Sulfonated Cellulose-Based Magnetic Composite as Useful Media for Water Remediation from Amine Pollutants

Round 1

Reviewer 1 Report

The research addressed it is interesting to move forward with the implementation of the IONPs on environment applications. Overall, the paper shows good work in the literature review, objective definition, material preparation, experimental procedure, and results. The conclusions are up-to-date and very interesting from an ecological point of view.

However, there are some minor comments that should be taken into account.

Comments can be found in the attached document.

Comments for author File: Comments.pdf

Author Response

1. In the text (line 48) and in the References paragraph, two new references were added, as suggested.
2. The supplier of elemental analyzer instrument (line 131) was indicated in the suggested form.
3. The Scheme 2 and Scheme 3 were redesign with a better quality of imagines.
4. The word microcrystals (line 262) was corrected.
5. Really, to our knowledge, there are not studies with magnetite-decorated sulfate cellulose nanoparticles (MDSCNs) or with ammonium salts to compare to our results. Therefore, a comparison of our results and data obtained with sulfonate cellulose not magnetic that employs amine (Water Sci. Technol. 2012, 66, 2638–2646,) and not ammonium ions would be inappropriate.

Reviewer 2 Report

In my opinion, some more details should be added in the manuscript about the characterization of the presented Magnetite-decorated sulfate cellulose nanoparticles (MDSCNs) composite material.

For example, XRD measurements and information about the composite material particle size should be added.

Some more detailed information about the ionic exchange mechanism during the adsorption process should be reported.

Moreover, the Authors should add experiments to demonstrate how physico-chemical

parameters, such as the contact time, amount of the adsorbent material, pH, temperature and ionic strength influence the adsorption process and adsorption capacity of the composite material.

Information about adsorption Isotherms, Kinetics and Thermodynamics should be reported.

Desorption experiments should be also performed in order to assess if the composite material can be reused for further adsorption processes.

Furthermore, XRD, XPS and FTIR measurements should be performed both before and after the adsorption process.

A comparison with previous literature should be performed by using a Table reporting the adsorption capacity of the presented adsorbent with those obtained in similar works.

At Line 278, please, correct error typo “to take parte”.

Author Response

1. The focus of our work was prevalently oriented towards the application of a synthesized nanomaterial as water remediation from amine pollutants. For this reason, we think that the characterization of our magnetite-decorated sulfate cellulose nanoparticles (MDSCNs)
   can be considered sufficient without XRD measurements. Moreover, our principal interest was the obtaining of a cellulose nanomaterial with magnetic characteristic; therefore, the determination of material particle size, which should be done by a TEM analysis, goes beyond our purpose.
2. As suggested, we have specified better the ionic exchange mechanism described in Scheme 3 (line 276).
3. As suggested, in the text a new sentence was added to explicate that the contact time and the temperature were selected from literature data (line 161). In particular, it was indicated that the amount of adsorbent material was calculated in function of sulfonate groups and that pH value corresponds to salification one of amines. (line 162). Moreover, it is correct to think that the ion strength can be influenced by the presence of cations in solution, but our work has to be considered as a first and initial study with a magnetic material to water remediate from amine pollutants, without the presence of interferences by other cations. Moreover, the adsorption capacity of magnetic nanocellulose not sulfonated was negligible (≅ 2%). A comment about this result was added in line 312.
4. Desorption experiments was conducted on N,N-diisopropylethylamine. The obtained result demonstrated that after the first cycle the composite material lost its adsorptive properties. In the text, a sentence was added to clarify this experimental evidence (line 321).
5. An IR spectrum was recorded after the absorption process of ammonium on the sulfonated nanocomposite, observing no detectable different of signals. All IR- spectra are collected in Supporting Information. A sentence was added in line 230 to explicate this observation.
6. Really, to our knowledge, there are not studies with magnetite-decorated sulfate cellulose nanoparticles (MDSCNs) or with ammonium salts to compare to our results. Therefore, a comparison of our results and data obtained with not magnetic sulfonate cellulose that employs amines (Water Sci. Technol. 2012, 66, 2638–2646,) and not ammonium ions, would be inappropriate.

Reviewer 3 Report

In this study, a micrometric composite material bearing an acidic function on cellulose’s surface was synthesized, which is capable of electrostatic interactions with hydrochloride amines for their effective removal and recovery. This study presents interesting results and could be accepted for publication after addressing following comments/suggestions:

1. The introduction section should contain a brief overview of the absorbents for amine removal with specific examples. In addition, the objectives of this study should be revised to indicate whether characterisation of the prepared composite material was the main aim of this study or the removal of amines.
2. Please include the purities of all the chemical/reagents used in this study
3. The discussion on the characterization of the prepared composite material should be expanded and the findings should be discussed considering the available literature. For instance, Summary of assignments for peaks in FTIR spectra as well as the significance of acid-based titration.
4. The major limitation of the study is the lack of focus on kinetic parameters as well as effect of operating conditions. Please present effect of pH or mixing time and/or reusability of the composite material.
5. This manuscript requires to be proofread thoroughly to weed out typos and grammatical errors.

Author Response

1. As suggested, in Introduction paragraph we have introduced a brief overview on the adsorbents for amine removals (lines 85). In particular, the focus of our work was prevalently oriented towards the application of synthesized cellulose magnetic nanoparticles as water remediation from amine pollutants and for this reason, we have clarified better this concept in Introduction section (line 66).
2. In the experimental section, it was already specified that the purity of all reagents was the commercial one; however, as suggested, now in the text we have added the sentence that this purity was controlled by GC analysis and relative GC chromatograms are reported in Supporting Information (line 101).
3. FT-IR spectra and the table with FT-IR data were reported in Supporting Information.
4. The pH value was chosen so as to transform the whole amount of amine into ammonium ion. In the text, a pH range was added to clarify this concept (lines 151 and 163). Desorption experiments was conducted on N,N-diisopropylethylamine. The obtained result demonstrated that after the first cycle the composite material lost its adsorptive properties. In the text, a sentence was added to clarify this experimental evidence (line 321).

Reviewer 4 Report

The article utilizes modified microcrystalline cellulose based material for purification of water from amine pollutants. The following points are recommended:

1. % modification of sulfonic acid groups should also be mentioned in 3.2.3 section in mol/mol terms.
2. Similarly, loading of magnetite should be quantified.
3. The materials should also be characterized through XRD for the magnetite peaks.
4. For adsorption experiments, control microcrystalline cellulose without sulfonic acid modification (with magnetite) should be performed to clearly demonstrate the benefit of the current method.
5. What is the adsorption time for the pollutants?
6. I believe, more rigorous classification and molecules are needed to comment on the effect of steric and electronic factors on the adsorption capacities.

The article can only be published after proper and rigorous implementation of the above comments.

Author Response

1. In the text (section 3.2.3) we used mol/g to indicate the percentage of modified sulfonic acid groups and not in mol/mol because the Molecular Weight of cellulose is unspecified.
2. The amount of obtained magnetite-decorated sulfate cellulose nanoparticles (MDSCNs) and magnetite were added in line 128. A sentence to clarify the percentage of used magnetite was added in line 196.
3. The focus of our work was prevalently oriented towards the application of a synthesized magnetic nanomaterial as water remediation from amine pollutants. For this reason, we think that the characterization of our magnetite-decorated sulfate cellulose nanoparticles (MDSCNs)
   can be considered sufficient without XRD measurements.
4. The adsorption capacity of magnetic nanocellulose not sulfonated was negligible (≅ 2%). A comment about this result was added in line 312.
5. The adsorption time was reported in paragraph 2.3. We specified it better in line 161.
6. We think that the reported experiments are sufficient for a preliminary study.

Round 2

Reviewer 2 Report

The authors have complied with the requested changes into the manuscript; so the paper can be published in the present form. In my opinion, I would to suggest to study Adsorption Isotherms, Kinetics and Thermodynamics about the adsorption processes for future research works.

Author Response

We thank you for the suggestion that we will try to exploit for a subsequent manuscript.

Reviewer 3 Report

The authors have improved the quality of the manuscript. Hence, the manuscript may be accepted for publication.

Author Response

Thank you so much

Reviewer 4 Report

Authors should address comment 6 or provide explanations for not addressing this. An international journal like Applied Sciences is not supposed to publish preliminary lab results with explanations not validated by experiments or supported by previous results.

Author Response

As suggested, we have inserted some sentences in the text (line 288-292; 301-302 and 307-309) to a more complete justification of obtained results with aliphatic and aromatic amines.