Development and Characterization of Na2CO3-Activated Mozambican Bentonite: Prediction of Optimal Activation Conditions Using Statistical Design Modeling
, António J. Cumbane 1, Asmina E. Sulemane 2 and Shepherd M. Tichapondwa 3
Round 1
Reviewer 1 Report
The activation of bentonites through the use of Na2CO3 is widely known, so the originality is related to Statistical Design Modeling. Regarding characterization techniques such as physical and rheological properties (which are typical in this type of study) they have not been studied.
Area BET results should be included.
There are some issues that should be clarified and improved:
On page 3, line 103, the composition of the base bentonite is indicated: 79.5 wt.% SiO2, 12.1 wt.% Al2O3, 3.44 wt.% Fe2O3, 0.44 wt.% CaO, 0.26 wt.% K2O, 1.17 wt. .% Na2O, 2.87 wt.% MgO, 0.01 wt.% MnO, 0.21 wt.% TiO2, and 0.02 wt.% P2O5. It can be seen that the Na content is greater than that of Ca, however in figure 7, the Na/Ca ratios for the base bentonites are lower, so this point should be clarified.
What is the Na and Ca content measured by XRF for all the samples in Figure 7?
The same color code should be used in figures 1 and 2, and their quality should also be improved.
Figure 2 should include the DTA and DTG curves for discussion.
Author Response
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Reviewer 2 Report
In this study, it is aimed to analyze the alteration of Ca-Bentonite to Na-bentonite statistically based on CEC and to investigate the effects of factors such as time, temperature and clay content and their interactions on CEC. For this, experiments based on the factorial design approach were performed and Response Surface Methodology was used to optimize the activation process conditions. It is a routine but well-organized experimental study performed according to factorial design. However, it cannot be said that the targeted change in terms of bentonite has emerged clearly. However, it cannot be said that the targeted change in terms of bentonite has emerged clearly. The observed variation in terms of CEC needs to be clarified on the dependencies of the selected variables and their interactions. In addition, the manuscript contains many grammatical errors in English. My questions, comments and suggestions about the manuscript are highlighted on the text and given as pop-up notes.
Comments for author File: Comments.pdf
Author Response
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Reviewer 3 Report
Comments for author File: Comments.pdf
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Round 2
Reviewer 1 Report
Based on the answers of the authors and the changes made, I consider that the paper can be published in the Minerals journal.
Author Response
Thank you very much for the valuable comments, these have helped us to substantially improve the quality of our work. Warm regards from Mozambique and South Africa
Reviewer 2 Report
The authors carefully corrected the sentence construction errors. However, the answers regarding the right shift of the smectite peak and the relatively small CEC value are speculative and not satisfactory. For example, a comparison and evaluation could be made by considering the XRD diffractogram of a known Na-Montmorillonite clay.
It is not consistent to suggest that CEC determination by methylene blue method and Na/Ca quantification by EDX technique are low sensitive, but attempting to interpret results accordingly.
If the methods mentioned have sensitivity problems, the same operations can be done with other techniques. Moreover, the methylene blue method is widely used for CEC determination and can give very good/accurate results.
Author Response
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