Synthesis and Characterization of Ca-ALG/MgO/Ag Nanocomposite Beads for Catalytic Degradation of Direct Red Dye
Round 1
Reviewer 1 Report
The subject matter is appropriate for Catalysts. The work is written in appropriate style. This is a good summary of experimental results obtained on the topic mentioned in the title and results will be of interests to researchers engaged in research of catalytic degradation of dyes. There are only a few things that need to be addressed and a few that can be improved. Thus, I recommend major revision of the paper.
1. The author should explain what the acronym ALG stands for in the abstract.
2. I can't agree with some parts of the manuscript. For example:
- “X-ray diffraction (XRD) investigations were carried out on an Ultima IV (Rigaku International Corp., Japan) with Cu-Kα radiation of λ = 1.54 Å in the 2θ =5-80 temperature range.”
This sentence should be corrected: X-ray diffraction (XRD) investigations were carried out on an Ultima IV (Rigaku International Corp., Japan) with Cu-Kα radiation of λ = 1.54 Å in the 2θ range from 5o to 80o.
- “EDX confirmed the presence of MgO and Ag NPs within the prepared Ca-ALG/MgO/Ag nanobeads.”
EDS analysis determines only the chemical composition, not the structure. The EDS spectrum in Figure 2 should show peaks corresponding to Mg, O, Ca, and Ag. Correct Figure 2a.
3. Find out active species by performing the scavenger studies.
4. Provide DOI for all references.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In my opinion the paper with title: “Synthesis and Characterization of Ca-ALG/MgO/Ag Nanocom-2 posite Beads for Catalytic Degradation of Direct Red Dye” could be published in the journal Catalysts if the authors will make the corrections and specifications suggested on the pdf format of the article attached.
The article needs major revision.
1. Please fill in the possible degradation mechanism of the dye in the Introduction chapter (lines 81-86). It is not understood how HO radicals act.
2. Please develop the Introduction chapter with references regarding the adsorption mechanism, models that can describe the process, kinetic studies, present in the literature for other dyes.
3. At the end of the Introduction, the author announces that he is doing studies on: the morphological behaviour before and after interactions was investigated using various parameters such as catalyst amount, equilibrium time, temperature, pH, and concentration of direct red dye solutions at the first stage. I have not seen where the influence of pH on the degradation of the dye is shown.
4. Please specify in chapter 2.2. what does pH mean under normal conditions?
5. Please correct Figure 1 - with the correct writing of the Ag NO3 formula (putting the number 3 as coefficient)
6. In chapter 2.6, please specify what the room temperature is.
7. Please insert in chapter 2 sub-chapters to explain how the experiments were carried out that focused on the dye degradation study, adsorption isotherms and the kinetic studies, the effect of the catalyst concentration, the effect of the nanotube concentration, how the degradation mechanism was determined (which method was used and which equipment was used)
8. In chapter 3.1. please specify that the average particle size was estimated to be 178 nm.
9. Figures 5 and 6 are similar (explain the same behaviour using different means). Please keep only one of them.
10. In fact, you could leave only Figure 7, which also includes Figure 6.
11. In Figure 8, only two curves can be seen, the third one is not visible. Please choose other colours to highlight the third one as well.
12. I recommend you to use other colours for Figure 9 so that the curves can be better distinguished.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Manuscript ID: catalysts-2065753
Title: Synthesis and Characterization of Ca-ALG/MgO/Ag Nanocomposite Beads for Catalytic Degradation of Direct Red Dye.
Hanan A. Albalwi reported“Synthesis and Characterization of Ca-ALG/MgO/Ag Nanocomposite Beads for Catalytic Degradation of Direct Red Dye”. They have chosen the interested field of water treatment by emerging advanced nanomaterials.Although work is transparent and can be published but still have some flaws especially in experimental part in manuscript in addition to careful reading which should be addressed before possible consideration in worthy journal Catalyst. I believe it will not take a long for the author to work on this revision. My comments are,
1. In Abstract, line 22, it should be 50 mg/L not 50 mg/ml.
2. No quantitative data/numerical values provided in abstract. Efficiency of catalyst should be mentioned in abstract.
3. There are so many techniques used for the removal of dyes in which various synthesized materials were applied for decontamination. Why author used degradation technique for the removal of direct red dye? In introduction part, line 30-50 enhance the novelty of this research by citing these latest article on photo degradation, Journal of Molecular Liquids 356 (2022) 119036, Chemical Physics Letters 805 (2022) 139939, 10.1080/24701556.2021.1980021.
4. In introduction section line 72 -89 should be replaced with more appropriate data.
5. Use same pattern throughout the manuscript. i.e min. or minutes, 300nm or 300 nm, also it should be mL not ml. please check
6. Fig. 3 is not appropriate, should be provided with better resolution and clearer Fig.
7. The expected mechanism for the degradation of direct red 83 dye is not appropriate. Should be discussed in detail, also replace Fig. 11 with more suitable one.
8. More and recent references should be included.
9. In Section 2.3 author is discussing about the preparation of metal oxide nano-dispersion. In this section, milky white suspension of MgO nano dispersion was washed with distilled water several times in order to remove the excess NaOH. After that author is saying that it was completed to 100ml with distilled water, WHAT DOES IT MEAN? What is he trying to say in this section after washing and it is not clear. Please rephrase it with.
10. In section 2.4, 10% of MgO nanodispersion was added in beakers containing a suitable volume of Alginate solution at a concentration of 3% wt/v. Author should mention the type of percentage (wt/v or v/v) of MgO nanodispersion as well as ratio of mixing of alginate solution.
11. In section 2.5, author is saying that the beads were removed from 1M AgNO3 solution and the process was repeated. WHY the process was repeated and what will happened if we increased the soaking time of beads in 1M AgNO3 solution?
12. In section 2.5, why nano beads were washed? as per my knowledge there is no need of washing as beads are fully saturated with Ag+ and this process is contaminated free. Moreover, after that Ag+ saturated nano beads were transferred in 50mL of NaBH4 in order to reduced the Ag+. Author should mention the concentration of NaBH4 and time duration of interaction of Ag+ saturated nano beads with NaBH4.
13. In section 2.6, WHY NaBH4 is added even Ca-ALG/MgO/Ag nanocomposite beads already treated with NaBH4 in section 2.5.
14. In section 3.1, author is saying that particle size by DLS is found to be 178 nm. Particle of size 178 nm is fall in the domain of nano size especially in the science of nanomaterial?
15. Moreover there is contradiction in particle size measurement by DLS and SEM/TEM. Author should explain this or correct this.
16. SEM and TEM images of synthesized materials should be provided.
17. Author should also find the particle size by Debye-Scherrer equation and compare with SEM/TEM/DLS.
18. In section 3.3.2, there is an ambiguous explanation regarding 0.5 g of catalyst that rate of reaction decreases because the dye molecules are not available for adsorption on active sites of the catalyst. But technically rate of reaction should be increased which in turns decreases the time of degradation with good efficiency as more active sites are available for adsorption.
19. Author should be carried out the BET analysis, if possible, as a supporting material in order to check the adsorption property as well as specific surface area available for adsorption.
20. Reusability test should be performed
21. Author should also incorporate the plots of other concentration in figure 10 as comparison.
22. If possible compare efficiency of synthesized material with reported materials.
23. There are so many grammatical, language, formatting and syntax errors. Should be revised by some native speaker and formatting should be checked.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I have carefully read the Authors' replies and I am inclining toward acceptance of their explanations. Therefore, I recommend the paper for publication.
Reviewer 2 Report
In my opinion the paper with title: “Synthesis and Characterization of Ca-ALG/MgO/Ag Nanocom-2 posite Beads for Catalytic Degradation of Direct Red Dye” could be published in the journal Catalysts should be published in the journal Sustainability. The authors made the corrections and specifications suggested.
Reviewer 3 Report
Accepted
If possible provide more clear figures with better resolution in proof reading process
