Reductive Degradation of N-Nitrosodimethylamine via UV/Sulfite Advanced Reduction Process: Efficiency, Influencing Factors and Mechanism

Round 1

Reviewer 1 Report

A very good presentation of your work. 

Author Response

Thank you for your comments

Reviewer 2 Report

It is a good work, and may be published. However, it would be better if the authors can determine the degradation products or paths experimentally.

good

Author Response

Thank you for your comment. The degradation products of NDMA by UV/sulfite ARP were investigated in our study and the results were showed in part 3.6 . We will confirm the mechanism of the reaction through experimental means in subsequent research.

Reviewer 3 Report

The authors present an interesting scientific study of the reductive degradation of N-nitrosodimethylamine by UV/sulfite advanced reduction process. The work should be on the interest of the readers of the journal. Generally proposed manuscript contains very important scientific approach to the problem. The manuscript is well written and structured. In my opinion, this paper can be published after a minor revision in such aspects:

GENERAL COMMENTS

1. Authors used the wrong way of reference citation in the text of manuscript (See: Instruction for Authors)

2. Authors used the wrong way of reference description in Reference section (See: Instruction for Authors);

3. The including of a scheme of technological system would significantly facilitate understanding of the report idea for readers

4. Manuscript needs a smooth correction of its editorial form

DETAILED COMMENTS:

Abstract:

Line 12: ARPs – abbreviation should be explained

Line 18: What kinetic order of chemical reaction was observed?

Materials and method:

Line 91: I do not understand what was “certain concentration”.

Line 98: Was the N₂ concentration determined?

Results:

Line 129: What order: zero, first, second reaction was observed? What method was used for reaction order determination?

Line 138: What is meaning of “DO” abbreviation? Abbreviation explanation is omitted. The rate constant is usually marked as “k”, capital “K” letter is used for equilibrium constant in general chemistry. I suggest mentioned change in whole manuscript.

Line 141 - 143: Citation of reference should be added.

Line 152 – 153: Was the speciation of sulfite species analyzed? After sentence about species distribution the reference should be added.

Fig 2., Fig 3, Fig 4: Plats are impossible for proper reading. Legend of plots is covered. In my opinion the inserted figure should be shifted to the right side of general figure.

Line 161: I do not understand the meaning “extensive electrons”.

Line 163: After “Previous studies” the reference citation should be added.

Line 214: “The Similar” should be changed to “The similar”. After “Botlanguduru” the citation should be added.

Line 231 – 233: The sentence should be supported by reference citation

Line 237: Figure 5 – figure caption: On the presented picture I can’t find effect on rate constant.

Line 245: What is meaning of “MA” abbreviation?

Line 273: Are Authors sure that Eq.1 starts from ground state NDMA? Is the ground state NDMA a radical?

Line 277: Please check the stoichiometry coefficient in Eq.4. In my opinion the formula of the reaction is not balanced (number of oxygen atom).

The same comment to the all reaction formulas in the whole 3.7. Chapter. Eqs. 5,6,13 – balance of hydrogen atoms

Language of manuscript is understandable, but contains some mistakes, generally as a typing errors. All manuscript text should be examined in this context.

Author Response

The authors present an interesting scientific study of the reductive degradation of N-nitrosodimethylamine by UV/sulfite advanced reduction process. The work should be on the interest of the readers of the journal. Generally proposed manuscript contains very important scientific approach to the problem. The manuscript is well written and structured. In my opinion, this paper can be published after a minor revision in such aspects:

GENERAL COMMENTS

1. Authors used the wrong way of reference citation in the text of manuscript (See: Instruction for Authors)

Answer: Thank you for your comment. It is our negligence that used the wrong way of reference citation in the text. We have carefully revised the whole text to ensure that all references are cited in numerical order. The revised references are highlighted in red in the manuscript.

2. Authors used the wrong way of reference description in Reference section (See: Instruction for Authors).

Answer: Thank you for your comment. It is our negligence that used the wrong way of reference description in Reference section. We have carefully revised the Reference section to ensure that all references are described in right format. The revised references are highlighted in red in the Reference section.

3. The including of a scheme of technological system would significantly facilitate understanding of the report idea for readers

Answer: Thank you for your comment. We feel sorry that we are unable to add a flowchart of technological system considering the length limitation of the manuscript. However, we think we have provided a very detailed introduction of technological system in the section of “Materials and method”.

4. Manuscript needs a smooth correction of its editorial form

Answer: Thank you for your comment. The editor has already helped us modify the editorial format of the article.

DETAILED COMMENTS:

Abstract:

Line 12: ARPs – abbreviation should be explained

Answer: Thank you for your comment. It is our negligence that forgets to explain the abbreviation of ARPs in abstract. We have carefully revised the mistake. The full name of ARPs is highlighted in red in the abstract.

Line 18: What kinetic order of chemical reaction was observed?

Answer: Thank you for your comment. The degradation of NDMA by UV/sulfite ARP followed first pseudo-first-order kinetics. It is our negligence that omits the “first” in the article. We have carefully revised the whole article to prevent similar error happening again.

Materials and method:

Line 91: I do not understand what was “certain concentration”.

Answer: Thank you for your comment. The initial concentration of NDMA was 0.1 mM. It is our negligence that forgets to describe the accurate concentration of NDMA. We have carefully revised the mistake and the accurate concentration is highlighted in red.

Line 98: Was the N₂ concentration determined?

Answer: Thank you for your comment. It is difficult to quantitative detect the concentration of nitrogen under our laboratory condition.

Results:

Line 129: What order: zero, first, second reaction was observed? What method was used for reaction order determination?

Answer: Thank you for your comment. The degradation of NDMA by UV/sulfite ARP followed first pseudo-first-order kinetics. It is our negligence that omits the “first” in the article. We have carefully revised the whole article to prevent similar error happening again.

Line 138: What is meaning of “DO” abbreviation? Abbreviation explanation is omitted. The rate constant is usually marked as “k”, capital “K” letter is used for equilibrium constant in general chemistry. I suggest mentioned change in whole manuscript.

Answer: Thank you for your comment. DO is the abbreviation for dissolved oxygen. It is our negligence that omits the explanation when it first appeared. We have carefully revised the mistake and full name of DO is highlighted in red. We agree with your suggestion that rate constant should mark as “k”. We have carefully revised the rate constant in whole manuscript and highlighted them in red.

Line 141 - 143: Citation of reference should be added.

Answer: Thank you for your comment. The reference is added.

Reference: Jung, B.; Nicola, R.; Batchelor, B.; Abdel-Wahab, A. Effect of low- and medium-pressure Hg UV irradiation on bromate removal in advanced reduction process. Chemosphere. 2014, 117, 663-672.

Line 152 – 153: Was the speciation of sulfite species analyzed? After sentence about species distribution the reference should be added.

Thank you for your comment. We did analyze the different sulfite species and the reference is added.

Reference: Chu Y.Y.; Xu, L.L.J.; Gan, L.; Qiao, W.C.; Han, J.G.; Mei, X.; Guo, H.; Li, W.; Pei, C.; Gong H.; Guo, X.W. Efficient destruction of emerging contaminants in water by UV/S(IV) process with natural reoxygenation: Effect of pH on reactive species. Water Res. 2021, 198, 117143.

Fig 2., Fig 3, Fig 4: Plats are impossible for proper reading. Legend of plots is covered. In my opinion the inserted figure should be shifted to the right side of general figure.

Answer: Thank you for your suggestion. We agree with your opinion. All of the inserted figures are shifted to the right side of general figure.

Line 161: I do not understand the meaning “extensive electrons”.

Answer: Thank you for your comments. The meaning of “extensive” in this place should be “more”. We have revised the expression in a more appropriate way.

Line 163: After “Previous studies” the reference citation should be added.

Answer: Thank you for your comment. The reference is added.

Reference: Fischer, M.; Warneck, P. Photodecomposition and photooxidation of hydrogen sulfite in aqueous solution. J Phy Chem. 1996, 100, 15111-15117.

Line 214: “The Similar” should be changed to “The similar”. After “Botlanguduru” the citation should be added.

Answer: Thank you for your comment. We have revised the incorrect format and added the citation.

Reference: Botlaguduru, V.S.V.; Batchelor, B.; Abdel-Wahab, A. Application of UV-sulfite advanced reduction process to bromate removal. J Water Proc Eng. 2015, 5, 76-82.

Line 231 – 233: The sentence should be supported by reference citation

Answer: Thank you for your comment. The reference is added.

Reference: Chu Y.Y.; Xu, L.L.J.; Gan, L.; Qiao, W.C.; Han, J.G.; Mei, X.; Guo, H.; Li, W.; Pei, C.; Gong H.; Guo, X.W. Efficient destruction of emerging contaminants in water by UV/S(IV) process with natural reoxygenation: Effect of pH on reactive species. Water Res. 2021, 198, 117143.

Line 237: Figure 5 – figure caption: On the presented picture I can’t find effect on rate constant.

Answer: Thank you for your comment. It is our negligence that forgets to add the figure of rate constant. We have revised the figure 5.

Line 245: What is meaning of “MA” abbreviation?

Answer: Thank you for your comment. MA is the abbreviation for methylamine. It is our negligence that forgets to use the full name of methylamine when it first appeared. We have carefully revised this mistake.

Line 273: Are Authors sure that Eq.1 starts from ground state NDMA? Is the ground state NDMA a radical?

Answer: Thank you for your comment. It is our negligence that adds a symbol representing free radical on the NDMA molecule. We have carefully revised the mistake.

Line 277: Please check the stoichiometry coefficient in Eq.4. In my opinion the formula of the reaction is not balanced (number of oxygen atom).

The same comment to the all reaction formulas in the whole 3.7. Chapter. Eqs. 5,6,13 – balance of hydrogen atoms

Answer: Thank you for your comment. Yes, you are right. The formula of the reaction is not balanced. It is our negligence that forgets to carefully check the reaction formulas. We have carefully revised the reaction formulas in Eq.4,5,6,13.

The revised reaction formulas :

(CH₃)₂NNO + hv→•(CH₃)₂NNO^-                                          (3)

• (CH₃)₂NNO^- +H₂O + e_aq^-→(CH₃)₂NH + NO₂^- + H⁺    (4)

(CH₃)₂NH + H⁺ + e_aq^- → CH₃NH₂ + •CH₃                                     (5)

CH₃NH₂ + H⁺ + e_aq^- → NH₃ + •CH₃                                          (6)

• NO + e_aq^- + 2H₂O → NH₂OH + 2OH^-   (13)

Author Response File: Author Response.pdf