Characterizing the Reactivity of Metallic Iron for Water Treatment: H2 Evolution in H2SO4 and Uranium Removal Efficiency
, Rui Hu 1, Willis Gwenzi 2, Achille Nassi 3 and Chicgoua Noubactep 1,4,*Round 1
Reviewer 1 Report
Iron has been used in metallic form in water pipes and many other cases and in some cases corrosion can be a serious problem but in some cases old iron pipes look like new ones. Iron as relatively cheap material have also other use. The paper has to be corrected before acceptance, but these corrections are mainly easy.
Abstract: Line 25 omit twelve!
Line 26 Calculate the result for 1 L (not 560 mL) and use this in all text.
Introduction: line 107 F0 -products
Materials and methods:
In line 121 you inform that ST1 and ST2 contained 8.6 % chromium, but then in Table 3 you inform the Fe-content over 97%. How this is possible?? If a part of raw material is stainless steel chromium can be ok, but Fe must be less.
Table 3: This table is better if you turn its position so that iron products are in columns and their chemical components are in rows. Thus, it is easier to compare the similarities and dissimilarities. After reading the whole paper, I would propose you to put the products ST1 and ST2 first (due to proposals in Table 4, which are not yet important for reader). We read English text row by row from left to right and therefore comparation is better done in the same row.
What is balance?
Figure 1 is not needed. Omit it!
Part 2.2.1. How many parallel tests were done?
Ok volume was determined. How often! When gas was formed, did you measure always the increase of gas volume or did you take the formed gas away and got a new volume always between readings?
Results and discussion:
See that the time scale (x-axis) is the same in figures 2 a, 2b and 2c.
Again, in Table 4 the number of parallel tests should be given. Turn again this table so that the iron products are in columns and the results in rows. Add an extra explanation row for time, which is 16 h for ST1 and ST2 (being first) and 28 h for the other ten products! This set up will allow the reader to see that ST1 and ST2 were totally different compared to the other iron products.
Figure 3 is not all clear. Make a new table instead and calculate the correlations between H2-prodution and U(VI) removal as well as the correlations between these and Mn (and maybe between sulfur and carbon). In this correlation Table you can calculate correlation coefficients and their statistical significances as p-values.
The Table 5 is not needed as well as the text in lines 285-300, since this part is very much out of context.
Your reference must be often corrected.
Use bold only for publication year. Omit all the other bold text. Omit also underlines or italics where it is not needed.
Author Response
Many thanks for your evaluation!
Dr. Noubactep
Author Response File: 
Author Response.pdf
Reviewer 2 Report
No special comments
Author Response
Many thanks for this evaluation!
Reviewer 3 Report
The manuscript ”Characterizing the Reactivity of Metallic Iron for Water Treatment: H2 Evolution in H2SO4 and Uranium Removal Efficiency” has a very important topic: characterization of the intrinsic reactivity of Fe(0) materials. For the research group headed by Dr. Noubactep this work is the continuity of several previous investigations on developing and revisiting tools for the characterization of Fe(0) reactivity: the EDTA test, the methylene blue discoloration method, the phenantroline test. With this work, the authors present a new, simple and affordable experimental protocol that can be applied for the characterization of Fe(0) intrinsic reactivity. However, while all the previous tests, conducted at circumneutral pH, are limited to characterizing Fe(0) initial reactivity, the H2 evolution at pH 2 address the long-term reactivity of Fe(0) materials. In addition, in this study, uranium was used as representative contaminant to discuss the suitability of H2 evolution as an alternative tool to assist Fe(0) selection for field application. The manuscript is written in a well-organized and systematic way, with a necessary chronological overview on the currently existing methods on characterization of Fe(0) reactivity. The objectives of this study, clearly presented in the ”Introduction” section, are followed consistently throughout the paper, and the obtained results are consistent. In addition, several future directions for the design of the next generation Fe(0)-based systems have also been discussed. Therefore, I would recommend publishing this paper after considering the following suggestions:
1) Line 111: Iron materials
Photographs of the 12 tested Fe(0) materials could provide added value to the manuscript.
2) Line 148: 2.2.1. Hydrogen evolution
Adding the schematic diagram of experimental setup used to study the hydrogen evolution would be useful; the cited source (32) is in German language, and, therefore, a bit difficult to understand the technical vocabulary, not being similar to English. And/or, a more detailed description of the experimental procedure should be added in text.
3) Lines 152-153: ” The total volume of the solution was 560 mL, and contained 2820 mg/L of SO42- and 10.5 mg/L of SiO2.”
Please explain what was the source/role of SiO2 in the experiment.
4) Line 156: 2.2.2. Uranium removal
Please add also the pH value of UO2 solution, in order to make more clear the near-neutral conditions
5) Line 156: ” In order words”
Replace ”order” with ”other”
6) Lines 256-258: ” Figure 3 compares the volume of produced molecular hydrogen (H2) and uranium removal efficiency as a function of the manganese content (% Mn) of the tested materials.
Please explain why volume of produced H2 and uranium removal efficiency was depicted in Fig.3 as a function of the manganese content. Why manganese? Why no other element, like sulfur or carbon who, as you mentioned, could have a favorable role in the decontamination process by inducing surface corrosion?
Author Response
Many thanks for your evaluation!
Dr. Noubactep
Author Response File: Author Response.pdf
Reviewer 4 Report
The manuscript reports the results of an interesting experimental work regarding the use of metallic iron as a reactive material in water treatment. The paper is well written, the research design is adequate and the results clearly discussed.
My only concern is the numbers of references, 81 cited papers are excessive for a research paper. Moreover, there is a large number of self-citations by the authors. Many of these should be removed, such as the papers not written in English or those that are not easily accessible.
Author Response
Many thanks for this evaluation!
The "huge" number of references is justified by the fact that we have summarized past efforts, all past efforts, including ours. Taking into account the fact that we were walking along in trying to characterize the intrinsic reactivity of ZVI materials since 2004 (see the referenced Li et al. 2019), we cannot be blamed for self-reference, we have even not considered some interesting aspets, like tests in column experiments which are also interesting to the reader.
Sincerely,
Dr. Noubactep
Round 2
Reviewer 1 Report
In this form the paper could s much better. There are anyhow, three comments.
I would omit the comment 1.
In line 357 is the comment. The second finding is calculated. Maybe the word "impossible" should be "lacking".
In line 442 as the comment 3. Future perspective would be better.
Author Response
In this form the paper could s much better.
Many thanks for this evaluation!
There are anyhow, three comments.
I would omit the comment 1.
Comment is deleted, thanks!
In line 357 is the comment. The second finding is calculated. Maybe the word "impossible" should be "lacking".
Many thanks, comment is deleted and "lacking" is adopted!
In line 442 as the comment 3. Future perspectives would be better.
Done thanks, Future perspectives is adopted!
We are very thankful for your help!
Sincerely,
Dr. Noubactep
