Preparation of Fe₃O₄/α-MnO₂ Magnetic Nanocomposites for Degradation of 2,4-DCP through Persulfate Activation

Round 1

Reviewer 1 Report

The article discusses the research on SR-AOP in a very interesting and clear manner. I offer the following suggestions to improve the content of the paper:

·         Revise the wording (mainly in the introduction) to reduce sentences that are too long (more than three lines).

·         The most of behaviors in kinetic analysis fit first-order models, although, in other situations (for example, kinetics at pH = 3), the data are obviously inconsistent with this kinetic model. I believe it is important to simply and clearly explain why the kinetics in this situation varies so drastically. Additionally, use the Initial Rate Analysis to determine the reaction order.

·         You stated that the data were adjusted to pseudo-first-order models, however in the reaction mechanism you explain a surface activation provided by electron transport. Considering this appreciation, I believe you should explain what assumptions were made to establish pseudo-first-order kinetics and how this relates to the surface activation of PS.

I recommend reviewing some of these articles that may be of interest to you.

https://0-doi-org.brum.beds.ac.uk/10.1007/s11814-016-0293-1

https://0-doi-org.brum.beds.ac.uk/10.1016/j.jes.2021.12.023

https://0-doi-org.brum.beds.ac.uk/10.1007/s11356-015-5952-y

https://0-doi-org.brum.beds.ac.uk/10.3390/ma15113957

Author Response

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Reviewer 2 Report

This paper investigates preparation of Fe₃O₄/α-MnO₂ magnetic nanocomposites for 2 degradation of 2,4-DCP through persulfate activation.

In sentence where is „2.705 g of FeCl₃•6H₂O“ please use other symbol for multiplication because • you are using as radical. The same is for FeSO₄•7H₂O.

What for were you using HPLC? Because 2,4-DCP you were measuring on spectrophotometer.

Please divide figure 1 on few figures.

You said in the section of optimization „When the proportion of Fe3O4 is further increased, the activation ability of the activator worsens“ but you did not explain why. Please use your chemical knowledge and literature for explaining this effect.

You kinetics show parabolic effect. Figures 4, 5, 6. Did you test your kinetics for other kinetics orders? Please test your kinetics and see what happens.

Why did you not use some design of experiments so that it can help you understand kinetics better? You changed pH, T, catalyst… but with only one at the time. You should check some DoE.

Author Response

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Reviewer 3 Report

Comments to the Authors:

In this manuscript authors prepared Fe₃O₄ magnetic nanoparticles (MNPs)  loaded  α-MnO₂ nanowires using an improved hydrothermal synthesis method combined with an ultrasonic co-precipitation method and the efficiency of the prepared Fe3O4/α-MnO2-activated persulfate (PS) system was tested for degradation of 2,4-dichlorophenol. This research has value for the researchers in the related areas. However, the paper needs improvement before acceptance for publication. My detailed comments are as follow:

1. In the introduction section authors should discuss the individual properties of magnetic nanoparticles and α-MnO₂. For this authors should use the following relevant articles:

a.      doi.org/10.1016/j.colcom.2019.10021

b.      doi.org/10.1007/s11164-020-04165-0

2.The quality of the Figure 1 (a) should be improved. In few figures the label of axis is not properly visible.

3.  In the bar diagram of reusability study error bar is missing.

4. Authors should provide a table of comparison of rate constant with previous studies.

5.  The writing of conclusion section should be improved.

6.  In the electron microscopic images authors should marked the diameter α-MnO₂ and size of the magnetic nanoparticles  

Author Response

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