Extracting Lithium from Brazilian α-Spodumene via Chlorination Roasting

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

#1: With reference to Figure 4, I'm curious why low lithium extractions (<50%) were observed in tests with just CaCl2 present? Fosu et al. (2022) have recently presented a pyrometallurgical synthesis of lithium chloride directly from α-spodumene by reaction with solid CaCl_2, and reported lithium extractions of almost 90%. Their optimal conditions of CaCl₂/spodumene molar ratio of 2.0, and 1000°C treatment for 1 h are similar to the current study so the reason for the difference in lithium extractions is not clear. See reference: 

FOSU, A. Y., KANARI, N., BARTIER, D., VAUGHAN, J. & CHAGNES, A. 2022. Novel extraction route of lithium from α-spodumene by dry chlorination. RSC Adv., 12, 21468-21481.

#2: Table 1, the heading of the table is incomplete. The summary of "alkaline processes" does not include the LieNa process under development for alkaline pressure digestion of finely sized spodumenes. See following reference among others: 

NAPIER, A. & GRIFFITH, C. 2019. Process for recovering lithium phosphate and lithium sulfate from lithium-bearing silicates, WO2019227158.

#3: Table 3: The composition is reported as p/p % which are not standard units and should be wt/wt%. Also the commas used in the results should be replaced with decimal points (e.g. 23.265 instead of 23,265). The results could also be reported to 2 significant figures (not 3) given the expected error in the analytical measurements. In line 258: the reference to Table 3 for the lithium extraction results is incorrect and should be removed.

Comments on the Quality of English Language

There are numerous typographically errors throughout the text and it needs to be checked and revised before re-submission. Some examples below but there are many others that need attention.

Line 150: chlorination torrefaction - not sure what this term relates to.

Line 184: three (not tree). There are many typos in this section and it needs to be rewritten.

Line 264: spodumenium should be spodumene

Line 320: determinated and betwen are misspelt.

 

 

Author Response

Comments 1: With reference to Figure 4, I'm curious why low lithium extractions (<50%) were observed in tests with just CaCl₂ present? Fosu et al. (2022) have recently presented a pyrometallurgical synthesis of lithium chloride directly from α-spodumene by reaction with solid CaCl₂, and reported lithium extractions of almost 90%. Their optimal conditions of CaCl₂/spodumene molar ratio of 2.0, and 1000°C treatment for 1 h are similar to the current study so the reason for the difference in lithium extractions is not clear. See reference:

FOSU, A. Y., KANARI, N., BARTIER, D., VAUGHAN, J. & CHAGNES, A. 2022. Novel extraction route of lithium from α-spodumene by dry chlorination. RSC Adv., 12, 21468-21481.

 

The sample of this study was characterized in the article presented in the reference below, where it was observed that the crystalline structure of spodumene undergoes complete decrepitation from the alpha phase to the beta phase at temperatures above 1050°C. However, at 1000°C, low percentages of alpha-spodumene are still present, as shown in Fig. 10 of the study by Fosu et al. (2022), which displayed an X-ray diffractogram in which alpha-spodumene is still present in the sample, albeit in low concentrations.

 

The pyrometallurgical and hydrometallurgical tests for calcination and leaching were conducted using different equipment. While Fosu et al. (2022) used a Carbolite Gero electric furnace for calcination and a Gerhardt laboratory thermoshaker for leaching, in this study, a static muffle furnace was employed for calcination, and leaching was carried out on a laboratory bench using a magnetic stir plate.

 

The differences in equipment operation modes and extraction procedures may have influenced the results, justifying the higher lithium extraction observed in the study by Fosu et al. (2022). Regarding the residence time in the muffle furnace, an extraction rate of less than 50% was observed in 120 minutes, whereas Fosu et al. (2022) reported approximately 90% extraction in just 60 minutes. These discrepancies may be related to differences in the sample matrices analyzed.

 

In the submitted article, higher temperatures were used to ensure the complete decrepitation of alpha-spodumene. Additionally, there is a significant difference in the reagents used: Fosu et al. (2022) employed analytical-grade CaCl₂, whereas in this study, calcium chloride dihydrate (CaCl₂·2H₂O) was used. This difference may have led to distinct intermediate reactions in the two experiments. Another relevant factor is the CaCl₂/spodumene ratio. Although the proportions are similar, a higher amount of chloride may have favored recovery in the present study.

 

The spodumene used in this study originates from the Jequitinhonha Valley, MG – Brazil, and is a concentrate obtained by gravity separation. In contrast, the sample investigated by Fosu et al. (2022) comes from the Pilbara region in Western Australia and results from the flotation of a lithium-cesium-tantalum-type pegmatite ore. Although both are spodumene ores, their mineralogical compositions may vary, influencing their chemical composition. This is evident in the characterization of the sample used by Fosu et al. (2022), which presents concentrations of Cs (116 ppm), Rb (1033 ppm), Ta (202 ppm), Nb (108 ppm), and Sn (140 ppm), whereas these elements are absent in the concentrate analyzed in this study.

 

BRIGIDO, CAROLINE RODRIGUES DOSA SANTOS; NEUMANN, REINER; BRAGA, PAULO FERNANDO ALMEIDA. CARACTERIZAÇÃO MINERALÓGICA, QUÍMICA E TECNOLÓGICA DO CONCENTRADO DE ESPODUMÊNIO , p. 315-325. In: 23º Seminário de Mineração, São Paulo, Brasil, 2024. ISSN: 2594-357X , DOI 10.5151/2594-357X-40790

 

Comments 2: Table 1, the heading of the table is incomplete. The summary of "alkaline processes" does not include the LieNa process under development for alkaline pressure digestion of finely sized spodumenes. See following reference among others:

NAPIER, A. & GRIFFITH, C. 2019. Process for recovering lithium phosphate and lithium sulfate from lithium-bearing silicates, WO2019227158.

 

We accepted the comment about the title of the table and corrected it to “Main reported methods for lithium recovery from minerals” (p. 2, line 34). We have given priority to articles published from 2018 onwards, but we have included the patent for the LieNa process. Thank you for your collaboration.

 

Comments 3: Table 3: The composition is reported as w/w % which are not standard units and should be wt/wt%. Also the commas used in the results should be replaced with decimal points (e.g. 23.265 instead of 23,265). The results could also be reported to 2 significant figures (not 3) given the expected error in the analytical measurements. In line 258: the reference to Table 3 for the lithium extraction results is incorrect and should be removed.

 

Accepted. The unit has been adjusted, commas have been replaced with periods, and the results have been rounded to two decimal places. Additionally, the reference to Figure 4 has been corrected as indicated.

 

Comments 4: Line 150: chlorination torrefaction - not sure what this term relates to.

 

The term has been changed to “chlorination roasting”

 

Comments 5: Line 184: three (not tree). There are many typos in this section and it needs to be rewritten.

 

Accepted, the section has been rewritten.

 

Comments 6: Line 264: spodumenium should be spodumene.

 

I accept. The term has been rewritten.

 

Comments 7: Line 320: determinated and betwen are misspelt.

 

I accept. The term has been rewritten.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript was interesting to read and addresses a highly relevant topic. The experiments performed were reasonable and represent important ground work for the acquisition of future lithium resources. I have two suggestions for improvement:

1. It would be interesting to learn in the introduction how lithium extraction for minerals relates to the brine process. E.g., how do energy consumption, waste products, and environmental impact compare? The authors mentioned that the high energy consumption and the waste occurrence are a problem, but to which extent? Is the minerals processing foreseeable to be performed on an industrial scale in the near future? What are the key points that need to be improved to make it attractive in comparison to the brine approach?
2. After the authors explained their approach of changing three reaction parameters in the experimental part, it would be more intuitive to also structure the results section this way. So I suggest to insert a sub-heading for the variation of the reaction time.

Comments on the Quality of English Language

Minor language issues, such as spelling, wrong tense of verbs or irritating order of words affect the flow of reading a bit. There are tools (e.g., deepl) which can help fix that quickly.

Author Response

Comments 1: It would be interesting to learn in the introduction how lithium extraction for minerals relates to the brine process. E.g., how do energy consumption, waste products, and environmental impact compare? The authors mentioned that the high energy consumption and the waste occurrence are a problem, but to which extent? Is the minerals processing foreseeable to be performed on an industrial scale in the near future? What are the key points that need to be improved to make it attractive in comparison to the brine approach?

 

Accepted. The characteristics of lithium extraction in brines and pegmatite rocks have been added to the introduction.

 

Comments 2: After the authors explained their approach of changing three reaction parameters in the experimental part, it would be more intuitive to also structure the results section this way. So I suggest to insert a sub-heading for the variation of the reaction time.

 

I accept. Deposits have been restructured for better understanding.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The work submitted for review is devoted to the actual topic of spodumene ore perarabotka and the presented results have a sufficient level of scientific novelty and practical significance in the field of increasing the efficiency of chlorine roasting process.

To improve the results' presentation , the authors are recommended to address the following issues:

STR 65 - It is recommended to correct the phrase " is resistant to the attack of chemicals agents". Maybe phrase "is resistant to the action of the chemical reagents" would be more suitable.

STR 109 - Eq. 1 is not balanced and presented with incorrect steheometric coefficients

STR 116 - For more sufficient proof of further authors reasoning in terms of spodumene transformation it is necessary to provide change of the Gibbs energy value for presented reactions in different temperature intervals.

STR 162 - Which classification operations were used during the experiments to control the yield of the -74 micrometer sieve class?

Figure 8. Why the molar ratio values are 30, 60, 90, 120. What do these values mean in terms of molar ratio? 

Author Response

Comments 1: STR 65 - It is recommended to correct the phrase " is resistant to the attack of chemicals agents". Maybe phrase "is resistant to the action of the chemical reagents" would be more suitable.

I accept. The term has been rewritten.

 

Comments 2: STR 109 - Eq. 1 is not balanced and presented with incorrect steheometric coefficients

I accept. Reaction 01 has been balanced.

 

Comments 3: STR 116 - For more sufficient proof of further authors reasoning in terms of spodumene transformation it is necessary to provide change of the Gibbs energy value for presented reactions in different temperature intervals.

Accepted. Gibbs energy has been included.

 

Comments 4: STR 162 - Which classification operations were used during the experiments to control the yield of the -74 micrometer sieve class?

The sample was sorted through a set of sieves and only the fraction of interest (-74 micrometers) was removed.

 

Comments 5: Figure 8. Why the molar ratio values are 30, 60, 90, 120. What do these values mean in terms of molar ratio?

These values refer to the sample's residence time in the muffle furnace.

Author Response File: Author Response.docx