Heterogeneous Photocatalysis of Amoxicillin under Natural Conditions and High-Intensity Light: Fate, Transformation, and Mineralogical Impacts
Round 1
Reviewer 1 Report
The manuscript covers the identification of the degradation products of amoxicillin under the influence of light, anatase (TiO2) and kaolinite.
As the authors write, "Study reports the photo-degradation of environmental amoxicillin and the formation of degradation products, which are highly mineralogy-dependent."
Research brings us closer to understanding the fate of amoxicillin once it has been released into the environment.
In the part describing the experiments, there is no data on the volume of the mixture in the reactor and the irradiated area. In the absence of this data, other researchers cannot verify and replicate the results.
The work seems to be properly written, however, there are errors in the descriptions that prevent publication.
Page 4, line 8: mistakenly used the name "diclofenac", another substance not covered in this work.
On page 4, the sentence "The kinetic of amoxicillin degradation is modeled as the pseudo-first-order using the equation ln C / C0 = -kt." is written twice.
The results of the statistical analysis of the results shown in Figures 1A and 4A and shown in Tables 1 and 2 are incorrect. The constant rates given in the tables are rounded to a single digit. Based on this insufficiently precise result, Half-time was calculated with a precision of 4 digits, which is mathematically completely wrong.
In both tables, the half-time is calculated by dividing 0.693 / rate constant.
Comparing the Half-time values ​​with the graphs reveals great differences.
The shape of the curve for Dark control (Fig 1A) also shows that this curve does not correspond to the equation ln (C / Co) = -kt in the range shown. In Table 1 it corresponds to the data named "Blank Dark"
Due to the above errors, paragraph (page 11): “Similar to the terrestrial light, anatase showed the highest degradation rate of amox-icillin (k = 0.02 h-1). This is a 2.5-fold increase compared to amoxicillin degradation under terrestrial light when mixed with anatase. The rate of degradation of amoxicillin in the Light Control was 0.01 h-1 which is a 5-fold increase from the terrestrial light. In the presence of kaolinite, the amoxicillin degradation rate showed a 10-fold increase compared to the AM 1.5G filter light. ", contains 5 wrong values.
Table 2 gives data for 3 instead of the 6 curves shown in Figure 4A
Authors should consider whether in Conclusions the word "showed" should not be replaced by "caused"
Author Response
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Author Response.pdf
Reviewer 2 Report
The authors studied the removal of amoxicillin from wastewater by a heterogeneous photocatalysis process. The effectiveness of catalysts such as anatase and kaolinite was compared with the photolytic process under high irradiance. Moreover, the degradation mechanisms of amoxicillin under different reaction and catalyst conditions were studied. One aspect to consider is the concentration of amoxicillin used. It is not realistic with the most frequent concentrations in real waters. This fact disables part of the conclusions such as the real effectiveness of the treatment. However, aspects such as the analysis of degradation products is an aspect that brings novelty to the current state of the art. Consequently, the authors are encouraged to consider the following points to improve the manuscript:
1. The abstract is correctly structured, however it should be completed with the most relevant figures.
2. The title of the article is confusing and should be modified. Heterogeneous Photocatalysis of Amoxicillin under Ecological Conditions and High-Intensity Light: Fate, Transformation, and Degradation Impacts
3. Add as a keyword: Contaminants of emerging concern; Heterogeneous photocatalysis
4. In the introduction (page 3, first paragraph) it should make clear the objective of the study, specifying that the study of degradation intermediates will allow future studies to determine toxicological impacts.
5. Please define the term "mineralogy-controlled".
6. In the analytical methodology used to monitor amoxicillin concentration, please include as supplementary information the analytical method validation and quality assurance.
7. In section 3.3. include the spectrum of the lamp used.
8. Review equations 1-19. It contains formatting mistakes.
9. In the reaction time shown in Figure 1A, did you consider the effect of adsorption before switching on the light source?
10. On page 6, replace the term "reaction 16" with "Equation 16".
11. It should be determined the pH pzc of anatase and kaolinite, to demonstrate the effect of protonation and deprotonation with pH. Please, add the band gap of both as well.
12. Section 3.5 should be explained in more detail. If amoxicillin is not being irradiated in the presence of a catalytic material, how is it possible under these conditions amoxicillin oxidation/degradation? Under these conditions it is assumed an adsorption process?
13. In the conclusions it should be specified that the light source used was not sufficient to activate the kaolinite. Consequently, the material acted as an adsorbent material.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Dear Authors,
I am glad having an opportunity to review the manuscript. It is a interesting paper. I particularly appreciate the main idea of this paper describing the decay pathways and mineralogical impacts on environmental amoxicillin degradation. Authors studied the role of anatase and kaolinite on amoxicillin degradation under irradiated and non-irradiated conditions.
While reading the submitted manuscript, several questions arose and inaccuracies were also noticed, which I recommend to fix.
1. Abstract: The aim and conclusions of the study must be clearly visible. Please improve the writing style and the mention the significance of the study in one sentence.
2. The purpose of the study should be clearly stated at the end of the introduction, preferably with hypotheses tested. The text in finish of introduction is vague and does not reflect the content of the study, in my opinion.
3. Charts and a record of chemical reactions need correction - see esspecially page 5 (direct photodegradfation and indirect photodegradation) and page 6 chemical formulas from 6 to 16, page 7 (formulas 17, 18, 19)
4. Are table were made in accordance with the guidelines for authors? Attention it concerns the size of the descriptions.
5. Drawings are signed behind large type. (figure 1-4)
6. You should have separate section results and separate discussion section.
6. Check in manuscript the typos and spaces, and put spaces everywhere between the value and the unit.
7. Check the font size because it is not correct.
Finally, the article needs a thorough review in English, both for typos, syntax and form of the English language, perhaps considering having it reread by a native speaker colleague
Thank you for your efforts in perfecting this article.
Thus, the topic is interested, however, some aspects must be revised before the acceptation for this Journal.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors corrected a number of mistakes in the descriptions of the experimental results. It was mainly about the number of significant digits in reporting the result of the pseudo-first-order rate constant. After adjustments, they increased the number of significant figures from one to two. In my opinion, three significant figures should be given. From this data, half-life values ​​are calculated.
After comparing half-time of atanase-dark given in Table 1 with value read from Figure 1A the problem of experiments arises. Namely, the "atanase dark" half-life value read from graph 1A is 175 +/- 2 instead of 150 given in Table 1. The shape of the curve in Figure 1A shows that this curve does not tend asymptotically to zero, but to a different C/Co value so the decay equation should be modified. The above conclusion also results from the visible shape of this curve in Figure S2-A. The line is not straight but slightly curved, which means that it does not follow the equation ln (C/Co) = a * t.
According to my assessment, not supported by calculations, the equation can be: C/Co = (1-B) * exp (-a * t) + B, where B equals to ca. 0.3
Authors should note this fact in their text and comment it. For example, they may write that they will investigate the reasons for this inconsistency in future work. Or, if they already know the cause, they should be clear about it.
Judging by values of R2 correlation coefficients lower than 0.99 for "dark" experiments, authors should consider using the modified equation for all "dark" experiments.
The title of the work is too imprecise. What the authors meant by "ecological conditions". Are there any conditions in which there are no water or air contaminants? Or did the authors mean the natural conditions that exist in reality? Then, instead of "ecological conditions", the term "natural conditions" should be used.
I suggest the authors to consider changing the title.
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
The authors improved the manuscript according to the guidelines. Consequently, I suggest its acceptance for publication.
Author Response
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Author Response File: Author Response.pdf
