Implementation of Solvometallurgical Processing in the Recovery of Valuable Metals from a Sulfide Ore

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The review on solvometallurgical methods of mineral processing presented for review is certainly of interest to the scientific community and clearly enough systematizes the prospects of using this approach to sulfide ores of different genesis. 

Nevertheless the reviewer recommends the authors to expand the description of the environmental aspects of the use of various solvents and additionally show how they should be utilized or regenerated to return to the process, which is one of the key aspects for assessing the efficiency and environmental friendliness of the presented processes.

Author Response

Dear Reviewer

May you find attached document responds to the reviewer

kind regards

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This review provides useful information about the solvometallurgical process.  However, the potential economic and environmental advantages that the authors like to emphasize are not convincing.  As they also pointed out in one of the sections (Section 5), that reducing costs and environmental impacts are still the challenges as there are no effective approaches to reduce the use of the solvents.  Also, the McCabe-Thiele diagram section needs more works as only some examples are mentioned without more in-depth review.  The quality of the diagrams used in the manuscript also needs to be improved.  Some of the words are blurry.  

Author Response

Dear reviewer

May you find attached document responds to the reviewer

kind regards

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Manuscript “Implementation of solvometallurgical processing in the recovery of valuable metals from a sulfide ore”.

The authors review the use of solvometallurgy, although different topics are addressed. Summary tables of the works found in the literature with the most important findings are not presented, and much information is not properly justified and/or cited. There is also theoretical information that can be found in some books on solvent extraction and they do not address the subject of the publication.  Therefore, this article does not present a sufficient level to be published. I leave below some comments so that you can improve your publication in a future submission.

1. Line 51. “In response to the limitations of pyrometallurgy, hydrometallurgical processes, which involve metal extraction using aqueous solutions at relatively…” The definition of SX it not adequate, and also SX is carried out using two immiscible phases, not “aqueous phase”.
2. Line 68. “pre-concentration methods to enhance the metal content of the ore before leaching…” This is very difficult to do without significantly increasing the cost, in fact I don't know of any economical/viable way to do it. If you have any studies where this is mentioned you should cite them.
3. Line 97. Put a “.” After the cite (19).
4. Line 93-95. Put more references. For example, which valuable metals were obtained selectively and separated from the gangue.
5. Line 97, you must cite this information.
6. In the introduction you need to add more literature sources than you mention, often you don't see a good literature review. This leads me to the point that they should also talk about the varied works that study solvometallurgy and how this new work differs from the others.
7. Figures 1 and 2 are of poor quality, please improve them.
8. Line 137. The term “extractant phase” is not right, it should be extractant diluted in a solvent phase, for example.
9. Line 139. The sentence “The extractant…” is not right. The part of (known as "the extractant,") does not make sense.
10. Line 155. What do you mean with Stabilization of the organic phase? Stabilization is related to a thermodynamic issue. Moreover, it is not justified why solvometallurgy would be appropriate, since the diluent of the feed phase and the extractant phase must be properly selected anyway. You should better justify their choice.
11. Line 157. If they mention that the “researchers” propose this solution for the aqueous phase, they should provide ideas on how it is solved and also cite the studies where this is indicated.
12. Line 195. Add a point after [10].
13. Line 195. “This effectiveness stems from the ability of organic solvents to penetrate…” Please indicate in which reported cases this has been found, because it is not a general rule, for example water with acid has a higher diffusion in solids due to its low molecular weight. Cite information.
14. Line 250. With what type of ILs? hydrophobic, hydrophilic, both?
15. In the thermodynamics and kinetics section they finally talk about SX, why do they do this if the publication is not about this? You should focus on describing the theory for these water-free systems, showing the expressions that best describe the non-aqueous system. This information they show is basic and can be found in any book in the field.
16. Fig2, the extraction stages are not touching the equilibrium line.
17. Line 478. mentioned that this proposal avoids the generation of aqueous residues and their subsequent treatment. This is not true, since there must be bleedings in the process in order to maintain the extraction after several extraction and stripping cycles. The use of a non-aqueous phase does not avoid this, in fact the use of non-polar solvents even generates pollution.
18. I find it hard to believe that electrowinning can be carried out in a non-aqueous medium in an economically viable way, because there must be charge carriers, otherwise the ohmic resistance makes it necessary to increase the temperature, which in mining is not possible due to the large amount of m3 treated every hour. There are studies that show that molten salts (ILs at high temperatures) can be used, but they do not have industrial applicability due to the above mentioned. It is a mistake to think that the whole process can be carried out without water. They should focus on where there are currently the most problems.
19. Minor topological errors are found. In addition, the wording and English need to be revised.
20. You do not cite works where the technical-economical feasibility of the solvometallurgy process is discussed. This is important in order to give ideas about its future implementation.
21. Another point they can add is phase recovery after SX. By using components with lower polarity difference there may be a distribution of certain components, such as the extractant.
22. Some references do not have the required information. You should check that they comply with the journal's guidelines.
23. Finally, the advantages of this process over conventional SX are not clear. They should also clearly mention the possible disadvantages. In this way it is shown as an objective review of the subject.

Author Response

Dear Reviewer 

May you find attached document responds to the reviewer

 

kind regards

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Implementation of solvometallurgical processing in the recovery of valuable metals from a sulfide ore is very interesting paper in nonferrous extractive metallurgy. Minor improvements are required.

Line 11. It has been demonstrated that the traditional hydrometallurgical method is still economically viable in several industrial applications (such as..)

Line 16, 17: (2) special linings are required in the material due to their corrosiveness and rendering all processes costly (in what temperature range?)

Line 22, 23: This review has examined the potential of solvometallurgical processes (solvoleaching) as viable alternatives for metal extraction from sulfide ores (in what temperature range? what id operation pressure in system?))

Line 76: optimized operating conditions (such as….)

Line 78: Furthermore, the formation of silica gel during leaching (what type of material? ores containing silica? Laterite ores?) can complicate downstream  processing

Line 97, 98: This is because organic solvents can often penetrate the mineral structure more effectively than aqueous solutions, leading to higher metal recoveries (in what temperature interval?)

Line 195, 196: This effectiveness stems from the ability of organic solvents to penetrate mineral structures more efficiently than aqueous solutions, ultimately leading to higher metal recovery rates  (what are mostly used reaction parameters: temperature,. Concentration of solution?)

Line 306: This strategic addition significantly improved the overall copper leaching yield (in what temperature range?)

Line 315, 316: These characteristics rendered diethyl ether a less effective solvent for most of the investigated metal salts (such as…), resulting in the observed disparities in metal distribution ratios.

Line 389 Furthermore, the negative ΔG value demonstrates that the copper extraction process in this system is spontaneous (in what temperature range? In which reactor)

Line 436: These experiments involve varying the concentration of a third variable and observing its effect on the extraction rate (what is duration of this studied process)

Line 438: The orders concerning the two constant concentrations are determined based on the changes in the extraction rate as these concentrations are altered (in what range?)

Line 481: Furthermore, solvometallurgy addresses challenges posed by carbonate-rich ores (what type of minerals and ores? bastnaesite? no silicate ores?)

Line 486: The reduced solubilization of silica in non-aqueous solvents minimizes silica gel formation (what is concentration of the leaching agents in solvometallurgy? What are reaction parameters?)

Conclusions

Line 519, 520: Non-aqueous solvent extraction (NASX) and other solvometallurgical unit technologies can enhance conventional metallurgical processes, offering economic and technical advantages (what is optimal temperature interval and the used concentration of leaching agent in solvometallurgy in contrast to hydrometallurgy?)

General question:

1. What are values of concentration of used leaching reagents in solvometallurgy in contrast to hydrometallurgy?

Author Response

Dear Reviewer 

May you find attached document Responses to the reviewer

kind regards

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The authors review the use of solvometallurgy, although different topics are addressed, which makes the review inconsistent with the title of the publication. Synoptic tables of the works found in the bibliography with the most important conclusions are not yet presented, and much information is not properly justified and/or cited. There is also theoretical information that can be found in some books on solvent extraction and they do not address the subject of the publication itself. There are no equations that model their proposal, so they are just repeating known information. Therefore, I still maintain that this article is not of a high enough standard to be published. I leave below some comments that are still not addressed, but the authors should rethink the publication due to the gaps in this review and the way they present the publication. 

 

1. Line 51. “In response to the limitations of pyrometallurgy, hydrometallurgical processes, which involve metal extraction using aqueous solutions at relatively…” Your sentence is still wrong, it is not using an aqueous phase, since that is where the metal is extracted from, it is “using an organic phase”.
2. Line 51. You have changed the text, but there is no cited information about this, as you mention in the responses.
3. The introduction does not yet mention how this review contributes to scientific society. The authors have responded that they have made changes, but these are not visible. There are several reviews that should mention what they focus on, what their gaps are, and therefore what you will cover in this work.
4. Figure 1 is still in low quality. Figure 2 should corroborate that they have the permissions. Anyway, this figure 2 has several editing problems.
5. Line 230. The fact that the conventional SX system has different hydrations of the metal, by using a different solvent, will not prevent several. Another point, because of what they say about the high amount of acid that is used in traditional SX. In their write up they do not mention that no acid was used to get to the Batchu 2020 experiments. By occupying that initial phase the leaching is slow. and obviously the metal will be extracted because it prefers to be solvated by a more affine phase, which is the extractant. Water as an initial source is very affine with the metal, that is why the yields are lower. You should show literature where you do not just add the metal salt directly to that non-polar phase. Also, after extraction they should do stripping, usually with acid to recover the metal, which is not stated if it is possible otherwise. So I still don't see the advantage of your proposal. No doubt there are advantages, but they should review the literature better.

Author Response

Dear Reviewer

 May you find attached the Response to the reviewer

kind regards

Author Response File: Author Response.pdf