Hydrodechlorination of Different Chloroaromatic Compounds at Room Temperature and Ambient Pressure—Differences in Reactivity of Cu- and Ni-Based Al Alloys in an Alkaline Aqueous Solution

Round 1

Reviewer 1 Report

Owing to the fact that the submitted for consideration manuscript is review-article, the authors shoud complete their reference section with important works by other authors devoted to the sam efield. Moreover, the experimental desigh is carried out again under the mild experimental conditions. For, instance reference [x] and the cited literature sources therein.

[x] Heptachlorepoxides: theoretical versus experimental study of the embedded samples in the matrixes of organic crystals
Bojidarka Ivanova & Michael Spiteller, Journal of Inclusion Phenomena and Macrocyclic Chemistry volume 76, pages415–426 (2013)

 

Corresponding discussion and comparative analysis among the different synthetic methods is expected by the authors.

 

 

Author Response

We thank the Reviewer for his/her kind assessment of our work.

The comments are added as the part of the enclosed file.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper deals with hydrodechlorination (HDC) of different chloroaromatic compounds with Cu- and Ni-based Al alloys in an alkaline aqueous solution and wastewater. It demonstrated that Devardas alloy is an effective HDC agent only in the case of highly chlorinated hexa- and pentachlorobenzene and pentachlorophenol. Also, Devardas alloy is quite efficient for dechlorination of meta- and ortho-chloroanilines. However, Al, Zn, and Cu are mainly converted to the corresponding (hydro)oxides and cannot be directly reused in the subsequent HDC step. In contrast, Raney Al-Ni alloy is a universal, robust, and very effective HDC agent for converting all the tested (poly)chlorinated aromatic compounds to the corresponding completely dechlorinated products. Besides, the dissolved aluminum together with the appropriate Ni contamination and part of the dechlorination products are efficiently removed by neutralization and removal of insoluble Al(OH)₃.

Besides the advantages of Raney Al-Ni alloy, this paper also provides mechanisms, applications, and critical influencing factors of HDC of chloroaromatic compounds with Raney Al-Ni alloy. However, authors need to uniformly use the names or terms of HDC agents to avoid misunderstanding. As for the kinetics study, the reaction order and reaction rate constants should be pointed out and calculated. Due to the longer reaction time, the effect of temperature on the reaction kinetics should be further investigated to accelerate the reactions. A major revision is recommended and the following specific comments on the work should be addressed:

1. The various names or terms of HDC agents, such as Cu- and Ni-based Al alloys (in the Title), aluminum-based alloys, Al-Ni and Al-Cu-Zn, Raney Al-Ni alloy, Devardas Al-Cu-Zn alloy, Al-based alloys (in Abstract), Devardas alloy, Al-based alloys, Cu-Zn alloy, Al-Ni alloy (in Text), Al-based Cu and Ni alloys, Al-Cu and Al-Ni alloys (in Conclusion), etc. appears in the whole paper. The names or terms should be uniformly used to be easily understood by the
2. Based on Fig. 1, 4, and 5, the reaction order and rate constants should be noted and calculated to compare with each other for kinetics study.
3. Temperature is a critical factor for chemical reactions and reaction kinetics. In particle, the reaction time is quite long (overnight). Therefore, the effect of temperature should be studied to understand the reaction kinetics.
4. Hydrodechlorination, chloroaromatic compounds should be regarded as keywords, while chlorobenzene; chloroaniline; chlorophenol should be removed from the Keywords.
5. Reaction conditions, such as volume, concentration, amount of catalyst, temperature, pH, reaction time, etc, should be noted in the Titles of Table 1, Table 2, Table 3, Fig. 1, Fig.3, Fig. 4, Fig. 5, Fig. 6, Fig.7, Fig. 8, Fig. 9.
6. The full names of all compounds should be noted in Table 1, Fig. 1, Fig.3, Fig. 4, Fig. 5, Fig.6, Fig.7, Fig. 8, Fig. 9.
7. Conversion rates of all compounds should be noted in Table 3.
8. The abbreviation HDC in the text should appear firstly with the full name.
9. Line 44 and 81, both Al-Cls and ArCl should be Ar-Cls or Ar-Cl. Is it right?
10. Line 107, “ in aqueous NaOH” should be “ in aqueous NaOH solution”. Is it right?
11. All symbols of “ oC” should be revised into “ ^oC”.
12. Line 447, “3000 ^oC” should be “ 300^oC”. Is it right?
13. The following sentences should be improved for understanding:

• Line 119-121, If HDC proceeds in the case of Devardas alloy action than is preferably in the position meta or eventually ortho towards the bound amino group.
• Line 148-149, The HDC reaction of nonpolar and in water very sparingly soluble polychlorobenzenes was performed in a methanol-H₂O mixture using different quantity of Devardas alloy.
• Line 204-205, The dechlorination of nonpolar and in water very sparingly soluble tri-, tetra-, penta- and hexachlorobenzene using Al-Ni alloy was performed in the methanol-H₂O mixture.
• Line 245-246, Due to this reason, Al-Ni in co-action with a commercial mixture of 12 wt.% NaBH₄ in 14 M NaOH was used as the source of NaOH.
• Line 461, The aqueous solution (1 mM, 100 mL, 1 mmol) of chlorinated aniline.

Author Response

We thank the Reviewer for his/her kind assessment of our work.

The manuscript was revised according to the reviewers comments, our answers to the Reviewer  comments are described in enclosed file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have not taken into account the comments on the second Reviewer.

In general, instead of a complete reference list on synthetic reactions on chlorination according to teh topic of the discussed manuscript as the second Reviewer has suggested, the authors just have commented on a more recent paper of other authors, which is completely out of the context of the topic of their paper.
Please, consider the second Reviewer's recommendation on missing references. Then, please, consider the text of the paper which the authors have commented on additionally. Yous shall see that the authors have focused their attention on other authors contributions, which are not however on the topic of the paper catalysts-870417 presented by the authors for review. Obviously, the authors have not understood the content of the paper which they comment on as answer to the uncited and completely different paper, which is recommended by the Reviewer. The two paper (the recommended by the Reviewer in the review and the discussed by the authors to their answer to the same review) are completely different as topic and content. The recommended manuscript by the Reviewer covers the authors' topic of their work. While the commented by the authors paper on their response to reviewer section is completely out of the topic of their work. Therefore, the authors have not focused attention to the recommended work by this reviewer, instead of they have carried out comments on a completely different work. They, the recommendations of the second reviewer do not be taklen into account for by the authors.

For this reason, the decision is 'Reject' and it remains reject.

Author Response

Dear Reviewer,

we accepted your recommendation and add citation of the mentioned article into Introduction and in the Reference chapter.

We hope that the innovated version of our manuscript will be accepted for you.

Thanks in advance.

Yours sincerely

Tomas Weidlich and co-authors

Round 3

Reviewer 1 Report

The authors have presented a significantly improved version of the paper owing to the fact that they not only have introduced reference, but also have added important experimental mass spectrometric data to the new vesrion of the supporting information section. The old version of the supporting information file lacks of these data. 

However, the ''scientific soundness'' of their work needs major revision, because of, the authors only present subfigures of experimental data, without their assignment and interpretation (Figure S6; supporting information file.)

However, the authors have claimed the following:

''It is evident from the results depicted in Table 6 and Figure S6 in Supplementary materials and from the significant decrease of adsorbable organically bound halogens (AOX) that chlorinated aromatic contaminants
are effectively reduced via HDC reaction to the non-chlorinated aromatic products using Raney Al-Ni and aqueous NaBH4/NaOH solution'' (rows 316-319, main text).

Thus, the authors have presented in Figure S6 mass spectra of the analytes without not only qualitative, but also quantitative outcomes evidencing their statement mentioned above. 

The mass spectrometry, however, is robust analytical approach, amongst others, to quantify analyses, in addition to, their structural determination. In this context, the authors should, additionally, comment on these experimental data in more detail, emphasizing the following:

1. The mass spectra should be added to the main text as new figure, highlighting, the isotope shapes of Cl-containing analyte species, like Figure 1 shown in reference [y] dealing with quantification of Cl-containing analytes mass spectrometrically.
2. [y] B. Ivanova, M. Spiteller, Electrospray ionization mass spectrometric solvate cluster and multiply charged ions: a stochastic dynamic approach to 3D structural analysis, SN Applied Sciences 2 (2020) Article number: 731 [https://doi.org/10.1007/s42452-020-2555-0].
3. Since, the MS variable 'intensity' is directly related with the concentration of the analyte in solution according to the theory shown in references [y] and [y1] via the DSD parameter according to equation (1) in reference [y], the authors should calculate these DSD parameters using the experimental intensity values of the MS peaks of few most important fragment ions their analytes as they have been shown in Figure S6 in their supporting information section. In addition, there should be added information about the concentration of the analytes in the solution yielding to their upper subfigure (Figure S6) and after time 't' when HDC is added (bottom subfigure, Figure S6.) The concentration of HDC should be detailed, as well. Because of, the relationship between DSD and the concentration of the analyte is linear (Consider references [y,y1].)
4. It is assumed that the authors, have carried out standard relationship between the analyte intensity of MS peaks with respect to the concentration of the dye and HDC as well as with the time. These data should be added to the supporting information section, as well. Because of, without quantitative and qualitative interpretation of the MS spectra according to points 1-5, herein, claims such the authors' ones shown above (rows 316-319 in the main text,) that it becomes ''evident'' from Figure S6 their conclusion, are completely unjustified. This affects negatively on the 'scientific soundness' of their paper.   
5. [y1] B. Ivanova, M.Spiteller, Quantitative Relations Among Temperature, Analyte Concentration in Solution, Stochastic Dynamic Diffusions and Mass Spectometric Variable Intensity,
   GRIN Verlag, Muenchen (2020), pp. 1 - 276, ISBN-13: 978-3346124401         

In other words, the current revised version of the text lacks of any interpretation of the newly presented by the authors experimental mass spectra, which are, however, used to proof of authors' claims (rows 316-319.) 

Author Response

Reviewer´s 1 comments and suggestions for authors, round 3:

1. The authors have presented a significantly improved version of the paper owing to the fact that they not only have introduced reference, but also have added important experimental mass spectrometric data to the new vesrion of the supporting information section. The old version of the supporting information file lacks of these data. However, the ''scientific soundness'' of their work needs major revision, because of, the authors only present subfigures of experimental data, without their assignment and interpretation (Figure S6; supporting information file.) However, the authors have claimed the following:

''It is evident from the results depicted in Table 6 and Figure S6 in Supplementary materials and from the significant decrease of adsorbable organically bound halogens (AOX) that chlorinated aromatic contaminants are effectively reduced via HDC reaction to the non-chlorinated aromatic products using Raney Al-Ni and aqueous NaBH4/NaOH solution'' (rows 316-319, main text).

Thus, the authors have presented in Figure S6 mass spectra of the analytes without not only qualitative, but also quantitative outcomes evidencing their statement mentioned above. 

Authors response:

We would like to thank the Reviewer for his/her kind assessment of our work. We rephrase the above-mentioned sentence and fulfilled it with additional information. However, our submitted manuscript is not MS study and the subchapter “2.3 Application of Al-Ni alloy for HDC of polychlorinated compounds mixture in actual waste water”  describing effectivity of hydrodechlorination process in case of aqueous wastewater stream from discontinuous processes used for different types of azo pigments production varies significantly in chemical composition, as was monitored by multiyear AOX measurements.

Note: In the Czech Republic, solely parameter AOX (adsorbable organically bound halogens) is authoritative for evaluation of water contamination with halogenated organic compounds. In the case of the described technological water stream, it is well known that concentration of AOX varried significantly in this wastewater due to the often changes in quantity and types of dyes and pigments production.

 Due to this reason the detailed quantification of contaminants is redundant. The aim of the subchapter 2.3 is to illustrate robustness of the Al-Ni/NaOH based hydrodechlorination procedure with the aim to produce non-chlorinated and more biodegradable products.

The mass spectrometry, however, is robust analytical approach, amongst others, to quantify analyses, in addition to, their structural determination. In this context, the authors should, additionally, comment on these experimental data in more detail, emphasizing the following:

1. The mass spectra should be added to the main text as new figure, highlighting, the isotope shapes of Cl-containing analyte species, like Figure 1 shown in reference [y] dealing with quantification of Cl-containing analytes mass spectrometrically.
2. [y] B. Ivanova, M. Spiteller, Electrospray ionization mass spectrometric solvate cluster and multiply charged ions: a stochastic dynamic approach to 3D structural analysis, SN Applied Sciences 2 (2020) Article number: 731 [https://doi.org/10.1007/s42452-020-2555-0].
3. Since, the MS variable 'intensity' is directly related with the concentration of the analyte in solution according to the theory shown in references [y] and [y1] via the DSD parameter according to equation (1) in reference [y], the authors should calculate these DSD parameters using the experimental intensity values of the MS peaks of few most important fragment ions their analytes as they have been shown in Figure S6 in their supporting information section. In addition, there should be added information about the concentration of the analytes in the solution yielding to their upper subfigure (Figure S6) and after time 't' when HDC is added (bottom subfigure, Figure S6.) The concentration of HDC should be detailed, as well. Because of, the relationship between DSD and the concentration of the analyte is linear (Consider references [y,y1].)
4. It is assumed that the authors, have carried out standard relationship between the analyte intensity of MS peaks with respect to the concentration of the dye and HDC as well as with the time. These data should be added to the supporting information section, as well. Because of, without quantitative and qualitative interpretation of the MS spectra according to points 1-5, herein, claims such the authors' ones shown above (rows 316-319 in the main text,) that it becomes ''evident'' from Figure S6 their conclusion, are completely unjustified. This affects negatively on the 'scientific soundness' of their paper.   
5. [y1] B. Ivanova, M.Spiteller, Quantitative Relations Among Temperature, Analyte Concentration in Solution, Stochastic Dynamic Diffusions and Mass Spectometric Variable Intensity,
   GRIN Verlag, Muenchen (2020), pp. 1 - 276, ISBN-13: 978-3346124401    

 

 

Authors response:

As we explained, our manuscript is not research focused on detailed MS study. Our manuscript is focused on hydrodechlorination process, which is in harmony with scope of proposed special Issue of Catalysts journal. We applied GC-MS for screening analysis of actual technological aqueous stream contaminated with chlorinated aromatic compounds like chlorinated anilines, chlorinated phenols and chlorinated aromatic hydrocarbons. The measured MS spectra of both chlorinated aromatic compounds and reduction products were added into the Supplementary Materials chapter.

Due to this reason we disagree with citation of article “[y] B. Ivanova, M. Spiteller, Electrospray ionization mass spectrometric solvate cluster and multiply charged ions: a stochastic dynamic approach to 3D structural analysis, SN Applied Sciences 2 (2020) Article number: 731 [https://doi.org/10.1007/s42452-020-2555-0].“ because this article is MS study based on application of Electrospray ionization technique which is completelly different in comparison with EI used in GC-MS mentioned in our manuscript. In addition, mentioned article does not study chlorinated aromatic compounds.

In addition, the book „B. Ivanova, M. Spiteller, Quantitative Relations Among Temperature, Analyte Concentration in Solution, Stochastic Dynamic Diffusions and Mass Spectometric Variable Intensity, GRIN Verlag, Muenchen (2020), pp. 1 - 276, ISBN-13: 978-3346124401“enforced by reviewer is completely non-available for us (at least in acceptable time period).

Each of above-mentioned reviewer promoted publications written by M. Spiteller and B. Ivanova is one-track focused on mass spectrometry application using MALDI or Electrospray ionization techniques, and is not focused on hydrodechlorination research area described in our manuscript.

    

In other words, the current revised version of the text lacks of any interpretation of the newly presented by the authors experimental mass spectra, which are, however, used to proof of authors' claims (rows 316-319.) 

 

Authors response:

The above mentioned controversial sentence was completely removed.

Author Response File: Author Response.pdf