Performance of CO₂ Adsorption on Modified Activated Carbons Derived from Okara Powder Waste: Impacts of Ammonia Impregnation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript has studied the performance of CO2 adsorption using modified activated carbons derived from solid waste, it fits to the journal scope and can be considered after major revisions. Specific comments are as below:

1.      Th activated carbons from waste have high surface area, however, the specific surface areas are not shown. The specific surface areas and pore distributions should be shown and analyzed deeply. And how the specific surface areas and pore structure affected the CO2 adsorption performance.

2.      Why the authors chose okara powder waste as raw material? How about its compositions? The proximate and ultimate analysis results should be shown.

3.      The error bars for adsorption amount of CO2 should be added to show the accuracy and reliability.

4.      How about the characteristics of N and S containing functional groups, and they should be analyzed by XPS.

5.      What are the important results of this work? The conclusions should show the emphasis of this work based on the research.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The discussion on SEM images is not getting correlated with the images. Most of the images have similar wall thickness and similar pore openings. Either provide some better distinguishing images or remove the discussion that you have claimed.

There is no proper justification on EDX results, why the K content increased dramatically in 72 hr treatment and and why N content decreases. The results are presented just like a black box.

The desorption results are also not justified properly. The net rate has shown significant improvement but was it a mono layer or multilayer adsorption, its better to carry out the BET analysis and provide the BET isotherms. Secondly, the TPD study the ammonia removal was significant. Can author give some highlights on regeneration temperature, pressure condition of the developed adsorbent and its performance in multiple cycles.

Comments on the Quality of English Language

Kindly use proper grammatical verbs and tenses through out the paper

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper titled, "Performance of CO2 adsorption on modified activated carbons derived from okara powder waste: impacts of ammonia impregnation" by Hoang et al investigated the adsorptive removal of CO2 via chemical modification of okara powder based ACs using NH4OH. In addition, they characterized ACs using FTIR and SEM EDX analysis. This study is in accordance with the aims and objectives of the journal "Processes".  It will aid the relevant scientific community related to climate change, CO2 removal, and adsorption. Therefore, I recommend this publication. However, there are certain major comments which are very important to address which can significantly improve the quality of the manuscript. These comments are as below:

 

1-   Table 1: Please replace “0” by “-”.

2-   Table 2: How can you justify the commercial aspect of modified okara based ACs as compare to commercial ACs, carrot peels peanut shell char, etc., which exhibited high adsorption capacity of CO2. In my opinion, please add a section for basic cost analysis to justify the application considering commercial aspects.

3-   Section 2.2. Modification of ACs: Why only 200 ^oC was used for auto claving?

4-   Why were the surface area measurements for ACs not considered?

5-   Line 126: Replace “Porosity” with “Pores”.

6-   In figure 6, in case of sample S3-AC-NH4-48h, please explain the reason of shoulder peak in the temperature zone of ~275-300 ^oC.

7-   In the light of FTIR results, please explain the chemistry and possible mechanisms related to the adsorption of CO2 on the surface of okara based ACs. Add this explanation at a suitable place within the manuscript.  

8-   If possible, please further characterize the ACs using Thermogravimetric and XRD analyses to improve the quality of paper.

Comments on the Quality of English Language

It is suggested to please review the manuscript with the respect to English Language and preferably get it proof read by a Native Speaker, since English language including reasonable choice of words, sentence structure and flow, etc., is not appropriate. Certain examples are given below;

 

1-   Line 13: Omit “toward CO2” with “Damaged”.

2-   Line 26: Insert abbreviation of MOF.

3-   Line 27-30: It is a length sentence “Among technological approaches……… scalability”. Break it into 2 sentences.

4-   Line 36: Remove the repeated words “or dry”

5-   Line 41: Use “H and N” instead of “H2, and N2”, since idea is to present radicals. Please ensure to correct is at other places within the manuscript.

6-   Line 103: Remove spacing between ” surface, chemically”

7-   Line 104: Insert a space between “mass spectrometry” and “(MS)”

8-   There are lot of spacing issues within the manuscript, please revise carefully and correct.

9-   Line 179: Capital “C” to be used in “Acs”.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I agree it to be accepted.

Reviewer 2 Report

Comments and Suggestions for Authors

All queries are answered statifactorily

Reviewer 3 Report

Comments and Suggestions for Authors

Authors have addressed all the comments carefully. Now, manuscript is recommended for publication.