Sulfadiazine Elimination from Wastewater Effluents under Ozone-Based Catalysis Processes

Round 1

Reviewer 1 Report

This paper investigated sulfadiazine elimination by PS and PMS assisted with ozone, which indicated that ozone can enhance the capacities of PS and PMS without other catalysts. Thus, I think this is an interesting study to be used for the in-field wastewater treatment. However, this system needs to be improved to increase its mineralization rate of sulfadiazine. Some specific comments are as follows.

1)     In the text, [ozone] cannot refer to the flow rate of ozone, [ozone] usually refers to the concentration of ozone.

2)     L297, How many duplicates were there in the experiments? In corresponding figures, an error bars should be used to indicate your duplicates.

3)     L305-307, ICP-MS or ICP-OES are employed to analyze elemental concentrations rather than ion concentration. I wonder how the authors uses ICP-MS or ICP-OES to analyze ion concentrations.

4)     The paper should provide the inlet and outlet concentrations of ozone in the experiments to demonstrate the utilization rate of ozone.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

It is a complete study of the degradation of the antibiotic sulfadiazine by advanced ozone-based oxidative processes. In general, it is an exciting work that addresses the evaluation of several process parameters: concentration of antibiotic, persulfate, peroxymonosulfate, pH and various anions present in water. However, the authors did not provide a context for the extensive and complete work. Within the scientific literature, how does the manuscript differ from other authors? Does the present work present novelties compared to so many others in the literature? This context should have been presented in the introduction. The novelties should have been presented clearly and unequivocally in the objectives (last paragraph of the introduction).

 

(1) The manuscript title is too long. Please, improve it. Researchers are busy, and there will always be more articles than time to read. Good titles help readers find your research and decide whether to keep reading. Search engines use titles to retrieve relevant articles based on users’ keyword searches. Once readers find your article, they will use the title as the first filter to decide whether your research is what they want. A strong and specific title is the first step toward citations, inclusion in meta-analyses, and influencing your field. Keep it concise and informative. What is appropriate for titles varies significantly across disciplines. Look at some articles published in your field, and check the journal guidelines for character limits. Aim for fewer than 12 words. Write for your audience. Consider who your primary audience is: Are they specialists in your field, cross-disciplinary, or non-specialists? Entice the reader. Please find a way to pique your readers’ interest and give them enough information to keep them reading. Incorporate important keywords. Consider what about your article will be most interesting to your audience: Most readers come to an article from a search engine, so take some time and include the important ones in your title!

 

(2) Abstract. Please, improve your abstract section. It must be more clear and concise in some aspects. Consider some questions below:

 

Background or Introduction: What is currently known?

Start with a brief, two or 3-sentence introduction to the research area. Why is it important to study the degradation and mineralization of the sulfadiazine antibiotic? Do not copy and paste statements from the Introduction section.

 

Objectives or Aims: What is the study, and why did you do it?

Clearly state the research question you are trying to answer.

 

Methods: What did you do?

 Please explain what you did and how you did it. Include important information about your methods, but avoid the low-level specifics. 

 

Results: What did you find?

Briefly give the key findings of your study. Include critical numeric data (including confidence intervals or p-values).

 

Conclusions: What did you conclude?

Tell the reader why your findings matter and what this could mean for the ‘bigger picture’ of this area of research. Do not copy and paste statements from the Conclusions section.

 

(3) Introduction. Please, see Comments above.

 

(4) Why did the authors place the Results and Discussion section before the Material and Methods section? Scientific writing follows a logic, that is. First, we need to understand the methodology. Considering that the methodology is robust, the reader can then assess the quality of the results that will support the conclusions of the manuscript.

 

(5) I encourage authors to separate the Results and Discussion section into two sections. First, the Results section, then present the Discussion section. In this way, it is much more apparent which information comes from the authors and the literature. It is a more organized way to present your information. Besides, the manuscript is long.

 

(6) The authors must present the experimental error for all figures that present degradation data and kinetic constants. The bar error must be in the figure itself. In the caption of each figure, make clear the number of experimental replicates necessary to reach such results.

 

(7) You presented a series of chemical reactions that support (theoretically) the degradation of the target pollutant. However, these reactions lack the values of kinetic constants (pseudo-first order or second order). With the values of the kinetic constants, it will be possible to evaluate the limiting reactions.

 

(8) The methodology used needs to be better than how it was presented. Please consider expanding the Methodology information and references used in these methodologies. List each consumable with the respective degree of purity (%). Despite making it clear that the reagents used were from Sigma-Aldrich, who were the suppliers of the gases? How pure was each gas? Was synthetic air or oxygen used (and in what purity?) for the TOC analyses? Was medicinal air (or oxygen) used to generate ozone? With what purity degree? Or did you use atmospheric air? Such information is relevant since atmospheric air, despite reducing operating costs, can generate nitric acid in the corona process. This acid can interfere with the advanced oxidative process. Describe in the methodology how the pH adjustment of the reaction medium was made. Was buffer used to control the pH? Which buffer? Did you use sulfuric acid or sodium hydroxide? If so, at what concentrations? How were PS and PMS added to the reaction medium? In solid form or as an aqueous solution? If as a solution, what concentration and how many mL were added to the reaction medium? No relevant information was given regarding the ICP. Was the sample digested? In what way? And the interferences of the analyzes? No bibliographic reference? Operational details of the equipment and consumables used with the degree of purity (%). Which gas was used for the ICP? Which TOC method was used? Which catalyst? What analysis temperature? The authors need to include more information. Mention references to the methodology used. The presented HPLC methodology could be better in the relevant information. Use highly cited scientific articles from analytical chemistry to replicate the presentation format of methodological information for chromatography.

 

(9) Please improve the quality of the figure representing the experimental setup. Place arrows, and use excellent representations for the parts of the experiment (ozone generator, ozone generator feed gas cylinder, NaOH solutions, H2SO4 etc.). There are free stock image banks that can be used.

 

(10) Was the choice of [SDZ], [PS], [PMS] concentrations, ozone flow and pH based on the literature or preliminary studies by the research group? Please adequately justify this set of process parameter choices and cite references where necessary.

 

(11) Please change the ozone dose in the unit L/min to mg/min in all text long. In the methodology, it is appropriate to inform the volumetric flow rate (L/min), but the mass flow rate is more relevant than the volumetric flow rate.

 

(12) The discussions made by the authors in Figures 1-8 are not conclusive without representing the experimental error.

 

(13) You should have compared the results achieved with results from the literature. How much more efficient are PS/PMS/O3 processes than other AOPs for SDZ degradation? Also, make a comparison with the literature for the pseudo-first-order constants.

 

(14) Are the transformation products listed by the authors different from those presented in the literature? Consider other advanced oxidative processes. Could these transformation products be more toxic than the studied antibiotic? Explain based on the literature. These considerations are important because there was no complete mineralization of the pollutant.

 

(15) Please make the Conclusions section simpler and more straightforward. It needs to extract in a general way the main findings of all the work presented in the previous sections. What are the main scientific contributions of this work?

Please hire, preferably, an editor with knowledge of the area. There are errors in the choice of technical terms and textual construction in English.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

1. Put the chapter Methodology before the chapter Results and discussion.

2. Some graphs have not appropriate vsiibility (Fig. 2-4, Fig. 8)

3. In my opinion is better to use present simple tense in formulation like Fig ... shows not showed.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

This paper can be considered for publication.

Author Response

Thank you very much for your efforts.

Reviewer 2 Report

The authors significantly improved the text, as requested in the review process. However, the authors need to include crucial information regarding methodological issues.

 

(1) Kindly request the information on the ozone generator supply gas.

(2) TOC analyses are performed with ultrapure oxygen or synthetic air. The authors reported using nitrogen, but this gas cannot transform the organic matter in the sample into carbon dioxide. I kindly ask for a correction.

(3) They continued to omit information from the TOC analysis method. EPA-approved methods for TOC oxidize organic compounds using either high-temperature combustion (SM 5310B or ASTM D7573) or wet chemical oxidation (SM 5310C or ASTM D4839). High-temperature combustion may occur by collision of a gaseous phase sample with oxygen or by collision with oxygen on the surface of a catalyst. The catalyst-assisted oxidation allows lower temperatures, increasing combustion tube life. Wet chemistry oxidation uses the persulfate ion. Persulfate oxidations are catalyzed by heat, UV irradiation, or a combination of the two. Please report the method and cite the appropriate methodological reference. Was a catalyst used? Which? What was the analysis temperature? Was the detector an NDIR?

(4) Please provide methodological information and citation for IC/MS analyses.

Minor revision required.

Author Response

请参阅附件。

Author Response File: Author Response.pdf