Functionalized Polyethyleneimine Adsorbent for Efficient and Selective Uranium Extraction from Aqueous Solution

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General comment:

The manuscript titled “Functionalized Polyethyleneimine Adsorbent for Efficient and Selective Uranium Extraction from Aqueous Solution” presents a relevant and well-structured study on a novel material for uranium extraction from wastewater. The work includes thorough characterization and shows promising adsorption performance and reusability. While the topic is important and the results are valuable, some issues need to be addressed. I recommend the manuscript for publication pending major revisions. Therefore, acceptance is contingent upon addressing the following points:

1. In the abstract, the abbreviation "PEI-PAC-AO" seems to be missing some details. "PEI" is clear, and "AO" probably refers to amidoxime, but it's not clear what "PAC" stands for. If it's meant to represent cyanobenzaldehyde or something else, please clarify and make sure all abbreviations are explained in the text.
2. Check the English grammar of the sentence: “The structure and performance of the adsorbents were characterized by FT-IR, TGA, SEM, CA, ICP-MS” in the abstract.
3. In the first paragraph, revise it “Nevertheless, the proven reserves of terrestrial uranium ore are relatively scant”.
4. The references in the 2nd and 3rd paragraphs are not linked. Please revise them.
5. Rewrite the last paragraph of the introduction. Please do not cite Fig. 1 at this point. The paragraph should highlight the improvements made in this study and explain how it addresses the previously mentioned gaps.
6. Ensure that every acronym is spelled out and explained the first time it appears in the text.
7. The authors gave only a brief description of the adsorbent preparation. It’s unclear whether the process involved agitation, what temperature was used, or which parameters were optimized. This crucial information is only found in the supplementary material. Provide a more detailed description of the adsorption material preparation method, especially, PAI-PAC.
8. The Materials and Methods section was too brief and should be expanded to provide sufficient detail and clarity regarding the experimental procedures. Thus, I recommend including in the manuscript a brief comment highlighting the key aspects investigated in this study. Additionally, indicate that the preparation of the uranium standard solution, the investigation of static adsorption properties, and the characterization methods are all described in detail in the supplementary material.
9. What is the difference between the FTIR spectra of PEI-PAC shown in red in Fig. 3a and in blue in Fig. 3b? To me, they appear to present the same data. I suggest putting the spectra on a single graph.
10. In line 140: “Six samples of PEI-PAC-AO were dried in a vacuum drying oven at 60 ℃ for 24 hours, and their thermogravimetric curves were measured under a nitrogen atmosphere” It is important to mention that these six samples have different concentrations of PA and PC. Furthermore, these values must be shown in the text.
11. Enhance the quality of Fig. 3; it is impossible to differentiate the materials based on the line colors. In Fig. 3b, why do half of the materials show a mass loss event around 300 °C, while the other half exhibit it around 450 °C? PEI-PAC-AO 3 is the only material that displays events in both regions of temperature. Would you explain the reason for this behavior?
12. In Fig. 5 change the names of the y-axis to 'Uranium adsorption’ instead of 'Uranium uptake (mg/g)' and in the x-axis to “adsorbent/ uranium solution ratio (g/L)” instead ‘m/v (g/L)’.
13. From lines 240 to 271: Please add literature references that support the discussion regarding pH effects.
14. In Fig. 7a change the name of the y-axis to 'Uranium adsorption’ instead of 'Uranium uptake (mg/g)'.
15. Line 304: Standardize the units used. Previously, temperature was reported in ºC; now it is reported in K.
16. Line 308-311 authors said the adsorption process is endothermic. Please check that and revise your literature background. In general, adsorption is an exothermic process.
17. Lines 308-311: The authors state that the adsorption process is endothermic. Please verify this statement and review the fundamental principles in literature, as adsorption is generally considered an exothermic process. How can the adsorption of uranium onto the PEI-PAC-AO adsorbent be an endothermic process?
18. Line 316: ‘FreundLich’. Revise it.
19. Line 327 – 330: “while the entropy change ΔS₀ value (56.83 kJ/mol) is greater than 0, indicating that the uranium adsorption process is spontaneous.” It is one more indicative that enthalpy of adsorption process is exothermic.
20. Please improve the resolution of Fig. 11.
21. Enhance the conclusion e clearly report the key outcomes of the study and explicitly highlight how they contribute to advancing the field.
22. Finally, please check the supplementary material for some minor grammatical and typographical errors. Furthermore, I believe the supplementary material contains relevant information that should be included in the main manuscript. Consider bringing them into the main text.

Author Response

We are truly grateful to yours and other reviewers’ critical comments and thoughtful suggestions. Based on these comments and suggestions, we have made careful modifications on the original manuscript. All the changes have been highlighted in red. We hope the new manuscript (revised manuscript) will meet the magazine’s standard. Followings are our point-by-point responses to the reviewers’ comments and questions:

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Please see attached file.

Comments for author File: Comments.pdf

Author Response

We are truly grateful to yours and other reviewers’ critical comments and thoughtful suggestions. Based on these comments and suggestions, we have made careful modifications on the original manuscript. All the changes have been highlighted in red. We hope the new manuscript (revised manuscript) will meet the magazine’s standard. Followings are our point-by-point responses to the reviewers’ comments and questions:

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Accepted.

Author Response

Dear reviewer，

       We are truly grateful to yours and other reviewers’ critical comments and thoughtful suggestions.

With best wishes!

Sincerely yours,

Jianwei Bai

Reviewer 2 Report

Comments and Suggestions for Authors

I thank the authors for addressing my comments and making the appropriate changes. However, the words "removal rate" are still used in figures 6, 9, and 10, and should be replaced with "removal extent". Otherwise the manuscript is ready for publication.

Author Response

Dear reviewer，

       We are truly grateful to yours and other reviewers’ critical comments and thoughtful suggestions. Based on these comments and suggestions, we have made careful modifications on the original manuscript. All the changes have been highlighted in red. We hope the new manuscript (revised manuscript) will meet the magazine’s standard.

With best wishes!

Sincerely yours,

Jianwei Bai

Author Response File: Author Response.pdf