Removal of Cesium from Radioactive Waste Liquids Using Geomaterials
Round 1
Reviewer 1 Report
Dear authors,
This is a well done adsorption study. Still, I would suggest a few improvements.
Please discuss the obtained textural characteristics of the materials in comparison with the results obtained by other studies on similar materials.
Please discuss the cation exchange adsorption mechanism.
Please better underline the new findings of the present study, in comparison with the multitude of adsorption studies from literature.
Author Response
General comment:
This is a well done adsorption study. Still, I would suggest a few improvements.
Response: Thank you for your comments. The comments are encouraging and helpful. We found that there are still many shortcomings in our manuscript. We checked the manuscript again and modified some parts which you point out.
Specific Comments:
Please discuss the obtained textural characteristics of the materials in comparison with the results obtained by other studies on similar materials.
Response: Thank you for your comment. Based on your comment, we have added the texture properties of the material obtained in this work and the comparison with those of other similar materials obtained by other studies. The description have been added in Section 3.2 in the revised manuscript (Line 248-259 in the revised manuscript, Page 8).
Please discuss the cation exchange adsorption mechanism.
Response: Thank you for your comment and suggestion. Based on your comment, the description of cation exchange adsorption mechanism has been added in Section 3.5 in the revised manuscript (Line 354-360 in the revised manuscript, Page 15).
Please better underline the new findings of the present study, in comparison with the multitude of adsorption studies from literature.
Response: Thank you for your comment and suggestion. Based on your comment, the description of new findings or originality of the present study have been added in Section 3.6 in the revised manuscript (Line 366-385 in the revised manuscript, Page 15).
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors have synthesized fly ash-based geomaterials as an adsorbent for removing cesium from liquid wastes. The materials characteristics were well determined using various analytical tools and its adsorption capacity and rate constant toward Cs was significant as well as previously developed adsorbents. However, several contents in the manuscript should be revised due to lack of clear evidence. Therefore I would like to recommend that the submitted manuscript should be revised before published in the journal.
- Abstract: Please describe the experiments results and conclusion not experimental method.
- Figure 2: Please describe the reason which the adsorption capacity was decreased at dosage with 0.85g.
- Figure 5: Since there is no the quantitative results, I cannot see any relationship between Cs and Na. Please describe more in detail regarding the "negative relationship"
- Line 274: The SEM results did not support the higher performance of fly-ash based geomaterials for Cs adsorption among the adsorbents.
- Figure 6 is not necessary. Please change the data with Concentration of Cs (Y-axis) vs Time (X-axis).
- Conclusion is too lengthy. Please summarize it.
Author Response
General comment:
The authors have synthesized fly ash-based geomaterials as an adsorbent for removing cesium from liquid wastes. The materials characteristics were well determined using various analytical tools and its adsorption capacity and rate constant toward Cs was significant as well as previously developed adsorbents. However, several contents in the manuscript should be revised due to lack of clear evidence. Therefore I would like to recommend that the submitted manuscript should be revised before published in the journal.
Response: Thank you for your comment. The comments are encouraging and helpful. We clearly know that there are still many shortcomings in our manuscript. We checked the manuscript again and modified some parts which you point out.
- Abstract: Please describe the experiments results and conclusion not experimental method.
Response: Thank you for your comment. We are sorry for the inappropriate description in Abstract. Based on your comment, we have revised the Abstract (Line 23-30 in the revised manuscript, Page 1).
- Figure 2: Please describe the reason which the adsorption capacity was decreased at dosage with 0.85g.
Response: Thank you for your comment. Regarding the result about “dosage with 0.85g”, to be honest, clear reason is not elucidated at present. As one possibility, it may be related to the precipitation generated by the adsorbent. For example, when the amount of adsorbent increases, the adsorbent will produce a certain amount of precipitation and solidification, and the contact area with adsorbate is reduced, leading to the reduction of adsorption.
- Figure 5: Since there is no the quantitative results, I cannot see any relationship between Cs and Na. Please describe more in detail regarding the "negative relationship".
Response: Thank you for your comment. We are sorry for not describing the relationship between Cs and Na in detail. Based on your comment, we have added the description of textural characteristics obtained from Figure 5 (SEM results) in Section 3.2 in the revised manuscript (Line 248-259 in the revised manuscript, Page 8).
The relationship between sodium and cesium is mainly based on the notation from the description of references [40, 41]. There is a citation description in Line 259 in the revised manuscript.
- Line 274: The SEM results did not support the higher performance of fly-ash based geomaterials for Cs adsorption among the adsorbents.
Response: Thank you for your comment and suggestion. Based on your comment, we have added the supplementary explanation about SEM results (Line 248-259 in the revised manuscript, Page 8).
- Figure 6 is not necessary. Please change the data with Concentration of Cs (Y-axis) vs Time (X-axis).
Response: Thank you for your comment. The data with “Concentration of Cs (Y-axis) vs Time (X-axis)” as you suggested has been already shown in Figure 3 in original manuscript. Figure 6 is important figure of analytical result obtained from data in Figure 3 as well as Figure 7. Figure 6 is obtained by Pseudo-first-order linear kinetic model, and Figure 7 is by Pseudo-second-order linear kinetic model. The comparison between Pseudo-first-order linear kinetic model and Pseudo-second-order linear kinetic model can better explain the mechanism of the adsorption process, then Figure 6 is necessary.
- Conclusion is too lengthy. Please summarize it.
Response: Thank you for your comment and suggestion. Based on your comment, we have reduced the description denoted in Conclusion and revised (Line 396-412 in the revised manuscript, Page 16).
Author Response File: Author Response.docx
Reviewer 3 Report
I have reviewed the article entitled " Removal of Cesium from Radioactive Waste Liquids Using Geomaterials ". In this manuscript, kinetic experiment and isotherm models were applied to evaluate the sorption characteristics of Cs on three geomaterials. The experiments were well conducted and the data got good fittings to the isotherm models, which well demonstrated the properties of sorption for Cs on these materials. Nevertheless, I still have the some comments and suggestions to the authors to revise this manuscript. If the authors answered the following questions and revised the manuscript, I suggested that the manuscript could be accepted for publication :
- For Fig. 1, the pH values are the initial pH. Are the final pH still the same with the initial values?
- The authors compared the adsorption performance of Cs of this studies on some other adsorbents in Table 5. However, the maximum sorption capacity data of Cs on this table are much less than what I have read from other reference. For example, the authors may refer the paper : “Removal of cesium through adsorption from aqueous solutions: a systematic review” , J Adv. Environ Health Res (2018) 6:96-106, DOI: 10.22102/jaehr.2018.104959.1048. The maximum sorption capacity of Cs in this article are more than 200 mg·g−1 (Table 1), however the data in Table 5 of this study are 5.99 mg·g−1. The authors should clearly explain the discrepancies of these two results.
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Author Response
General comment:
I have reviewed the article entitled " Removal of Cesium from Radioactive Waste Liquids Using Geomaterials ". In this manuscript, kinetic experiment and isotherm models were applied to evaluate the sorption characteristics of Cs on three geomaterials. The experiments were well conducted and the data got good fittings to the isotherm models, which well demonstrated the properties of sorption for Cs on these materials. Nevertheless, I still have the some comments and suggestions to the authors to revise this manuscript.
Response: Thank you for your comments. The comments are encouraging and helpful. We found that that there are still many shortcomings in our manuscript. We checked the manuscript again and modified some parts which you point out.
Specific Comments:
- For Fig. 1, the pH values are the initial pH. Are the final pH still the same with the initial values?
Response: Thank you for your comment. The pH values are surly the initial pH. The large change of pH after adsorption experiment was not observed. Then the final pH is almost the same with the initial value.
- The authors compared the adsorption performance of Cs of this studies on some other adsorbents in Table 5. However, the maximum sorption capacity data of Cs on this table are much less than what I have read from other reference. For example, the authors may refer the paper : “Removal of cesium through adsorption from aqueous solutions: a systematic review” , J Adv. Environ Health Res (2018) 6:96-106, DOI: 10.22102/jaehr.2018.104959.1048. The maximum sorption capacity of Cs in this article are more than 200 mg·g−1 (Table 1), however the data in Table 5 of this study are 5.99 mg·g−1. The authors should clearly explain the discrepancies of these two results.
Response: Thank you for your valuable comment and suggestion.
Firstly, based on your comment, we have added some data (particularly, related to inorganic minerals) by literature references.
Next, regarding the maximum sorption capacity, we have the following view and thoughts.
For many adsorption studies, the performance of the adsorbent is generally estimated and expressed by the maximum (or equilibrium) adsorption capacity as shown in Table 5 in our original manuscript (or Table 1 in J Adv. Environ Health Res (2018) 6:96-106, DOI: 10.22102/jaehr.2018.104959.1048). However, the maximum adsorption capacity is sensitively affected by the initial loading concentration of target pollutant (or more specifically what is left after sorption reaction).
(If sorbent is exposed to higher concentration of targets, it is apt to exhibit higher adsorption capacity. On the other hand, if the sorbent is exposed to lower levels of target species, it will show lower capacities.)
Then, in addition to maximum adsorption capacity, it is effective to estimate using the concept of partition coefficient (PC) as explained below (See the following our previous references).
PC=Adsorption capacity / Final concentration
(or = Adsorption capacity / (Initial concentration * removal ratio)).
Zhang, S., Kano, N., Mishima, K., Okawa, H.: Adsorption and Desorption Mechanisms of Rare Earth Elements (REEs) by Layered Double Hydroxide (LDH) Modified with Chelating Agents. Appl. Sci. 2019, 9, 4805, https://doi.org/10.3390/app9224805
Feng, S., Du, X., Bat-Amgalan, M. Zhang, H., Miyamoto, N., Kano, N.: Adsorption of REEs from aqueous solution by EDTA-Chitosan modified with zeolite imidazole framework (ZIF-8). Int. J. Mol. Sci. 2021, 22, 3447.
https://doi.org/10.3390/ijms22073447
Incidentally, our result of maximum adsorption capacity in this work is 89.32 mg·g-1 (not 5.99 mg·g-1 that you pointed out, which is the data of natural zeolite in Reference [44] in original manuscript).
In revised manuscript, we have removed the data of 5.99 mg·g-1 because an accurate PC cannot be estimated for the lack of the data of the final concentration, and the data came from a report by a Japanese chemical company (only Japanese report, no English literature). Instead, some new reference have been added [44-45] and [48-52] in revised manuscript.
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
I suggested that the manuscript could be accepted for publication based on the replies from the authors.
