Eco-Friendly Cellulose Nanofiber Extraction from Sugarcane Bagasse and Film Fabrication

Round 1

Reviewer 1 Report

Shahi et al reported the ultrasound-assisted extraction of CNF from sugarcane bagasse and used it for film fabrication. The work involves environmentally friendly ultrasonication-assisted method and organic solvent-free medium for film fabrication of CNF for biomass residuals. Comprehensive characterization of the materials are conducted and the writing is clear. This research aligns well with the topic of the journal. I recommend publishing the manuscript after addressing the following issues.

1. What is the aspect ratio of the extracted CNF? The SEM images doesn't clearly morphology of extracted CNF. From the structure characterization, it seems the extracted material is between CNC and CNF.
2. How it can be hot compressed when a dried CNF film has already formed? There should be a lot of hydrogen bonding between the fibers after drying, which makes it difficult to flow and reprocessed.
3. The direct comparison between solution cast film contains 30% of glycerol and the hot compressed film is not reasonable. It is more reasonable to prepare a solution casting film from the initial CNF water suspension followed by oven drying.

Author Response

Reviewer-1

Comments and Suggestions for Authors

Shahi et al reported the ultrasound-assisted extraction of CNF from sugarcane bagasse and used it for film fabrication. The work involves environmentally friendly ultrasonication-assisted method and organic solvent-free medium for film fabrication of CNF for biomass residuals. Comprehensive characterization of the materials are conducted and the writing is clear. This research aligns well with the topic of the journal. I recommend publishing the manuscript after addressing the following issues.

1. What is the aspect ratio of the extracted CNF? The SEM images doesn't clearly morphology of extracted CNF. From the structure characterization, it seems the extracted material is between CNC and CNF.

The reviewers are correct. We did not measure the aspect ratio of CNF and its is very difficulty to measre from SEM images. These CNF are continues and find more CNC in  Ultrasonication for 3 h (CNF-US3). Also it was difficult to measue the aspect ratios in TEM because of the continues fibers. Added a new sentence on line 347 in the manuscript

1. How it can be hot compressed when a dried CNF film has already formed? There should be a lot of hydrogen bonding between the fibers after drying, which makes it difficult to flow and reprocessed.

Oven dry was performed to evaporate the water from hydrogel, during the process hydrogel was not completely dried.

1. Film was not completely dried. Oven was used to precondition the filtered hydrogel by evaporating  maximum water. The direct comparison between solution cast film contains 30% of glycerol and the hot compressed film is not reasonable. It is more reasonable to prepare a solution casting film from the initial CNF water suspension followed by oven drying.

We used both oven and the hot press of the filtered hydrogel due to the following reasons:

• Oven dry produced wrinkled films due to the formation of strong surface hydrogen bonds and consequences of which it is more brittle.
• Direct hot press of hydrogel to produced films is also not effective because water evaporation is a difficult process from metallic platens (mold). Besides, it is more likely to loss of hydrogel during high-pressure compression.
• Therefore, we pre-conditioned the hydrogel by removing the maximum water content using an oven and then hot press to make smooth films.

Reviewer 2 Report

This is a well-written paper with a lot of supportive data and results. Although the extraction of CNFs from sugarcane bagasse and the preparation of CNFs film are not a new topic, the full experiment process and material characterization would definitely help current research on cellulose and its derivatives. There are two concerns in this manuscript summarized below:

1. Not sure why 2.4. characterization is present. From 2.5 to 2.8, spectroscopic and microscopic plus thermal characterization have been well depicted. The content of 2.4 may be removed or re-edited to be combined with 2.5-2.8, unless the spectroscopic, microscopic and thermal characterization are different from the ones described in 2.5-2.8.
2. Not sure how the schematic illustration of Raw sugarcane bagasse, cellulose, and CNFs are painted in Figure 1. The authors believe a small amount of lignin and hemicellulose are still present in cellulose and CNFs after rigorous processing. No relevant data and results are provided in this study. The authors should cite a few references and discuss it.

Author Response

Reviewer-2

Comments and Suggestions for Authors

This is a well-written paper with a lot of supportive data and results. Although the extraction of CNFs from sugarcane bagasse and the preparation of CNFs film are not a new topic, the full experiment process and material characterization would definitely help current research on cellulose and its derivatives. There are two concerns in this manuscript summarized below:

1. Not sure why 2.4. characterization is present. From 2.5 to 2.8, spectroscopic and microscopic plus thermal characterization have been well depicted. The content of 2.4 may be removed or re-edited to be combined with 2.5-2.8, unless the spectroscopic, microscopic and thermal characterization are different from the ones described in 2.5-2.8.

As suggested we have edited the section 2.4 and combined with preceding sections.

1. Not sure how the schematic illustration of Raw sugarcane bagasse, cellulose, and CNFs are painted in Figure 1. The authors believe a small amount of lignin and hemicellulose are still present in cellulose and CNFs after rigorous processing. No relevant data and results are provided in this study. The authors should cite a few references and discuss it.

References added with discussion

Reviewer 3 Report

The overall presentation of the manuscript is finely defined. All the aspects and characterization techniques justified well; however, if authors would provide a couple of digital images of the finally synthesized thin film, the results could be better. 

Author Response

Reviewer-3

Comments and Suggestions for Authors

The overall presentation of the manuscript is finely defined. All the aspects and characterization techniques justified well; however, if authors would provide a couple of digital images of the finally synthesized thin film, the results could be better. 

Digital images of the film developing process and developed films are presented in graphical abstract and also included in supporting files. 

Round 2

Reviewer 1 Report

The authors address the comments well. I  recommend publishing the manuscript in the current form.