Evaluation of L-arginine as an Eco-Friendly Activator for Malachite Sulfidization Flotation

Round 1

Reviewer 1 Report

This study aimed to investigate the use of L-arginine (LA) as an activator to change the malachite surface and increase the sulfidization flotation recovery.

Additionally, the adsorption experiments, the zeta potential measurements, and SEM-EDS and XPS analyses were carried out to explain the mechanism.

The results obtained from the experiments and analyses are very interesting and presented very well.

However, the authors could write the manuscript better based on the results obtained from this study.

For this reason, the manuscript should be accepted after the major corrections.

Please also consider the following points:

·      Figure 1: Please make the letter of the atoms clear in the figure.

·      Figure 1: Type the colour of each atom here such as the blue colour "N"

·      What is the purity of the malachite sample used in this study?

·      What do you mean when it is said: "manual cleaning" for the sample?

·      What is the purity of the reagents roughly?

·      What was the reason for using two collectors in the studies?
Pure HCl??? make it clear.

·      DI water: Company, model, country, resistivity, etc.

·      Include the subtitle “Methods”.

·      Change “micro-flotation” to flotation.

·      How long was the suspension stirred for the flotation experiments?

·      What was the flowrate for the flotation experiments?

·      What was the wavelength (λ) used for the calculation of the amount of adsorption? 

·      Eq. 1: Change "0" and "x" to "i" and "r", respectively.

·      How was the filtration performed after the adsorption experiments?

·      Change “measurements” as “analysis” in the case of SEM-EDS and XPS.

·      Figure 4a: There is almost no change in terms of recovery. Not clear why two collectors were used.

·      What was the hydrophobicity (contact angle) of the sample used in this study?

·      Were the contact angle measurements carried out?

·      or is there any data regarding this?

·      Figure 6: Please order them as;

o   With LA and Na2S

o   With Na2S

o   Without LA and Na2S

·      Figure 7: Ci or Cr concentration?

·      Figure 8: Almost no difference!

·      Figure 13: Move the figure after the text!

·      Figure 14: Make the reagents bigger.

·      In addition to them, the manuscript contains some grammatical problems and must be carefully edited again in terms of grammar and writing.

·      Please see the attached file where you can find my corrections/comments, and respond to them carefully one by one.

Overall, the manuscript can be accepted after a major revision to be published in the journal of Minerals.

 

Comments for author File: Comments.pdf

Author Response

Dear Editors and Reviewers:

Hope this letter finds you well.

 

We are very grateful for your constructive suggestions and comments of our manuscript entitled “Evaluation of L-arginine as an eco-friendly activator for malachite sulfidization flotation” (ID: minerals-1955936). Those comments are all valuable and very helpful for improving our paper. Each comment has been carefully considered, and we have revised the manuscript in detail. Following is a point-to-point response to the reviewers’ comments, and the modified parts can be identified by the red font in the version of revised manuscript with changes marked. We sincerely hope that the revised manuscript could be considered suitable for publication on Minerals.

 

Many thanks and best regards.

Yours sincerely,

Jianyu Zhu

 

Corresponding author:

Name: Jianyu Zhu

E-mail: [email protected]

Central South University

 

Response to Reviewer #1:

Comment 1: Figure 1: Please make the letter of the atoms clear in the figure. Figure 1: Type the color of each atom here such as the blue colour "N".

Response: Thank you very much for your helpful comments. We have made the letter of the atoms in the figure clear and type the color of each atom.

Comment 2: What is the purity of the malachite sample used in this study?

Response: According to the results of XRD and XRF, the purity of the sample is above 96%.

Comment 3: What do you mean when it is said: "manual cleaning" for the sample?

Response: The malachite block part is closely connected with other gangue, and the part connected with gangue is removed manually.

Comment 4: What is the purity of the reagents roughly?

Response: Thank you for your comments. The purity of industrial grade butyl xanthate and amyl xanthate is about 86%, and the purity of industrial grade foaming agent is about 80%.

Comment 5: What was the reason for using two collectors in the studies? Pure HCl??? make it clear.

Response: Thank you for your comments. Butyl xanthate and amyl xanthate are the most common collectors in malachite sulfidization flotation. In this paper, the flotation effects of the two collectors were compared, and the most suitable collector was selected to study the effect of LA. 38% analysis of pure HCl was used in this study.

Comment 6: DI water: Company, model, country, resistivity, etc.

Response: The deionized water used in this study was prepared by 15T/H deionized water equipment, produced by Zhongshen Environmental Protection Co., LTD., in China.

Comment 7: Include the subtitle “Methods”. Change “micro-flotation” to flotation.

Response: Thank you very much for your considerate comments. I have changed the second section accordingly.

Comment 8: How long was the suspension stirred for the flotation experiments?

Response: The suspension was stirred for 1 min before adding reagents, and for 12 min during the whole flotation process.

Comment 9: What was the flowrate for the flotation experiments?

Response: Thank you for your comments. The flotation process is carried out in the flotation tank, and the flow in the tank is agitated by the rotation of the impeller, so the flow rate is determined by the speed of the impeller, and changes with the change of the distance of the impeller.

Comment 10: What was the wavelength (λ) used for the calculation of the amount of adsorption?

Response: When using UV spectrophotometer to measure the residual concentration of xanthate, the absorption wavelength used is 300.5 nm.

Comment 11: Eq. 1: Change "0" and "x" to "i" and "r", respectively.

Response: Thank you very much for your comments. I have revised the equation.

Comment 12: How was the filtration performed after the adsorption experiments?

Response: The reaction slurry was drawn using a syringe and then filtered using a filter membrane.

Comment 13: Change “measurements” as “analysis” in the case of SEM-EDS and XPS.

Response: Thank you very much for your considerate comments. I have revised the problem.

Comment 14: Figure 4a: There is almost no change in terms of recovery. Not clear why two collectors were used.

Response: Thank you for your comments. Two collectors are used in figure 4 a in order to select the best collector and achieve the highest recovery rate of malachite sulfidization flotation. LA can improve the flotation recovery based on the highest recovery of malachite.

Comment 15: What was the hydrophobicity (contact angle) of the sample used in this study? Were the contact angle measurements carried out? or is there any data regarding this?

Response: The hydrophobicity (contact Angle) of the sample used in this study is about 10-15 degrees. The malachite sample used in this study is the same as that in article "New insights into the promotion mechanism of (NH4)2SO4 in sulfidization flotation: a combined experimental and computational study". The study in article " New insights …." has proved that the contact angle of malachite surface increases and the hydrophobicity increases after the collector is added.

Comment 17: Figure 6: Please order them as “With LA and Na2S; With Na2S; Without LA and Na2S”. Figure 7: Ci or Cr concentration? Figure 8: Almost no difference! Figure 13: Move the figure after the text! Figure 14: Make the reagents bigger.

Response: Thank you very much for your valuable comment. In figure 7 and 8 the concentration is Ci concentration. In Figure 8, it is obvious that the adsorption amount of xanthate increases after adding LA. At low dosage, the adsorption capacity increased linearly with the increase of xanthate dosage. Addition of LA does not increase growth. I have optimized these images.

Comment 18: In addition to them, the manuscript contains some grammatical problems and must be carefully edited again in terms of grammar and writing.

Response: Thank you for your comments and your revision of the paper. We have modified the language of the paper (as shown below). Thank you again and wish you every success in your work.

• Please see the attachment for details

Author Response File: Author Response.pdf

Reviewer 2 Report

 

This work by Hu et al. investigates the usage of L-arginine (LA) as an activator for

 Malachite in flotation. Particularly, the authors observed the mineral surface alteration by LA at varying pH conditions. Adsorption experiments, Zeta potential, scanning electron microscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) were also carried out to understand the mechanism of interaction between reagents and malachite surface.

 I believe that there is a lot of value in studies on novel “green” reagents, and I think this work should be considered for publication after the necessary additions and revisions.

Recommendation: Major revisions are needed as noted.

 

Abstract

1.      “The performance was evaluated by flotation experiments” should be “The performance of LA was evaluated by flotation experiments”.

2.      “Furthermore, the mechanism was investigated by adsorption experiments” should be “The mechanism of interaction between LA and the malachite surface was investigated by …”

3.      Remove “Furthermore” in the abstract

4.      Remove “in addition”

Introduction:

5.      The introduction covers everything that is needed (state the problem, current methods to tackle the problems, shortcomings) but there are a lot of short sentences that affect the flow of content.

6.      References should refer to the original paper and primary source, not recent publications.

7.      Why LA was first introduced as a sulfidization activator to enhance sulfidization flotation of malachite? Because of its structure? What might be the interaction? What is the hypothesis? What was the reason for choosing his specific reagent as an activator? are there any other references from previous publications that used this reagent?

 

8.      What is the chemical formula L-arginine and source, a charge of LA at pH 7 and 9 or 9.5, soluble or insoluble in water? molecular weight? monomer? be more specific and put as much information as you have about LA.

 

 

2. Materials and methods

2.1. Materials and reagents

9.      obtain mineral of -0.074 mm (p50? p80? p90?)

2.2. Micro-flotation tests

10.    clarify the solid concentration wt.% based on 6 g malachite and 140ml Water.

11.   140 mL unit instead of 140ml (capita L for litre)

12.   Deionized water? tap water? Specify the type of water used for flotation

13.   State the pH value for flotation experiments in the method section

14.   The dosage or range of dosages for LA as the activator and other reagents should be mentioned in the method section too.

15.   What was the air flow rate in flotation?

2.3. Adsorption experiments

16.   Γ is the adsorption amount (mg/g); specify mg/g (mass of?/ mass of ?)

3. Result and discussion

Overall, the mechanism of interaction between reagents and the malachite surface is not well explained for flotation and other experiments. Cite the previous publications using the same reagents as well to support your hypothesis.

3.2. Adsorption tests

17.   This phenomenon could be attributed to LA increasing the adsorption of S species on the surface of minerals; what is the reason? Support and explain the mechanism, and why it is happening. Why LA increase the adsorption of S on the surface of minerals?

18.   Fig 13. Is the average amount of Zeta potential used? Charge of LA at different pH?

19.   Clarify your hypothesis for hydrogen bondings, it is because of the interaction between what functional groups in the structure of LA and the mineral surface.

 

 

Conclusion

20.   Explain the mechanism of interaction in one or two sentences for each experiment in the conclusion section.

21.   Fig 14 should be in the results section instead of the conclusion.

References:

22.   The format should be consistent (lower-case for titles e.g., No. 16, 18, 26)

Comments for author File: Comments.pdf

Author Response

Dear Editors and Reviewers:

Hope this letter finds you well.

 

We are very grateful for your constructive suggestions and comments of our manuscript entitled “Evaluation of L-arginine as an eco-friendly activator for malachite sulfidization flotation” (ID: minerals-1955936). Those comments are all valuable and very helpful for improving our paper. Each comment has been carefully considered, and we have revised the manuscript in detail. Following is a point-to-point response to the reviewers’ comments, and the modified parts can be identified by the red font in the version of revised manuscript with changes marked. We sincerely hope that the revised manuscript could be considered suitable for publication on Minerals.

 

Many thanks and best regards.

Yours sincerely,

Jianyu Zhu

 

Corresponding author:

Name: Jianyu Zhu

E-mail: [email protected]

Central South University

 

 

 

 

Response to Reviewer #2:

Comment 1: “The performance was evaluated by flotation experiments” should be “The performance of LA was evaluated by flotation experiments”.

Response: Thank you very much for your valuable comment. I have revised this part.

Comment 2: “Furthermore, the mechanism was investigated by adsorption experiments” should be “The mechanism of interaction between LA and the malachite surface was investigated by …”

Response: Thank you for your considerate comment. I have fixed this statement problem.

Comment 3: Remove “Furthermore” in the abstract and remove “in addition”.

Response: Thank you for your considerate comment. I have removed these words.

Comment 4: The introduction covers everything that is needed (state the problem, current methods to tackle the problems, shortcomings) but there are a lot of short sentences that affect the flow of content.

Response: Thank you very much for your considerate comment. I have carefully revised the introduction and removed some short sentences.

Comment 5: References should refer to the original paper and primary source, not recent publications.

Response: Thank you for your comments. I have proofread and revised the references. Thanks again for your comments.

Comment 6: Why LA was first introduced as a sulfidization activator to enhance sulfidization flotation of malachite? Because of its structure? What might be the interaction? What is the hypothesis? What was the reason for choosing his specific reagent as an activator? are there any other references from previous publications that used this reagent?

Response: In the process of sulfidization flotation of copper oxide, ammonium sulfate, ammonium carbonate and ammonium chloride have been proved to have the effect of activating malachite sulfide flotation. What they have in common is ammonium. Based on this point, we explored the ammonium-containing substances in organic matter, and selected L -arginine as the activator after considering the price of substances.

Comment 7: What is the chemical formula L-arginine and source, a charge of LA at pH 7 and 9 or 9.5, soluble or insoluble in water? molecular weight? monomer? be more specific and put as much information as you have about LA.

Response: LA, with a molecular formula of C6H14N4O2 and a molecular weight of 174.2, is easily soluble in water and slightly soluble in ethanol. LA is alkaline in aqueous solution, NH3 will combine with H+ in water to form NH4+, and HH4+ ionic amino acids are more abundant at PH 7. With the increase of basicity, HH4+ ionic amino acids decreased, while NH3 amino acids increased. I have enriched the information of LA in the introduction.

Comment 8: obtain mineral of -0.074 mm (p50? p80? p90?)

Response: After grinding and sieving, we obtained samples with particle size below 0.074mm, which is the optimal range for flotation.

Comment 9: clarify the solid concentration wt.% based on 6 g malachite and 140ml Water.

Response: The solid concentration was about 4.3%, which was added in the article. Thanks again for your comments.

Comment 10: 140 mL unit instead of 140ml (capita L for litre).

Response: Thanks for your advice. I have carefully revised the unit.

Comment 11: Deionized water? tap water? Specify the type of water used for flotation.

Response: Thank you for your comments. In order to reduce the influence of ions on the test, the water used in this study is deionized water.

Comment 12: State the pH value for flotation experiments in the method section.

Response: Thank you for your comments. I have state the pH value of flotation experiments.

Comment 13: The dosage or range of dosages for LA as the activator and other reagents should be mentioned in the method section too.

Response: Thank you for your kind advice. It is not possible to give all the dosage in the methods section because the dosage of reagent is not the same for different flotation experiments. The dosage for each experiment is given in the chart.

Comment 14: What was the air flow rate in flotation?

Response: The flotation is carried out on XFG-type flotation machine. The flotation process is carried out by stirring and self-priming of flotation machine, and no other gases are passed.

Comment 15: Γ is the adsorption amount (mg/g); specify mg/g (mass of?/ mass of ?)

Response: Γ is the amount of adsorbed agent per gram of mine, and its unit is mg/g.

Comment 16: Overall, the mechanism of interaction between reagents and the malachite surface is not well explained for flotation and other experiments. Cite the previous publications using the same reagents as well to support your hypothesis.

Response: Thanks for your comments. This study has confirmed through experiments that the addition of LA can enhance the electropositivity of mineral surface, which is conducive to the formation of S2- electrostatic adsorption on mineral surface. That can promote the sulfidization of the surface. Just like the common inorganic ammonium activators at present, it has been reported that HN4+ can accelerate the sulfurization rate and mediate the formation of sulfide. However, HN4+ do not react with the mineral surface, so how HN4+ promote the sulfurization of malachite remains to be determined. However, LA used in this study is the first time to be used as an activator of malachite sulfurization, so there is no relevant literature reference.

Comment 17: This phenomenon could be attributed to LA increasing the adsorption of S species on the surface of minerals; what is the reason? Support and explain the mechanism, and why it is happening. Why LA increase the adsorption of S on the surface of minerals?

Response: The zeta potential experiment results proved that the addition of LA would increase the positive electric properties of the mineral surface, while the sulfuration agent (HS-/S2-) was negative. The positive electric properties of the mineral surface were conducive to the electric adsorption of the vulcanizing agent, thus promoting the sulfide of the mineral surface.

Comment 18: Fig 13. Is the average amount of Zeta potential used? Charge of LA at different pH?

Response: In this study, the zata potential was measured three times. After removing the value with the largest error, the other two were used to calculate the average value. As a water-soluble amino acid, the electrical properties of LA cannot be detected in aqueous solution.

Comment 19: Clarify your hypothesis for hydrogen bondings, it is because of the interaction between what functional groups in the structure of LA and the mineral surface.

Response: N in LA has strong polarity, and there are lone pair electrons, which can form hydrogen bonds with the adsorbed hydroxide ions on the mineral surface.

Comment 20: Explain the mechanism of interaction in one or two sentences for each experiment in the conclusion section.

Response: Thanks for your considerate comments. I have explained the mechanism of each experiment in the conclusion section.

Comment 21: Fig 14 should be in the results section instead of the conclusion.

Response: Thanks for your considerate comments. I've moved Fig.14 to the results section.

Comment 22: The format should be consistent (lower-case for titles e.g., No. 16, 18, 26).

Response: Thanks for your comments. I have standardized the format of the references.

We are very grateful for your constructive suggestions and comments.

• Please see the attachment for details.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors assess the effect of L-arginine, a natural amino acid, on the flotation of a copper mineral using bench flotation tests, microscopy, and spectroscopy.  The article fits the scope of the journal. A few additions are needed, and comments are as follows:

1) In the introduction, it's worth adding some recent studies on the flotation of copper minerals, especially the overall optimization of the process. E.g.: Brest et al (doi.org/10.1016/j.rineng.2021.100207)

2) Methods: You indicated that you milled the sample to the sub-74 micron. Could you add the particle size distribution of the sample? Please refer to doi.org/10.1016/j.heliyon.2021.e06559,

 

Author Response

Dear Editors and Reviewers:

Hope this letter finds you well.

 

We are very grateful for your constructive suggestions and comments of our manuscript entitled “Evaluation of L-arginine as an eco-friendly activator for malachite sulfidization flotation” (ID: minerals-1955936). Those comments are all valuable and very helpful for improving our paper. Each comment has been carefully considered, and we have revised the manuscript in detail. Following is a point-to-point response to the reviewers’ comments, and the modified parts can be identified by the red font in the version of revised manuscript with changes marked. We sincerely hope that the revised manuscript could be considered suitable for publication on Minerals.

 

Many thanks and best regards.

Yours sincerely,

Jianyu Zhu

 

Corresponding author:

Name: Jianyu Zhu

E-mail: [email protected]

Central South University

 

 

Response to Reviewer #3:

Comment 1: In the introduction, it's worth adding some recent studies on the flotation of copper minerals, especially the overall optimization of the process. E.g.: Brest et al (doi.org/10.1016/j.rineng.2021.100207)

Response: Thanks for your comments. This is a valuable study and I have included it in Ref. 3.

Comment 2: You indicated that you milled the sample to the sub-74 micron. Could you add the particle size distribution of the sample? Please refer to doi.org/10.1016/j.heliyon.2021.e06559.

Response: Thank you for your kind comments. I was greatly inspired by article “The effects of partially replacing amine collectors by a commercial frother in a reverse cationic hematite flotation”, which I have added to Ref. 9.

• Please see the attachment for details.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I see that the authors have successfully responded to each comment one by one.

Now, the manuscript can be accepted for publication in the journal of Minerals.

Reviewer 2 Report

 

I have read the response, and most comments have been addressed but still there are  few concerning comments that should be covered too.

·        It should be mentioned the percentage of materials that have the size of -0.074 mm, (50%, 80% or 90 %).

·        The unit of water in the schematic in the flotation experiments section still hasn’t been addressed yet (showing ml not mL).

·        The responses for comments No. 16, 17 and 19 regarding the mechanism of interaction between LA and malachite surface, and hydrogen bondings should be mentioned in the manuscript too not in the cover letter only.

·        The unit for Γ (mg/g) hasn’t been explained yet in the manuscript.

 

 

 

 

Comments for author File: Comments.docx