Valorization of Grass Clipping Waste: A Sustainable Approach to Cellulose Extraction and Paper Manufacturing

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Requirements

1.      Linee 29-30. “…of microfibrillar cellulose fibers.” Change this expression. You can use: “…of microfibrillar cellulose chains.”, or “…of cellulose microfibrils.”

2.      Line 60. “…libriform cells predominate, often attaining lengths of 50-60 mm”. From this expression it seems to be understood that plant cells have a length of 50-60 mm, which is impossible. Please make the necessary correction.

3.      Line 64.” Lignin, an undesirable component…”. To be better understood, please complete the following: “…in the pulp and paper industry...”. It should also be specified that lignin is located in the middle lamella of the cells (with the main role of adhesion), and cellulose is the majority of the secondary layer of the cell walls, with the main role of resistance.

4.      Line 110. A greater detailing of the purpose and objectives of the work is necessary, such as highlighting the properties of the obtained paper and the methods of its realization.

5.      Lines 113-114. In this part of the work, in order to highlight the feasibility of the work at industrial level, the authors must estimate the amount of grass that would result in one year from this park (or at national level), respectively the amount of resulting cellulose.

6.      Line 132. “rpm”. In order for all readers to understand this issue, the first appearance of this abbreviation must be explained "rotations per minute", after which the direct abbreviation can be used.

7.      Line 182. Inside of Figure 2 it is not visible what the last position of the flow of manufactures is. Please fill in, probably the properties of the manufactured paper.

8.      Lines 186-188. All standards must have the year of publication or the year of recent modification. Also, the standards should be found in the bibliographic list with all the necessary data.

9.      Line 222. When explaining the terms in Eq. 2, the explanation for “A_ic” is missing, here the term “A_am” is different in the equation compared to the explanation. Please make the necessary correction.

10.   Line 230. “The paper density (ρ) was calculated by dividing the paper weight by the paper thickness”. Pay attention, to obtain density, the mass is divided by volume.

11.   Line 272. “The yield of α-cellulose after alkaline treatment and bleaching processes was 42.99 and 39.40 %, respectively”. This phrase must have an explanation. How was this calculated? Isn't it "before"?

12.   Line 507. The thickness of the sheet must be stated (otherwise the values ​​have no importance), especially if these two are different.

13.   Line 513. Here, in the table, it must be specified that "W" represents moisture content.

14.   Lines 603-604. Due to the small amount of raw material resulting from a park and the enormous amount of wood (several wagons per day) required for a pulp and paper factory, in the conclusions you must specify how you see this problem. Is there compatibility between the mowed grass and the base wood material, what could change in the manufacturing flow, what additional implications are visible at this moment? These are only some of the future problems of your research, at this moment only one phrase is needed to explain your vision.

15.   Lines 628-793. Not all references are formatted correctly: journals are not in italics or are not abbreviated, etc. Also, within the work, some references are not cited correctly, both the name and the first name of the authors have been written (Ex pag 225.)

Author Response

Reviewer 1

Comments #1: Linee 29-30. “…of microfibrillar cellulose fibers.” Change this expression. You can use: “…of microfibrillar cellulose chains.”, or “…of cellulose microfibrils.”

Response #1: We appreciate the reviewer's suggestion. We have revised the expression to “...of cellulose microfibrils” to enhance clarity and accuracy.

Comments #2: Line 60. “…libriform cells predominate, often attaining lengths of 50-60 mm”. From this expression it seems to be understood that plant cells have a length of 50-60 mm, which is impossible. Please make the necessary correction.

Response #2: Thank you for pointing out this error. We have corrected the expression to reflect the accurate cell length.

Comments #3: Line 64.” Lignin, an undesirable component…”. To be better understood, please complete the following: “…in the pulp and paper industry...”. It should also be specified that lignin is located in the middle lamella of the cells (with the main role of adhesion), and cellulose is the majority of the secondary layer of the cell walls, with the main role of resistance.

Response #3: We appreciate the reviewer's suggestion. We have revised the text to specify the roles of lignin and cellulose in plant cells and clarified that lignin is an undesirable component in paper production.

Comments #4: Line 110. A greater detailing of the purpose and objectives of the work is necessary, such as highlighting the properties of the obtained paper and the methods of its realization.

Response #4: We appreciate the reviewer's suggestion. We have expanded the description to include the purpose and objectives of the study, highlighting the properties of the obtained paper and the methods used to achieve these properties.

Comments #5: Lines 113-114. In this part of the work, in order to highlight the feasibility of the work at industrial level, the authors must estimate the amount of grass that would result in one year from this park (or at national level), respectively the amount of resulting cellulose.

Response #5: We appreciate the reviewer's suggestion. We have included statistical data to estimate the annual grass yield from Almaty's green zones and the resulting cellulose yield. This highlights the feasibility of the work at an industrial level.

Comments #6: Line 132. “rpm”. In order for all readers to understand this issue, the first appearance of this abbreviation must be explained "rotations per minute", after which the direct abbreviation can be used.

Response #6: Thank you for the suggestion. We have revised the text to explain the abbreviation "rpm" as "rotations per minute" at its first occurrence.

Comments #7: Line 182. Inside of Figure 2 it is not visible what the last position of the flow of manufactures is. Please fill in, probably the properties of the manufactured paper.

Response #7: Thank you for the feedback. We have revised Figure 2 to clearly show the final step in the process flow, highlighting the properties of the manufactured paper.

Comments #8: Lines 186-188. All standards must have the year of publication or the year of recent modification. Also, the standards should be found in the bibliographic list with all the necessary data.

Response #8: We appreciate the reviewer's suggestion. We have included the publication years of the standards and ensured they are listed in the bibliography with complete details.

Comments #9:  Line 222. When explaining the terms in Eq. 2, the explanation for “A_ic” is missing, here the term “A_am” is different in the equation compared to the explanation. Please make the necessary correction.

Response #9: Thank you for pointing out this oversight. We have corrected the equation and provided an explanation for the terms used.

Comments #10: Line 230. “The paper density (ρ) was calculated by dividing the paper weight by the paper thickness”. Pay attention, to obtain density, the mass is divided by volume.

Response #10: We appreciate the reviewer's suggestion. We have corrected the text to accurately describe the calculation of paper density.

Comments #11: Line 272. “The yield of α-cellulose after alkaline treatment and bleaching processes was 42.99 and 39.40 %, respectively”. This phrase must have an explanation. How was this calculated? Isn't it "before"?

Response #11: Thank you for the suggestion. We have provided an explanation of how the α-cellulose yield was calculated based on the initial and final mass of the materials.

Comments #12: Line 507. The thickness of the sheet must be stated (otherwise the values ​​have no importance), especially if these two are different.

Response #12: We appreciate the reviewer's suggestion. We have included the thickness of the paper sheets to provide complete information on the paper samples.

Comments #13: Line 513. Here, in the table, it must be specified that "W" represents moisture content.

Response #13: Thank you for the suggestion. We have clarified in the table that "W" represents the moisture content.

Comments #14: Lines 603-604. Due to the small amount of raw material resulting from a park and the enormous amount of wood (several wagons per day) required for a pulp and paper factory, in the conclusions you must specify how you see this problem. Is there compatibility between the mowed grass and the base wood material, what could change in the manufacturing flow, what additional implications are visible at this moment? These are only some of the future problems of your research, at this moment only one phrase is needed to explain your vision.

Response #14: We appreciate the reviewer's suggestion. We have expanded the conclusions to address the compatibility of mowed grass with the base wood material and the potential implications for the manufacturing process.

Comments #15: Lines 628-793. Not all references are formatted correctly: journals are not in italics or are not abbreviated, etc. Also, within the work, some references are not cited correctly, both the name and the first name of the authors have been written (Ex pag 225.)

Response #15: We appreciate the reviewer's attention to detail. We have reviewed and corrected the formatting of all references to ensure consistency and adherence to the journal's style guidelines. All journal names are now in italics and properly abbreviated, and author names are correctly cited.

 

Reviewer 2 Report

Comments and Suggestions for Authors

After studying this manuscript, the following shortcomings were discovered.

Lines 53-55. Furthermore, studies such as that by [15] have demonstrated the feasibility of cellulose production from specific grass species, such as Meghatyrsus maximus, achieving remarkable alpha-cellulose content of 98.50% through delignification methods. Remark: From [15] it follows that a high alpha-cellulose content of 98.50% can be archived not after lignification, but after delignification and bleaching. Thus, after “delignification” the authors should be added “bleaching”, i.e., write “through delignification and bleaching”.

Lines 70-72. ...sodium hydroxide facilitates a reduction in lignin content within the biomass, achieved through the disruption of bonds between cellulose and hemicellulose and within lignin units [27]. Remark: The statement that delignification occurs due to “breaking the bonds between cellulose and hemicellulose” is incorrect. In fact, during alkaline delignification, the disruption of bonds between lignin and hemicellulose is carried out, along with the disruption of bonds within lignin. Thus, “the disruption bonds between cellulose and hemicellulose” should be replaced with “the disruption bonds between lignin and hemicellulose”.

Lines 73-86. Research indicates that incorporating minerals into paper production can significantly enhance its barrier properties... Remark: Mineral fillers (calcium carbonate, kaolin, titan dioxide, etc.) are introduced into pulp mainly to save expensive cellulose, reduce the cost of paper, increase its weight, to improve the whiteness and printability of paper. I recommend including these features of mineral fillers, along with the ones mentioned in this manuscript in lines 73-86. 

Line 87. Despite extensive research on cellulose mineralization.... Remark: The term “mineralization” is not appropriate here, and it should be replaced with the term “filling”; thus it should be written “Despite extensive research on the filling of cellulose, ...

Line 97. ...distinctive properties.  Remark: The term “distinctive” is not appropriate here, and should be replaced with the term “special”.

Lines 106-108. Numerous factors influence paper's consumer properties, .... Remark: The authors omitted such a significant process (stage) of papermaking as beating (pulp milling); therefore, this process (stage) must be included, since without milling of the pulp is impossible to produce high-quality paper.

2.1. Materials Remark: Among various materials, the authors omitted barite used here as filler and commercial cellulose used in FT-IR spectra. The authors should add barite and commercial cellulose in Materials; besides, the authors should indicate the source, origin, and characteristics of barite and commercial cellulose.

Lines 121-122. The feedstock was pulverized in a Stegler LM-250 mill operating at 28,000 rpm for 5 minutes to remove small mechanical impurities such as dirt, dust, and other solid waste. Remark: By grinding (pulverizing) is impossible to remove mechanical impurities. Vice versa, during this process the impurities will be mixed with the grass and remain in the feedstock. To remove dirt and other impurities from the raw material, foremost it is necessary to use such equipment, as cyclones, separators, etc. Then, the raw material should be carefully washed and dried. And only after that, the dry purified raw material (grass) should be pulverized. In addition, the authors should indicate the average particle size of the initial feedstock (or standard sieve No) after pulverizing. 

Lines 126-129. 5 grams of pretreated raw material were combined with 50 ml of 5 M concentrated NaOH solution, maintaining a solid-to-liquid ratio of 1:10. The suspension underwent thorough stirring. It was subjected to studies at a temperature of 120 °C for a soaking 128 duration of 180 minutes. Remark: Are you sure that to isolate cellulose you need to use 5 M or 17.5% NaOH and not diluted alkali, 0.4-2% or 5% NaOH as recommended in the literature? (see e.g., https://doi.org/10.1016/j.heliyon.2019.e02937; https://www.osti.gov/servlets/purl/1327732;

https://doi.org/10.1155/2022/5155552; etc.).

If biomass is treated with 5M NaOH, then instead of isolated cellulose fibers having CI structure you receive alpha-cellulose or mercerized cellulose having CII structure (see e.g., https://www.nature.com/articles/s41598-021-88040-x; Yue et al. Bioresources, 2013, 8, 6460-6471; etc.). Moreover, high-temperature treatment (at 120^oC) of biomass with concentrated alkali leads to reduced cellulose yield and oxidation of isolated alpha-cellulose.

Lines 138-140. Alkaline pretreatment was performed using a 5M NaOH solution at a ratio of 1:20 (raw material: solution). The suspension was heated to 90 °C under constant mechanical stirring at 400 rpm for 3 hours. Remark: Are you sure that before cellulose bleaching you need to use 5 M or 17.5% NaOH and not diluted alkali, 1% NaOH, as recommended in the literature (see e.g., https://doi.org/10.1155/2020/9765950)? If cellulose is treated with 5M NaOH, then instead of cellulose fibers having CI structure you receive alpha-cellulose or mercerized cellulose having CII structure (see e.g., https://www.nature.com/articles/s41598-021-88040-x; Yue et al. Bioresources, 2013, 8, 6460-6471; etc.).

Lines 146-160. “The material then underwent a second bleaching process, following the same systematic procedures but with a NaOH concentration of 2 % and the addition of H2O2 occurring 2 hours after the start of the reaction. But after that, the authors write that “in the second step, alkaline treatment was conducted using a 5% NaOH solution at 90 °C for 3 hours”. “Subsequently, the material underwent the first bleaching treatment, employing a solution consisting of 5% H2O2, 1% NaOH, and 0.1% MgSO4, maintained at 35 °C for 24 hours. The second bleaching process followed identical conditions to the first but at a temperature of 45 °C”. Remark: The description of the bleaching process is unclear. The question: it is unclear, do the authors mean that the two-stage bleaching was repeated under other conditions? The author must clearly describe the bleaching process without contradiction and repetitions.

Figure 1. Remark: The explanations (legends) of images are difficult to read, and these should be improved. I recommend writing these explanations (legends) horizontally below the images.

Lines 173-174. The resulting suspension underwent ultrasonic pretreatment at 80 °C for 30 minutes. Remark: (1). It was aqueous dispersion of cellulose mass & barite, not suspension. (2). The authors should indicate the concentration of this dispersion. (3). The authors should indicate Schopper-Riegler's degree of dispersion after sonication.

Line 184. 2.4.1. Compositional analysis. Remark: This section should be supplemented by methods of determining the content of cellulose, hemicelluloses, and lignin in initial grass, alkali-treated, and bleached samples.

Line 236. 3.1.1. Compositional Analysis. Remark: This section should be supplemented by experimental data on the content of cellulose, hemicelluloses, and lignin in initial grass, alkali-treated, and bleached samples (additional Table or Figure).

Line 248. Hemicellulose, akin to cellulose... Remark: This statement is incorrect. Hemicelluloses are a class of polysaccharides, pentosans, and hexosans, that differ from cellulose not only in their smaller molecular weight but also in their different chemical structure.  For example, the well-known pentosan is glucuronoxylan, while the well-known hexosan is a galactomannan.

 Lines 253-254. a reaction with sodium hydroxide, hemicellulose undergoes hydrolysis, ... ... Remark: The process with alkali, sodium hydroxide, is called destruction, not hydrolysis, which is performed by acids. Thus, this sentence should be corrected, as follows, “a reaction with sodium hydroxide, hemicellulose undergoes destruction” ...

Lines 272-273. The yield of α-cellulose after alkaline treatment and bleaching processes was 42.99 and 39.40 %, respectively. Remark: This sentence is incorrect and should be corrected, as follows, “The cellulose content in alkaline-treated and bleached samples was 42.99 and 39.40 %, respectively.

Lines 305-308. Following alkaline treatment, the average fiber diameter significantly decreases, typically measuring around 13.5 microns. Subsequent bleaching results in a further reduction in fiber diameter, averaging approximately 4.5 microns. Remark: These results should be complemented by experimental data on the average fiber length for alkali-treated and bleached samples without ultrasonication and after sonication at 80 °C for 30 min (for casting paper sheets).

Figure 7. FT-IR spectra... Remark: In this Figure, also FT-IR spectrum of initial grass sample should be indicated.

 Figure 8. XRD patterns... Remark: The authors used the outdated indexation of Mayer-Misch peaks from the 30s of the 20th century. This outdated indexation should be replaced with a modern one (see table)

Оutdated indexation	Modern indexation
101	1-10
10-1	110
002	200
040	004

 

See also: Alina I. Chiriac et al. Cellulose, 2014, 21, 203–219.

Additional remark: After treatment with 5M NaOH the alkaline-treated and bleached cellulose samples should have CII crystalline structure with peaks at 2ϴ of 12, and 19-21 degrees instead of 14-16, and 22-22.5 degrees for CI crystalline structure. However, the XRD patterns for these samples shown in Figure 8 related to CI and not to CII. Thus, there is a clear contradiction here. If the X-ray diffraction patterns of alkali-treated and bleached pulp samples have a CI structure, this means that an error was made in the alkali concentration and the samples were treated not with 5M NaOH (as indicated in sections 2.2.2 and 2.2.3) but with 0.5M or 5% alkali. On the other hand, if the alkali concentration is indicated right (5M NaOH), then X-ray diffraction patterns of CI-structure for alkali-treated and bleached pulp samples are incorrect and those should be replaced with XRD patterns of CII or removed as false.

In addition, for samples with a CII crystalline structure, the Segal crystallinity index method is not suitable. In this case, only the deconvolution method can be used to estimate the crystallinity index, while the Segal method should be excluded.

Table 1 - Physical and strength characteristics of hand paper samples. Remark: In this Table, the authors used the terms “Folding endurance” and “Burst tensile”. These terms are unconventional and should be replaced with conventional terms such as “Fracture strength” and  “Tensile strength”, respectively.

Comments on the Quality of English Language

The English should be checked and corrected 

Author Response

Reviewer 2

Comment #1: Lines 53-55. Furthermore, studies such as that by [15] have demonstrated the feasibility of cellulose production from specific grass species, such as Meghatyrsus maximus, achieving remarkable alpha-cellulose content of 98.50% through delignification methods. Remark: From [15] it follows that a high alpha-cellulose content of 98.50% can be achieved not after lignification, but after delignification and bleaching. Thus, after “delignification” the authors should be added “bleaching”, i.e., write “through delignification and bleaching”.

Response #1: Thank you for pointing out this oversight. We have revised the text to include "bleaching" after "delignification" to accurately reflect the process.

Comment #2: Lines 70-72. ...sodium hydroxide facilitates a reduction in lignin content within the biomass, achieved through the disruption of bonds between cellulose and hemicellulose and within lignin units [27]. Remark: The statement that delignification occurs due to “breaking the bonds between cellulose and hemicellulose” is incorrect. In fact, during alkaline delignification, the disruption of bonds between lignin and hemicellulose is carried out, along with the disruption of bonds within lignin. Thus, “the disruption bonds between cellulose and hemicellulose” should be replaced with “the disruption bonds between lignin and hemicellulose”.

Response #2: We appreciate the reviewer's correction. We have revised the text to accurately describe the disruption of bonds during alkaline delignification.

Comment #3: Lines 73-86. Research indicates that incorporating minerals into paper production can significantly enhance its barrier properties... Remark: Mineral fillers (calcium carbonate, kaolin, titan dioxide, etc.) are introduced into pulp mainly to save expensive cellulose, reduce the cost of paper, increase its weight, to improve the whiteness and printability of paper. I recommend including these features of mineral fillers, along with the ones mentioned in this manuscript in lines 73-86.

Response #3: We appreciate the reviewer's suggestion. We have revised the text to include additional features of mineral fillers, such as saving expensive cellulose, reducing the cost of paper, increasing its weight, and improving the whiteness and printability of paper.

Comment #4: Line 87. Despite extensive research on cellulose mineralization.... Remark: The term “mineralization” is not appropriate here, and it should be replaced with the term “filling”; thus it should be written “Despite extensive research on the filling of cellulose, ...

Response #4: We appreciate the reviewer's suggestion. We have replaced the term "mineralization" with "filling" to improve clarity.

Comment #5: Line 97. ...distinctive properties.  Remark: The term “distinctive” is not appropriate here, and should be replaced with the term “special”.

Response #5: We appreciate the reviewer's suggestion. We have replaced the term "distinctive" with "special" to improve clarity.

Comment #6: Lines 106-108. Numerous factors influence paper's consumer properties, .... Remark: The authors omitted such a significant process (stage) of papermaking as beating (pulp milling); therefore, this process (stage) must be included, since without milling of the pulp is impossible to produce high-quality paper.

Response #6: Thank you for the suggestion. We have included the beating (pulp milling) process in the text to acknowledge its significance in papermaking.

Comment #7: 2.1. Materials Remark: Among various materials, the authors omitted barite used here as filler and commercial cellulose used in FT-IR spectra. The authors should add barite and commercial cellulose in Materials; besides, the authors should indicate the source, origin, and characteristics of barite and commercial cellulose.

Response #7: We appreciate the reviewer's suggestion. We have revised the text to include barite used as a filler and commercial cellulose used in FT-IR spectra, along with their sources, origins, and characteristics.

Comment #8: Lines 121-122. The feedstock was pulverized in a Stegler LM-250 mill operating at 28,000 rpm for 5 minutes to remove small mechanical impurities such as dirt, dust, and other solid waste. Remark: By grinding (pulverizing) is impossible to remove mechanical impurities. Vice versa, during this process the impurities will be mixed with the grass and remain in the feedstock. To remove dirt and other impurities from the raw material, foremost it is necessary to use such equipment, as cyclones, separators, etc. Then, the raw material should be carefully washed and dried. And only after that, the dry purified raw material (grass) should be pulverized. In addition, the authors should indicate the average particle size of the initial feedstock (or standard sieve No) after pulverizing.

Response #8: We appreciate the reviewer's detailed feedback. We have revised the text to accurately describe the process of removing mechanical impurities.

Comment #9: Lines 126-129. 5 grams of pretreated raw material were combined with 50 ml of 5 M concentrated NaOH solution, maintaining a solid-to-liquid ratio of 1:10. The suspension underwent thorough stirring. It was subjected to studies at a temperature of 120 °C for a soaking 128 duration of 180 minutes. Remark: Are you sure that to isolate cellulose you need to use 5 M or 17.5% NaOH and not diluted alkali, 0.4-2% or 5% NaOH as recommended in the literature? (see e.g., https://doi.org/10.1016/j.heliyon.2019.e02937; https://www.osti.gov/servlets/purl/1327732; https://doi.org/10.1155/2022/5155552; etc.).

Response #9: Thank you for your insightful comment. We acknowledge that lower concentrations of NaOH are commonly used in cellulose isolation as recommended in the literature. However, our study explores two distinct methods for isolating cellulose mass from mowed grass: the first method involves chemical-thermal treatment using a concentrated alkaline solution, while the second method employs multi-stage treatment with alkali and acid under more benign conditions. The choice of using a 5 M NaOH solution and a temperature of 120 °C in the first method is based on the following considerations:

1. Nature of the Herb's Origin: Grass clippings, particularly from Festuca arundinacea, possess a complex lignin-carbohydrate matrix that is more resistant to delignification compared to other sources of cellulose like wood. The robust lignin and hemicellulose bonds in grass require more aggressive treatment to break down effectively.
2. Optimization Based on Experimental Work: Previous experimental trials conducted with various concentrations of NaOH and different temperature conditions showed that lower concentrations and milder temperatures were insufficient for complete delignification and resulted in lower yields of cellulose. The selected parameters of 5 M NaOH and 120 °C were found to be optimal, ensuring efficient separation of cellulose with higher yields and better quality.
3. Efficiency of Delignification: The concentrated NaOH solution at elevated temperatures facilitates the rapid breakdown of lignin and hemicellulose, improving the overall efficiency of the delignification process. This is critical for obtaining cellulose with desirable properties for subsequent applications.

Comment #10: If biomass is treated with 5M NaOH, then instead of isolated cellulose fibers having CI structure you receive alpha-cellulose or mercerized cellulose having CII structure (see e.g., https://www.nature.com/articles/s41598-021-88040-x; Yue et al. Bioresources, 2013, 8, 6460-6471; etc.). Moreover, high-temperature treatment (at 120oC) of biomass with concentrated alkali leads to reduced cellulose yield and oxidation of isolated alpha-cellulose.

Response #10: Thank you for your valuable comment and for providing relevant literature references. We acknowledge the potential structural transition from cellulose I (CI structure) to cellulose II (CII structure) when treated with 5M NaOH at high temperatures, as well as the possibility of reduced cellulose yield and oxidation. Due to this following (wrong) sentence has been removed from the manuscript: (Chemical-thermal treatments, whether alkaline or bleaching, serve to enhance the struc-tural organization of cellulose chains, thereby augmenting the strength and thermal re-sistance of the material).

Comment #11: Lines 138-140. Alkaline pretreatment was performed using a 5M NaOH solution at a ratio of 1:20 (raw material: solution). The suspension was heated to 90 °C under constant mechanical stirring at 400 rpm for 3 hours. Remark: Are you sure that before cellulose bleaching you need to use 5 M or 17.5% NaOH and not diluted alkali, 1% NaOH, as recommended in the literature (see e.g., https://doi.org/10.1155/2020/9765950)? If cellulose is treated with 5M NaOH, then instead of cellulose fibers having CI structure you receive alpha-cellulose or mercerized cellulose having CII structure (see e.g., https://www.nature.com/articles/s41598-021-88040-x; Yue et al. Bioresources, 2013, 8, 6460-6471; etc.).

Response #11: Thank you for your comment. Unfortunately, during the writing of the experimental section, the stages of raw material processing were incorrectly formulated. We have two methods: 1) alkaline treatment using 20% NaOH (5M), and 2) a multi-stage treatment using weak alkaline (5% NaOH, which corresponds to a molarity of 1.25 M) and bleaching in several stages. We apologize for the misleading information; the experimental section has been corrected to prevent similar misunderstandings for future readers.

Comment #12: Lines 146-160. “The material then underwent a second bleaching process, following the same systematic procedures but with a NaOH concentration of 2 % and the addition of H2O2 occurring 2 hours after the start of the reaction. But after that, the authors write that “in the second step, alkaline treatment was conducted using a 5% NaOH solution at 90 °C for 3 hours”. “Subsequently, the material underwent the first bleaching treatment, employing a solution consisting of 5% H2O2, 1% NaOH, and 0.1% MgSO4, maintained at 35 °C for 24 hours. The second bleaching process followed identical conditions to the first but at a temperature of 45 °C”. Remark: The description of the bleaching process is unclear. The question: it is unclear, do the authors mean that the two-stage bleaching was repeated under other conditions? The author must clearly describe the bleaching process without contradiction and repetitions.

Response #12: Thanks for pointing out the ambiguity in our description. We have revised the text to clearly describe each method. Our work examines two methods for producing cellulose from plant raw materials: Method 1 involves an alkaline treatment; Method 2 involves a multi-stage alkaline and bleaching treatment.

Comment #13: Figure 1. Remark: The explanations (legends) of images are difficult to read, and these should be improved. I recommend writing these explanations (legends) horizontally below the images.

Response #13: Thank you for your suggestion. We have revised Figure 1 to ensure that the explanations (legends) are written horizontally below the images for improved readability.

Comment #14: Lines 173-174. The resulting suspension underwent ultrasonic pretreatment at 80 °C for 30 minutes. Remark: (1). It was aqueous dispersion of cellulose mass & barite, not suspension. (2). The authors should indicate the concentration of this dispersion. (3). The authors should indicate Schopper-Riegler's degree of dispersion after sonication.

Response #14: Thank you for your valuable comments and suggestions. We have addressed each of your points as follows: (1) We have clarified that the mixture was an aqueous dispersion of cellulose mass and barite, rather than a suspension; (2) we have indicated the concentration of the dispersion. The mixture of cellulose mass and barite in a weight ratio of 6:4 was combined in a glass container and diluted with distilled water to a total volume of 200 ml. The concentration of this dispersion was 5% by weight; (3) while we did not calculate the Schopper-Riegler degree of dispersion after sonication, we have provided additional details regarding the preparation and processing of the dispersion.

Comment #15: Line 184. 2.4.1. Compositional analysis. Remark: This section should be supplemented by methods of determining the content of cellulose, hemicelluloses, and lignin in initial grass, alkali-treated, and bleached samples.

Response #15: Thank you for your suggestion. We have supplemented this section with the methods used to determine the content of alpha-cellulose, ash, moisture, dry matter, and lignin in the initial grass, alkali-treated, and bleached samples.

Comment #16: Line 236. 3.1.1. Compositional Analysis. Remark: This section should be supplemented by experimental data on the content of cellulose, hemicelluloses, and lignin in initial grass, alkali-treated, and bleached samples (additional Table or Figure).

Response #16: Thank you for your suggestions. We have supplemented Section 2.4.1 with the methods used to determine the content of alpha-cellulose, ash, moisture, dry matter, and lignin in the initial grass, alkali-treated, and bleached samples. The results of these analyses are presented in Table 1. Additionally, Section 3.1.1 has been updated to include the detailed methods and results of the compositional analysis using the Van Soest method, and Table 1 has been included to present these data.

Comment #17: Line 248. Hemicellulose, akin to cellulose... Remark: This statement is incorrect. Hemicelluloses are a class of polysaccharides, pentosans, and hexosans, that differ from cellulose not only in their smaller molecular weight but also in their different chemical structure.  For example, the well-known pentosan is glucuronoxylan, while the well-known hexosan is a galactomannan.

Response #17: We appreciate the reviewer's correction. We have revised the text to accurately describe hemicelluloses.

Comment #18: Lines 253-254. a reaction with sodium hydroxide, hemicellulose undergoes hydrolysis, ... ... Remark: The process with alkali, sodium hydroxide, is called destruction, not hydrolysis, which is performed by acids. Thus, this sentence should be corrected, as follows, “a reaction with sodium hydroxide, hemicellulose undergoes destruction” ...

Response #18: Thank you for pointing out this mistake. We have revised the text to correctly describe the process.

Comment #19: Lines 272-273. The yield of α-cellulose after alkaline treatment and bleaching processes was 42.99 and 39.40 %, respectively. Remark: This sentence is incorrect and should be corrected, as follows, “The cellulose content in alkaline-treated and bleached samples was 42.99 and 39.40 %, respectively.

Response #19: We appreciate the reviewer's suggestion. We have revised the text to correctly describe the cellulose content.

Comment #20: Lines 305-308. Following alkaline treatment, the average fiber diameter significantly decreases, typically measuring around 13.5 microns. Subsequent bleaching results in a further reduction in fiber diameter, averaging approximately 4.5 microns. Remark: These results should be complemented by experimental data on the average fiber length for alkali-treated and bleached samples without ultrasonication and after sonication at 80 °C for 30 min (for casting paper sheets).

Response #20: We appreciate the reviewer's suggestion to complement the fiber diameter data with average fiber length measurements. However, at this time, we only have data on the diameter of the fibers. Our experimental setup and measurements focused on the changes in fiber diameter following the treatments. Future studies will aim to include fiber length measurements to provide a more comprehensive understanding of the morphological changes in the fibers.

Comment #21: Figure 7. FT-IR spectra... Remark: In this Figure, also FT-IR spectrum of initial grass sample should be indicated.

Response #21: Thank you for your suggestion to include the FT-IR spectrum of the initial grass sample. We considered this, but the spectrum of the initial sample contains a significant amount of noise due to organic impurities, which prevents us from obtaining useful information for our study. Therefore, we decided to focus on the spectra of the treated samples, which provide more accurate and meaningful data for analysis.

Comment #22: Figure 8. XRD patterns... Remark: The authors used the outdated indexation of Mayer-Misch peaks from the 30s of the 20th century. This outdated indexation should be replaced with a modern one (see table)

Оutdated indexation	Modern indexation
101	1-10
10-1	110
002	200
040	004

See also: Alina I. Chiriac et al. Cellulose, 2014, 21, 203–219.

Response #22: Thank you for highlighting this issue. We have revised Figure 8 to use the modern indexation convention for the XRD patterns.

Comment #23: Additional remark: After treatment with 5M NaOH the alkaline-treated and bleached cellulose samples should have CII crystalline structure with peaks at 2ϴ of 12, and 19-21 degrees instead of 14-16, and 22-22.5 degrees for CI crystalline structure. However, the XRD patterns for these samples shown in Figure 8 related to CI and not to CII. Thus, there is a clear contradiction here. If the X-ray diffraction patterns of alkali-treated and bleached pulp samples have a CI structure, this means that an error was made in the alkali concentration and the samples were treated not with 5M NaOH (as indicated in sections 2.2.2 and 2.2.3) but with 0.5M or 5% alkali. On the other hand, if the alkali concentration is indicated right (5M NaOH), then X-ray diffraction patterns of CI-structure for alkali-treated and bleached pulp samples are incorrect and those should be replaced with XRD patterns of CII or removed as false. In addition, for samples with a CII crystalline structure, the Segal crystallinity index method is not suitable. In this case, only the deconvolution method can be used to estimate the crystallinity index, while the Segal method should be excluded.

Response #23: Thank you for your comment and for highlighting an important issue regarding the crystalline structure of the cellulose samples. We acknowledge the possibility of a structural transition from cellulose I (CI) to cellulose II (CII) when treated with 5M NaOH at high temperatures, which is characterized by XRD peaks at 2θ levels of 12 and 19-21 degrees for CII, as opposed to 14-16 and 22-22.5 degrees for CI. Our experimental procedures included two methods: 1) alkaline treatment using 20% NaOH (5M), and 2) a multi-stage treatment using a weak alkaline solution (5% NaOH, corresponding to a molarity of 1.25M) and subsequent bleaching. After the alkaline treatment, we observed crystalline peaks with low intensity characteristic of the CII structure. Since an aggressive 5M NaOH environment was not used during the bleaching process, it is logical that the transition from CI to CII did not occur.

Comment #24: Table 1 - Physical and strength characteristics of hand paper samples. Remark: In this Table, the authors used the terms “Folding endurance” and “Burst tensile”. These terms are unconventional and should be replaced with conventional terms such as “Fracture strength” and  “Tensile strength”, respectively.

Response #24: Thank you for your suggestion. We have replaced the unconventional terms “Folding endurance” and “Burst tensile” with the conventional terms “Fracture strength” and “Tensile strength” in Table 1.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Additional corrections are needed, namely: 

Line 277. ... sucrose rings.... Remark: Delete the inappropriate word “sucrose”

Lines 421- 427. During the deconvolution process .... of samples. Additionally, reflections 1-10 and 110 .....in crystalline domains. Remark: This fragment is incorrect and must be corrected, as follows, “Through a deconvolution process using the Voigt function, crystalline XRD reflections (1-10, 110, 200, and 004) were identified. Then, from the X-ray diffraction patterns of the sample, the areas corresponding to the scattering of crystalline and amorphous domains were isolated. Of particular importance, is the most intense crystalline reflex (200) corresponding to the interplanar distances between cellulose chains, since it is a marker of cellulose crystallinity. The reflections (1-10) and (110) are observed due to scattering from planes located in the diagonal directions of the crystalline lattice. In addition, the reflex (004) refers to X-ray scattering from planes located perpendicularly to the direction of cellulose chains in the crystalline lattice”.

Comments on the Quality of English Language

English language should be checked and improved 

Author Response

Dear Reviewer,

We would like to express our gratitude for your valuable comments and suggestions, which have helped us to improve the quality of our manuscript. Below are our detailed responses to the comments provided.

In addition to addressing the specific comments, we have performed a comprehensive review and improvement of the English language throughout the manuscript. These changes were made to ensure that the manuscript meets high standards of scientific writing and is easily understandable by the readers.

 

Comments #1: Line 277. ... sucrose rings.... Remark: Delete the inappropriate word “sucrose”

Response #1: Thank you for pointing out this error. We have removed the word "sucrose" to correct the text.

 

Comments #2: Lines 421- 427. During the deconvolution process .... of samples. Additionally, reflections 1-10 and 110 .....in crystalline domains. Remark: This fragment is incorrect and must be corrected, as follows, “Through a deconvolution process using the Voigt function, crystalline XRD reflections (1-10, 110, 200, and 004) were identified. Then, from the X-ray diffraction patterns of the sample, the areas corresponding to the scattering of crystalline and amorphous domains were isolated. Of particular importance, is the most intense crystalline reflex (200) corresponding to the interplanar distances between cellulose chains, since it is a marker of cellulose crystallinity. The reflections (1-10) and (110) are observed due to scattering from planes located in the diagonal directions of the crystalline lattice. In addition, the reflex (004) refers to X-ray scattering from planes located perpendicularly to the direction of cellulose chains in the crystalline lattice”.

Response #2: We appreciate the reviewer’s suggestion. The fragment has been corrected as advised to improve accuracy and clarity.