A Study on the Mechanisms of Coal Fly Ash to Improve the CO₂ Capture Efficiency of Calcium-Based Adsorbents

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

The topic of the work is current and interesting. You have presented numerous results, although I would like to make a few suggestions and remarks about your work.

Change and modify the title of the work only.

Shorten the introductory part of the work. Be concise.

You didn't describe the experimental part well. What kind of ash did you use and where did you get it from?

Regarding calcination, was it calcination or carbonization... What were the specific conditions, describe the process.

Did you optimize the process parameters?

I didn't see in your work that you did a return.

Images 3 and 4 are enlarged and technically arranged.

Explain in more detail table 3. Also, the trend of decline and growth, as well as the mandatory display of adsorption and desorption isotherms, as well as the pore distribution diagram.

You showed the SEM results, why didn't you do EDS and on the SEM images you could use the program to group the particle sizes.

In the paper, it seems that you just threw the results. You did not specifically and in detail explain all the analyzes and results, and you did not connect them nicely as a whole.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

General Comments:

The work evaluates modified materials for CO₂ adsorption, contributing to the advancement of the technique regarding to increasing the added value of co-products or industrial waste. On the other hand, the article contains some gaps to be filled, such as adequate report of characterization methodologies and some essential definitions for the correct scientific evaluation and consequent publication. Below are some specific comments:

Specific Comments:

[1] – [line 52 p2] - Although it is correct, highlighting the concept of Taman temperature is appropriate for better understanding, or some change in terms of diffusion mobility to explain the phenomenon.

[2] – How the composition analysis of limestone and ash was carried out? (Also check for excess space before punctuation in table 2)

[3] – [l 151-152 p4] – The sentence is confusing due to the repetition of carbonation. It should be rewritten.

[4] – [l 159-160 p4] - Wouldn't it be a calcination atmosphere with 100% N₂ at this stage?

[5] – There is a large information gap in the methodology. How were the CO2 levels was measured/detected? What type of detector was used? Some information could be better written in clearer scientific terms: What would be a “intelligent temperature control meter”?

[6] – The presentation of the adsorption efficiency calculation is confusing (correct gas constant R to include kPA). Is the CO₂ concentration given as mol/mol% concentration? Please standardize results as a fraction or percentage (e.g., carbonation conversion rates CaCO3/FA (0%) and CaCO3/FA (10%) were 0.68 and 0.59 or 68 and 59%).

[7] – [l 192-199 p5] – Please elaborate that. Specific surface area analysis wasn’t detailed previously in the methodology section. At this point in the work, it is beneficial to have physical, chemical and morphological characterization data before the adsorption results. Consider presenting these results first to clarify the discussion.

[8] – It is really difficult to understand if there is any difference between the results presented in Figures 3-A and Figure 3-C.

[9] – Figure 4: correct graph legend (letter c in image a)

[10] – [l 309-315 p9] - The correlation of this conclusion with the results presented previously is complicated. The work does not clearly define the adsorption capacity and adsorption decay rate of the materials tested. The data become more understandable when evaluating the X(%) rate according to the various cycles (fig. 3). Modifications in the discussion of these results are convenient to clarify the conclusions.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

 

The article is devoted to the experimental study of adsorbents. The work highlights a well-developed literature review on the topic. It includes modern works. The study itself was conducted using various methods. The work appears to be up-to-date and can be published after major revision.

However, the presentation of the work needs to be improved, for this it is necessary to correct the following comments:

1) Line 52 Check Last name (Taman) https://www.britannica.com/biography/Gustav-Tammann

2) Line 148. It is needed to specify the detector model

3) Line 160. carbonation atmosphere was 100% N 2? Possible missword

4) Line 169. Many questions about the formula for calculating x.

- It is necessary to give definitions of all quantities and their dimensions (V, n0, etc.).

- In the formula w in the description of W, it is necessary to unify.

- The description says that Ce is measured in %. Then 1- Ct can give a negative value.

- What is the relative molecular mass of CaO. Give a more specific definition. Relative to what? If this is a constant value independent of the composition of the adsorbent, then it is necessary to provide a value.

5) Figure 2 in the figure XN in the formula 1 x. Also in the text it is indicated in fractions and in the figure in %. It is necessary to unify.

6) line 196. It is said about the surface and on line 200 about the pore volume. However, in the experimental part it is not indicated on what equipment the measurements were carried out.

7) Line 216. in the text indicate specifically which figure to look at (Figure 3 b)

8) Figure 3 how does Figure (a) differ from Figure (c)?

9) Line 245. It is necessary to describe in the experimental part the equipment on which the analysis was carried out.

10 ) Figure 4 It is necessary to remove the typo (c) from Figure (a)

11) It is necessary to indicate in experimental part on what equipment the FT-IR was carried out

12) Line 290. Describe the microscope model in the experimental part

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The above-mentioned comments were promptly corrected.