Surface Chemistry Tuning Solutions for Flotation of Fine Particles
, Nikolay A. Grozev 1, Kristina Mircheva 1, Seher Ata 2, Ghislain Bournival 2, Svetlana Hristova 3 and Orhan Ozdemir 4
Xinyang Wang
Round 1
Reviewer 1 Report
Comments
The paper Surface chemistry tuning solutions for flotation of fine particles is interesting. It presents a summary of methods used previously in other studies. The main comments and observations are:
1. Technical English should be improved to be clearer and more concise; waste of words and repetition must be avoided. Language for a scientific paper is a formal text written in an impersonal, objective, neutral and professional way. The writing must be concise with specific wordings and formulations. The writing should be clear as well and lead to a deeper understanding of the subject. Avoid needless words.
2. Author(s) used personal pronouns (I, we, one can ..) do not fit the objective of a scientific paper.
3. The author(s) should demonstrate the capacity for synthesis. The abstract is too extensive and with unnecessary information and comments, i.e., calculations of colleagues of ours, unfortunately, …. Also, in the abstract acronym CA was not defined (first time used)
4. In general, tables and figures are after the explanation.
5. What is the innovation? As it is presented old methodology and results of others Fig 15, 17, and your previous work.
6. Is the application only for silicate and carbonates in tailings? How do your results provide a solution for lost fine sulphide minerals?
Specific observed lines:
In theoretical background
Line 137-139 and in other lines: Author(s) reference themselves (13) and mentioned that ’the problem of the fine particles floatation is not the low rate of collision with bubbles’’ This is in discrepancy with one reference (12).
Do you define ‘Low rate’ as ‘low probability?
Also, author(s) stated that the reason is the low efficiency of collision.
I must say that it was demonstrated that the low recovery of fines is attributed to hydrodynamic conditions of the process that cause a reduction in the particle-bubble collision probability as the particle size decreases (Reay & Ratcliff, 1973; Fuerstenau, 1980; Sivamohan, 1990; Schubert , 2008). Since fine particles have little mass and therefore low inertial force, they are deflected by hydraulic drag forces generated by rising bubbles. Consequently, the fines tend to follow the flow lines (streamlines) around the bubbles instead of colliding with them (Yoon & Luttrell, 1989; Dai, et al., 2000; Leistner, et al., 2017).
Low efficiency of collision is due to hydrodynamic conditions and in general, the Efficiency of collection is the sum of the efficiency of attachment, collision and stability.
I think, the problem of fine flotation could be due to both low probability and low efficiency of collision, but not only the last and you overdo your own reference (13)
In Materials
Lines 241-271, Author(s) used dot points for reagents, minerals and mineral particles with unnecessary repetition of suppliers. Please, write in the form of paragraphs and concisely.
In methodology
Line319, microflotation there is no specification of grams floated. How many grams were in the concentration of 1 wt.% (Is 0.1% of 90 ml?)
Lines 332-333. What is the practicality of using the slurry of 1% w/w in a cell of 3.5 L? how does this represent the real solid percentage in a flotation plant?
Line 337-338. How was the superficial gas velocity (Jg) set to 0.5 cm/sec?.
Line 346, what is very flotation? or must be true flotation?
Line 380 How is this statement, ’we set a goal to search for different ways to manipulate the surface properties of the particles’ depicting a methodology?
Line 441 said ’was processed by software of the setup’ What software was used? Complete information must be considered.
Results and discussion
Line 446. What type of ‘wetting films’ differs significantly from wetting films formed at the very clashing of bubbles and particles under high turbulence? Please, rewrite this.
Lines 515-516 Author(s) said ‘The coarse particle according to Figure 11 approaches the bubble significantly slower, thus requiring an induction time significantly larger than the contact time of the bubble particle encounter’. This statement is contradictory and not true as coarse particles, are able to deviate from the flow lines and approach faster since they have a greater inertial force and mass.
Line 591, Said ‘Thee’ must say ‘the’
Line 598-599 Repetition of provider of gangue-Steriles, already said in materials (unnecessary information that belongs to a different section), same in line 601
Line 637 ’one can see photos of the flotation test in Figure 16, please change for a more technical writing, same in the whole document... i.e., Figure 16 shows two flotation tests conducted……
Line 675 This is an example of passive voice used in this paper ‘Shown in Figure 19’. This must be reviewed in the whole text and changed to active voice, i.e., ‘Figure 19 shows …’. Check other Lines 697
Line 689 The author is concluding, should there be a discussion of results?
Line 677-679, 684-686 This text doesn’t add any value (or discussion) to the result shown in Figure 19 and it is vague ‘has been defined’.
Line 706, said ‘collector’, must it be collection?
Line 707, ‘To continue this study, it should be asked’, is this necessary? do not ask rhetorical questions, Same in lines 734-735
Line 723-724, From the froth and Figure 20, how could you indicate that there are large number of captured particles? What is the support to state this?
Line 796 Said ‘In our opinion…’ How is this objectively and supported?
Line 819 Author(s) already here made a conclusion that could be in 6. Conclusion
Line 824-837 Conclusions are weak and don’t show how the obtained results are shown in these conclusions.
The quality of the English Language must be improved, see my comments above
Author Response
Dear Reviewer 1,
We would like to thank you for the detailed comments and suggestions aiming to improve our draft. We took into consideration them and revised the draft in line with them. We hope you will be satisfied with the new version of the manuscript and with the response to your questions.
Best regards,
Stoyan Karakashev
The paper Surface chemistry tuning solutions for flotation of fine particles is interesting. It presents a summary of methods used previously in other studies. The main comments and observations are:
- Technical English should be improved to be clearer and more concise; waste of words and repetition must be avoided. Language for a scientific paperis a formal text written in an impersonal, objective, neutral and professional way. The writing must be concise with specific wordings and formulations. The writing should be clear as well and lead to a deeper understanding of the subject. Avoid needless words.
Response: We revised the draft with in line with your suggestion and hope you will be satisfied. We certainly know that we are not naïve speaking English, but at least we did our best.
- Author(s) used personal pronouns (I, we, one can ..) do not fit the objective of a scientific paper.
Response: We changed it.
- The author(s)should demonstrate the capacity for synthesis. The abstract is too extensive and with unnecessary information and comments, i.e., calculations of colleagues of ours, unfortunately, …. Also, in the abstract acronym CA was not defined (first time used)
Response: We revised it.
- In general, tables and figures are after the explanation.
Response: We hope the reviewer will not mind if leave them as they are.
- What is the innovation? As it is presented old methodology and results of others Fig 15, 17, and your previous work.
Response: The drainage of the wetting film during the bubble – particle clash has been considered as part of the whole process and the drainage time as part of induction time. We show that the drainage is not important, but the deformation of the bubble and the precipitation of the dissolved gases. We shed new light on the processes occurring in the bubble – particle encounter. For this reason, this paper is continuation of the previous one. Significant part of the paper is not published before as well.
- Is the application only for silicate and carbonates in tailings? How do your results provide a solution for lost fine sulphide minerals?
Response: Yes, but the general principles for fine particle flotation can be applied to every mineral.
Specific observed lines:
In theoretical background
Line 137-139 and in other lines: Author(s) reference themselves (13) and mentioned that ’the problem of the fine particles floatation is not the low rate of collision with bubbles’’ This is in discrepancy with one reference (12).
Response: Ref. (12) is review paper on the fine particle flotation. It reports indeed that the problem consists in the low probability of the fine particle – bubble encounter in line with many literature sources. However, these sources are based on the on the theoretical approach of von Smoluchowski and Sutherland, which assumes low Reynold number of the system. This theory has been advanced by Yoon and Luttrell to Re = 400. In reality this approach is not valid for systems at high turbulence. For this reason, there is another theory of Abrahamson and later by Schubert, reporting that at high turbulence the probability of such encounter is much higher. So, one of the impacts of this paper and the former one is that the scientific community has been misled following the first theoretical approach, because the real flotation cells work at high turbulence.
Do you define ‘Low rate’ as ‘low probability?
Response: Of course these parameters are different but in reality describe the same thing – low probability of collision causes small rate of collision.
Also, author(s) stated that the reason is the low efficiency of collision.
I must say that it was demonstrated that the low recovery of fines is attributed to hydrodynamic conditions of the process that cause a reduction in the particle-bubble collision probability as the particle size decreases (Reay & Ratcliff, 1973; Fuerstenau, 1980; Sivamohan, 1990; Schubert , 2008). Since fine particles have little mass and therefore low inertial force, they are deflected by hydraulic drag forces generated by rising bubbles. Consequently, the fines tend to follow the flow lines (streamlines) around the bubbles instead of colliding with them (Yoon & Luttrell, 1989; Dai, et al., 2000; Leistner, et al., 2017).
Low efficiency of collision is due to hydrodynamic conditions and in general, the Efficiency of collection is the sum of the efficiency of attachment, collision and stability.
Response: Thank you. Yes, what you state is in line with the many of the literature sources and I understand it. Yet, according to the hydrodynamic theory of particle collisions at high turbulence there are no streamlines but the picture is similar to the kinetic motion of gas molecules (molecular-kinetic theory). This causes significantly higher rate of clashing between the particles. According to ref. (Schubert 2008) “There is absolutely no question that a key role for an effective fine particle flotation plays the achievement of sufficiently high flotation velocities by means of large collision rates between the value mineral particles and bubbles in the strongly turbulent rotor (impeller) stream of the flotation machines.”
I think, the problem of fine flotation could be due to both low probability and low efficiency of collision, but not only the last and you overdo your own reference (13)
Response: Yes, if the Reynolds number varies up to Re = 400.
In Materials
Lines 241-271, Author(s) used dot points for reagents, minerals and mineral particles with unnecessary repetition of suppliers. Please, write in the form of paragraphs and concisely.
Response: It is corrected.
In methodology
Line319, microflotation there is no specification of grams floated. How many grams were in the concentration of 1 wt.% (Is 0.1% of 90 ml?)
Response: It was prepared 1 wt.% suspension and 90 ml of this suspension were put in Hallimond tube.
Lines 332-333. What is the practicality of using the slurry of 1% w/w in a cell of 3.5 L? how does this represent the real solid percentage in a flotation plant?
Response: We did it with a reason. We achieved about 90% recovery with 1 wt.% suspension of fine silica particles for 2 minutes in Hallimond tube. We wanted to see if the results will be the same with professional flotation machine. It is just a laboratory experiment.
Line 337-338. How was the superficial gas velocity (Jg) set to 0.5 cm/sec?.
Response: The gas flow rate has been set in cm3/s units. This value is divided to the cross-sectional area of the cell.
Line 346, what is very flotation? or must be true flotation?
Response: We made correction. By “very flotation” I meant flotation.
Line 380 How is this statement, ’we set a goal to search for different ways to manipulate the surface properties of the particles’ depicting a methodology?
Response: Our aim was to help fine particle float with high recovery for short time. So, we sought ways to manipulate the surface forces between bubbles and particles. One of them is to find a proper collector.
Line 441 said ’was processed by software of the setup’ What software was used? Complete information must be considered.
Response: Our authomatical tensiometer/goniometer (Model 290, Rame – Hart Ltd. USA) works with commercial software by the same company. This software controls the setup and calculates the values of the surface tension by means of profilometry and the contact angle when a very small droplet is positioned on a plate.
Results and discussion
Line 446. What type of ‘wetting films’ differs significantly from wetting films formed at the very clashing of bubbles and particles under high turbulence? Please, rewrite this.
Response: We added words explaining better this sentence.
Lines 515-516 Author(s) said ‘The coarse particle according to Figure 11 approaches the bubble significantly slower, thus requiring an induction time significantly larger than the contact time of the bubble particle encounter’. This statement is contradictory and not true as coarse particles, are able to deviate from the flow lines and approach faster since they have a greater inertial force and mass.
Response: Thank you. I will be glad to discuss this with you personally. According to the hydrodynamic theory the coarse particle has larger contact area with the bubble and significant drag force when they clash to bubble. Even they have large momentum, it vanishes very fast due to the large drag force in normal direction to the bubble. For this reason, they usually slide following the contours of the bubble and can be captured if the deformation of the bubble and the hydrophobicity of the particle are sufficient. I made calculation taking in mind silica particles and calculated the time of approach from 1 μm to 0.02 μm and was surprised to see the results. This changed my view about the bubble – particle collision.
Line 591, Said ‘Thee’ must say ‘the’
Response: Thank you. It was corrected.
Line 598-599 Repetition of provider of gangue-Steriles, already said in materials (unnecessary information that belongs to a different section), same in line 601
Response: Thank you. It was corrected.
Line 637 ’one can see photos of the flotation test in Figure 16, please change for a more technical writing, same in the whole document... i.e., Figure 16 shows two flotation tests conducted……
Response: We designed in this way Fig. 16 with a reason. We float 1 wt.% Sterile particle on left with 10 ppm MIBC and on write with 0.05 ml/L Hexylamine. The reader can see the difference visually. I hope the reviewer will not mind if we leave it as it is.
Line 675 This is an example of passive voice used in this paper ‘Shown in Figure 19’. This must be reviewed in the whole text and changed to active voice, i.e., ‘Figure 19 shows …’. Check other Lines 697
Response: Thank you. It was corrected.
Line 689 The author is concluding, should there be a discussion of results?
Response: Thank you. It was corrected.
Line 677-679, 684-686 This text doesn’t add any value (or discussion) to the result shown in Figure 19 and it is vague ‘has been defined’.
Response: This is explanatory text to the figure giving additional details on the experiment. I hope the reviewer will not mind if we leave it as it is.
Line 706, said ‘collector’, must it be collection?
Response: Thank you. It was corrected.
Line 707, ‘To continue this study, it should be asked’, is this necessary? do not ask rhetorical questions, Same in lines 734-735
Response: Thank you. It was corrected.
Line 723-724, From the froth and Figure 20, how could you indicate that there are large number of captured particles? What is the support to state this?
Response: The big bubble in the photo is white.
Line 796 Said ‘In our opinion…’ How is this objectively and supported?
Response: The fine bubbles have large internal pressure and dissolve faster than the coarse bubbles in water.
Line 819 Author(s) already here made a conclusion that could be in 6. Conclusion
Response: Thank you. It was corrected.
Line 824-837 Conclusions are weak and don’t show how the obtained results are shown in these conclusions.
Response: Thank you. It has been a broad discussion in the text to derive these concussions. In fact, they are the impact of the paper.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper shows that the drainage of the wetting film is unimportant, but the deformation of the bubble by the particle, the rate of air’s dissolution from the bubble, the hydrophobicity of the particles, the existence of electrostatic attraction between them and the bubbles and the presence of fine bubbles are the keys for flotation of fine particles with high recovery for a short time. The work is interesting and meaningful. However, the research article is too long to focus on your main points.
1. Most introduction part (background) is less related to your experiment in this paper. It is too long.
2. For Figure 7, the diagram is wrong for the surface of the magnesite mineral before and after the reaction.
3. I suggest to remain one between Fig.10 and Table.1.
4. The overall structure of the analysis section in Results Part needs to be revised. It is a research paper rather than a thesis. It should be concise and comprehensive.
Author Response
Dear Reviewer 2,
We would like to thank you for the comments and suggestions aiming to improve our draft. We hope you will be satisfied with the new version of the manuscript and with the response to your questions.
Best regards,
Stoyan Karakashev
This paper shows that the drainage of the wetting film is unimportant, but the deformation of the bubble by the particle, the rate of air’s dissolution from the bubble, the hydrophobicity of the particles, the existence of electrostatic attraction between them and the bubbles and the presence of fine bubbles are the keys for flotation of fine particles with high recovery for a short time. The work is interesting and meaningful. However, the research article is too long to focus on your main points.
- Most introduction part (background) is less related to your experiment in this paper. It is too long.
Response: We agree that the introduction is long, but it tells the story of our study in details and our thoughts on this scientific topic. We hope the reviewer will understand us. Yet, we modified it and hope the reviewer will be satisfied.
- For Figure 7, the diagram is wrong for the surface of the magnesite mineral before and after the reaction.
Response: Thank you. We added to the figure the chemical equation of this reaction. We hope the reviewer will be satisfied.
- I suggest to remain one between Fig.10 and Table.1.
Response: Thank you. In our opinion the reader will have better view on these results in form of graphic and a table if we leave it as it is. We hope the reviewer will not mind.
- The overall structure of the analysis section in Results Part needs to be revised. It is a research paper rather than a thesis. It should be concise and comprehensive.
Response: Thank you. We understand the reviewer’s view. We agree that most of the research papers are concise and clear with the presentation of their results and analysis, but this paper is aimed to be different. We tell the story of our understanding of fine particle flotation following the scientific logistics and way of thinking. We hope the reviewer will not mind if we leave our style and length of the paper as it is.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Fine. I think it can be accepted.
