A Review of Activation Persulfate by Iron-Based Catalysts for Degrading Wastewater

Round 1

Reviewer 1 Report

Details of activation of persulphates using UV,Ultrasound other energy means need to be cited.

Motivation behind choosing the Fe based catalyst and persulphates need to explain

There are few data about the mechanism, kinetics and product formed using this activation method

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors, the article is very interesting and novel, however the Tables that you put in the review are very poor, you should look for more works related to the topic you are discussing and add them. I leave several recommendations to be considered in the new review of the article.

Introduction

- Line 28, verify this sentence, since the hydroxyl radical is and will be the molecule with the highest oxidation potential (2.8 V) after fluorine (3.0 V). It is recommended to discuss this sentence and base it with other papers.

2. Activation persulfate by various iron-based catalysts

- You must add at least 5 more papers to Table 1, it is too poor for a review.

2.2 MeFe2O4 combined with the carrier

- Line 71, place the meaning of the acronym "rGO" and "GO" in line 77.

- They must add at least 6 more papers to Table 2.

2.3 Activation persulfate by Fe0

- They must add a minimum of 4 more papers to Table 3

2.4 Fe3O4

- They must add at least 5 more papers to Table 4.

4.1 Photocatalytic activation

- Line 242 and 243. Reaction 12 and 13, the molecular formula of the hydroxyl radical is wrong.  

- Line 263. It says "Table.5" and it should be "Table 5." 

- They must add at least 5 more papers to Table 5.

4.2 Piezoelectric catalytic activation

- Line 284. There is a letter "s" where it shouldn't be.

- They must add at least 5 more papers to Table 6. 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Abstract:

1. Line #8: “With the development of modern industry..” Please reconstruct the sentence.
2. Line #11: “With advantages and disadvantages..” Please reconstruct the sentence.

Introduction:

1. Line #19: “The use of organic matter..” The sentence is incomplete.
2. Line #28: “Sulfate radical ions not only..” The formation of water and CO₂, is it organic compound dependent? Or it can convert any compound to H₂O and CO₂?
3. Line #30: “It can also be applied..” Please clarify this sentence.
4. Line #36: “The advanced oxidation technology..” What is meant by advanced oxidation technology of persulfate was introduced?
5. The introduction needs more detailed discussion on the persulfate technology and its various application on water decontamination processes.

Activation persulfate by various iron-based catalyst:

1. Line #47: What kind of secondary pollution is generated? Please discuss.
2. Line #54: “Taking CuFe₂O₄ as an example..” Please clarify the sentence.
3. Line #57: “G. Xian comprehensively compared..” This paragraph needs further discussion.
4. Line #64: “It can be seen from the table..” What is meant by the effect is slightly worse?
5. Table 1: It is stated in Line #62, that in table 1 effect of activated PS/PMS is shown in “different kinds of wastewater”. However, the table 1 shows only one pollutant in each case. Were the studies performed on a single pollutant or on different wastewater? Please clarify.
6. Line #69: “As mentioned earlier, the carrier recombination..” Please specify where it was discussed.
7. Line #72: “After combination with the carrier..” This sentence needs clarification.
8. Fig 1 &2: Are these figures created or copied from. Please mention.
9. Table 2: It is stated in Line #91, “different kinds of wastewater”. However, the table 2 shows only one pollutant in each case. Were the studies performed on a single pollutant or on different wastewater?
10. Line #127: “Table 3 shows the degradation..” Please change the words “Different kinds of wastewater”.
11. Line #142: “He et al. pointed out..” Please reconstruct the sentence.
12. Line #145: “Fig 8 shows the SEM..” When a figure is given, its significance should also be included.

Comparison of the performance of different iron-based catalyst:

1. Fig. 9: Are model compounds same for all these studies? If not, then how can they be compared on the basis of time taken and % degradation?
2. Line #165: “In the degradation of Wastewater..” What is meant by wastewater? All the previous tables given; the studies have been done on a single model compound. No results have been provided with wastewater.
3. Fig. 9: This section does not make sense if they are not applied to the same model compound or similar wastewater assays.
4. Line #185: “The first group of materials..” What type of pollutant is described here? Please mention clearly.
5. Line #188: “By increasing the content of rGO..” This sentence does not make any sense. Please reconstruct.
6. Section 3.2: This section essentially is detailing the same information that is already given in the Fig 9. with some additional details. This section needs to provide more critical evaluation of the processes under consideration.

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 4 Report

In their work, the authors have briefly reviewed the role of various iron-based catalysts in the activation of persulfate.
The manuscript should be reviewed taking into consideration the following comments :

-Line 29-30, CO2 is not an environmentally friendly product!!
-Authors are invited to add a paragraph about the synthesis techniques of such catalysts
-In All tables, it is recommended to add the number of cycles of each catalyst and also the technique used to synthesize the catalyst
-Some tables need to be developed (Table one for example)
-Equation 2 is not balanced
-What are the costs of synthesis and applications of such catalysts
-It is preferred to add a table summarizing the advantages and disadvantages of such catalysts to be clear to the reader.‎

Author Response

Dear Editor and Applied Sciences Reviewer,
Recently we received revision request from Applied Sciences for our submitted manuscript (ID: applsci-1463413) entitled “A review of activation persulfate by iron-based catalysts for degrading wastewater” for publication in Applied Sciences. Following reviewer’s comments and suggestions, we have made point by point response to the reviewer and editor’s comments and concerns (mark up using the “Track Changes” function and highlighted in yellow) as following:

Reviewer #4: In their work, the authors have briefly reviewed the role of various iron-based catalysts in the activation of persulfate. The manuscript should be reviewed taking into consideration the following comments: Question 1 Line 29-30, CO2 is not an environmentally friendly product!!

Response: Thanks for the referee’s suggestion. We mean that CO2 is almost nontoxic compared with organic pollutants of wastewater before degradation. Sorry for unclear expression. CO2, which is often regarded as the most important greenhouse gas, is really not an environmentally friendly product. We strongly agree with the reviewer. We have deleted the “environmentally friendly”. Please see Line 38. Sorry for this mistake.

Question 2 Authors are invited to add a paragraph about the synthesis techniques of such catalysts.

Response: We thank reviewer very much for pointing this out. We have added five paragraphs about the synthesis techniques of such catalysts. Please see Line 62-73. Sorry for this mistake.

Question 3 In All tables, it is recommended to add the number of cycles of each catalyst and also the technique used to synthesize the catalyst.

Response: We thank reviewer very much for pointing this out. We have added the number of cycles of each catalyst and also the technique used to synthesize the catalyst in the Table 1-6. Please see the tables of the revised manuscript. Sorry for this mistake.

Question 4 Some tables need to be developed (Table one for example).

Response: We thank reviewer very much for pointing this out. We have added 4-6 new literatures to the Table 1-6. Please see the tables of the revised manuscript. Sorry for this mistake.

Question 5 Equation 2 is not balanced.

Response: We thank reviewer very much for pointing this out. Equation 2 is balanced now. Please see Line 150. Sorry for this mistake.

Question 6 What are the costs of synthesis and applications of such catalysts?

Response: We thank reviewer very much for pointing this out. This is an interesting question. Unfortunately, it is different that the types, the brands and the dosages of the raw materials for the synthesis of such catalysts, also for the organic pollutants of degradation. By the way, we reviewed the research of other researchers instead of our experiments. It's not that we don't want to do it. It is very difficult for us to accurately and objectively count the costs of synthesis and applications of such catalysts reported in the literature. We’re terribly sorry.

Question 7 It is preferred to add a table summarizing the advantages and disadvantages of such catalysts to be clear to the reader.

Response: Thanks for the referee’s suggestion. We have added Table 7 summarizing the advantages and disadvantages of such catalysts. Sorry for this mistake.

Finally, we are very grateful to the editor and our reviewer for valuable comments and great suggestions. We thank you very much in advance for considering our work for publication in Applied Sciences.

Sincerely yours,

Keke Zhi, Ph.D, lecturer,
Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The manuscript is revised accordingly and it is satisfactory. The manuscript can be accepted in its current form.

Reviewer 4 Report

The authors have correctly answered the asked comments, the revised manuscript can be then accepted for publication.