Kinetics of Decolorization of Reactive Textile Dye via Heterogeneous Photocatalysis Using Titanium Dioxide
, Luz Genara Castañeda-Pérez 2, Daril Giovani Martínez-Hilario 3, Juan Taumaturgo Medina-Collana 4,*, Julio Cesar Calderón-Cruz 3, César Gutiérrez-Cuba 3, Héctor Ricardo Cuba-Torre 5, Alex Pilco Núñez 6 and Sonia Elizabeth Herrera-Sánchez 3
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsPlease find pdf file
Comments for author File: 
Comments.pdf
It needs to be improved
Author Response
Good evening Mr. Expert.
The comments made have been lifted and the responses and the article with their modifications are sent.
cordial greetings
Luis Carrasco Vengas and Juan Medina Collana
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsThe work entitled "Kinetics of reactive textile dye discoloration by heterogeneous catalysis with titanium dioxide and Eolic agitation" addresses the study of the degradation of textile dyes by TiO2 nanoparticles. Mainly the effect of the concentration of nanoparticles and the pH of the solution to be decolorized is evaluated. The kinetics of catalytic degradation of dyes is evaluated by UV-Vis spectroscopy. The reaction is carried out in the presence of sunlight and with constant stirring in reactors designed to take advantage of wind power. The degradation takes place for more than 780h. The results are interesting, however the experimental design of this research is flawed due to the lack of replications. The test was only performed once, which means that there is no statistical evidence to ensure the reproducibility of the results. Therefore, there are no average values with their respective standard deviations. It would have been better to sacrifice a pH value and create at least one replica of each sample or reactor.
1) The text contains long paragraphs that impede readability. For instance, consider paragraph lines 53 to 57: “Solar energy, along with other renewable resources, could play a key role in the mass production of fine chemicals and in solving environmental problems, as recent advances in the use of solar energy such as solar photocatalysis have shown that solar photocatalytic technology is effective in treating groundwater, drinking water, industrial wastewater, and air and soil pollution [4].”
2) The meaning of the sentence is not understood. Rewrite it.
“Photocatalysis allows how the change in the rate of the reaction or its initiation occurs due to the effect of UV, visible, or IR radiation in the presence of a substance called catalyst…”
3)In lines 133-134 the number 3 corresponding to the figure was missing. It should say figure 3. The same on line 143. The figure number is not there.
4) In line 160, change semicolons (;) to dot sign (.). In general, review the use of semicolons.
5) In line 169, remove the dot sign before the reference [36].
6)In line 172, check text after the dot sign.
7) In line 197 remove dot sign before of reference [43].
8) In line 209 remove dot sign before of reference [44].
9) In line 214 remove dot sign “… when increases. radiation…”
10) At the end of the introduction, include a paragraph that talks about the objectives of this work.
11) Section 2.1 Materials, equipment and reagents is very difficult to read. Use the dot sign to separate materials from equipment and reagents. In this section, specify the brands and models of the equipment used. Also indicate from which companies the dyes, TiO2 nanoparticles and sulfuric acid were purchased.
12) In Table 1, the heading of the second column (Reactive dye concentrations) does not make sense because the initial concentration of both dyes is 1000 ppm. Also, the second column corresponds to the reactors with sumifix supra lemon yellow e-xf dye. The way the information is organized in the table is confusing. It may be more convenient to use only 3 columns (Reactors, pH, and ppm) and the 26 rows corresponding to each sample. Review and correct the table.
13) How did you collect 2 ml of sample from the reactors? Was the content of the reactors homogenized before sampling or was the sample taken from the top?. It is important to clarify this in the experimental procedure (section 2.4).
14) Were the samples taken from the reactors centrifuged to remove the nanoparticles before reading in the UV-vis spectrophotometer?. It is important to clarify this in the manuscript.
15) On line 333, replace A10 with A9.
16) On line 373, do the authors refer to Figure 7 and Figure 8?
17) On line 414, separate kinetics by 1⁄2.
18) In Table 5, change the column titles: Orden by Order
19) In line 418 remove the dot sign in front of the reference [2],[47],[48].
20) On line 425, remove the dot sign "...rate constant. adsorption...".
21)In line 453 change equation number (2) to (25).
22)In line 455 correct figur5 by figure 14.
23)In line 472 replace Figur5 by Figure 14.
24)In line 487 correct (e-, h+ y 𝐻𝑂∙) by (e-, h+ and 𝐻𝑂∙)
25) In line 536, the figure of the Pareto chart must be referred to by the corresponding figure number (Figure 15).
26) The numbering of the last 3 figures in their captions and in the text needs to be corrected.
27) In the conclusions the authors argue the following: “The time required for degradation is considerably high for both dyes, indicating a strong dependence on the intensity of solar radiation, oxygen concentration in the solution, NPs concentration, and pH.” However, in the manuscript there is no evidence about the catalytic response when varying the oxygen content in the reactors or when varying the intensity of solar radiation (for example, in summer and winter). Therefore, the conclusions must be rewritten.
Comments on the Quality of English LanguageThe text contains long paragraphs that impede readability. For instance, consider paragraph lines 53 to 57: “Solar energy, along with other renewable resources, could play a key role in the mass production of fine chemicals and in solving environmental problems, as recent advances in the use of solar energy such as solar photocatalysis have shown that solar photocatalytic technology is effective in treating groundwater, drinking water, industrial wastewater, and air and soil pollution [4].”
Author Response
Good evening Mr. Expert.
The comments made have been lifted and the responses and the article with their modifications are sent.
cordial greetings
Luis Carrasco Vengas and Juan Medina Collana
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Editor, dear Authors,
I carefully read your manuscript entitled “Kinetics of reactive textile dye discoloration by heterogeneous catalysis with titanium dioxide and Eolic agitation” that you send for consideration for publication in Journal Water.
English should be improved greatly.
For the beginning I found Title misleading: it rose expectation in reader that it will be original in some photocatalytic kinetics way in which model dyes are discolored, but no- it is slightly original in construction of the reactor platform and the way of stirring of reaction solutions. So, it has to be changed in a way that will reflect the real content of the manuscript. The other thing is putting “Eolic agitation” in the Title without dealing with actual wind conditions during irradiation of the samples. Maybe it should not be in the Title at all. On the other side the role of Titanium dioxide is named only by “heterogenous catalyst” it should be stressed that the way TiO2 is used here is as photocatalyst. Which is not anything original, TiO2 is the most studied photocatalyst and is ability to photodegrade dyes is well known for a long time and studied in numerous laboratories (more than 4000 papers per year).
Specific comments:
The Abstract is a little confusing because we have here degradation instead of discoloration, and samples are named in unexplained way. It is not clear do you change concentration of the dyes (1000 ppm) or quantity of the TiO2 which is also presented in ppm, that is not usual. The used quantity of the TiO2 is rather high: 0.8 g/L. Dependence of the rate of dyes discoloration is dependent on pH of solutions and presence of the photocatalyst, that is not new.
Introduction is too long, more than 4 pages. The reactions that follow absorption of UV light by TiO2, page 3, reactions 1-11, should be accompanied with potentials at which they can happen, especially formation of super oxide anion radical, -0.33 V. Be very careful when you claim that TiO2 can make super oxide anion radical. At which potential is the conduction band edge of TiO2?
In Figures 3 and 4 (a), (b), (c) parts should be denoted.
Design of the reactors support (Figures 4 and 5) does not provide homogenous illumination of all reactors at once. Is there any proof that you don’t have discrepancy of the results due to different Solar irradiation exposure? Reactors in the center of the support get the same amount of light and under the same angle as those at the sides?
It would be useful to know chemical formulas of the dyes and their UV/Vis absorption spectra. That would be the proof that max for “red” and “yellow” dye are just 1nm apart.
Table 1 have wrongly assigned column 2- there are no concentration gradient of the dyes, it is always 1000 ppm (1g/L). Also, it should be stressed that “red” dye is denoted with R and “yellow” with A.
Light intensity was measured during experiment, but no data about wind.
Results & Discussion
A lot of interesting, but not new, data were presented. Obviously, pH has effect on the discoloration but it would be more precise if we know pK of model dyes. In which for are they present in solution at a given pH. The surface of the TiO2 is positively charged in all working pH (IOP for TiO2 is at about pH=6.5). So, adsorption of the dyes at working pH should be important (you should measure adsorption of the dyes during equilibration of solutions before illumination in the dark). That would give a reason why you need highest concentration of TiO2 and pH between 3 and 4 for the best discoloration of “red” dye. For “yellow” dye all experimental setups are working nice, except lowest concentration of TiO2.
Conclusions
In conclusions authors mixed again discoloration with degradation. Among other claims, the chemical structure of the materials is denoted as the most significant factor for discoloration, so this data must be included in the manuscript before consideration for publication.
It would be nice of Authors to write what is novelty brought by this manuscript.
Best regards
Comments for author File: Comments.pdf
No comments
Author Response
Good evening Mr. Expert.
The comments made have been lifted and the responses and the article with their modifications are sent.
cordial greetings
Luis Carrasco Vengas and Juan Medina Collana
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAccept
Author Response
good morning
the modifications of the comment made are sent
greetings
Juan Medina
Author Response File: Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsI have read the authors' response and the corrected version. Most of the indications were addressed. New evidence supporting some of the conclusions were incorporated, the length of some paragraphs was adjusted and in general the requested corrections were made. I consider that in the present version the manuscript can be approved for publication.
Comments on the Quality of English LanguageThe lengths of the paragraphs were adjusted and some sentences were rewritten to improve the clarity of the idea. Some punctuation marks that were indicated were corrected and some Spanish words were replaced by their appropriate translation. Overall, although the English wording can still be refined, I consider the manuscript suitable for publication in this corrected version.
Author Response
good morning
the modifications of the comment made are sent
greetings
Juan Medina
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors,
There are still some mistakes which should be corrected. Please see attached .pdf for specific comments.
Best regards
Comments for author File: Comments.pdf
There are some grammar problems (fullstops!). All Spanish parts should be translated to English!
Author Response
good morning
the modifications of the comment made are sent
greetings
Juan Medina
Author Response File: Author Response.docx
