Synthesis, Characterization, and Performance of Nano-Metal-Oxide (Al₂O₃) Blended Biochar for the Removal of Iron from Contaminated Water for Enhanced Kinetic and Adsorption Studies

Round 1

Reviewer 1 Report

"Synthesis, characterization, and performance of Nano-Metal Oxide (Al2O3) blended biochar for the removal of iron for enhanced kinetic and adsorption studies" is a good topic and fits the aim and scope of Processes. However, I do not recommend its publication until the authors can revise the following points;

1.     Please, adjust equation 1.

2.     The terms of equation 9 should be defined.

3.     The adsorption mechanism of iron should be explained.

4.     The quality of the whole tables and figures should be improved.

5.     SEM of BC and NMOBC should be added to the manuscript.

6.     The removal % of iron by NMOBC was lower than BC, so what is the value of Al2O3.

7.     The adsorption aptitude of Al2O3 should be studied.

8.     The manuscript organization and language need further improvements.

English language needs further improvements.

Author Response

Dear Reviewer

We appreciate the valuable comments and suggestions provided by you, which have greatly contributed to enhancing the quality of our work. We have carefully considered all the comments and have made the necessary revisions to our manuscript. We believe that this revision/update has significantly improved the manuscript and it will meet your expectations to consider it fit for publication.

Author Response File: Author Response.docx

Reviewer 2 Report

See the attached file.

1. Title Revision:

• The current title does not accurately reflect the specific application of the research, which focuses on wastewater treatment. I recommend rewording the title to more clearly highlight this aspect, ensuring it aligns with the paper's aim and findings.

2. Chemical Notation:

• There are inconsistencies in the chemical notation used throughout the paper. For instance, on line 125, Al2O3 should be written with the appropriate subscripts. This applies to all chemical formulas mentioned in the text to maintain scientific accuracy and readability.

3. Notation for Coefficient of Determination:

• The notation for the coefficient of determination is incorrectly presented as R^2. It should be corrected to R² (R superscript 2) throughout the document to adhere to standard scientific notation.

4. Infrared (IR) Spectroscopy Data:

• The IR spectra provided do not show the bands at 3640, 3280, and 2920 cm-1 on the graph as mentioned in the text. It's essential to include a high-quality figure that clearly presents these peaks for validation of the discussed findings. Authors can also repeat the spectra or explain why the intensities of these peaks are very low and completely diminished.

5. Scanning Electron Microscopy (SEM) Analysis:

• The paper presents SEM micrographs c and d, but there appears to be no significant difference between them. This observation needs clarification or additional data to support the claimed differences. Moreover, the iron peak from EDX shows a change from 0.9 to ~1, which is not significantly evident. This section would benefit from a more detailed analysis or presentation of more pronounced results.

6. Conclusion Revision:

• The current conclusion is redundant and lacks clarity. It fails to succinctly summarize the key findings and implications of the study. I suggest a complete rewrite of the conclusion to make it more concise, focused, and reflective of the research outcomes. The revised conclusion should eliminate vague statements and instead provide clear, meaningful insights derived from the study.

7. Results and Discussion:

• Ensure consistency in the presentation of data and its discussion.
• Consider adding a comparative analysis with similar studies for a more comprehensive context.

Author Response

Dear Reviewer

We appreciate the valuable comments and suggestions provided by you, which have greatly contributed to enhancing the quality of our work. We have carefully considered all the comments and have made the necessary revisions to our manuscript. We believe that this revision/update has significantly improved the manuscript and it will meet your expectations to consider it fit for publication. Regards

Prof. Dr. Tariq

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript entitled "Synthesis, characterization, and performance of Nano-Metal- Oxide (Al₂O₃) blended biochar for the removal of iron for enhanced kinetic and adsorption studies" submitted by Aftab Ahmad Khan, Javed Iqbal, Muhammad Tariq Bashir, Muhammad Tahir Amin, Muhammad Ali Sikandar, Muhammad Muhitur Rahman, Md. Arifuzzman is a well-organized study.

The article is interesting, neatly written, bringing some useful information. I think that the manuscript has a potential to be published in the journal.

I also suggested some minor corrections as follows:

- Please add the affiliation of the second author. Also, correlate the authors' numbers with those in their affiliation list.

- In the Materials and Reagents chapter, you stated that you use sulfamethoxazole (SMX) and bisphenol A (BPA), but I did not find anywhere in the article where exactly you have use them. Please clarify this aspect.

- In paragraph 2.6. Iron Adsorption Process on BC and NMOBC you wrote: “... the mixtures were filtered to separate the adsorbents, and the iron cation concentration of the filtrate was measured...”. How do you know that the filter does not retain Fe³⁺ ions, thus changing the concentration of the filtrate?

- please review carefully the writing of the chemical formulas in the entire manuscript. E.g., at L125, L138, write formula with subscripted indexes

- L191 - Please correct formula (1)

- Figure 3. please replace ” SEM/EDX” with ” EDX/SEM” in the title

- The EDX spectra are very small and not quite visible. Please replace the spectra in figure 3 with larger and clearer ones.

- In table 2, please fill with Pseudo - second order on NMOBC

Please carefully check the English.

Author Response

Dear Reviewer

Unfortunately, the wrong file was uploaded in your section. We appreciate the valuable comments and suggestions you provided, which have greatly contributed to enhancing the quality of our work. We have carefully considered all the comments and have made the necessary revisions to our manuscript. We believe that this revision/update has significantly improved the manuscript and will meet your expectations of considering it fit for publication. Please find attached the correct file. Regards

Prof. Dr. Tariq

Author Response File: Author Response.docx

Reviewer 4 Report

The paper entitled “Synthesis, characterization, and performance of Nano-Metal-Oxide (Al₂O₃) blended biochar for the removal of iron for enhanced kinetic and adsorption studies” reported the removal of iron cations from water. This study seems incomplete yet. The major reasons are

11. Effect of Al₂O₃ is not clear.

22. The adsorption isotherm is not suitable to discuss the adsorption mechanism.

33. Some authors’ explanations are not based on the data (although authors also seem to be confused with their samples).

Therefore, I recommend to check and revise whole of the manuscript and resubmit it.

Line 7: the affiliations were not matched with the author list.

Line 246: How did the authors prepare BC-Fe and NMOBC-Fe?

Line 253: The peak at 2920 cm⁻¹ can not be recognized.

Line 286: The sentence said that Figure 3c is iron-intercalated NMOBC while the figure caption said 3c is Iron loaded BC. Which is correct?

Line 287: Please explain how “noticeable differentiation”.

Line 290: Although the EDX in Figure 3a is hard to see, it seems that BC does not include iron. Moreover, the authors claimed that BC and NMOBC showed Fe-O band in IR at line 261 without 540 cm⁻¹. What is the reason?

Line 298: Scale bars in SEM and EDXs can not be recognized due to low resolution of the figures.

Line 394: The good fitting results by the 3 equations were thought to be due to the low concentration of iron. Please show higher concentration result.

Line 496: The adsorption isotherm seems not to reach to plateau. It is hard to discuss the mechanism from the data. The author should show an adsorption isotherm with wider concentration range.

Line 544: Finding 1 is not based on the experimental data.

Line 547: The authors did not explain about finding 2 very well.

The manuscript includes many typos and grammatical errors, for example,

2 and 3 of Al2O3 should be subscript.

Line 119: degree signs in this paragraph are strange.

Line 127: 5 grams

Line 128: 150 ml and 50 ml.

Line 193: the units for k₁ and k₂ are missing. k₂ should be K₂.

Line 274: Wavelength is not suitable for x-axis of IR spectra.

Author Response

Dear Reviewer

We appreciate the valuable comments and suggestions provided by you, which have greatly contributed to enhancing the quality of our work. We have carefully considered all the comments and have made the necessary revisions to our manuscript. We believe that this revision/update has significantly improved the manuscript and will meet your expectations of considering it fit for publication. Regards

Prof. Dr. Tariq

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript has been carefully revised, so I recommend its publication in the present form.

Author Response

Dear Reviewer,

We extend our thanks for your encouraging comments regarding accepting the manuscript that states "The manuscript has been carefully revised, so I recommend its publication in the present form".

We extend our thanks for your encouraging comments regarding accepting the manuscript.

Reviewer 2 Report

The authors have addressed all comments. The manuscript is now ready for publication in its current format.

Author Response

Dear Reviewer,

We extend our thanks for your encouraging comments regarding accepting the manuscript that states, "The authors have addressed all comments. The manuscript is now ready for publication in its current format."

Reviewer 4 Report

I think this result can be explained simply by increase of surface area by adding nanoparticles, although the authors did not show data about particle size of nanoparticles and surface area of biochars. In order to explain their opinion, further experiments seem to be necessary.

Line 348: It is better to show EDS mapping to show the white particles are Al₂O₃ and Al₂O₃ acted as adsorption sites for Fe.

Line 348: the morphology of BC and NMOBC seems totally different. What is the reason?

Line 424: What is the evidence to claim that Al₂O₃ had porosity?

Line 442: The pH_PZC values for BC and NMOBC were almost same. What is the reason why the authors thought electrostatic attraction?

Line 557: The adsorption isotherms seem at just initial stages. Especially, Figure 7a is almost linear, although slightly bending downwards. I think even line fitting would give reasonable R² value. Thus, discussion based on this data is no meaning.

The manuscript still includes several grammatical errors. Please check.

Author Response

Dear Reviewer

We appreciate the valuable comments and suggestions provided by you, especially adding further experimentation about the surface area of both adsorbents. This paper is part of a mega project, and we have collected sufficient data. In response to your valuable comments, we have added a section (3.3). The background is also improved considerably in the introduction. We believe that this further revision/update has improved the manuscript and it will meet your expectations to consider it fit for publication. See the attached file for a response.

Regards

Prof. Dr. M Tariq Bashir

Author Response File: Author Response.docx

Round 3

Reviewer 4 Report

It seems that the novel point of this paper is that synthesis of biochar-alumina hybrid with an easy way (just mixing), although the adsorption isotherms are not sufficient. Please add this point. However, the porosity of alumina is quite important for this research. I guess the porosity of alumina is not high, suggesting that the author’s way still have possibility of improvement by utilizing high porous alumina.

Line 309: Reference 31 and 32 did not mention about crystallinity of biochar, although they synthesis their metal-biochar hybrid pyrolysis which may affect the crystallinity of biochar. However, the authors prepared the hybrid just mixing. It is hard to think crystallinity changed.

Line 375: Please add the data of the alumina and show adsorption isotherms.

Line 424: Porosity of alumina (with/without porous, shapes and diameter) totally depends on type of alumina. The authors bought the alumina from Merk, which means the alumina is deferent from those reported in reference 18 and 19 (reference 20 was not related to alumina). Please check the porosity.

Line 52: pi should be π.

Author Response

Dear Reviewer,

We do understand your expertise in the area of adsorption and appreciate your recognition of the novelty of our approach in conducting this research study. But, we guessed that there was some sort of misunderstanding. We did not prepare a biochar-alumina hybrid by just mixing. Instead, we employed a well-defined method which is illustrated in section 2.3. Regarding your observation on the porosity of alumina, we acknowledge its critical role in the effectiveness of our Alumina blended biochar material. Contrarily, in our study, we opted to use a specific amount of aluminum oxide nanoparticle, primarily to balance between performance and economic feasibility. We used only 1% of aluminum oxide nanoparticles keeping the aim to maintain an economical approach, which is crucial for the practical application (Section 2.3). The separate study of the adsorption capacity of Al₂O₃ (nanometal) is beyond the scope of this research study.

Regards