UV Stimulated Manganese Dioxide for the Persulfate Catalytic Degradation of Bisphenol A
, Bo Liu 1, Stanislav R. Stoyanov 2,*, Yiqi Cao 1, Min Yang 1 and Baiyu Zhang 1Round 1
Reviewer 1 Report
Abstract: What are the most commonly produced chemicals worldwide?
Abstract: Any better wording than "a parallel system"? Did the authors study MnO2 and UV?
Abstract: Please omit " but also provide an effective PS catalytic strategy for the treatment of persistent and emerging organic pollutants" because only BPA was successfully treated in this work.
Line 164: 'Synergetic effect' is better changed to 'synergistic effect'.
https://www.google.com/search?q=synergetic+vs+synergistic&rlz=1C1GCEA_enCA864CA864&oq=synergetic+&aqs=chrome.3.69i57j0l3j0i10l2j46i175i199l2j0j46i175i199.11502j0j7&sourceid=chrome&ie=UTF-8
Page 3: Please balance charges on both sides of equation (3).
Page 6: Equations (6) and (7) may not be needed.
Page 6: Equation (9) is speculative. It does not really elucidate the mechanism and pathways of BPA degradation as stated in the abstract.
Line 208: Could the authors elaborate on "Consequently, radical conversion reactions and degradation of BPA also occurred in this process (Eqs. 4–8)". What evidence do they have?
Page 7: What purpose does equation (10) serve?
Lines 216-217: Change 'enhance BPA decomposition' to 'decompose BPA'.
Line 218: It is speculative/liberal for the authors to say, "All the above reactions (Eqs 2–10) could occur in the synergetic process." How do they know it was "all"? Could it be just 'some'?
Line 229: What are those constituent species?
Line 236: What activation can PS bring to the MnO2 surface?
Lines 242-243: Could the authors explain clearly what "the electron binding energies of both Mn and O on MnO2 surface could be increased after UV irradiation [47,48]" has to do with their present work?
Lines 244-245: It is not clear to me how (a) the stimulated surface activity of MnO2 generate –OH groups in the presence of PS, and (b) then facilitate more ROS generation.
Line 251: Change 'leached' to 'leaching'.
Line 252: How could "limited Mn leaching" "indicate that only a small amount of MnO2 was involved in BPA oxidation"?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript presents a research study in which synergetic effect between MnO2, UV and persulfate was shown for the degradation of bisphenol A. The manuscript is rather well written and presented. Original and interesting results were obtained but material and methods section needs more description (e.g. UV and toxicity tests).
Detailed comments:
Line 118 – 119. I would rewrite this sentence by simply stating that the low mineralisation of BPA is probably due to the high and rapid consumption of PS in the UV/PS system.
Line 141 – 142. The acid dissolution of MnO2 is a rather slow process at pH 3.6. I therefore do not think that the dissolution of MnO2 at acidic pH can explain the lower efficiency of the MnO2/PS system. The change in the reactivity of the MnO2 surface and the use of different buffers would more likely explain the role of pH. The analysis of the Mn leached from the MnO2 would make it possible to conclude to a possible dissolution of the MnO2.
Line 279. XRD analysis can also be use to describe the different phases of the MnO2 used in this study. That would help for comparison with other MnO2 phases.
Lines 326 – 346. The toxicity results are not very clear. Interpretation is very hazardous in the absence of data on the effect of pH and buffer. Phosphate buffer can also affect the bioluminescence response. It is necessary to neutralise the samples before toxicity but the use of phosphate buffer should be avoided. Firstly, the authors should state the EC50 value of BPA and compare it to literature values. Secondly, the authors should indicate that they are using an initial concentration of BPA corresponding to 20% of the EC50 after dilution by 4.
Material and methods. It is not clear how the UV treatment was carried out. The authors wrote that the experiments were carried out in glass bottles, but glass absorbs the UV radiation. UV efficiency also depends on the energy of the lamp, the length of the path, the distance between the sample and the lamp, ..... Please describe more precisely the methodology used for the UV treatment.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Recommendation: Minor Revision
Although the authors have used commercially available MnO2 in this study, a detailed study has been carried out for the degradation of BPA. The finding may be useful for researchers in the area of photocatalysis, environmental protection, or material sciences.
- Did the author check the optical properties of MnO2 such as light absorbance and bandgap?
- How about the adsorption capacity of the materials?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
