Magnetically Separable Mixed-Phase α/γ-Fe₂O₃ Catalyst for Photo-Fenton-like Oxidation of Rhodamine B

Round 1

Reviewer 1 Report

 

 

(1)      What’s the meaning of “c” in line 23, pls explain.

(2)      Content in lines 25-26 is redundance, pls revise.

(3)      Line 42: there are two full stops before and after [1], pls delete the former.

(4)      Lines 43-44: Fenton process only refer to hydrogen peroxide and ferrous ion, pls revise.

(5)      Lines 86-86: pls refer https://doi.org/10.1016/j.jece.2020.103903.

(6)      Line 96: the writing style of equation 1 should be revised.

(7)      Line 198: Subtitle of “Catalytic activity in Fenton-like process” should be 2.2.

(8)      Are there any error bars in Figure 4 and other figures?

(9)      The writing style of radicals should be corrected according to the following reference: “Koppenol, W. (2000). "Names for inorganic radicals (IUPAC Recommendations 2000)." Pure and Applied Chemistry 72(3): 437-446.”

(10)   Section 2.2: pH is a vital influencing parameter for Fenton-like reactions, pls add some essential experiments to investigate the influences of pH.

(11)   What about the Fe ions leaching during the RhB degradation, pls provide related data.

(12)   What about the mineralization of RhB during treatment?

 

 

Author Response

We are grateful to the reviewer for a careful review of our work and for valuable comments. We tried to answer all questions and made corrections in accordance with his suggestions.

• What’s the meaning of “c” in line 23, pls explain.

Corrected

 

• Content in lines 25-26 is redundance, pls revise.

Corrected

• Line 42: there are two full stops before and after [1], pls delete the former.

Corrected

 

• Lines 43-44: Fenton process only refer to hydrogen peroxide and ferrous ion, pls revise.

Corrected

• Lines 86-86: pls refer https://doi.org/10.1016/j.jece.2020.103903.

Added

 

• Line 96: the writing style of equation 1 should be revised.

Revised

• Line 198: Subtitle of “Catalytic activity in Fenton-like process” should be 2.2.

Corrected

• Are there any error bars in Figure 4 and other figures?

The experimental error is less than 5%, so it makes no sense to indicate an error bar.

• The writing style of radicals should be corrected according to the following reference: “Koppenol, W. (2000). "Names for inorganic radicals (IUPAC Recommendations 2000)." Pure and Applied Chemistry 72(3): 437-446.”

Corrected

• Section 2.2: pH is a vital influencing parameter for Fenton-like reactions, pls add some essential experiments to investigate the influences of pH.

Thanks for the suggestion, we have presented data on the dependence of catalytic activity on pH.

As can be seen, the pH of the medium has no effect on the activity of the photo-Fenton-like process. It is added to supplementary materials.

• What about the Fe ions leaching during the RhB degradation, pls provide related data.

We analyzed the post-process solution for iron content. The most sensitive photometric determination method is the determination of iron (II) with nitroso-P-salt. Before determination, all dissolved iron was converted to 2+ by adding Na2SO3. The results showed that from the initial mass of the catalyst, the loss was 0.17%, and the concentration in the solution after the process was 0.33 mg/l. This indicates a slight leaching.

• What about the mineralization of RhB during treatment?

Thanks for the question. In our short communication, we wanted to demonstrate the activity of a mixed phase catalyst in a heterogeneous Photo-Fenton process. Of course, we agree with the reviewer that the percentage of degradation is not indicative of mineralization. However, these studies will already go beyond the scope of a short report.

Author Response File: Author Response.pdf

Reviewer 2 Report

Type of manuscript: Communication

Title: Magnetically separable mixed-phase α/γ-Fe2O3 catalyst for photo-Fenton-like oxidation of Rhodamine B

Journal: Catalysts

Comments to the Corresponding Author:

As I read this paper, I found some issues that make it unsuitable for publication in its current state. The authors can however enhance the work by considering the following comments to be considered for publication in the journal:

1. Why is photo-Fenton-like used instead of photo-Fenton? Can you explain what photo-Fenton-like is and how it differs from actual photo-Fenton?

2. In the abstract section, the removal rates of color were 99,2%. RhB's solution was what color?

3. It is recommended that authors include the advantages and disadvantages of photo-Fenton in the oxidation of dyes.

4. What is the toxicity, and permissible limits of RhB dye, as well as include recent articles on its degradation? One reference to cite is as follows: https://doi.org/10.1016/j.molliq.2020.113399

5. In the manuscript, the Fenton process is often used in conjunction with the photo-Fenton process. How do they differ? The process name should be used consistently throughout the manuscript.

6. Math software should be used to rewrite equations.

7. Describe the percentage analysis of each element in an EDS table.

8. In line 184 of page 6, the presence of 2+ is noted. Could you please explain what 2+ means here?

9. On page 8, avoid unnecessary spacing.

10. At line 244, on page 8, there is α-Fe2O3. Subscripts should be used.

11. Make sure the references in the section on materials and methods are correct.

12. The effect of pH on the degradation of RhB should be investigated.

 

13.  Conduct a regeneration study of the used catalyst.

Author Response

Comments and Suggestions for Authors

Type of manuscript: Communication

Title: Magnetically separable mixed-phase α/γ-Fe2O3 catalyst for photo-Fenton-like oxidation of Rhodamine B

Journal: Catalysts

Comments to the Corresponding Author:

As I read this paper, I found some issues that make it unsuitable for publication in its current state. The authors can however enhance the work by considering the following comments to be considered for publication in the journal:

We are grateful to the reviewer for a careful review of our work and for valuable comments. We tried to answer all questions and made corrections in accordance with his suggestions.

1. Why is photo-Fenton-like used instead of photo-Fenton? Can you explain what photo-Fenton-like is and how it differs from actual photo-Fenton?

We are grateful to the referee for his question. We wrote "photo-Fenton-like" not from ignorance of termilogy, but based on the fact that pure Fenton processes mean homogeneous processes (photo-Fenton, sono-Fenton et al.). To avoid confusion in terminology, it is customary to indicate Fenton's heterogeneous processes with the prefix Like.

2. In the abstract section, the removal rates of color were 99,2%. RhB's solution was what color?

 Thanks for the question. The color of the solution was light pink. For persuasiveness, we present the absorption spectra over the process time. 99.2% corresponds to the degree of discoloration of the solution due to the destruction of the chromophore bond in the dye molecule.

3. It is recommended that authors include the advantages and disadvantages of photo-Fenton in the oxidation of dyes.

Thanks for the recommendation. We have added to the introduction of Line 59 and beyond

4. What is the toxicity, and permissible limits of RhB dye, as well as include recent articles on its degradation? One reference to cite is as follows: https://doi.org/10.1016/j.molliq.2020.113399

Added

5. In the manuscript, the Fenton process is often used in conjunction with the photo-Fenton process. How do they differ? The process name should be used consistently throughout the manuscript.

Thanks for pointing it out. We have used the same terminology throughout the text. photo-Fenton-like when it comes to a process that used a heterogeneous catalyst and hydrogen peroxide under light irradiation. Fenton-like in the case where the process used a heterogeneous catalyst and hydrogen peroxide without irradiation.

 6.Math software should be used to rewrite equations.

Fixed

7.Describe the percentage analysis of each element in an EDS table.

We added an EDX spectrum in supplementary file (Figure S1) and wrote down the percentage of all elements.

8. In line 184 of page 6, the presence of 2+ is noted. Could you please explain what 2+ means here?

Fixed to Fe²⁺

9. On page 8, avoid unnecessary spacing.

Fixed

10. At line 244, on page 8, there is α-Fe2O3. Subscripts should be used.

Fixed

11. Make sure the references in the section on materials and methods are correct.

Fixed

12. The effect of pH on the degradation of RhB should be investigated.

Thanks for the question. We have brought the data in supplementary file (Figure S1)

13. Conduct a regeneration study of the used catalyst.

Thanks for the question. We used our catalysts in 5-fold cycling experiments. Before use, the catalyst was washed with deionized water 3 times and dried in a vacuum oven at 40°C. No additional actions are required for regeneration.

Author Response File: Author Response.pdf

Reviewer 3 Report

In this manuscript, the authors reported the synthesis of a mixed mixed-phase α/γ-Fe2O3 catalyst for the photo-Fenton-like oxidation of Rhodamine B. A series of materials characterization techniques were employed, including SEM, XRD, XPS, Raman spectroscopy, and VSM. The effects of operating parameters on the performance of the photocatalysts were also investigated. Overall, the authors did quite a lot of work, however, I found insufficient analysis of the experimental data and lack of insightful explanations or solid conclusions. Therefore, I suggest a major revision before considering this manuscript for publication. My comments are as follows:

1.         Throughout the abstract and conclusion sections, I only found the description of the experiments they did and the experimental data they got, no further interpretations or analysis over these experimental data were made. They only described how good their catalysts performed but gave no convincing explanations or solid conclusions. Bot the abstract and the conclusion sections should be rewritten then.

2.         Figure 1, the elemental mapping images are meaningless without the EDX spectra data. Therefore, the EDX spectra data should be provided along with the elemental mapping images in Figure 1.

3.         Figure 3, the samples were analyzed by XPS, and the complex peaks were deconvoluted for different species. Therefore, the deconvolution results and parameters for different species should be provided in a separate table, including the atomic ratio, the peak positions, FWHM. The XPS data cannot be reliable without the presentation of these data.

4.         Figure 5b), more description of the images should be provided, what are the materials in both vials? Why did they show different magnetic properties in the presence of a magnetic field?

5.         Again, even in the Results section, the authors just displayed their experimental results piece by piece in the manuscript with no sufficient analysis and interpretation of their experimental data. For example, they determined the mixed phase of α/γ-Fe2O3, then what are the functions for the α and γ-Fe2O3 phases during the photocatalytic degradation of RhB, respectively? Both Fe3+ and Fe2+ were identified by deconvoluting the XPS peaks, then what are the functions for these cations, respectively? There are too many questions that need to be answered.

 

6.         No control experiments were designed, only one sample was synthesized and studied throughout the whole manuscript.

Author Response

Comments and Suggestions for Authors

In this manuscript, the authors reported the synthesis of a mixed mixed-phase α/γ-Fe2O3 catalyst for the photo-Fenton-like oxidation of Rhodamine B. A series of materials characterization techniques were employed, including SEM, XRD, XPS, Raman spectroscopy, and VSM. The effects of operating parameters on the performance of the photocatalysts were also investigated. Overall, the authors did quite a lot of work, however, I found insufficient analysis of the experimental data and lack of insightful explanations or solid conclusions. Therefore, I suggest a major revision before considering this manuscript for publication. My comments are as follows:

We are grateful to the reviewer for a careful review of our work and for valuable comments. We tried to answer all questions and made corrections in accordance with his suggestions.

1. Throughout the abstract and conclusion sections, I only found the description of the experiments they did and the experimental data they got, no further interpretations or analysis over these experimental data were made. They only described how good their catalysts performed but gave no convincing explanations or solid conclusions. Bot the abstract and the conclusion sections should be rewritten then.

Fixed

2. Figure 1, the elemental mapping images are meaningless without the EDX spectra data. Therefore, the EDX spectra data should be provided along with the elemental mapping images in Figure 1.

Fixed

3. Figure 3, the samples were analyzed by XPS, and the complex peaks were deconvoluted for different species. Therefore, the deconvolution results and parameters for different species should be provided in a separate table, including the atomic ratio, the peak positions, FWHM. The XPS data cannot be reliable without the presentation of these data.

Thanks for the recommendation. We have added an additional file and included the spectra along with table values for the deconvoluted peaks. Careful analysis after rechecking showed that the ratio of peaks indicated in the original version of the article 70:30 was erroneous. The analysis from the figure below showed that the ratio of the integral areas of the 3+ and 2+ peaks is 60:40.

4. Figure 5b), more description of the images should be provided, what are the materials in both vials? Why did they show different magnetic properties in the presence of a magnetic field?

Thanks for the question. For clarity, the second vial contains a commercial powder of non-magnetic pure α-Fe2O3

5. Again, even in the Results section, the authors just displayed their experimental results piece by piece in the manuscript with no sufficient analysis and interpretation of their experimental data. For example, they determined the mixed phase of α/γ-Fe2O3, then what are the functions for the α and γ-Fe2O3 phases during the photocatalytic degradation of RhB, respectively? Both Fe3+ and Fe2+ were identified by deconvoluting the XPS peaks, then what are the functions for these cations, respectively? There are too many questions that need to be answered.

  Thank you for your questions. Our work is devoted to the study of non-photocatalytic properties of the obtained material, although these data are also given as control data. The main goal is to obtain a magnetically separable catalyst based on Fe2O3 and to study its activity in Fenton-like processes (both in the dark and under irradiation). As is known, it is the presence of Fe3+ and Fe2+ species on the surface that contributes to the occurrence of redox processes with the generation of highly oxidizing reactive oxygen species.

6. No control experiments were designed, only one sample was synthesized and studied throughout the whole manuscript.

Since we set the task of synthesizing a mixed-phase magnetically separated catalyst based on Fe2O3, since there are many reports that α-Fe2O3 exhibits good activity in Fenton-like processes. We have successfully synthesized such a 0.8α/0.2γ-Fe2O3 catalyst, which has a high magnetization. Based on this, as control experiments, this short communication presents data on photocatalysis (catalyst + light), photolysis (light), and oxidation with hydrogen peroxide without a catalyst and light (Figure 4a).

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

accept

Reviewer 2 Report

The paper has been improved by the authors, and now it can be accepted as it stands.

Reviewer 3 Report

I don't see sufficient improvement in the revised manuscript, my concerns were not well addressed.

I cannot agree to publish this manuscript in the current version.