Zeolitized Clays and Their Use for the Capture and Photo-Fenton Degradation of Methylene Blue
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors This paper reported the preparation of photocatalytically-active MFI-type zeolites, which were characterized and evaluated for the capture and the photo-Fenton degradation of methylene blue (MB) in aqueous solution. Several issues should be carefully adressed. 1 The XRD patterns In Fig. 1 need to be indexed. The XRD pattern of reference ZSM-5 zeolite shoud be test rather than refer to the previous study. 2 TEM observation should be carried out for SYNT-MFI, MTK-MFI, and MONT-MFI, respectively. 3 The phase composition and microstructure of Catalysts after stability test need to be characterized. 4 The catalytic mechanism shoud be discussed in detail, otherwise it will be an experimental report.
Author Response
We would like to thank the reviewer for his/her time and feedback. Our manuscript catalysts-3410321 submitted to Catalysts and entitled “Zeolitized clays and their use for the capture and photo-Fenton degradation of methylene blue” has been revised by incorporating the suggestions made by the reviewer. Our answers are given in the attached PDF, including new figures. We are grateful for the many constructive suggestions.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThis research article deals with the preparation of photocatalytically-active MFI-type zeolites followed by supporting iron oxide nanoparticles. The article could be considered for publication after addressing the following comments:
1. Why did the authors not determine the band gap of the materials?
2. Blank experiments (without H2O2 and light) should be performed.
3. Figire 5(a) can hardly be called as "MB degradation kinetic after 1 hour of adsorption equilibrium under photo-Fenton conditions". Figure 5(a) shows degradation curves or activity of different materials.
4. It is necessary to calculate the kinetic rate constants of photodegradation.
5. The products of MB degradation and/or degree of mineralization of MB should be investigated.
6. The results should be compared with those obtained previously on photocatalysts of a similar nature.
Author Response
We would like to thank the reviewer for his/her time and feedback. Our manuscript catalysts-3410321 submitted to Catalysts and entitled “Zeolitized clays and their use for the capture and photo-Fenton degradation of methylene blue” has been revised by incorporating the suggestions made by the reviewer. Our answers are given in the attached PDF, including new figures. We are grateful for the many constructive suggestions.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsComments to the paper „Zeolitized clays and their use for the capture and photo-Fenton degradation of methylene blue” by Koffi Simeon Kouadio, Ekou Tchirioua and Jérémy Dhainaut
A brief summary
The above paper presents the synthesis of Fe2O3/MFI catalysts using either kaolinite or montmorillonite as aluminium source and as partial Si source. The catalysts were compared to Fe2O3/MFI catalyst prepared by classical method. The prepared samples were characterized by several methods and tested in the photocatalytic degradation of methylene blue using UV-a light. One of the novel catalysts, Fe/MTK-MFI showed better catalytic activity than the catalyst prepared on classical way.
General comments
The manuscript presents detailed characterization of three Fe/MFI samples using adequate methods. The catalysts were applied in a reaction with high environmental relevance and showed good activity and one of them showed very good recyclability. However, I have the following comments that aim to improve the quality of the manuscript.
- I miss the explanation why it was necessary to apply heat treatment to kaolinite and acidic treatment to MTK and to montmorillonite before using them for zeolite synthesis as Al and Si source.
- It should be discussed why the adsorption tests (section 2.2) were carried out on samples without iron oxide particles. If similar adsorption tests were done on Fe/MFI samples, their results should be presented and discussed as well.
- In the introduction, only examples with Fe3O4 catalysts were mentioned. In the present work Fe2O3 particles seem to have similar catalytic activity. This issue should be shortly discussed in the paper.
- Was the product of MB degradation analysed?
Specific comments
- Fig.S1 should be mentioned and briefly discussed in section 2.1.
- It would be useful to add diffraction pattern of MTK before acid treatment to Fig.S1.
- Particle size units are incorrect in lines 111, 114 and 124.
- It would be useful to add N2 physisorption isotherm of MTK before acid treatment in Fig.S3 b, as the result of this isotherm is shown in Table 1 (MTK).
- The isotherms presented in Fig.3 are overlapping. It is necessary to present them vertically shifted, to make all hysteresis loops evident.
- The explanation in lines 159-160 I don’t find well-founded, since all three samples contain mesopores. I find the same problem in the explanation in lines 166-167!
- It would be worth to discuss briefly the possible reason of the difference between qe exp and qe theor for sample SYNTH-MFI (Table 2).
- In line 239, the unit of grain size is not correct.
- In section 3.1, the ratio of weight of MTK or montmorillonite and the volume of HCl solution should be given.
- In section 3.2, the amount of Ludox HS 40 mixed to 1 g of clay should be given.
- It would be interesting to add Na content to Table S2. Molar amount of Na is expected to be equal of molar amount of Al incorporated in the zeolite framework (AlF). The difference of total amount of Al and AlF gives the amount of extra-framework Al (EFAl).
- The dealumination of the catalysts found during MB degradation is discussed in lines 219-226. It should be mentioned that Ref. [25] tested the hydrothermal stability of ZSM-5 in distilled water and not in acidic media.
- In section 3.4, the digestion method used before ICP analysis and the description of ICP-OES equipment is missing.
- To section 3.5: Was the volume of aliquots sampled regularly, negligible compared to the initial volume (38 mL)?
- The kinetic equation in line 307 is not correct, must be corrected.
- In section 3.6, „similar conditions” should be explained more. Were fresh Fe/MFI samples used in photocatalytic tests? I.e. did it start with a new adsorption test?
- In section 3.6, the method applied for testing the recyclability should be given.
- Abbreviation MTK should be added to line 367.
- In Fig.S1 Kaolinite in the figure legend is mistyped.
- In figure capture of Fig.S5, the meaning of qe and qt should be added.
- In figure capture of Fig.S6, colour of the reference Fe2O3 is not correct. Parentheses for colours should be added.
- In the figure capture of Fig.S7, the scale bar for (b) is not correctly given.
Author Response
We would like to thank the reviewer for his/her time and feedback. Our manuscript catalysts-3410321 submitted to Catalysts and entitled “Zeolitized clays and their use for the capture and photo-Fenton degradation of methylene blue” has been revised by incorporating the suggestions made by the reviewer. Our answers are given in the attached PDF, including new figures. We are grateful for the many constructive suggestions.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsIn this work, an economical synthesis method was used to produce ZSM-5 zeolites and their supporting iron oxide nanoparticles starting from clays (metakaolin and montmorillonite) as an alternative source of Si and Al. Some characterizations were done to analyze the structure and morphology. The capture and the photo-Fenton degradation of methylene blue in aqueous solution were used to evaluate its absorption and photocatalytic properties. This work has some novelty, however, some issues should be addressed prior to considering acceptance.
1. As Fe3O4/ZSM-5 zeolite had been used in the MB degradation. It is needed to clarify the difference from previous work and the innovative points of the work in the introduction.
2. The MTK-MFI and MONT-MFI firstly appear without any illustration in the Line 94, related descriptions about these samples should be provided.
3. The influence of homogeneous photo-Fenton catalytic performance should be added by using equal quantity of leached Fe irons.
4. Why does the presence of residual montmorillonite clay significantly reduce the loading content of iron in Fe/MONT-MFI?
5. More photocatalytic degradation experiments with control samples are considered to add, such as MTK-MFI, MONT-MFI in H2O2/UV systems, the H2O2 systems without UV.
6. Why was an equilibrium reached within 10 minutes with any catalyst in the Figure 5a? Why didn't the reaction continue? The change of H2O2 concentration could be detected during the process.
Author Response
We would like to thank the reviewer for his/her time and feedback. Our manuscript catalysts-3410321 submitted to Catalysts and entitled “Zeolitized clays and their use for the capture and photo-Fenton degradation of methylene blue” has been revised by incorporating the suggestions made by the reviewer. Our answers are given in the attached PDF, including new figures. We are grateful for the many constructive suggestions.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsI believe that a more correct and specific response to this comment (No. 6) would be to present the data in Table. More specifically, this Table should show a comparison of the results obtained by the authors of the manuscript with those obtained earlier in other studies. This would enhance the scientific significance of the manuscript.
After addressing all the commnets I originally proposed, the manuscript could be accepted for publication.
Author Response
Comment: I believe that a more correct and specific response to this comment (No. 6) would be to present the data in Table. More specifically, this Table should show a comparison of the results obtained by the authors of the manuscript with those obtained earlier in other studies. This would enhance the scientific significance of the manuscript. After addressing all the comments I originally proposed, the manuscript could be accepted for publication.
Reply: Thank you for your comment. No. 6 comment was “The results should be compared with those obtained previously on photocatalysts of a similar nature.” As suggested by Reviewer 2, a comparative Table has been added in ESI and is discussed in the revised manuscript. Please see the attached PDF for full details.
Author Response File: Author Response.pdf
