Experimental Study on the Treatment of Landfill Leachate by Electro-Assisted ZVI/UV Synergistic Activated Persulfate System
Round 1
Reviewer 1 Report
The manuscript, despite its aim in a subject of crucial importance for the environment, lacks scientific novelty and discussion. There are previous works on the use of ZVI in the removal of organic compounds (https://doi.org/10.1021/ie400387p).
The authors only describe the results, without a phenomenological discussion of the process. Furthermore, more in-depth characterization studies of both the sample and the catalyst are needed in order to be able to propose the mechanism of the process.
Author Response
On behalf of my co-authors, we would like to thank you very much for allowing us to revise our manuscript; Thank you for your positive and constructive comments and suggestions on our manuscript entitled "Experimental Study on the Treatment of landfill leachate by electro-assisted ZVI/UV synergistic Activated persulfate System."We studied your comments carefully and marked the changes in red on the paper. We have tried to revise our manuscript according to the comments. I have attached a revised version that we would like to submit for your consideration. We want to thank you again for your comments on our paper.
Our research is a further improvement on using ZVI to remove organic compounds. Using ZVI alone to activate PS has obvious advantages but also inevitable disadvantages. Once ZVI is depleted, the reaction efficiency will slow down significantly. Continuing to add ZVI will increase the cost and create a large amount of metal sludge. In our study, electrochemical oxidation was introduced to assist. Fe2+ can be continuously regenerated on the cathode surface, reducing the amount of ZVI and secondary pollution caused by the accumulation of metal sludge.
Considering your suggestion, we have made a significant revision to the Discussion section of the paper and supplemented the free radical identification test. We performed first-order kinetic fitting of COD degradation data under different conditions. We further analyzed the synergy of electro-assisted ZVI/UV/PS to explore this system's mechanism for landfill leachate treatment. Unfortunately, we cannot further characterize the catalyst due to the impact and time constraints of the current outbreak. Hope to get your understanding.
Thanks again for your comments and suggestions.
Reviewer 2 Report
Article entitled "Experimental study on the treatment of landfill leachate by
electro-assisted ZVI/UV synergistic activated persulfate system" deals with investigation of treatment efficacy of the electro-assisted (zero-valent iron) ZVI/ UV synergistic activated PS system to treat landfill leachate. The research idea is not innovated. The impact is not clear.
Author Response
Dear Reviewer
On behalf of my co-authors, we would like to thank you very much for allowing us to revise our manuscript; Thank you for your positive and constructive comments and suggestions on our manuscript entitled " Experimental study on the treatment of landfill leachate by electro-assisted ZVI/UV synergistic activated persulfate system." We studied your comments carefully and marked the changes in red on the paper. We have tried to revise our manuscript according to the comments. I have attached a revised version that we would like to submit for your consideration. We want to thank you again for your comments on our paper.
UV-activated PS is easy to handle, safe, and non-toxic. However, due to the high turbidity and chromaticity of the leachate, UV light cannot enter the leachate to activate PS. Iron has apparent advantages as a cheap and readily available PS catalyst, but Fe2+ cannot be regenerated in the Fe2+/PS system, and once exhausted, the reaction will stop quickly. In our electrically assisted ZVI/UV/PS system, the above problems are avoided, and the stability and processing effect of the system is improved. Considering your suggestion, we have significantly revised the Discussion section of the paper and supplemented the free radical identification test. We performed a first-order kinetic fit to the COD degradation data under different conditions. We further analyzed the synergistic effect of electro-assisted ZVI/UV/PS and explored the mechanism of this system in landfill leachate treatment.
Thanks again for your comments and suggestions.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The electro-assisted ZVI/UV/PS synergistic process was used to treat landfill leachate, the data amount was medium, but the depth of research was deficient. A major revision could be given in this status.
1. The font of formula should be unified, normal? or italic?
2. Many format errors should be revised in the main text, which should be unified to English format.
3. Figure 7, horizontal axis, Wavelight? It should be Wavelength.
4. Figure 6, there lacked deep discussion for the synergistic effect for electrically assisted UV/ZVI/PS, please improve this part. The authors should improve the discussion part for the whole paper, otherwise this paper looks like an experimental report.
5. There lacked mechanism investigation, include radical scavenging test.
Author Response
Dear Reviewer
On behalf of my co-authors, we would like to thank you very much for allowing us to revise our manuscript; Thank you for your positive and constructive comments and suggestions on our manuscript entitled "Experimental study on the treatment of landfill leachate by electro-assisted ZVI/UV synergistic activated persulfate system." We studied your comments carefully and marked the changes in red on the paper. We have tried to revise our manuscript according to the comments. I have attached a revised version that we would like to submit for your consideration. We want to thank you again for your comments on our paper.
First, we apologize for several formatting errors (including font, spelling, etc.). We have corrected the above and hope to be forgiven. Secondly, based on your suggestion, we have made a significant revision to the Discussion section of the paper, performed first-order kinetic fitting of the COD degradation data under different conditions, and further explored the synergistic effect of electro-assisted ZVI/UV/PS. At the same time, the radical identification test was also supplemented to examine further this system's mechanism in treating landfill leachate.
Thanks again for your comments and suggestions.
Author Response File: Author Response.pdf
Reviewer 4 Report
This paper on “Experimental study on the treatment of landfill leachate by electro-assisted ZVI/UV synergistic activated persulfate system” reports the positive effect of combining electro assisted UV and ZIV on persulfate methodologies as an interesting advanced oxidation process very useful for the treatment of wastewater.
The paper is well structured and discussed. The hypothesis are well discussed and the conclusions seems reasonable and well supported and in overall it deserves publication as it is.
Some aspects that could have also been discussed for further improvement:
11. In the analysis of wastewater characteristics, it is true that a decrease in aromaticity and therefore toxicity of wastewater seems to be obtained. I wonder if the by-products obtained by partial oxidation could be of similar toxicity characteristics in the same way that occurs when, for example, ozonization. Is it possible to state that the toxicity of byproducts after oxidation is lower?
22. The overall results are promising. The question is: can the process be used in a large scale for wastewater treatment. Is it economically viable? Or is it only of interest in the case of highly concentrated leachates?
Author Response
Dear Reviewer
On behalf of my co-authors, we would like to thank you very much for allowing us to revise our manuscript; Thank you for your positive and constructive comments and suggestions on our manuscript entitled "Experimental study on the treatment of landfill leachate by electro-assisted ZVI/UV synergistic activated persulfate system." We studied your comments carefully and marked the changes in red on the paper. We have tried to revise our manuscript according to the comments. I have attached a revised version that we would like to submit for your consideration. We want to thank you again for your comments on our paper.
Considering your suggestion, we have revised the paper's Discussion section and added aggressive recognition tests. We performed first-order kinetic fitting on COD degradation data under different conditions, and we further analyzed the synergistic effect of electro-assisted ZVI/UV/PS to explore the mechanism of this system in landfill leachate treatment. We then calculated the energy consumption based on your comments, and the final calculation was satisfactory. But at the same time, affected by the epidemic, the toxicological analysis of water samples before and after treatment cannot be carried out in the short term. I hope to have your forgiveness.
Thanks again for your comments and suggestions.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript has been corrected and can be published.
Reviewer 3 Report
This paper can be accepted now.
