Visible Light-Driven Organic Pollutant Removal Using Fe-Based Photocatalysts Supported by Wheat Straw Biochar
and Guangru Zhang 3
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript is presented well, describing utilizing of biochar in the generation of photocatalysts. The adopted methods can be improved considering literature support and additional investigations. Here are some specific comments:
1. Introduction needs more literature support better to compare biochar-based materials used in such applications and highlight the advantages of using them.
2. All the figures incorporated are of low resolution in the manuscript. High resolution figures should be provided.
3. What is the significance of band gap calculation of the composite? When there is no apparent change in the band gap of the composite, BC and other photocatalyst prepared in this study.
4. Authors, discussed about surface area and porosity, it’s better to include the BET surface area investigation of the photocatalysts.
5. In Photocatalysis no supporting studies like, chronoamperometry, linear Sweep Voltammetry etc. are provided. Authors should add these studies. Only photodegradation is not enough.
Comments on the Quality of English Language
Can be improved.
Author Response
Thank you for your comments and suggestions. They were all accepted and the required changes have been implemented in the revised manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsManuscript title: “Visible Light-Driven Organic Pollutant Removal Using Fe-Based Photocatalysts Supported by Wheat Straw Biochar”.
The current work reports the development of highly functional photocatalyst materials using environmentally friendly and sustainable resources. The study is interesting, as the authors justified the impact of doping copper (Cu), chromium (Cr), and zinc (Zn) to enhance the photocatalytic activity of BC-Fe-based catalysts for the removal of methylene orange (MO) from water. However, there are some suggestions and opinions to improve the overall look of the manuscript. Thus, my suggestion is “MINOR REVISION”.
1. The introduction is well written and covers the topics in an orderly manner. There are a few suggestions that should be included.
Ensure that the content is up-to-date and informative by adding recently published articles.
The novelty and future perspectives should be added at the end of the introduction.
It is recommended that the full name be used instead of the short form if the characterization name is repeated.
2. The purity percentage of each precursor should be included in section 2.1.
3. In section 2.2.1, add the complete information regarding the preparation of BC. Like as, the condition regarding carbonization, washing etc.,
4. Figure 1. It is suggested to include reaction steps in the complete process instead of naming.
5. The author requires to calculate the crystallite size using corresponding values from XRD data.
6. The values of the band gap have not been specified precisely. Revise the values and confirm the position of the tangent drawn.
7. Figure 2. Provide the EDX spectra to confirm the elements presence in the final product.
8. Authors must provide the reusability test of the photocatalyst with different usage cycles.
9. A hot filtration test could be provided for the examination of the heterogeneous or homogeneous behavior of synthesized catalyst.
10. Authors should provide a table for the comparison of previous work so that readers can better gain knowledge about the pros and cons of their study.
11. The authors should make the necessary modifications and responses before acceptance.
Author Response
Thank you for your comments and suggestions. They were all accepted and the required changes have been implemented in the revised manuscript.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsManuscript ID: catalysts-2778150
Manuscript title: "Visible Light-Driven Organic Pollutant Removal Using Fe-Based Photocatalysts Supported by Wheat Straw Biochar"
The manuscript reports on the photocatalytic properties of Fe/Cu/Zn/Cr-biochar nanocomposites obtained by co-precipitation. Although the study is of interest and practical importance, at the current stage, manuscript has a considerable room for improvement.
Major comments:
1) Although authors discuss EDS mapping, they don't present the elemental composition of the structures derived from EDS. Elemental composition should be discussed in detail to address the following points: was -NO3 removal efficient; do the synthesized materials contain impurities; what is the Fe/Cu/Zn/Cr/C ratio and why: does the particular ratio ensures the most efficient catalytic properties of the materials? Can the enhancement of the BC-Fe-Cu/Cr/Zn catalytic properties in comparison to BC-Fe be explained by the increase of the catalytic sites (i.e., increase of the metal content) rather than by some Fe-Cu/Cr/Zn synergy?
2) Role of Fe, Cu, Zn and Cr in the photocatalytic process should be addressed in more detail. Conceptually, what is the advantage of bimetallic composites, how does the presence of 2 metals increases the photocatalytic effect?
3) As biocarbon is a part of all of the investigated materials, its structure and its variation should be discussed in more detail: what in the sp2/sp3 ratio, do sp2/sp3 content and carbon disorder change with metal incorporation?
4) Line 302-303, "The interaction between the metal photocatalyst and non-metallic dopants enables visible light or direct solar activation": currently there is no evidence that carbon is a dopant in the metal structure. On the contrary, metals used in the study are incorporated in carbon matrix, and, according to Fig. 2(f), they don't demonstrate any lattice distortions or incorporated carbon nanoparticles. Additionally, I don't think that carbon incorporation into Cr and Fe will result in the metals' doping by C atoms: as Cr and Fe are carbide-forming, one would expect Fe3C and Cr3C2 formation as a result of such interaction rather than Cr and Fe doping by carbon.
To sum up, current presentation doesn't allow to verify the "metallic dopants" presence and related effects suggested by authors. Either the hypothesis regarding metal-carbon influence on photocatalytic performance of the structure should be reformulated or carbon doping is to be proven by additional analysis techniques: HRTEM would allow to detect carbon incorporation into metal; XPS will supposedly make it possible to detect Fe3C and Cr3C2 bonding.
Minor comments:
5) Lines 53-54, "Moreover, carbon in the BC serves as a non-metallic dopant and enhances photoactivity of metal photocatalyst [16,17]": please explain in more detail why metal photocatalyst needs a dopant and how carbon enhances metal photoactivity.
6) Line 107, how was carbon content determined?
7) Fig. 3 should be named "EDS mapping..." rather than "EDS spectra...". In (a1)-(d1), the legend is not visible, and, therefore, types of mapped elements are unclear.
8) In Fig. 4, types of lattices marked with star/rhomb/triangle/circle types of dots are not communicated.
9) In Table 1, only 2 lines of biocarbon are presented. However, its diffraction (fig. 4a) shows at least 7 intensive lines. What is the origin of the remaining lines?
10) In Table 1, consider identifying the crystals which reflections were detected. In current stage, the table seems confusing, as the (002) diffractions from graphite and Fe are peaking at various diffraction angles.
11) In Fig. 4(c), what is the origin of the line at ~62°? In Fig. 4(e), what is the origin of lines at ~18°, ~42°, ~71°, ~73°?
12) Line 265, by "Fe2O3", do you mean γ-Fe2O3 (maghemite) or α-Fe2O3 (hematite)?
13) In the discussion of Table 2, please elaborate on how SSA, pore size and pore volume were assessed. In Table 2, by "pore size", do you mean "average pore size"?
14) Line 288, "2θ = 23.00º" does the precision of XRD technique allowes to determine this value with up to 4 significant figures?
15) Fig. 5(b): as Y scale range is arbitrary for all of the subfigures, why does "BC" dependence is plotted so the majority of the graph is empty? If the plots are normalized to a similar value, consider communicating it in the text and indicating the Y tick values in the subfigures.
16) In the caption of Fig. 6, please communicate what is shown in the inset. In the inset table, please indicate what is the measurement unit of Qe.
17) Lines 373-374, "smallest calculated atomic radii, with 142, 373
compared to Cu (145 and Cr (166)": what are the measurement units of the radii?
18) Line 134, rephrase " were examines".
19) Lines 230-231, rephrase "magnification times of 1800".
20) Line 290, is "exfoliation" term used correctly in current case? Maybe you've meant "etching"?
21) Lines 291-292, consider revising "mesoporous pore" phrasing.
Author Response
Thank you for your comments and suggestions. They were all accepted and the required changes have been implemented in the revised manuscript.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have improved the manuscript and addressed certain comments with relevant details. The manuscript can be accepted in the present form.
Comments on the Quality of English LanguageMinor editing and proof reading is required.
Reviewer 3 Report
Comments and Suggestions for AuthorsManuscript: "Visible Light-Driven Organic Pollutant Removal Using Fe-Based Photocatalysts Supported by Wheat Straw Biochar"
ID catalysts-2778150
Although most of the major concerns regarding the study were resolved after the revision, authors have only partially addressed my comments. Additional work should be done to make the manuscript ready for publication.
1) The reply to question 4 indicated that authors have agreed that "carbon doping" term should be omitted in current manuscript. However, relatd phrasing have only been corrected once. I suggest such term to be reformulated in all of the manuscript rather than in 1 place. See lines 53-54, "carbon in the BC serves as a non-metallic dopant", line 501, "size of doped BC", line 571, "carbon-based dopant".
2) Lines 54-55, "Carbon does not possess semiconducting properties": it actually does -- in sp-carbon form, such as polyyne [10.3390/molecules27185829]. Consider reformulating the sentence.
3) Insents of Fig. 3(b-d): why carbon content is not presented?
4) Reply to q. 10 indicates that "We have identified the crystals observed in the XRD spectra of all the prepared samples and included them in Table 1 of the revised manuscript for the readers’ better understanding". However, the required change (identifying the particular crystals with associated diffraction angles and Miller indices) wasn't done. Current notation is confusing, as, for example, in BC-Fe-Zn, there are 2 (110) reflexes of various crystals at 39.9º and 53.1º.
5) Line 61, "was able to ameliorates"
