Application of Unconventional External-Field Treatments in Air Pollutants Removal over Zeolite-Based Adsorbents/Catalysts

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The review is interesting to know what it is done in the field and keep on improving the catalytic behaviour of zeolite-based catalysts., providing a good guide for different treatments. On this way it is easy to fix some parameters in function of the objectives of the new research. They describe the importance of the parameters for synthesis and further treatments, and how it impacts on the adsorbent and catalytic properties of zeolites to be employed as adsorbents/catalysts for decontamination of air pollutants, focused on NO_x and VOCs.

However, the introduction is scarce for the review, why zeolites are used should be commented, as well as its properties (crystal defects, porosity, acidity) and how it relates to the external-field treatments to the zeolite and moreover to co-catalysts based on zeolites. .

 

 

The manuscript could be improved following some suggestions I made above.

·         Title: add external-field treatments, as it is written some substantive is missing after external-fieled.

·         MV is used during all the manuscript except for the first time (12 times), line 70: microwave (MW), Maybe MV should be MW but if MV is not microwave it should be clarified.

·         A list of abbreviations is useful.

·         As it is a review, I consider appropriate to list the sections of the review, before or at the end of the introduction. With bullets if it is possible.

 

1.       Introduction

·         Line 49. Typo: provides for provided

·         You can explain a little more about the contaminants where they are produced and if the suggested materials are thought to be used as catalyst on the source of pollution, therefore these materials could be subjected to extreme conditions (high temperatures of the stream, poisonous species, or the mass flow of the stream). Definitely, in which systems are placed the type of catalyst introduced in this review?

·         Can you introduce a little more other zeolite-based catalysts? Adding Pt is the only way to catalyse these reactions? Are there more affordable and efficient combinations? Why Pt if, actually, the current trend is lower the use of PGM-based catalyst because they are scarce and expensive? Later on the text you introduce other metals, as iron, copper or nickel, there should be a brief introduction of the selection of this transition metals before, as it is done for Pt.

·         A little introduction of zeolites would be interesting, some aspects about the synthesis, why each structure is better for each process (textural properties, acidity and surface groups), the conventional synthesis, some strategies that are being developed now…. (give a context about the properties are you talking about during the review)

 

·         Line 99. Can you add a usual range of working temperatures?

·         Line 106. If it is possible, list the steps using bullets. As a suggestion, a scheme would clarify the text.

·         Line 159. Rephrase the sentence: Wang et al.[39] modified NaY zeolite using non-thermal plasma, and found that the pore size, specific surface area and pore volume grow significantly from 0.62 nm, 222.14 m2/g, 0.19162 cm3/g to 0.72 nm, 618.09 m2/g, 0.36 cm3/g, respectively, accompanied with the greatly increasing adsorption capacity of 167% for naphthalene.

·         Line 170. Figure 1. It is preferred to compare images with the same magnification to easily see the different sizes. In fact, the particles treated by plasma are smaller than it seems.

·         Line 170. Figure 1. Explain the nomenclature 10-P, 20-P and 30-P, the same for C. What it means? Does it refer to the metal loading? And the same for alfa and gamma oxygen, I suppose that gamma is the lattice oxygen , what about alfa?

·         Line 252. How decrease the lifetime of the catalyst when it is continuously exposed to plasma regarding the two-step system?

·         Line 459. Typo. mesopoles by mesopores. If not, explain it.

·         Line 536. During all the review it is focused on the treatment of zeolite-based catalysts for the abatement of air pollutants, but on this section the point is more related to synthetic characteristics, and it is a little bit repetitive. It could be summarized in order to follow the scheme of the review.

·         Line 617. Figure 8.b and c. the image seem that the particle size is larger at lower times of synthesis. This should be commented on the text. Moreover, as it is compared the results of hydrothermal and MW synthesis there should be a SEM micrograph to also compare the morphological properties or a comment in the text comparing it to the same crystal structure but obtained by hydrothermal synthesis.

·         Line 633. One of the more important characteristics of zeolites is their tuneable porosity, I think it could be a little more explained. It is not only the specific surface are but the porosity is the key of the selectivity and conversion results.

·         This section is totally different from the above sections. Therefore, it should be clarified why, and maybe, this section is more suitable to be the first one, because it introduces the most common synthesis of zeolites and some characteristics that made them suitable for adsorption and catalysis processes.

·         Line 722. Figure 9C-F or Figure 9E-F?

·         Line 727. There are not figures 9 G and I

 

·         Prospect section: it should be a little more discussed the current actuations regarding the external-field treatments. which are the next steps? How can this techniques improve even further the catalysts? Which are the limitations to scale this to industrial applications and how could it be solved or which points require more research to finally apply this technologies to the industry. 

Comments on the Quality of English Language

There are some typos, listed in the comments and suggestions for authors. 

the text should be thoroughly reviewed to avoid comprehension errors, incomplete sentences, and typos; but also to improve the overall understanding of the text. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for the opportunity to read your article and act as a reviewer. The paper is devoted to the important and relevant topic of application of unconventional processing methods for activation of zeolite materials used for air purification from NOx and VOCs.

In general, the paper makes a good impression and contains valuable information on the potential of non-thermal plasma and microwave radiation to improve the properties of zeolites. However, the paper needs some revision for publication in the journal.

1.    There are many typos and stylistic errors in the text - careful editing is required.

2.    Insufficient attention is paid to the energy efficiency of processing methods. Comparative analysis with traditional methods is not given.

3.    There is a lack of systematic comparison of non-thermal plasma and microwave efficiencies for different types of zeolites.

4.    It is necessary to provide a comparative table with the parameters of zeolites that are required for similar functional properties (cell parameters, density, porosity, crystallite size, etc.).

5.    I would also like to see a separate block on synthesis methods, what synthesis methods will be applied for zeolites (MW, hydrothermal, sol-gel, precipitation, etc.). (10.1016/j.ceramint.2021.10.164, 10.1016/j.jeurceramsoc.2022.02.007, 10.1016/j.net.2022.04.005)

Comments on the Quality of English Language

-

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I agree with all the changes, and the responses. Thank you for your efforts.

Just perform a final proofreading of the document to correct minor typos. 

Comments on the Quality of English Language

^{the quality of English has been improved, now is more affordable and clear, i only suggest to correct some typos, but nothing related to  grammar or syntax issues.}