Removal of Magnesium in Zinc Hydrometallurgical System via Freezing Crystallization: From Laboratory Experiments to Industrial Application
, Min Du 3, Xingguo Luo 1,*, Chang Wei 1, Zhigan Deng 1 and Minting Li 1
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsComments to the authors
Manuscript Submission sustainability-2683179
Title: Removal of Magnesium in Zinc hydrometallurgy system via freezing crystallization: From laboratory experiments to industrial application
General comments:
The study aimed at the novel crystallization process for Mg separation from Zn in hydrometallurgical process. Results seems promising but the manuscript needs improvement and answer some basic questions. There are some citations missed in the manuscript as well.
Abstract
Why the authors considered Mg as valuable metal? Price? Risk of supply interruption? Applications?
Decreasing of Mg concentration represents about 40% of Mg removal/recovery. Is it a good number? Why not achieve around 90%?
“The crystallized electrolyte could be returned to Zn hydrometallurgy system” which crystallized? Mg product?
“The crystallization product is a mixture of MgSO4·7H2O and ZnSO4·7H2O” what is the %Mg content?
“In the industrial application process, the average removal….” Information repeated.
Introduction
The first paragraph misses a reference in the last sentence.
“In this process, the Zn electrolysis process will be effected by fluoride ion.” Why and how?
Page 2 line 54-64: an example with efficiencies and parameters is necessary to contribute with authors’ agreement.
Why cementation is not an alternative for Mg removal?
Methodology
Figure 1b was already reported in literature - https://linkinghub.elsevier.com/retrieve/pii/S0959652620327827. Please, cite properly.
Results and discussion
Subtitles must be improved. For instance – Chapter 3.1.3. Effect of time OR Crystallization kinetic; Chapter 3.1.5 Effect of stirring…
Better explanation and comparison to the literature for results presented in Figure 4 is necessary.
Use rpm instead of r/min.
SEM images need improvement.
Chapter 3.3 – it should be presented in Abstract section.
The mass balance in Figure 9 is also required.
Final decision
Major revision.
Comments on the Quality of English Language
There are typos in the manuscript.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Editor,
please find attached my evaluation of the manuscript "Removal of Magnesium in Zinc hydrometallurgy system via freezing crystallization: From laboratory experiments to industrial application" submitted by Jin et al. The study shows an impressive achievement of bridging the gap between small scale experiments in the laboratory and the industrial scale. However, due to several short-comings I cannot recommend the manuscript in its current state for publication.
The authors might have a detailed look on the following points:
- Uniform style of figures (font, font size, figure size)
- Uniform usage of units (g/L, g·L–1, mg/mL, etc.)
- A space is required between all values and units
- The references need to be unified in style
- It is necessary to explain to the readers, what the "Zn hydrometallurgy process" is (e.g., line 27)
- Line 15: How can this be the optimal conditions, if the separation efficiency is only ~40%?
- Line 17 & others: What is the crystallized electrolyte and how can this be re-used?
- The claims on separation and energy efficiency (e.g. Line 61) need to be supported by references and benchmarking.
- Line 40: What does "In this process, the Zn electrolysis process will be effected by fluoride ion." mean?
- Line 46: What does "Nevertheless, the organic phase remained in the aqueous phase during the extraction process and reagent costs may limit its application." mean? If one can see an organic phase that implies that it is separated from the aquaeous phase and not in it.
- Line 62: How can you add ammonium, that is a cation, so what is the chemical compound which is added?
- Line 97: Please add the acceleration voltage used for SEM
- Line 101: What is argon air atmosphere. Please be specific on the gas atmosphere used. Another question is that the reviewer cannot see thermal analysis results in the manuscript.
- Line 111: Please check the stated temperature range, since currently it is overlapping with the T range mentioned before.
- Line 158: Why exactly 163.7 g/L H2SO4 was selected as initial concentration? Additionally, be careful in the later section 163.0 g/L are stated.
- Line 176: Please provide the reader some guidance, what are the observed ranges (values needed)
- Laboratory experiments: How many experiments have been carried out to determine the error bars?
- Chapter 3.1.3: Within error bars all concentrations are the same, how is then the selection of 90-120 min justified.
- Line 198: The addition of CaCO3 is in disagreement with the statement that the process does not required additional chemicals
- Line 207: The reviewer does not see why under the selected experimental conditions radicals shall form. The effect has to be described in more detail and supported by literature.
- Line 235/236: The meaning of this statement remains unclear to the reviewer. Is a seed crystal needed for the process? If yes, how low one can go?
- Chapter 3.1.5: It should be explained why the authors expect an effect of the agitation intensity at all.
- Lines 256-260 need to be supported by experimental data
- Line 289 and later: No X-ray spectrum was measured, but a diffractogram
Comments on the Quality of English Language
The manuscript contains a lot of grammatical errors and is inconsistent in the tenses used.
This needs to be strongly improved before publication.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for Authors
The work titled " Removal of Magnesium in Zinc hydrometallurgy system via
freezing crystallization: From laboratory experiments to industrial application" showcases results that hold significant relevance within the field of metallurgy, particularly due to its potential for extracting magnesium impurities based on solubility differences, all without the need for introducing additional reagents. This approach profoundly aligns with sustainability principles. Beyond its relevance, the study comprehensively examines a wide array of potential variables that could be controlled during the magnesium recovery process, even if they may not exert a significant influence on the outcome. Moreover, the results not only encompass laboratory-scale investigations but also demonstrate practical application within an industrial setting, greatly enriching the overall study. Provided below are some recommendations/corrections for your careful consideration before proceeding with the publication.
1- I encourage authors to standardize the units in Figure 1, especially on the ordinate axis. Perhaps they should all be presented in molality or percentage.
2- In line 177 replace the word 'obviously' with another word like 'notoriously'. The results are not obvious to the reader.
3- In line 207 replace effect of sulfate ‘radical’ for effect of sulfate anion.
4- Show in the text the reference used to compare the diffractometry data or the codes of the database cards. Figure 8 has low resolution and apparently there are different peaks to be characterized. Could it be impurities or other byproducts like MnSO4? In the same figure, indicate the experimental conditions (temperature, etc.) that resulted in the products analyzed by XRD and SEM/EDS.
5- In line 342 separate the number from measurement unit – 15g/L.
6- Provide a brief explanation for the different results shown in Table 4. The initial concentrations of Magnesium are close, and this indicates that there are other interferences in magnesium removal besides temperature. The data is discrepant, especially for Aug2021.
7- Thermal analyses results are not showed. This way, it is not necessary to include in the methodology.
8- Write in the methodology how the ions were quantified. I assume it is by EDTA titration, but this is written in the temperature analysis.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 4 Report
Comments and Suggestions for AuthorsThe paper deals with the purification of zinc electrolyte from magnesium, showing the results of laboratory experiments on the effect of various parameters on the degree of magnesium precipitation from solution, as well as the results of industrial tests. In general, the results are interesting, but the article requires careful revision before publication. Comments:
28-80 The authors use very many introductory words, literally in every sentence, which makes the article difficult to understand.
118 Here it must mean at different temperatures?
144 Here it is probably not the effect of these parameters on Mg2+ but on magnesium precipitation efficiency?
Figure 1. Why are the concentrations given in different dimensions? How can these graphs be compared?
Figure 2: For Figures C,D,E an another scale of y-axis should be taken, otherwise the level of influence is not obvious.
186 Crystallisation temperature?
245 In Figure 2 and in the text, g/L is used rather than just in g.
249 "on the on the"
251 are listed?
255 rodman??
270 Why is mg/l here? Please keep it uniform.
337 Do you get the metal directly or do you mean calculated on metal mass basis?
380 The list of References is not arranged according to the journal's requirements.
Comments on the Quality of English Language
Extensive editing of English language required
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript can be published after these revisions.
Author Response
Please see the attachmentAuthor Response File: Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Authors,
the reviewer appreciates the efforts undertaken to revise the manuscript and most remarks on the initial version have been properly addressed. Before publication, I kindly request the authors to carry out the following minor corrections.
- Comment 10/lines 141-143: I suggest to say "...the organic phase partially remains..."
- Comment 17: It will be appreciated, if the quality statement on aspect ratio and glaze surface can be added to the manuscript.
- Comment 19: The authors are referring to the sulfate anion (SO42-) which is fundamentally different from a radical. The latter has unpaired electrons and is therefore very reactive, e.g., a chlorine atom. Please remove the term "radical" and use "anion" instead.
- Comment 23: Please also exchange in lines 588/589 and line 628 "spectrum" by XRD pattern.
Comments on the Quality of English LanguageA few small typos are remaining.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
Comments and Suggestions for AuthorsThe authors corrected all comments, but there are still a few small comments that should be addressed.
Figure 1. There used to be two figures where the solubility of magnesium sulfate and zinc was shown, but they were in different concentration dimensions. Now, the authors have left one figure, in which the dimensions for concentrations are still different. It is also not clear how it is possible to determine the position of the dotted line for the crystallization of zinc sulfate in these coordinates. Furthermore, I think the size of the figure needs to be increased.
Line 790. The references are still not made according to the requirements of the journal.
Comments on the Quality of English LanguageEnglish level become better.
Author Response
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Author Response File: Author Response.docx
Round 3
Reviewer 1 Report
Comments and Suggestions for Authorsthe manuscript can be accepted.
