Water Contaminated by Industrial Textile Dye: Study on Decolorization Process
, Paola Foglia 2, Carlo Siciliano 3, JÃ nos B. Nagy 2 and Anastasia Macario 2,*Round 1
Reviewer 1 Report
The manuscript " Water contaminated by industrial textile dye: study on decolorization process " had been reviewed.
7) The novelty of the paper compering to the literature it is not clear. However, this conclusion is only based on the decoloration rate, the mechanism is not studied.
8) Figures 15-18 are still of poor quality
The article still looks like a research report, not like a scientific publication.
Author Response
Dear Referee,
We thank you for the time spent on the review of our manuscript. Below are our answers to your suggestions.
Point 7) The novelty of the paper compering to the literature it is not clear. However, this conclusion is only based on the decoloration rate, the mechanism is not studied.
Author’s Answer. “The observed decolorizing of water solutions containing the Reactive Black 5 dye, is mainly due to the photo-induced cleavage of the azo bond in its structure, affording several differently hydroxylated by-products. In all experiments, it can be supposed that dye molecules are oxidized by hydroxyl radicals generated by the TiO2-assisted photocatalytic process in the presence of H2O2 as additive under UV-irradiation [96, 97]. This process is also pH-sensitive, and the mechanism has been already reported [98]. As a consequence, the photo-degradation mechanism was not further investigated. Although the photo-degradation was not performed upon acidic pH values, the basic conditions adopted for the set of experiments, in order to simulate the textile industry dye fixing process, highlighted that the action of the system TiO2/H2O2/inorganic salt was not accelerated comparing the same process performed in the absence of the basic salt. By considering the anionic form of the Reactive Black 5 dye at basic pH, the formation of an excess of anionic charges on the photocatalyst surface was supposed to be responsible for the kinetic observed in the case of water samples not containing the inorganic salt. This evidence was finally supported by the literature data [98].”
The previous sentences were entirely added to the revised version of the manuscript (page 18 of 23, lines 394-407). References 96-98 were added to the Bibliography.
“The research in the field of treatment of waste water produced by textile industries is challenging. Today, the exploitation of bio-sustainable and chemical bio-compatible methods for remediation of waters containing azo dyes needs new impulses. The novelty of the presented work consists in the investigation of the Reactive Black 5 degradation, when this dye is treated with well-known economic and environmental friendly methods which can be modified by the presence of basic salts in waste water generated by the industrial colour fixing process. Being aware that the photocatalytic system TiO2/H2O2/UV-light has been widely experimented, the use of inorganic salts as cheap and chemically bio-compatible partners of the above cited system has only seldom been reported and investigated.”
The previous sentences were entirely added to the revised version of the manuscript (page 3 of 23, lines 119-121 and lines 131-136).
Point 8) Figures 15-18 are still of poor quality
Author’s Answer. The figures have been redone
Referee: The article still looks like a research report, not like a scientific publication.
Author’s Answer. We adopted a simple look in writing the article. This Author’s choose has been motivated by the desire to display the obtained results in a rather concise than a broad discursive form, aiding Readers to directly point attention to the Figures and the respective data collections and discussions.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper is well written. The authors gave an explicit literature review on the application of different photocatalytic materials, and made a careful experimental design to investigate the influence of hydrogen peroxide and sodium carbonate on the photocatalytic activity of TiO2 during decolorization of Reactive Black 5 azo dye. This study fills the gap for the society’s understanding of the roles of the inorganic salt sodium carbonate in the photodegradation of Reactive Black 5 azo dye, suggesting that such material does not have significant impact. I recommend acceptance of this paper for publication after the following minor modifications are made:
The authors should comb through the manuscript carefully to eliminate typos. Some examples include “_” in line 25 and “)” in line 394. Caption for Figure 3 was missing. The authors stated that “the results indicated that decolorization of Reactive Black 5 went to completeness in 30 minutes, under the optimal experimental conditions …” (line 28), but based on the results there were still at least 50% residual concentration of dye and the system was still colored after half an hour of UV exposure. The authors should give more clear statement here.
Author Response
Dear Referee,
We thank you for the time spent on the review of our manuscript. Below are our answers to your suggestions.
The manuscript has been corrected
The caption in Figure 3 has been added
The expression on line 28 has been corrected and clarified
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I accept the corrections
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
see the file attached.
Comments for author File: Comments.pdf
Reviewer 2 Report
The manuscript " Water contaminated by industrial textile dye: study on decolorization process " had been reviewed. Comments to improve the quality of this manuscript are listed below.
· What was the intensity of irradiation during the photocatalytic proces?
· Why the author proposed such concentrations of H2O2 (30%)?
· Did you measure adsorption–desorption equilibrium in photocatalytic experiments? How long (2 min)?- this is very important in photocatalytic process.
· There is no inforamtion about photocatalysts TiO2 (pore size, morphology etc)
· What is novelty in this article?
· What was the role of Na2CO3 and H2O2 – there is no information?
· There is no correlation of results with literature
· In my opinion, if you modify the TiO2 surfaces, the efficiency will be much better
· In my opinion the manuscript is lack of sufficient novelty.
· The all Figures are of poor quality.
Reviewer 3 Report
Luca et al describe their finding on the decolorization process in the water contaminated by the industrial textile dye. The present manuscript lacks novelty and presents serious conceptual mistakes. So, I do not recommend it for publication in Environments-MDPI. Authors need to examine their writing, figures styles/format and made a major improvement. Moreover, some particular comments are written below.
1. The research question is not clear. Why do they want to use additional salt (NaCO3) and redox additive (H2O2) for the photocatalytic reaction? It should need more discussion in the introduction part with recent studies in the literature.
2. The content of the two paragraphs in the second page (from 59 to 90) are not matching with the overall manuscript. For example, “Photoelectrochemical treatments by iron mesh double layer as anode, electrocoagulation using sacrificial iron electrodes, or metal plates activated with carbon materials, have been proved to be efficient auxiliary methods for the remediation of azo dye polluted waters [53-55]. Sawdust, coal-based activated carbon, carbon char, and simple or functionalized multi-walled carbon nanotubes (MWCNTs) have been proposed as adsorbents [56,57]. Among the available nanomaterials, cellulose nanocrystals-reinforced keratin bioadsorbents, zero-valent nano-copper, protein nanofibrils, loading of Ag/AgCl nanoparticles, have been proposed for the remediation of wastewater. These methods allow coagulation and/or homogeneous and heterogeneous oxidation of textile azo dyes by the Fenton reaction, which can be carried out also on nanotube arrays [58].”
3. What are the particle size and crystal structure of TiO2 nanoparticles?
4. Only photocatalytic measurement and H-NMR analysis are not enough to understand the interface about the presence of sodium carbonate on the photodegradation of the reactive Black 5 azoic dye, both in systems containing only titanium oxide and those containing titanium oxide and hydrogen peroxide. Additional characterization methods are needed.
5. What is the light intensity of UV light? The power of light doesn’t give any information about how much light can be used for photocatalytic reaction.
6. What is the source of the color images?
7. Authors should explain why H2O2 adding improves the photocatalytic activity of TiO2. They should provide a detailed mechanism about it.
8. Authors should explain why NaCO3 adding does not improve the photocatalytic activity of TiO2. They should provide a detailed mechanism about it.
