Features of the Hydrosulfate Method for Processing Alumina-Containing Raw Materials in a Closed Reagent Cycle
Round 1
Reviewer 1 Report
It is necessary to provide a schematic diagram of the experimental equipment.
Add a table with the chemical composition of the concentrated (nepheline concentrate), % or ppm, and X-ray diffraction.
Adding a table with the experimental conditions in each process stage is imperative.
Tables 5 and 6 must present the results according to the elemental composition, not in the form of oxides
Add a metallurgical balance at each stage and provide an overall mass balance for the proposed flowsheet.
You need to provide a mass balance for at least Al and Fe to confirm the accuracy of your analytical technique. Using your solution concentrations and residue assay, you should back-calculate your head assay and compare it to the actual head assay.
Author Response
Responses to the comments of the reviewer 1
We thank the reviewer for a careful reading of the work and comments made.
1) It is necessary to provide a schematic diagram of the experimental equipment.
A scheme of experiments was made and inserted into the text of the article (Fig. 4). Laboratory experimental equipment consisted of several flasks, plastic containers, a Buchner filter and a magnetic stirrer, which were used repeatedly at different stages.
2) Add a table with the chemical composition of the concentrated (nepheline concentrate), % or ppm, and X-ray diffraction.
X-ray diffraction patterns (Fig. 3) were added to the table of chemical composition of nepheline concentrate (Table 1)
3) Adding a table with the experimental conditions in each process stage is imperative.
In the diagram in Fig. 4, made in response to the reviewer's remark 1, all the experimental conditions for each experiment are written in detail. We hope the reviewer will agree with this form of presentation, since the table would be cumbersome and incomprehensible.
4) Tables 5 and 6 must present the results according to the elemental composition, not in the form of oxides
Done
5) Add a metallurgical balance at each stage and provide an overall mass balance for the proposed flowsheet.
As mentioned in the introduction, the general flow diagram shown in Fig. 1 was developed by us earlier (refs. 7,8,18). Therefore, this article is not related to material flows and balances at each stage and to the overall balance in the process and we cannot include them in the text of this article. In addition, as also written in the introduction, figure 2 does not show part of the material flows for the processing of nepheline, relating to alkali and alkaline earth metals. However, to familiarize the reviewer with the efficiency of the method proposed, we specially attach to the answer to his questions the more simple and complete diagram with the main material flows for Al and Fe for bauxite processing (the last list in the Appendix to the responses).
In this article, we studied the fundamental possibility of improving three stages: 1) selection of conditions for the primary crystallization of alum to reduce the iron content in them; 2) selection of chemicals to be added at the recrystallization of ammonium alum to increase their purity; 3) simplification of the precipitation process of the precursor - aluminum hydroxide. This article is not a technological regulation, but is a scientific study of applied importance.
6) You need to provide a mass balance for at least Al and Fe to confirm the accuracy of your analytical technique. Using your solution concentrations and residue assay, you should back-calculate your head assay and compare it to the actual head assay.
This is done for one of the experiments to study the distribution of Al and Fe between solid alum and liquid phases after cooling of the hot filtrates after leaching. The new Table 2 was inserted into the text. Hope, these examples demonstrate the analytical accuracy of our experiments.
On behalf of the authors
Victor A. Zaitsev
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors covered an interesting study on features of the hydrosulfate method for processing alumina containing raw materials in a closed reagent cycle. This is interesting for use of waste containing lean Alumina and low-grade alumina ore. However, the following few comments are for the author to attend to.
Line 118: The authors need to state that those minerals were determined by XRD. If they were determined in their previous paper, they need to cite it here.
Line 126: Here it is advised for the authors to take note of the subscript.
Line 145: I think the authors meant ICP-AES.
Figures 3 and 5. Graduation marks need to be added to these figures and if possible, avoid plotting points as curves.
Is there a particular reason why repeats for all the experiments were done?
I think the abstract and conclusion should at least the results’ figures (values) for the benefit of the would-be readers.
Author Response
Responses to the comments of the reviewer 2
We thank the reviewer for a careful reading of the work and comments made.
The authors covered an interesting study on features of the hydrosulfate method for processing alumina containing raw materials in a closed reagent cycle. This is interesting for use of waste containing lean Alumina and low-grade alumina ore. However, the following few comments are for the author to attend to.
Line 118: The authors need to state that those minerals were determined by XRD. If they were determined in their previous paper, they need to cite it here.
Done. a picture with a diffraction pattern of the original concentrate is added in Fig.3 (Line 142 in the revised article)
Line 126: Here it is advised for the authors to take note of the subscript.
Done (Line 147 in the revised article)
Line 145: I think the authors meant ICP-AES.
Yes, fixed
Figures 3 and 5. Graduation marks need to be added to these figures and if possible, avoid plotting points as curves.
Graduation marks are added.
Is there a particular reason why repeats for all the experiments were done?
Information is added to the text of the article. We first made experiments with alum, obviously enriched with impurities, in order to brighten the difference in the behavior of the components. (Lines 184-186 in the revised article)
I think the abstract and conclusion should at least the results’ figures (values) for the benefit of the would-be readers.
Following your advice, we added a graphical abstract to the text.
On behalf of the authors
Victor A. Zaitsev
Author Response File: Author Response.docx
Reviewer 3 Report
Review report of the manuscript no. applsci-1961409
The manuscript. No. applsci-1961409 submitted to the journal has the merits to be considered after minor revisions. The comments are summarized below.
1. Abstract: The objective and critical finding of this work is to be incorporated
2. Introduction: This section is too long and needs to be abridged. Since author discuss about decomposition of (NH4)2SO4 and the following article may be reffered:
e.g. Decomposition of ammonium sulphate from demanganised leach solution of manganese nodules by lime treatment, Transactions of the Indian Institute of Metals (Springer), 60(5), (505-509) 2007.
3. Results and Discussions: The presentation of Fig.4 & Fig.5 may be improved.
4. Please check and ensure correct representation of all the notations/labelling of all
figures .
5. What is the novelty of this study and how it would be beneficial on recycling of
alumina?
6. Conclusion: This section may be rewritten by improving style of presentation and
emphasizing on key findings of this work
Author Response
Responses to the comments of the reviewer 3
We thank the reviewer for a careful reading of the work and comments made.
The manuscript. No. applsci-1961409 submitted to the journal has the merits to be considered after minor revisions. The comments are summarized below.
- Abstract: The objective and critical finding of this work is to be incorporated
The abstract has been edited so that the relevance and purpose of the work are clear. The main achievements are listed in points A, B and C.
- Introduction: This section is too long and needs to be abridged. Since author discuss about decomposition of (NH4)2SO4and the following article may be refered:
Thanks. The article “Transactions of the Indian Institute of Metals (Springer), 60(5), (505-509) 2007” was taken to be referred. Some abridges of the introduction section have been made
- Results and Discussions: The presentation of Fig.4 & Fig.5 may be improved.
Done. Figure 5 was redrawn, figure 4 was improved and the ticks were added to the axis.
- Please check and ensure correct representation of all the notations/labelling of all figures.
The representation of the notations/labelling of all figures was checked. Corrections were made, for example, in the caption under the figure 3 and the figure 5 was redrawn.
- What is the novelty of this study and how it would be beneficial on recycling of alumina?
Bisulfate method for processing of low grade alumina raw materials with high silicon content is attractive in connection to the possibility of organization of closed-loop processes with low or without consumption of chemicals. Three fundamentally important improvements were introduced into this process: optimization of the conditions for the stage of separation of primary alum from the mother liquor after their leaching, further purification by simple methods of recrystallization with the use of minor additions sodium thiosulfate, and isolation of ammonium aluminum carbonate hydroxide as a precursor for obtaining alumina. This made it possible to eliminate the need for expensive methods of deep purification by chelate sorbents or liquid extractants.
- Conclusion: This section may be rewritten by improving style of presentation and emphasizing on key findings of this work
Done. Hope, the conclusion became clearer.
On behalf of the authors
Victor A. Zaitsev
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The suggested changes were implemented
