Resource Utilization Potential of Red Mud: A Study on the Micro-Mechanism of the Synergistic Effect of Multiple Solid Waste Filling Materials
, Shaoqi Kong *, Jiajun Li, Gang Li, Zhiguo Ge and Jinjing Huang
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis manuscript used red mud, gangue, desulfurization gypsum and silicate cement to prepare red mud-based composite filler material, and the optimization and micro-structural of filler material were explored. Some specific comments and suggestions are listed below:
1. The specific results of element analysis in Fig. 13 need to be listed.
2. In Section 3.4. In order to express the changes in early and final intensity of RMC more clearly, a schematic diagram of strength development of RMC throughout the hydration process needs to be provided.
3.The differences between the RMC in this study and those in other studies need to be discussed.
4. The possible usages of RMC need to be provide.
5. A conclusion that can present the key messages in the research results need to be provided.
Author Response
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Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors presented a promising solution to the reuse of red mud and other industrial waste. The mechanism behind is also well investigated. Overall the work is well written. I think this work can be strengthened if the following issues can be addressed:
1) Based on Line 258-259 on Page 9 and Fig 6 on Page 10, the compressive strength of the RMC is pretty high as a filling material used for mine filling. It is related to the relatively high weight percent of silicate cement (20%) used in this work based on the Table 2. I am curious about the estimated cost for one tone of RMC-8. Could you provide the estimated cost? For mine or abandoned quarries filling, compressive strength larger than hard soil (>0.4 MPa) is enough. To apply this in a large scale, it is better to reduce the use of the cement, otherwise, it is still too costly.
2) It would be great if leaching test can be done to cover heavy metal, boron, arsenic, total dissolved salts (TDS or conductivity) and pH of leachate. Because the motivation of this work is to develop red mud based filling materials to do mine filling or quarries filling. There are two biggest obstacles to prevent these tech from being commercially applied: 1) cost; 2) risk to the groundwater. Please consider these factors or at least put these factors in the discussion part to show that the team consider about it. This is the most important part for practical usage.
3) On page 15, for all the discussion about Figure 12 and together with the figure, better to place them in the supporting information rather than in the manuscript as it is really weak evidence to show the difference in pores, that will significantly weaken your work.
Comments on the Quality of English LanguageOverall the work is well written. Here are some grammar errors or typos or improper description:
Line 9 on page 1, Better if use flue gas desulfurization gypsum or FGD gypsum as an abbreviation.
Line 125 on page 4, better to add "below" behind 33].
Table 2 the last column C2, typo: C2 ratio should be colon not comma
Line 244 Figure 4, y-axis unit is missing
Line 273 page 9 and other places, Please explain what is C-S-H gel. It is repeated so many times in the manuscript but has never been explained
Figure 10 on page 10, unit is missing
Author Response
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Reviewer 3 Report
Comments and Suggestions for Authors1. The manuscript touches upon topical questions of processing and disposal of man-made waste, including hazardous to the environment and human health with the development of new technological approaches.
2. The title corresponds to the content of the manuscript and the journal.
3. Lines 51-71: For wider comparison, recent representative contributions concerning extracting of the extraction of valuable metal elements, especially rare ones, from red mud could be cited additionally:
- Extraction of Valuable Elements from Red Mud with a Focus on Using Liquid Media—A Review. 2021 Recycling 6(2):38. DOI: 10.3390/recycling6020038
- High purity scandium extraction from red mud by novel simple technology 2021 Hydrometallurgy 202(11):105597 DOI: 10.1016/j.hydromet.2021.105597
- Composition and Properties of Iron Oxides in the Products of Hydrothermal Treatment of Red Mud and Bauxites. Russ. J. Inorg. Chem. 67, 1101–1107 (2022). https://doi.org/10.1134/S0036023622060183
- Iron Recovery from Red Mud Using Carbothermic Roasting with Addition of Alkaline Salts. J. Sustain. Metall. 7, 858–873. 2021. https://doi.org/10.1007/s40831-021-00400-z
Early [*] the possibility of using two types of red mud instead of a part of sand in building industry concerned with cement and concrete works was demonstrated. It was found zeolites (aluminosilicates and aluminohydro-calcium, and carbonate–aluminum phases) in the red mud are effective sorbents for CO2.
* Recovery of sludge from alumina production. Russ J Appl Chem 85, 1649–1653 (2012) https://doi.org/10.1134/S107042721211002X
3. Unfortunately, there is no percentage of minerals in the initial red mud and other raw.
4 out of 6 minerals of RM contain CaO. The amount of CaO in RM from Table 1 is less than 1%. How to explain the interpretation of X-ray diffraction for RM? 8% TiO2 is in Table 1. Which minerals contain titanium?
For PC, the three phases contain calcium and silicon according to X-ray diffraction. According to Table 1, the amount of calcium is three times more than silicon. How can this be explained?
4. There is also no information on the phase composition of synthesized samples containing various additives. This will allow authors to discuss in subjects the processes of hydration and carbonation of calcium and other minerals in raw materials, the interaction of alkalis with the components of mixtures, and other processes.
5. There are many decimal places in numeric data on particle size and surface area. What is the measurement error? Are these redundant digits after the decimal point significant?
6. What is C-S-H gel? There is no decryption.
7. To study porosity by the SEM method, it is necessary to use a smooth sample, but not a powder. The SEM shows the presence of aggregates and agglomerates, but not pores. I think the discussion about the porosity of samples is incorrect.
Comments on the Quality of English LanguageThere is a repetition of the paragraph in sections 3.3.3 and 3.4.1. Check the text for repetition and typos.
Author Response
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Reviewer 4 Report
Comments and Suggestions for AuthorsPlease see my attached comments and questions.
Comments for author File: Comments.pdf
There are some small mistakes. In general, the manuscript is well written.
Author Response
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Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe 1. Introduction needs to strengthen the description of the environmental harm caused by red mud, and the references below may of interest to you to further your discussion for a more expanded enrichment of information.
[1] Recovery of valuable metals from red mud: A comprehensive review [J]. Science of the Total Environment, 2023, 904: 166686.
[2] Comprehensive utilization status of red mud in China: A critical review [J]. Journal of Cleaner Production, 2021, 289: 125136.
Author Response
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Reviewer 4 Report
Comments and Suggestions for AuthorsThank you for revising the manuscript. The authors replied to all my comments and questions. They modified the manuscript appropriately.
Comments on the Quality of English LanguageThere are only minor English errors.
Author Response
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