Role of Oil Palm Empty Fruit Bunch-Derived Cellulose in Improving the Sonocatalytic Activity of Silver-Doped Titanium Dioxide

Round 1

Reviewer 1 Report

 

• The abstract section should be rewritten and look very general and not informative. In the abstract authors should mention the importance of the article briefly.
• In the introduction section, write the novelty of the work and the problem statement clearly. Provide detailed research objectives at the end of the introduction.
• Abbreviations must be clearly followed throughout the manuscript. Parameters are defined several times in the manuscript. Some parameters like COD are not described.

• Figure 1 must be clearly arranged. Higher-resolution required. Scale bar and other factors are not visible to the readers. All the figure captions must be discussed in more detail with experimental conditions.
• Figure 2- All the diffraction peaks need to be indexed and discussed appropriately.
• In experimental sections, the authors optimized the silver doping quantity over TiO₂. No detailed evidence about it in the characterization sections.
• Figure 2-7- all the figures are not uniformly arranged. Different notations have been used. Hard to differentiation between the used legends.
• N2-sorption discussion needs to be discussed in detail.
• The performance of the present composites needs to be compared with literature.
• Regeneration and reusability studies of the composited need to be presented.
• English and grammar mistakes are present. The author should check the manuscript by a native English Speaker to improve the quality of the manuscript.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript titled “Role of oil palm empty fruit bunch-derived cellulose in improving the sonocatalytic activity of silver-doped titanium dioxide” describes fabrication, characterization and application of nanocomposite Ag/TiO2/cellulose for catalytic degradation of dye. It possesses some merits for applications and can be considered to publish in Polymers after the corrections. The authors should follow the below comments:

1. In result and discussion, the authors should describe study route and mention which samples used for physicochemical characterizations and applications.
2. FTIR spectra of cellulose, TiO2/cellulose and Ag/TiO2/cellulose must be measured.
3. The catalyst Ag/TiO2/cellulose after the catalysis process should be measured TEM.
4. In experimental section, the authors prepared Ag:TiO2 = 0.05: 1 and cellulose:TiO2 = 0.1:1 but in conclusion, the authors claimed “cellulose/Ag/TiO2 with the mass ratio of cellulose:Ag:TiO2 = 0.05:0.05:1 was successfully prepared”. Please explain the difference.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.docx

Reviewer 3 Report

In the manuscript titled “Role of oil palm empty fruit bunch-derived cellulose in improving the sonocatalytic activity of silver-doped titanium dioxide”, the authors show the synthesis of a novel sonocatalyst based on cellulose/Ag/TiO₂ nanocomposite obtained by a hydrothermal method in which the cellulose was extracted from oil palm empty fruit bunches (OPEFB). This new nanocomposite was characterized by FESEM, EDX, HRTEM, XRD, UV–Vis DRS, PL, and XPS.

I do recommend this paper to be published in Polymers, after major revisions. The detailed comments are below:

• lines 58-60, Introduction: I advise the authors to insert some references at the end of this sentence, for example, Materials Science in Semiconductor Processing 2020, 112, 105019; Applied Catalysis B: Environmental 2019, 244, 1021–1064; ACS Omega 2018 3, 11270–11277; International Journal of Biological Macromolecules 2020, 164, 2477–2496.
• What grinding method did the authors use to obtain the OPEFB fibers (< 600 μm)?
• How were the Ag nanoparticles obtained? The authors add silver sulphate to the mixture according to the mass ratio of Ag:TiO₂ equal to 0.05:1 under stirring conditions for 30 min. How was reduced Ag²⁺ to Ag⁰? Which reducing agent did they use? The authors should well clarify this unclear point of the synthesis of Ag/TiO₂.
• Authors should correct “X-Ray photoelectron spectroscope” in “X-Ray photoelectron spectroscopy”. In the comments of the XPS spectra, the authors show binding energy values up to the second digit after the decimal point (For example, the high-resolution XPS spectra of the Ti 2p and the two characteristic peaks located at binding energies of 459.58 and 465.28 eV were corresponded to Ti 2p_3/2 and Ti 2p_1/2, respectively.). What is the instrumental energy resolution? What is the pass energy used?
• Authors should replace the words “overall spectrum” with “wide scanning XPS spectrum”.
• Therefore, the authors should add at the end the sentence lines 323-326, the following references (Adv. Mater. 2008, 20, 4135–4139; Chemical Engineering Journal 2020, 379, 122309) to have further experimental evidence confirming the presence of the anatase phase of the synthesized TiO2. Furthermore, they could rewrite the sentence as follows: Figure 5 (b) shows the high-resolution XPS spectra of the Ti 2p and the two characteristic peaks located at binding energies of 459.58 and 465.28 eV were corresponded to Ti 2p3/2 and Ti 2p1/2, in agreement with already reported literature data for the anatase phase (insert references).
• In order to really evaluate which electronic interactions take place in the cellulose/Ag/ TiO₂ nanocomposite, the authors should comparison the XPS spectra of this system with the XPS spectra of pure TiO₂, cellulose/TiO_2, and Ag/TiO₂ In fact, the shift of about 1.6 eV at a higher binding energy of the Ti 2p peaks for the cellulose/Ag/TiO₂ sample compared to the pure TiO₂ of literature is too high to be able to talk of an electronic interaction without a significant variation in the oxidation states of the elements involved. Therefore, I advise the authors to compare these values with those obtained from the XPS analysis of the TiO₂ synthesized by them.
• The authors wrote in the manuscript that all the binding energies were referenced to the C 1s peak at 284.6 eV. In fact, a carbon peak is always present in all air-exposed materials and nowadays is used for calibration. Therefore, this peak is assigned to both aliphatic and aromatic backbones. However, the authors assign this peak due to C – C, C = C or C – H bonds at higher binding energies (285.48 eV). While generally such signals are assigned to 284.6 or 285.0 eV (see Briggs, D.; Grant, J. T. Surface Analysis by Auger and X-Ray Photoelectron Spectroscopy, IMP, Chichester, UK, 2003) depending on the calibration used. The authors should review these calibrations. Furthermore, the peak located at 289.78 eV can also be attributed to carboxylic or carbonate groups generally present on the surface of metal oxides.
• The Ti2p states shift to higher binding energies for the Cellulose/Ag/TiO₂ system indicates an electronic depletion of the TiO₂. To whom are these electrons transferred? Since the Ag 3d states are not shifted.
• The authors made an XPS analysis on the cellulose/Ag/TiO2 nanocomposite. The referee suggests that the same type of study would be more important (and convincing) after sonocatalytic degradation to be able to evaluate any changes to the electronic structure of the system.
• English needs to be a little improved, as there are some misused conjunctions and technical flaws to correct in the manuscript.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Accept the draft

Reviewer 2 Report

Although the TEM images are not provided, the authors well revised manuscript. Now, I recommend for publication in polymers.

Reviewer 3 Report

Thanks to the authors for the answers to my questions and for the improvement of the manuscript text. However, there are still a few suggestions for the revised version:

Please, the authors are asked to review and insert reference ACS Omega 2018, 3, 11270-11277 not mentioned in the article (line 58).