Simulation to Recover Niobium and Tantalum from the Tin Slags of the Old Penouta Mine: A Case Study
, Alicia Valero 1, Guiomar Calvo 1, Francisco J. Alguacil 2 and Félix Antonio López 2Round 1
Reviewer 1 Report
The subject of this manuscript is of great scientific relevance. The article is well written. The structure is well organized. The followed approach is original. In my opinion this paper could be accepted for publication as long as some minor changes are made.
Figure 1 could be improved by simply changing the colours as when it is printed in black and white, the three categories do not stand out
Figure 3 has too low a resolution. The labels are not read.
In lines 194 to 196, the authors specify the name of the used software. In this case it could be briefly explained why this software was chosen.
In discussing the results, in lines 329 to 338, the authors present a possible environmental problem and hint at ways to mitigate it. In this regard, the authors could refer to the use of a systematic method to support this phase, without proposing solutions but explaining that with it, some solutions could be found. Authors could refer for example to the following publication.
Russo, D., & Spreafico, C. (2020). TRIZ-based guidelines for eco-improvement. Sustainability, 12(8), 3412.
Author Response
The subject of this manuscript is of great scientific relevance. The article is well written. The structure is well organized. The followed approach is original. In my opinion this paper could be accepted for publication as long as some minor changes are made.
First, we would like to thank the reviewers for taking the time to check our paper and providing valuable comments to improve it. Below is a point-by-point answer to the comments.
Figure 1 could be improved by simply changing the colours as when it is printed in black and white, the three categories do not stand out
Figure 1 has been modified, not only the colours but also the shape of it to highlight the different categories shown.
Figure 3 has too low a resolution. The labels are not read.
We have updated the most relevant labels of the figure to improve readability.
In lines 194 to 196, the authors specify the name of the used software. In this case it could be briefly explained why this software was chosen.
We have incorporated the following information:
“This software allows to assess costs and optimise processes [43]. In particular, for this paper, it has been applied for thermodynamic and mineral processing calculations, such as mineral extraction, beneficiation, and mineral refining [33].”
In discussing the results, in lines 329 to 338, the authors present a possible environmental problem and hint at ways to mitigate it. In this regard, the authors could refer to the use of a systematic method to support this phase, without proposing solutions but explaining that with it, some solutions could be found. Authors could refer for example to the following publication.
Russo, D., & Spreafico, C. (2020). TRIZ-based guidelines for eco-improvement. Sustainability, 12(8), 3412.
The paper has been modified in order to explain the future outcomes that is possible to face in the upcoming years. Furthermore, the reference suggested has been included to support the Eco-design solution, for devices as well as other technologies.
“However, even if they are included in small quantities on each device, the total amount used at the world level is considerable. Moreover, their future availability could be dangerously compromised as the primary sources, meaning the places where they are mined are limited [16]. They are considered critical by many countries and institutions, as their current and future availability, or the concentration of supply, could put at risk many economies [17]–[19].
Therefore, securing a stable supply of certain raw materials is essential for many governments, such as the European Union, which promotes the so-called circular economy [20]. Unfortunately, current technologies are not designed to recover all the components and valuable metals from the waste of electric and electronic equipment (WEEE). This could be eventually solved following eco-design guidelines [21].”
Reviewer 2 Report
1) Using a list of lumped references is not helpful to the readers. At least a short justification should be provided - individually.
2) It is necessary to describe the novelty of the work more in relation to the existing articles. There is a need to comment more on the benefits and weaknesses in existing publications. And describe the motivation for the creation of this article. This point is described very briefly in the text.
3) Check the format of the numbers, use the dot as a decimal separator and use the comma as thousand separators. See Fig. 1 etc.
4) Check the quality of the figures. Fig. 3 is not very legible.
5) Typing error: "1200ºC"
6) References: Unify style. See "[5]" vs. [9] etc.
Author Response
First, we would like to thank the reviewers for taking the time to check our paper and providing valuable comments to improve it. Below is a point-by-point answer to the comments.
1) Using a list of lumped references is not helpful to the readers. At least a short justification should be provided - individually.
Certain references mentioned in the paper have been revised and modified when necessary, including a large description of its content to better show why each reference was used and in what context.
2) It is necessary to describe the novelty of the work more in relation to the existing articles. There is a need to comment more on the benefits and weaknesses in existing publications. And describe the motivation for the creation of this article. This point is described very briefly in the text.
Further explanations have been added to the paper, clarifying the motivation of the paper and comparing it with other studies.
“This process has been widely studied by different authors [41], [42] as coltan has become one of the most important minerals in industry. Additionally, its scarcity and concentration of supply are also well known. Hydrometallurgy processes used to recover these two elements are based on strong acids, which are economically and environmentally challenging. One of these studies considers a greener approach for the selective dissolution of the amorphous slag matrix, obtaining a concentration similar to commercial grade [41]. This same study reflects the high mass losses produced by sequential acid and alkaline leaching, while the sequential Acid-Basic-Acid leaching is the most favourable, with concentrations of 63% [41]. One of the main disadvantages of this process is the high amount of chemicals needed to purify the metals. Another study analyses the availability to purify Nb and Ta from tin slags with a very low ore grade [42]. Although the recovery ratio of the metals is very high and the results are very promising, a vast amount of processes, time, and a high amount of chemicals are required [42]. As a result, the environmental impact is very high, and with the reagents applied, it makes this process less cost efficient compared with the process proposed in this paper.
In this study, alternative chemicals as those proposed in the literature are used during the leaching process, thereby reducing material losses as well increasing the metal yields. In that same line, in our case study, the aim is to reuse reagents as much as possible to decrease the environmental impact of the whole process.”
3) Check the format of the numbers, use the dot as a decimal separator and use the comma as thousand separators. See Fig. 1 etc.
The tables and the text have been deeply revised and we have modified those numbers that used comma as decimal separator and changed them with dots.
4) Check the quality of the figures. Fig. 3 is not very legible.
We have updated the most relevant labels of the figure to improve readability.
5) Typing error: "1200ºC"
The text has been modified.
6) References: Unify style. See "[5]" vs. [9] etc.
References have been carefully checked and they have been changed to the same format, unifying the style.
Reviewer 3 Report
Dear authors,
your manuscript titled "Simulation to recover niobium and tantalum from the tin slags of the Penouta mine: a case study" is very well written and presents a very interesting study case on industrial processes aimed to recovery rare minerals from mine wastes, which is a topic of primary importance in the development in the green, circular economy.
My opinion is that your work is worthy of publication as it is
Author Response
your manuscript titled "Simulation to recover niobium and tantalum from the tin slags of the Penouta mine: a case study" is very well written and presents a very interesting study case on industrial processes aimed to recovery rare minerals from mine wastes, which is a topic of primary importance in the development in the green, circular economy.
My opinion is that your work is worthy of publication as it is.
We want to thank the reviewer for these comments and for taking his/her time to check the paper and we really appreciate the feedback provided.
