! Minor Improvements are required.
Line 9: Demand for antimony has increased over the last few years (as well as its price). That is why antimony belongs to the group of critical metals
Line 14, 15: This research was conducted to develop a viable technology for hydrobromic acid as a leaching reagent and add sustainability to current industrial processes (in what temperature interval?) while minimizing waste products in recycling processes
Line 16, 17: The preliminary results showed that bromine, specifically hydrobromic acid, could be a leaching reagent for antimony under the right conditions (such as..) comparable to hydrochloric acid.
Line 125: Table 4. Experimental Design of Tests Conducted in Single-Stage Leaching (Please to add a reaction time for these experiments)
Line 127: Table 5. Experimental Design of Tests Conducted in Two-Stage Leaching. ((Please to add a reaction time for these experiments)
Line 156: As we increase the acid concentration, the antimony dissolution increases (in what temperature interval?).
Line 163, 164, 165: Although the formation of antimony-bromide complexes had a small area in the Pourbaix diagrams from Chapter 5, lead is still one of the main elements that reduced the amount of available bromide ions and bromine to get a higher recovery of antimony. Unfortunately you did not evaluate Eh-value and pH value during your experiments, and no comparison between its theoretical and real values. Pourbaix diagrams are presented for single elements, but you have mixed systems of elements. Can you discuss a leaching selectivity for Lead in Antimony and Tin Recovery from Recycled Lead Acid Battery Dross in Hydrobromic Acid Solution!
Line 225: Table 8. Elemental Recoveries (%) for Three-Stage Leaching Tests (please to add Temperature, and reaction time)
Line 230: It addresses the effect of acid concentration, solid-liquid ratio, (reaction time) and temperature.
Conclusion is missing in this work. Please to add conclusion in this work!
General questions:
Line 95: Once the temperature had been reached, the appropriate solids were added to the hot solution. Did you perform sampling during time?
Line 161, 162: Additionally, longer leaching times were not evaluated in this project, but there is a high possibility that the recovery of antimony would not surpass 30% recovery due to the amount of lead present in the system. Additionally, shorter leaching time under high pressure in an autoclave (future work) and kinetics of this process were not evaluated in this project!
Author Response
Line 9: Demand for antimony has increased over the last few years (as well as its price). That is why antimony belongs to the group of critical metals
Thank you for pointing this out. We agree that demand and prices have increased. Thus, we have added prices to the initial abstract sentence.
Line 14, 15: This research was conducted to develop a viable technology for hydrobromic acid as a leaching reagent and add sustainability to current industrial processes (in what temperature interval?) while minimizing waste products in recycling processes
We agree that there was missing information regarding time intervals in the abstract. We have made the appropriate changes to demonstrate the temperature intervals used.
Line 16, 17: The preliminary results showed that bromine, specifically hydrobromic acid, could be a leaching reagent for antimony under the right conditions (such as..) comparable to hydrochloric acid.
We agree that the sentence was vague and more information was necessary. We have changed the information in the abstract to cover this and other reviewer’s comments.
Line 125: Table 4. Experimental Design of Tests Conducted in Single-Stage Leaching (Please to add a reaction time for these experiments)
Since we are testing different reaction times depending on the Trial. Adding the reaction time of these experiments in Table 4’s caption might create a misunderstanding.
Line 127: Table 5. Experimental Design of Tests Conducted in Two-Stage Leaching. ((Please to add a reaction time for these experiments)
We agree that there was reaction time for this set of experiments was missing. We have added the reaction time tested during these experiments in Table 5’s captions.
Line 156: As we increase the acid concentration, the antimony dissolution increases (in what temperature interval?).
We agree that mentioning the temperature intervals in the acid concentration section was important. We have added the temperature intervals in the sentence.
Line 163, 164, 165: Although the formation of antimony-bromide complexes had a small area in the Pourbaix diagrams from Chapter 5, lead is still one of the main elements that reduced the amount of available bromide ions and bromine to get a higher recovery of antimony. Unfortunately you did not evaluate Eh-value and pH value during your experiments, and no comparison between its theoretical and real values. Pourbaix diagrams are presented for single elements, but you have mixed systems of elements. Can you discuss a leaching selectivity for Lead in Antimony and Tin Recovery from Recycled Lead Acid Battery Dross in Hydrobromic Acid Solution!
Thank you for pointing this out. We agree that showing the Eh and pH values during experiments to compare to theoretical values from Pourbaix diagrams is necessary. We have added two tables to do comparisons. These tables are for both set of experiments regarding the HBr. Additionally, we have added a Pourbaix diagram of a Sb-Pb mixed system.
Line 225: Table 8. Elemental Recoveries (%) for Three-Stage Leaching Tests (please to add Temperature, and reaction time)
We agree that reaction time in Table 8’s caption was missing; however, the temperature
Line 230: It addresses the effect of acid concentration, solid-liquid ratio, (reaction time) and temperature.
We agree that we had neglected reaction time when discussing the results shown. We have added the two words.
Conclusion is missing in this work. Please to add conclusion in this work!
We had conclusions mixed with the discussion section. We agree that this may cause confusion among readers. We have separated them into two separate sections to avoid it.
General questions:
Line 95: Once the temperature had been reached, the appropriate solids were added to the hot solution. Did you perform sampling during time?
We did not performed sampling in while the trial was still running. Sampling was performed at the beginning and at the end of each trial.
Line 161, 162: Additionally, longer leaching times were not evaluated in this project, but there is a high possibility that the recovery of antimony would not surpass 30% recovery due to the amount of lead present in the system. Additionally, shorter leaching time under high pressure in an autoclave (future work) and kinetics of this process were not evaluated in this project!
We have yet to perform any high pressure leaching which is ideal for future work. The kinetics of the process is a current work in progress and we are hoping the be able to submit a manuscript with this information when finished.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn this paper, the authors develop a viable technology using hydrobromic acid as a leaching reagent and adding sustainability to current industrial processes while minimizing waste products in recycling processes. It is an interesting content, but needs to be improved. Therefore, it needs revision before it is published in this journal. Some issues should be carefully addressed.
- The title of the paper needs to be revised because there is something wrong with the presentation.
- The entire abstract should be rearranged. The standard format of abstract normally includes four parts: 1-what is the problem; 2- what did the author did to solve the problem; 3-what are the results; 4-what are your conclusions and potential applications of the findings in real field. Thus, highly recommend the authors to rewrite the entire Abstract of the manuscript.
- Authors should clearly mention the novelty of the study in Section 1 (Introduction).
- The writing style of the paper need to be improved, including the upper and lower scripts.
- Flotation is a useful method to upgrade metal in solid particles before leaching, so the authors are suggested to describe the method in the “Introduction”, and several relevant references may be added to support this point, such as Int. J. Min. Sci. Technol. 34 (2024) 1741; Trans. Nonferrous Met. Soc. China 35 (2025) 313.
- Chemical composition analysis and XRD results of bulk samples should be provided in the paper.
- It is recommended that the author add error to the leaching test data, which will help to evaluate the reliability and reproducibility of the results.
- The application prospect of this study should be clarified in the paper.
The English could be improved to more clearly express the research.
Author Response
The title of the paper needs to be revised because there is something wrong with the presentation.
With the changes to address the comments we hope that the title better reflects the content of the manuscript.
The entire abstract should be rearranged. The standard format of abstract normally includes four parts: 1-what is the problem; 2- what did the author did to solve the problem; 3-what are the results; 4-what are your conclusions and potential applications of the findings in real field. Thus, highly recommend the authors to rewrite the entire Abstract of the manuscript.
Thank you for detailing the standard format of an abstract. We agree that parts 2 and 3 were lacking information while part 4 was completely missing. We have changed the abstract to better reflect the four parts.
Authors should clearly mention the novelty of the study in Section 1 (Introduction).
We have mentioned bromine’s usage in other metals than antimony that had success or mentioned success in their manuscripts.
The writing style of the paper need to be improved, including the upper and lower scripts.
Thank you for pointing this out. We agree that there was no consistency withing the lower scripts for chemical formulas such as HNO3. We have made changes to all chemical formulas to better represent the lower scripts.
Flotation is a useful method to upgrade metal in solid particles before leaching, so the authors are suggested to describe the method in the “Introduction”, and several relevant references may be added to support this point, such as Int. J. Min. Sci. Technol. 34 (2024) 1741; Trans. Nonferrous Met. Soc. China 35 (2025) 313.
We do agree that flotation is a useful method to upgrade metal in solid particles before leaching. However, we felt that the beneficiation of the solids through flotation was outside the scope of this research. The scope was an exploratory test of them to see the behavior of antimony and tin in hydrobromic acid.
Future work on flotation before leaching should be explore and will be kept in mind.
Chemical composition analysis and XRD results of bulk samples should be provided in the paper.
Thank you for pointing this out. We agree that there should be a chemical composition analysis aside from the single table outlined. We have added an SEM and AMICS analysis performed on the bulk samples.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article is dedicated to the recovery of antimony and tin from lead acid battery dross using HBr. The topic is relevant to the field of extractive metallurgy as a study of waste recycling to extract valuable elements. Authors tried to test the new solvent for antimony and tin leaching. However, the article is too short and shallow; some methods and results are not described properly. The conclusion is absent. The content of the article is insufficient to be published as full-length article. My recommendation is to reject the article. However, if the authors considerably improve the paper, it can be resubmitted as short communication or full-length article again.
General comments:
- On the positive side, it should be noted that an attempt was made to explore a new method for extracting antimony and tin from lead dross. It is always important to explore new reagents to improve recovery valuable elements.
- On the positive side, the application of DoE is encouraged. However, the DoE method used is insufficiently described in the manuscript.
- The references cited in this manuscript is too old. The introduction should contain recent relevant references on the topic of lead dross processing with the recovery of valuable elements. Hence it is unclear why HBr and HNO3 pretreatment were chosen.
- Poor work with results. For example, Fig. 1, 2, 5 are given, but not described. The quality of figures is low; improving the images are necessary.
- There are unsuccessful obtained results: antimony and tin recovery rates are too low. It is not evident whether results can be better.
- The results are insufficiently deep. There is a lack of characterization of the obtained products (XRD, SEM), explanation of valuable elements behavior during the leaching. It is not clear in what forms are antimony and tin present in the dross? Therefore, it is not clear, why did you obtain such low recovery degrees?
Specific comments:
l. 66. It is better to write these equations.
l. 69. Fig.2. Typo in caption. Sn instead of Sb.
l. 86, 87. Table 1-2. It is unclear why did you choose such concentration of the reagents.
l. 92-120. A repetition of the same experimental route. The repetition is redundant.
l. 158. A reference is needed to prove the existence such complexes.
l. 187. Table 6 is redundant. It is not clear which reaction thermodynamic characteristics are given.
Author Response
General comments:
- On the positive side, it should be noted that an attempt was made to explore a new method for extracting antimony and tin from lead dross. It is always important to explore new reagents to improve recovery valuable elements.
- On the positive side, the application of DoE is encouraged. However, the DoE method used is insufficiently described in the manuscript.
Thank you for pointing this out. We agreed that there was a lack on explanation on the DoE. We believed that it was not necessary to delve into a detailed explanation of the DoE, but have made changes to the manuscript to explain slightly DoE method. (Line 130-140)
- The references cited in this manuscript is too old. The introduction should contain recent relevant references on the topic of lead dross processing with the recovery of valuable elements. Hence it is unclear why HBr and HNO3 pretreatment were chosen.
We are aware that some of the references in the manuscript are too old. Some are patents from initial testing of bromine compounds on precious metals; however, at the time of experimentation, we were unable to find literature that would use HBr as a leaching reagent on antimony.
- Poor work with results. For example, Fig. 1, 2, 5 are given, but not described. The quality of figures is low; improving the images are necessary.
Thank you for pointing out that the results were poor. The figures indeed were of low quality. We agreed that changes needed to be made. We have enlarged the Figures 1 and 2 for better quality.
- There are unsuccessful obtained results: antimony and tin recovery rates are too low. It is not evident whether results can be better.
We are aware that the results yield lower dissolution rates than expected; however, with the lack of knowledge around HBr as a leaching reagent for antimony and tin this manuscript should be base of future work. There can be room for improvement if we are able to further understand bromine compounds behavior with antimony and tin. We are currently working on optimizing the system and performing leaching kinetics.
- The results are insufficiently deep. There is a lack of characterization of the obtained products (XRD, SEM), explanation of valuable elements behavior during the leaching. It is not clear in what forms are antimony and tin present in the dross? Therefore, it is not clear, why did you obtain such low recovery degrees?
Thank you for pointing this out. We have added characterization data on the sample from SEM and AMICS prior to any treatment. We agree that we did not clearly detailed the forms in which tin and antimony were present.
Specific comments:
- 66. It is better to write these equations.
Thank you for pointing out the missing equations. We agree that they should be displayed. They were intended to be, but missed them at the end.
- 69. Fig.2. Typo in caption. Sn instead of Sb.
We confirmed the typo and made the change from Sb to Sn to correctly display the caption of the figures
- 86, 87. Table 1-2. It is unclear why did you choose such concentration of the reagents.
The values for nitric acid were selected based on Ichlas’ paper from 2020 on selective nitric acid leach. This has been added in the text to further explain the DoE.
- 92-120. A repetition of the same experimental route. The repetition is redundant.
Thank you for pointing out this. Since the full detail of procedure was asked, we decided to fully write the procedure. We agree there is redundancy, especially if the is only thing that change was the acid. We have made a decided to keep the first and second paragraph describing the procedure as is since they have slight differences in the procedure, but just mention that the third paragraph with the procedure will follow the same as the second procedure but with changing acid and concentrations to avoid too many repetition.
- 158. A reference is needed to prove the existence such complexes.
Thank you. We have added a reference from PubChem to prove that SbBr3 exists.
- 187. Table 6 is redundant. It is not clear which reaction thermodynamic characteristics are given.
Thank you for mentioning this. After reviewing the content, we agree that it didn’t have a big effect on the text and have removed it to avoid confusing the reader.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript was improved significantly. However, major revision is still required to publish the paper.
Comments:
- There are a lot of recent relevant references on the topic of lead dross processing with the recovery of valuable elements. It is not necessarily to look for literature that use HBr, but some relevant references, which deals with lead dross processing using various methods, are needed. It can provide an opportunity to declare that you are working on a trending topic and help to promote your article. Thus, good Introduction is needed.
- l. 97-105. Mineralogical composition of the dross is still unclear. Could you state and prove clearly, what forms are lead, antimony, and tin found in? Pb0.87Sb0.03O0.1 – what is the base crystal lattice? In my opinion, you just need XRD analysis of the original dross. The local SEM analysis did not provide any clarity: 5 identified slag compositions contain a majority of elements. It is impossible to understand the mechanism of the process and further possibilities without understanding the forms of presence of the leached elements.
- l. 298-311. The conclusion section resembles part of the discussion section. It would be better to provide briefly the best conditions and main findings without any references.
Author Response
- There are a lot of recent relevant references on the topic of lead dross processing with the recovery of valuable elements. It is not necessarily to look for literature that use HBr, but some relevant references, which deals with lead dross processing using various methods, are needed. It can provide an opportunity to declare that you are working on a trending topic and help to promote your article. Thus, good Introduction is needed.
Thank you for the guidance on the reference topic. We have made changes to the introduction that have recent publications on lead dross processing methods. The additions are highlighted in light blue.
- l. 97-105. Mineralogical composition of the dross is still unclear. Could you state and prove clearly, what forms are lead, antimony, and tin found in? Pb0.87Sb0.03O0.1 – what is the base crystal lattice? In my opinion, you just need XRD analysis of the original dross. The local SEM analysis did not provide any clarity: 5 identified slag compositions contain a majority of elements. It is impossible to understand the mechanism of the process and further possibilities without understanding the forms of presence of the leached elements.
Thank you for pointing this out. The sample received had a very complex composition and the characterization report received didn’t detail the phases as desired. At the time, we contacted the person in charge but couldn’t give a definitive answer on the phases which is when we contacted the suppliers for additional information.
We agree that an XRD analysis on the original composition would solve this problem; however, we are not able to perform one as of today since we no longer have sample feed to perform XRD analysis.
- l. 298-311. The conclusion section resembles part of the discussion section. It would be better to provide briefly the best conditions and main findings without any references.
Thank you for pointing out the similarities between the conclusions and the discussion section. We have decided to remove the discussion section to combine the information between both. Additionally, we have mentioned the best conditions found.
Author Response File: Author Response.pdf
