Recycled Paper Sludge (RPS)-Derived Nanocellulose: Production, Detection and Water Treatment Application
Round 1
Reviewer 1 Report
The recycled paper sludge is an industrial waste that needs to be properly treated. It is feasible and meaningful to use pulp as raw material to produce nanocellulose，and the application of nanocellulose in water treatment is also a research field worthy of attention. In general, the methods of this work are scientific and reasonable, and the results obtained are interesting. I think this paper can be published after some revision.
- More detailed information (a least a brief introduction) should be given in the Experimental methods, especially those related to QA & QC. Besides, we would like to see the standard deviation of the data.
- The innovation of your research compared to the others?
- In the conclusion section, in addition to the summary of the main conclusions of the paper, please give a brief description of the limitations of this paper.
- The references are out of date. Please cite more latest references.
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
The experimental design is good, and the results and discussion are acceptable. Hence, my suggestion is publication of the work in your journal after minor revision considering the following comments:
1) Line 36: should be changed to "In Israel, for example, RPS is mainly...".
2) Line 50: should be changed to "[22-27]".
3) Line 106: it should be 5.54 g of pure NC...". Same note for lines 116, 130, 133, 142, 153, 190 and 425.
4) Line 116: it should be "80 µl of 9 M KOH solution...". Same note for lines 121 and 395.
5) It would be better to use the equation editor on line 144.
6) Lines 155, 176, 191 and 222: it should be "ºC".
7) Please discuss the morphological observations in detail. Also, correct the caption in Fig. 8.
8) What do orange line represent in Fig. 10a? Is it a fitting curve? Should the absorbance increase just after 30 min? Please explain.
9) Why did the authors choose a concentration of 0.02 ppm for the acid red 131 dye adsorption tests?
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 3 Report
The paper “Recycled paper sludge (RPS) derived nanocellulose: production, detection and water treatment application” by A. Maslennikov is a preliminary study on the synthesis of nanocellulose and on its potential uses in water decontamination.
The paper is interesting and it deserves attention, but some revision is necessary. In fact:
1) The authors propose a double treatment of paper sludge, relying upon the sequential action of O3 and H2SO4. They claim that the presence of nanocellulose can be detected/monitored by a fluorescence signal. However, many cases exist where the presence of mineral acids (like H2SO4) or even alkalies on carbohydrates or on its polymers may trigger the formation of elemental carbon nanoparticles (NPs) by hydrothermal carbonization even at low temperatures in the presence of water, and these NPs may give a signal in UV-VIS analysis that may interfere with that of nanocellulose. See, for example, the short review “A Critical Analysis on Green and Low-Temperature Methods for the Production of Carbon Nanoparticles”, (http://doi.org/10.3303/CET2186135)
The authors should be aware of this phenomenon, acknowledge this paper and discuss the problem, trying to understand what is the real origin of their UV-VIS signal.
Moreover, have the authors detected a progressive change toward a yellow-red-brown color during the treatment with O3 and particularly with aqueous H2SO4? This is a typical sign of starting hydrothermal carbonization.
2) In Section 3.4, dealing with the determination of the phenolic content, there is no discussion about some possible negative effects of these compounds on the final product. Please consider this aspect, including possible toxic effects.
3) In Fig. 10, the experimental conditions concerning the tests on dye adsorption are somewhat vague and undefined. What are the concentration of NC and the initial concentration of dye in the hold-up?
4) A section of conclusions is lacking. This section should be added, as usually required by standard papers.
5) Minor observations:
In Eq. 1, please avoid using “dt”, as it may erroneously indicate a differential of time. Please use another symbol (for example, the greek capital delta, to indicate a finite time gap).
The paper is globally satisfactory as far as the language is concerned, but there are some typos (example: "remaimung" in section 3.7, etc…)
Author Response
Please see the attachment
Author Response File: Author Response.docx
Reviewer 4 Report
Maslennikov et al presented a thorough study on the extraction of nanocellulose from recycled paper sludge and their detection thanks to the calcoflour white fluorescence. They described adequately the state of art and the results are clearly present. I believe their work is quite interesting and finds multiply applications for green technologies. I would suggest to improve the quality of the graphs, as in Figure 5 the scale bar are barely legible.
Author Response
Response to Reviewer 4
Maslennikov et al presented a thorough study on the extraction of nanocellulose from recycled paper sludge and their detection thanks to the calcoflour white fluorescence. They described adequately the state of art and the results are clearly present. I believe their work is quite interesting and finds multiply applications for green technologies. I would suggest to improve the quality of the graphs, as in Figure 5 the scale bar are barely legible.
Reply to comment: The authors thank the referee for the supportive comments. All figures were reviewed, edited and their quality was improved.
Round 2
Reviewer 3 Report
The Authors have given a sufficient answer to points 2,3,4,5.
As for point 1, the authors gave an elusive answer and they should discuss in the text the problem of hydrothermal carbonization that may lead to the formation of carbon NPs, as recommended since the first refereeing report. These NPs may interfere with fluorescence signals of different origin, like the one induced by NC activated by Calcofluor White. It should be noted that a fluorescence signal related to carbon NPs is remarkable even in clear dispersions. The suggested paper to be cited, namely:
“A Critical Analysis on Green and Low-Temperature Methods for the Production of Carbon Nanoparticles”, (http://doi.org/10.3303/CET2186135)
though it may seem (to the authors) apparently unrelated to their study, is just related to this overlapping phenomenon that continues to be overlooked by the authors. This paper should be cited in the context of this discussion. After these adjustments are made, the paper can be accepted.
Author Response
Please see the attachment
Author Response File: Author Response.docx
