Robust Enhancement of Direct Air Capture of CO₂ Efficiency Using Micro-Sized Anion Exchange Resin Particles

Round 1

Reviewer 1 Report

The manuscript under review discusses research on CO2 capture materials, focusing on an ion exchange resin material IRA-900 processed to different scales through grinding to evaluate its CO2 adsorption performance and potential future applications. The article introduces detailed experimental design, such as grinding through a grinder and sieving to different diameter ranges, and systematic testing methods, such as constructing a stable testing system, to comprehensively evaluate the material's performance. It explores the adsorption performance of water with different diameters and investigates the impact of its stacking density on adsorption, while comparing it with other common CO2 adsorption materials, such as typical amine-based materials. The study also includes simulation analysis using COMSOL multi-physics software, with simulation results matching experimental findings. The manuscript encompasses experimental design, testing procedures, results interpretation, and comparative analysis, providing a comprehensive and in-depth platform for discussing the material's impact on CO2 capture technology. The overview of the manuscript is clear and concise, laying a solid foundation for subsequent content, while also sparking further discussion and analysis to drive the advancement of the field.

I recommend this manuscript for publication in this journal, after the following reviews:

1.     Experimental Design and Methods:

The manuscript provides detailed descriptions of the experimental setup and testing methods, which is commendable. In the article, it is mentioned that "At 5000 ppm, we observe a leakage rate of 30 ppm/h, and at 1000 ppm, it ranges from 1-5 ppm/h." It is well known that the sealability of the testing system directly affects the reliability of the experimental results. I would like to inquire whether the authors have test data on the airtightness of the testing system to ensure the credibility of the data. Additionally, the manuscript states, "Following this, 5 grams of the particles are removed and placed in a grinder (brand) for 20 seconds." I am also curious about the specific grinding method chosen by the authors as the processing method. There are various devices available for grinding, such as mortar and pestle, ball mills, etc. Did the authors investigate whether different grinding machines would affect the degree of grinding? Moreover, it would be beneficial to discuss the potential impact of these factors on the material's performance.

Clarify the testing system's airtightness by providing test data to ensure the reliability of experimental results, especially considering the observed leakage rates.

Specify the grinding method employed for processing the particles and discuss whether different grinding machines were investigated for their impact on the degree of grinding and subsequent material performance.

2.     Results Analysis:

Although the results analysis is clear and concise, there is still room for further interpretation of the research findings. It is noted that the authors initially treated the resin particles IRA-900 with deionized water. However, in the testing phase, the manuscript mentions, "The water in the bubbling bottle had been allowed to stand in ambient air for over a week to minimize its impact on CO2 absorption." It raises the question of whether the water used in the humidification pathway of the measurement system is deionized water or tap water. If tap water was used, it would be beneficial to discuss whether there were any tests conducted with deionized water for the humidification part. Conversely, if deionized water was utilized, it would be valuable to present test results using tap water. Exploring potential differences in the performance of IRA-900 resin particles in deionized water versus regular tap water environments could be insightful for future practical applications.

Elaborate on the choice between deionized water and tap water for the humidification pathway in the measurement system, discussing the potential differences in performance and providing test results for both scenarios.

Provide further interpretation of the research findings, especially regarding the impact of water choice on CO2 absorption and its relevance to practical applications.

3.     Multiple Simulations:

The manuscript discusses the results of 100 simulations, demonstrating the excellent performance of IRA-900 material. However, in Figure 6.b of the article, there is a sudden decrease in H2O oscillations around 18 hours, which persists thereafter. I would like to inquire whether the authors have any explanation for this phenomenon and whether it is possibly influenced by external factors. Additionally, is this phenomenon likely to impact the adsorption and desorption behavior of IRA-900 particles?

Address the sudden decrease in H2O oscillations observed around 18 hours in Figure 6.b, discussing possible explanations for this phenomenon and its potential influence on the adsorption and desorption behavior of IRA-900 particles.

Good

Author Response

Thanks for the reviewer’s comments concerning our manuscript entitled “Robust enhancement of direct air capture of CO2 efficiency using micro-sized anion exchange resin particles” (ID: sustainability-2936407).

Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

Thank you so much for your careful check!

We sincerely thank the editor and reviewers for their valuable feedback, which we have used to improve our manuscript. Four reviewers’ comments are laid out below in blue, and the specific concerns have been numbered.

Author Response File: Author Response.pdf

Reviewer 2 Report

This research article entitled “Robust Enhancement of Direct Air Capture of CO2 Efficiency Using Micro-Sized Anion Exchange Resin Particles” reports the successful synthesis of amine-based anion exchange resins and the use for the capture of CO2 with high efficiency. This article was well structured and the conclusion was supported properly with the experimental findings. To the reviewer, it can be published by addressing the following concerns:

1. Some words, such as the number in H2O in page 3 line 120, are not presented correctly.

2. In Figure 2, the scale bar is too small to be seen clearly, also suggest the authors to add a histogram for the particles size distribution.

3. What’s the morphology and size after use? Any insights from this?

4. Do the Table 1 and Figure 7 tell the same? If yes, suggest keeping one, please.

5. The abbreviation should be made together with the full name/expression for the first appearance in the manuscript.

6. The introduction background can be extended to by considering the following related references:

https://doi.org/10.1021/acs.est.2c01944

https://pubs.acs.org/doi/10.1021/acsenergylett.3c02678

It looks fine totally. 

Author Response

Thanks for the reviewer’s comments concerning our manuscript entitled “Robust enhancement of direct air capture of CO2 efficiency using micro-sized anion exchange resin particles” (ID: sustainability-2936407).

Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

Thank you so much for your careful check!

We sincerely thank the editor and reviewers for their valuable feedback, which we have used to improve our manuscript. Four reviewers’ comments are laid out below in blue, and the specific concerns have been numbered.

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors in the present manuscript show that to develop low-cost techniques to reduce the IRA-900 anion exchange resin to micro size and observe significant performance enhancement on CO2 capture efficiency contingent on reducing the particle diameters. This performance disparity is attributed to the differential water adsorption capacities inherent in particles of diverse diameters. Our results reveal that smaller resin particles out-perform their larger counterparts, exhibiting accelerated adsorption rates and expedited transitions from wet to dry states. Notably, these smaller particles display a quintupled enhancement in adsorption efficacy relative to non-treated particles and a marked increase in relative adsorption capacity. Upon treatment, IRA-900 demonstrate robust CO2 processing efficiency, achieving a peak adsorption rate of 1.28 g/mol*h and a maximum desorption rate of 1.18 g/mol*h. Also, the material is subjected to almost 100 cycles of testing, and even after 100 cycles, the resin particles maintain a capacity of 100%. Moreover, our material can be fully regenerated to 100% efficiency by simply immersing it in water. Simultaneously, storing it in water allows for long-term maintenance of its performance without other treatment method. The authors should address the following issues and information’s before publication acceptance in the prestigious ‘Sustainability’ Journal:

1. In Introduction, authors should add a Table that compares the amine-based anion exchange resins, preparation method, particle size and CO2 adsorption values with published literatures.  

2. In Materials and Methods, can authors explain how to measure particle size of the samples?

3. On what basis did the authors decide these amine-based anion exchange resins for this study?

4. In Figure 3, authors should improve the quality of the figure for better understanding.

5. In Figure 5e, why did the CO2 adsorption capacity decrease on the third adsorption cycle for sample particles?

6. In Introduction, authors should add some details about different materials and catalysts for adsorption. Authors may go through these two publications for more details and cite accordingly: https://doi.org/10.1007/s11814-024-00111-7 & https://doi.org/10.1007/s11665-018-3192-2    

Minor editing of English language required.

Author Response

Thanks for the reviewer’s comments concerning our manuscript entitled “Robust enhancement of direct air capture of CO2 efficiency using micro-sized anion exchange resin particles” (ID: sustainability-2936407).

Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

Thank you so much for your careful check!

We sincerely thank the editor and reviewers for their valuable feedback, which we have used to improve our manuscript. Four reviewers’ comments are laid out below in blue, and the specific concerns have been numbered.

Author Response File: Author Response.pdf