Animal Biopolymer-Plant Biomass Composites: Synergism and Improved Sorption Efficiency

Round 1

Reviewer 1 Report

There are things that must be improved in the Method and the Results and Conclusions:

Why were selected the S-C different contents “(wt.%): 10% (CS-10), 30% (CS-30) and 50 %(CS-50)”? There are previous works to justify this selection? Why you did not use statistical design of experiments (sample mix design) to select the levels of the content factor? The Straw content is the only factor that is studied by your method. Are you sure that the same results would be achieved under other experimental conditions? For example with other additives presence, etc.

What is the estimation error in the thermal analysis (Table 1)? How can you know if there are significant differences between 113 and 121 ºC or 105 and 101 ºC? At least the standard deviation and the experimental error must be provide in order to answer this question.

Author Response

Authors Response to Reviewers Comments on MS ID jcs-689174

Reviewer #1

There are things that must be improved in the Method and the Results and Conclusions:

Why were selected the S-C different contents “(wt.%): 10% (CS-10), 30% (CS-30) and 50 %(CS-50)”? There are previous works to justify this selection? Why you did not use statistical design of experiments (sample mix design) to select the levels of the content factor? The Straw content is the only factor that is studied by your method. Are you sure that the same results would be achieved under other experimental conditions? For example with other additives presence, etc.

Response: The choice of the of straw content (wt%) was guided by results herein and from previous studies. Previous work (see citations below) related to the cross-linking of chitosan resulted in materials with tunable adsorption properties according to the level of cross-linker (from low to high) according to pillaring effects of its fibrils upon cross-linking. We hypothesized that different levels of straw incorporation (wt%) in the chitosan matrix of the pellets may alter the adsorption properties since the straw was hypothesized to create defects in the polymer network, in parallel manner as cross-linking. By trial and error testing, we noted that the upper bound limit of straw content (ca. 50 wt.%) was a maximum value due to mechanical deterioration of the composite at higher levels (>50 wt.%). The lower bound limit (ca. 10%) was deduced based on the onset of an observable change according to variation in the TGA onset temperatures for straw (cf. Section 2.2.1 Pellet Preparation). The intermediate region (ca. 30%) between these limits was set to the midpoint region between the lower and upper bound limits. See the following references for related effects due to cross-linking:

(1)       Mohamed, M. H.; Udoetok, I. A.; Wilson, L. D.; Headley, J. V. Fractionation of Carboxylate Anions from Aqueous Solution Using Chitosan Cross-Linked Sorbent Materials. RSC Adv. 2015, 5 (100), 82065–82077. https://doi.org/10.1039/C5RA13981C.

(2)        Udoetok, I. A.; Wilson, L. D.; Headley, J. V. Self-Assembled and Cross-Linked Animal and Plant-Based Polysaccharides: Chitosan-Cellulose Composites and Their Anion Uptake Properties. ACS Appl. Mater. Interfaces 2016, 8 (48). https://doi.org/10.1021/acsami.6b11504.

(3)        Poon, L.; Wilson, L. D.; Headley, J. V. Chitosan-Glutaraldehyde Copolymers and Their Sorption Properties. Carbohydr. Polym. 2014, 109 (0), 92–101. https://doi.org/http://dx.doi.org/10.1016/j.carbpol.2014.02.086.

(4)        Poon, L.; Younus, S.; Wilson, L. D. Adsorption Study of an Organo-Arsenical with Chitosan-Based Sorbents. J. Colloid Interface Sci. 2014. https://doi.org/10.1016/j.jcis.2014.01.003.

 

Under different experimental conditions, similar results may be obtained if the materials exhibit properties that are similar similar to straw. Although the straw has weak adsorption affinity for the dyes, its hydrophobic nature in solution may contribute to surface effects and alteration of the textural properties that favour dye binding with chitosan.

 

 

What is the estimation error in the thermal analysis (Table 1)? How can you know if there are significant differences between 113 and 121 ºC or 105 and 101 ºC? At least the standard deviation and the experimental error must be provide in order to answer this question.

Response: The standard deviation of the thermal analysis results are now included in the revised manuscript.

The authors wish to acknowledge Reviewer #1 for the insightful and constructive comments on the above manuscript. We have further edited the manuscript for language, clarity, and syntax throughout to meet the high publication standards of this journal.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper is focused on the preparation and characterization of biocomposite materials based on chitosan and wheat straw. Furthermore, their sorption capacity towards dyes was explored. The topic falls within the scope of the journal. I recommend its publication after the following revisions:  

Paragraph 2.1. Please report the molecular weight and the deacetilation degree for chitosan. Paragraph 2.2.2.2 Nitrogen flows for both balance and sample should be indicated. Paragraph 2.2.2.3 Nitrogen flow for DSC analyses should be reported. DSC measurements. Did the authors perform two heating/cooling cycles on the same sample to study the “history” of the investigated materials? I suggest to report the thermogravimetric curves of the investigated samples. TGA and DSC results could be presented in an additional table. Introduction could be updated by quoting recent references on the production of biocompatible composite materials based on chitosan that were employed for drug delivery [Coatings 2019, 9(2), 70] and packaging [New J. Chem., 2018,42, 8384-8390; Compos. Sci. 2018, 2(3), 41] purposes.

Author Response

Authors Response to Reviewers Comments on MS ID jcs-689174

Reviewer #2

The paper is focused on the preparation and characterization of biocomposite materials based on chitosan and wheat straw. Furthermore, their sorption capacity towards dyes was explored. The topic falls within the scope of the journal. I recommend its publication after the following revisions:  

Paragraph 2.1. Please report the molecular weight and the deacetilation degree for chitosan.

Response: The molecular weight and degree of deacetylation of chitosan are now included in the revised manuscript.

Paragraph 2.2.2.2 Nitrogen flows for both balance and sample should be indicated.

Response: The Nitrogen flow for both balance and sample is now included in the revised manuscript

Paragraph 2.2.2.3 Nitrogen flow for DSC analyses should be reported.

Response: The Nitrogen flow for DSC analyses is now included in the revised manuscript

DSC measurements. Did the authors perform two heating/cooling cycles on the same sample to study the “history” of the investigated materials?

Response: Only one heating cycle was performed as our interest was to elucidate the effects of introduction of the different wt% of straw on the hydration properties of the pellets. The merits of this approach finds support in a study focused on the hydration of biopolymer materials (see doi: 10.1021/acsomega.8b01663). No cooling cycle was performed since the instrument was not equipped with a cooling unit to enable such measurements.

 

 

I suggest to report the thermogravimetric curves of the investigated samples.

Response: The thermogravimetric curves are now included in the revised manuscript. See figure 3A

TGA and DSC results could be presented in an additional table.

Response: A table with the TGA and DSC results is now included in the revised manuscript. See Table 2.

Introduction could be updated by quoting recent references on the production of biocompatible composite materials based on chitosan that were employed for drug delivery [Coatings 2019, 9(2), 70] and packaging [New J. Chem., 2018,42, 8384-8390; Compos. Sci. 2018, 2(3), 41] purposes.

Response: The introduction has been revised and the recommended references are now included in the revised manuscript.

The authors wish to acknowledge Reviewer #2 for the insightful and constructive comments on the above manuscript. We have further edited the manuscript for language, clarity, and syntax throughout to meet the high publication standards of this journal.

 

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Although the design method the conclusions derived from this could be improved using statistical design of experiments, the authors completely and clearly justify the factors levels in this conditions. Also, they provide the experimental errors to support their analysis and conclusions, improving the paper quality. for this reason this case study can be publicated and find interesting for the journal readers.

Reviewer 2 Report

The paper was improved according to the reviewers' suggestions. I recommend its publication in the current form.