Basic Research on the Adsorption Capacity and Enhancement of Bamboo Charcoal for the Prevention of Nitrate Groundwater Pollution

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article titled "Basic research on the adsorption capacity and enhancement of bamboo charcoal for the prevention of nitrate groundwater pollution" is authored by Nur Maisarah Mohamad Sarbani et al. It aims to explore the potential application of bamboo charcoal and its modified materials in adsorbing nitrate from soil to prevent groundwater pollution. This study enhances the adsorption capacity of bamboo charcoal through magnesium treatment and gelation, and evaluates its performance in soil. The following suggestion and comments should be taken:

• The section on adsorption experiments still includes material preparation, which is not reasonable.
• Line 148 of the manuscripts mentions "A total of 101.65 g of magnesium chloride hexahydrate was placed in a 1 L beaker" and line152. It seems that I didn't see any magnesium in the test filtrate. Is there a significant loss of magnesium chloride, resulting in waste?
• Line 277 of the manuscripts mentions “Previous studies also reported that surface modification with monovalent chloride ions……magnesium chloride treatment also contributed to a similar effect.“. It is generally believed that Mg is responsible for modifying the surface (such as increasing hydroxyl groups, etc.), and chloride ions should have no particular effect. So in my opinion, there is no need to quote this article, and it cannot be said to have the same impact.
• Some formatting aspects need to be noted, such as line 187.

Author Response

For research article

Response to Reviewer 1 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. I would like to thank you also for giving suggestions and examples. Please find detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

 

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: The section adsorption experiments still includes material preparation, which is not reasonable.

Response 1: Thank you very much for pointing out this matter. I agree with this and have made changes to it. Kindly refer to the revised manuscript.

 

Comments 2: Line 148 of the manuscripts mentions "A total of 101.65 g of magnesium chloride hexahydrate was placed in a 1 L beaker" and line152. It seems that I didn't see any magnesium in the test filtrate. Is there a significant loss of magnesium chloride, resulting in waste?

Response 2: Thank you very much for pointing out this matter. We apologize for the error. We already included the data in the result and discussion (characterization section). There is no significant loss. The magnesium concentration was significantly reduced after 24 hours of treatment with bamboo charcoal, indicating successful interaction with bamboo charcoal. The residual Mg concentration was measured using ion chromatography, and the adsorbed amount was calculated to be 105 mg/g. This information has been added to the revised manuscript. Kindly refer to the highlighted section (grey) in the revised manuscript.

 

Comments 3: Line 277 of the manuscripts mentions “Previous studies also reported that surface modification with monovalent chloride ions……magnesium chloride treatment also contributed to a similar effect.“. It is generally believed that Mg is responsible for modifying the surface (such as increasing hydroxyl groups, etc.), and chloride ions should have no particular effect. So in my opinion, there is no need to quote this article, and it cannot be said to have the same impact.

Response 3: Thank you very much for your comment and suggestion. I agree with you about this because the adsorption of NO₃ mainly relies on the magnesium ions. I have modified the sentences and reference accordingly to support the statement on the effective treatment of magnesium. Kindly refer to the highlighted text (grey) in the revised manuscript.

 

Comments 4: Some formatting aspects need to be noted, such as line 187.

Response 4: Thank you very much for noticing this. I already adjusted the format of the equations accordingly in the revised manuscript. Kindly refer to the highlighted text (grey).

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Comment 1: In the last paragraph of introduction, Please clearly state the novelty of this work.

Comment 2 : The section on the effect of pH needs to be further detailed. For example, it should be specified in what volume of solution 0.1 g of adsorbent is introduced.

Comment 3 : replace ‘’Mg was analyzed by changing the analytical column of the ion chromato-154 graph to that of cations’’ with ‘’Magnesium was analyzed by replacing the analytical column in the ion chromatograph with one designed for cation analysis’’.

Comment 4: Page 4, Line 141: "(3) Effect of temperature on nitrate-nitrogen". It is essential to provide the exact value of the stirring speed. Has this parameter been optimized?

Comment 5 : Authors repported ‘’50 g of bamboo charcoal was placed in a 1 L beaker’’ Why do they write : ‘’the samples were washed with tap water’’ ? Are the 50 g divided into several sub-samples before the washing step?

Comment 5: 2.2.3. Preparation of hydrogel of Mg-BC and adsorption test".

• Is the preparation method developed by the manucript authors, or is it a procedure reported by other researchers? If so, the authors should provide references.
• Please provide the size of the prepared beads?

Comment 6 : 2.3. Soil Column experiment section ‘’A nitrate ion solution of the specified concentration was gently poured into the column’’

• Specify the nitrate concentration.
• Specify the solution volume poured into the column.

Comment 7 : Add a space between the number and the unit as well as between the word and the opening parenthesis throughout the manuscript.

Comment 8 : page 5, 2.4. Evaluation parameter section : This section needs to be thoroughly revised, with more detailed information and an improved presentation.

Comment 9 : On page 4, line 164, the authors indicate that they prepared a phosphate solution. It would be helpful to clarify the purpose or use of this solution.

Comment 10 : page 6 : lines 219 and 221 : correct che-mical, ferti-lizers and dec-omposes

Comment 11 : ‘’This indicates that nitrate-nitrogen can be sufficiently within 217 if the time provided is at least 10 hours’’. This sentence appears to be incomplete :’’ within a certain range", "within acceptable limits’’ ?

Comment 12 : line 293 : ‘’in this study are attributed to the modification of magnesium and chloride ions and finer cosmetic particles’’.To which cosmetic particles does this refer?

Comment 13 : 3.2.1. Mg-BC and Hydrogel of Mg-BC section.This section requires a thorough revision to ensure scientific rigor.

Comment 14 : Line 307 : Prior studies using chitosan-based entrapment methods showed adsorption capacities of 92.1 mg/g and 35.03 mg/g [31-32], indicating that entrapment still offers a certain degree of adsorption capacity. What substance is being adsorbed and under what experimental conditions? Do these values correspond to the maximum amounts adsorbed?

Comment 15 : Page 10, ‘’Figure 13…were observed 324 thereafter’’.  This section lacks clarity and is difficult to understand. Could you please rephrase it by adding more explanations and details to make it easier to comprehend?

Comment 16 : The tables 3 and 4 do not belong in the conclusion

Comment 17 : The conclusion should not contain new data, lengthy tables or charts, nor detailed technical information, which should be presented in the main body of the text. It  should present the main results obtained, provide a clear answer to the addressed problem, and optionally suggest potential perspectives.

Author Response

For research article

Response to Reviewer 2 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. I would like to thank you also for giving suggestions and examples. Please find detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

 

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: In the last paragraph of introduction, Please clearly state the novelty of this work.

Response 1: Thank you very much for your comment. We have mentioned the novelty of this work in the revised manuscript. Kindly refer to the highlighted text (yellow) in the revised manuscript.

 

Comments 2: The section on the effect of pH needs to be further detailed. For example, it should be specified in what volume of solution 0.1 g of adsorbent is introduced.

Response 2: Thank you very much for pointing out this matter. We apologize for this. We already included the information on the volume of solution used in the adsorption experiment was 50 ml as highlighted (yellow) in the revised manuscript.

 

Comments 3: replace ‘’Mg was analyzed by changing the analytical column of the ion chromato-154 graph to that of cations’’ with ‘’Magnesium was analyzed by replacing the analytical column in the ion chromatograph with one designed for cation analysis’’.

Response 3: Thank you very much for your suggestion. I have edited the sentences as recommended in the revised manuscript. (yellow highlight)

 

Comments 4: Page 4, Line 141: "(3) Effect of temperature on nitrate-nitrogen". It is essential to provide the exact value of the stirring speed. Has this parameter been optimized?

Response 4: Thank you very much for pointing out this matter. I have provided exact information on the stirring speed, which was 500 rpm during the adsorption process in the revised manuscript. Kindly refer to the highlighted text (yellow) in the revised manuscript.

 

Comments 5: Authors reported ‘’50 g of bamboo charcoal was placed in a 1 L beaker’’ Why do they write : ‘’the samples were washed with tap water’’ ? Are the 50 g divided into several sub-samples before the washing step?

Response 5: Thank you very much for noticing this matter. We apologize for the grammatical error. No, the 50g sample was not divided into sub-samples. We already corrected the sentences in the revised manuscript. Kindly refer to the highlighted text (yellow) in the revised manuscript.

 

Comments 6: 2.2.3. Preparation of hydrogel of Mg-BC and adsorption test".

• Is the preparation method developed by the manuscript authors, or is it a procedure reported by other researchers? If so, the authors should provide references.
• Please provide the size of the prepared beads?

Response 6: Thank you very much for your comments and suggestions. The preparation of Mg-bamboo biochar hydrogel was produced according to the procedure reported by???? We have included the reference in the revised text. In addition, we also have measured the size of the hydrogel ( ) and provide the information in the manuscript.  Kindly refer to the highlighted text (yellow)…………….

 

Comments 7: 2.3. Soil Column experiment section ‘’A nitrate ion solution of the specified concentration was gently poured into the column’’

• Specify the nitrate concentration.
• Specify the solution volume poured into the column.

Response 7: Thank you very much for the comments. We already specified the nitrate concentration used was 22mg/L and the solution volume poured into the column was 10 ml as revised in the manuscript.

 

Comments 8: Add a space between the number and the unit as well as between the word and the opening parenthesis throughout the manuscript.

Response 8: Thank you very much for pointing this out. We apologize for the format error. We have thoroughly corrected it in the revised manuscript.

 

Comments 9: page 5, 2.4. Evaluation parameter section : This section needs to be thoroughly revised, with more detailed information and an improved presentation.

Response 9: Thank you very much for pointing this out. We have revised and improved this section thoroughly according to the correct format. Kindly refer to the highlighted text (grey).

 

Comments 10: On page 4, line 164, the authors indicate that they prepared a phosphate solution. It would be helpful to clarify the purpose or use of this solution.

Response 10: Thank you very much for pointing this out. We apologize for this error. We have removed the word phosphate from the manuscript.

 

Comments 11: page 6 : lines 219 and 221 : correct che-mical, ferti-lizers and dec-omposes.

Response 11: Thank you very much for noticing this. We apologize for this typing error. We have corrected the word in the revised manuscript. Kindly refer to the highlighted text (yellow).

 

Comments 12: ‘’This indicates that nitrate-nitrogen can be sufficiently within 217 if the time provided is at least 10 hours’’. This sentence appears to be incomplete :’’ within a certain range", "within acceptable limits’’ ?

Response 12: Thank you very much for pointing this out. We agree with this comment. We have adjusted the sentences into “This indicates that nitrate can be sufficiently adsorbed within a certain range of at least 10 hours” to make it easier to comprehend. Kindly refer to the highlighted text (yellow) in the revised manuscript.

 

Comments 13:  line 293 : ‘’in this study are attributed to the modification of magnesium and chloride ions and finer cosmetic particles’’. To which cosmetic particles does this refer?

Response 13: Thank you very much for your comment. We apologized for the misunderstanding. The cosmetic particles referred to the bamboo charcoal that we used in this experiment. It was purchased from LATEST Co.,Ltd, where the bamboo was manufactured according to the cosmetic-grade ingredients. This study used commercially available fine-grained bamboo charcoal powder, and the instructions said that it was the size used as an ingredient in cosmetics. To prevent misunderstandings, we have added the word “bamboo charcoal” in the revised manuscript “’in this study are attributed to the modification of magnesium and chloride ions and finer cosmetic particles of bamboo charcoal’’. Kindly refer to the highlighted text (yellow) in the revised manuscript.

 

Comments 14: 3.2.1. Mg-BC and Hydrogel of Mg-BC section. This section requires a thorough revision to ensure scientific rigor.

Response 14: Thank you very much for your suggestion. I have revised the overall section 3.2.1 for better comprehend. Due to revision made, section 3.2.1 has been changed to section 3.3 in the revised manuscript.

 

Comments 15: Line 307 : Prior studies using chitosan-based entrapment methods showed adsorption capacities of 92.1 mg/g and 35.03 mg/g [31-32], indicating that entrapment still offers a certain degree of adsorption capacity. What substance is being adsorbed and under what experimental conditions? Do these values correspond to the maximum amounts adsorbed?

Response 15: Thank you very much for your comment. The substance being adsorbed is nitrate under optimum experimental conditions of pH 3 at 30. I have revised the sentences with more details, to show that the reference value (35.03 mg/g) is comparable to our findings. Kindly refer to the highlighted (yellow) text in the revised manuscript.

 

Comments 16: Page 10, ‘’Figure 13…were observed 324 thereafter’’.  This section lacks clarity and is difficult to understand. Could you please rephrase it by adding more explanations and details to make it easier to comprehend?

Response 16: Thank you very much for your comment. We have rephrased and revised the overall text by adding explanation and more detailed information to make it easier to understand. Kindly refer to the highlighted text (yellow) in the revised manuscript.

 

Comments 17: The tables 3 and 4 do not belong in the conclusion

Response 17: Thank you very much for your comment. I agree with this. I have revised the conclusion and placed the table on the last section before the conclusion. Kindly refer to the highlighted text (yellow) in the revised manuscript.

 

Comments 18: The conclusion should not contain new data, lengthy tables or charts, nor detailed technical information, which should be presented in the main body of the text. It  should present the main results obtained, provide a clear answer to the addressed problem, and optionally suggest potential perspectives.

Response 18: Thank you very much for your comment and explanation. I agree with this. I have revised the conclusion accordingly as suggested. Kindly refer to the highlighted text (yellow) in the revised manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors, thank you for prividing your basic research on bamboo charcoal and nitrate adsorption.

The topic is very important and the material is very interesting. However, from my point of view, it was hard to follow the manuscript, due to poor quality.

Find below my recommendation.

Lines 15-17: sentence not clear and broken

Introduction: You write about "nitrate-nitrogen" (that is absorbed by plants, e.g. L. 40). In general I would recommend to write "nitrate" since NO3-N might only be relevant if you provide values for nitrogen mass balances. This you do not do within the introduction.

L. 57: "nitrate-nitrogen compounds" - there are no different compounds from nitrate.

L. 64 ff.: no references are given. what is "high" or "great" porosity and ion exchange.

L. 68: "this approach" and L. 70 "these techniques" are not clear to which you refer to.

L 70 ff: the last paragraph of the introduction does not introduce your study properly.

Materials and Methods:

L. 89: name all your devices, don't write "using equipment capable..." - this applies for the whole manuscript. Also provide sufficient details, e.g. the columns you used for ion chromatrography.

L. 90 & L. 110: there is a mismatch of the equiment you name.

L. 95 ff. until the end of the paragraph should be moved to the introduction.

Table 1 and Tabel 2 are of bad formatting, please indicate column headers. When investigating adsoroption and refering to ion exchange, you should show surfacarea or exchange equivalents.

L. 132: be more precise, don't only write "predetermined time intervals"

L. 168: What kind of soil did you use? Please provide information and characteristics.

Results and Discussion: You did not mention FTIR analysis and Boehm titration in the materials and methods section. All the details regarding the methods need to be moved to the respective section. Otherwise it is mixed up and the structure hardly can be followed.

You find pH 2 beeing the condition with highest adsorption capacity (not rate that would refer to a time dependend value, but you are in equilibrium). However, pH 2 is no value we could expact in soil or any other envorinmentally realistic condition. It would be more interesting analyzing pH ranges of 6-8.

 

 

Comments on the Quality of English Language

There are many broken sentences, typos and wrong references along the whole manuscript. 

For example: L. 66 missing space, L. 214 "showas", L 233 "Figure.3",

Author Response

For research article

Response to Reviewer 3 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. I would like to thank you also for giving suggestions and examples. Please find detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

 

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: 15-17: sentence not clear and broken.

Response 1: Thank you very much for your comment. We have modified the sentences to make it clear and easy to understand. Kindly refer to the highlighted (turquoise) text in the revised manuscript.

 

Comments 2: Introduction: You write about "nitrate-nitrogen" (that is absorbed by plants, e.g. L. 40). In general I would recommend to write "nitrate" since NO3-N might only be relevant if you provide values for nitrogen mass balances. This you do not do within the introduction.

Response 2: Thank you very much for pointing out this matter. We totally agree with this matter. We have replaced the word “nitrate-nitrogen” into nitrate in the revised manuscript.

 

Comments 3: L. 57: "nitrate-nitrogen compounds" - there are no different compounds from nitrate.

Response 3: Thank you very much for your comment. We have revised this text in revised manuscript (turquoise highlight).

 

Comments 4: L. 64 ff.: no references are given. what is "high" or "great" porosity and ion exchange.

Response 4: Thank you very much for your comment. We have added reference to this sentence and explain it to make it easier to understand. Kindly refer to the highlighted (turquoise) text in the revised manuscript.

 

Comments 5: L. 68: "this approach" and L. 70 "these techniques" are not clear to which you refer to.

Response 5: Thank you very much for your comment. We apologized for the misunderstanding. We have rearrange the sentences and modified the overall paragraph to make it clear. “these techniques” refer to the removal techniques such as biological denitrification, reverse osmosis, and ion exchange. "this approach" refers to our research (adsorption by bamboo charcoal). Kindly refer to the highlighted (turquoise) text in the revised manuscript.

Comments 6: L 70 ff: the last paragraph of the introduction does not introduce your study properly.

Response 6: Thank you very much for your comment. We have revised the last paragraph of the introduction to explain clearly the aim, overview and novelty of this research. Kindly refer to the highlighted (yellow) text in the revised manuscript.

 

Comments 7: L. 89: name all your devices, don't write "using equipment capable..." - this applies for the whole manuscript. Also provide sufficient details, e.g. the columns you used for ion chromatrography.

Response 7: Thank you very much for your comment. We have provided a clear name for the device we are using in the whole manuscript. Kindly refer to the highlighted (turquoise) text in the revised manuscript.

 

Comments 8: L. 90 & L. 110: there is a mismatch of the equipment you name.

Response 8: Thank you very much for noticing this. We have corrected the equipment as in the highlighted (turquoise) text of the revised manuscript.

 

Comments 9: L. 95 ff. until the end of the paragraph should be moved to the introduction.

Response 9: Thank you very much for your suggestion. We also agree with this suggestion. We have moved the sentences to the introduction part in the revised manuscript.

 

Comments 10: Table 1 and Tabel 2 are of bad formatting, please indicate column headers. When investigating adsorption and refering to ion exchange, you should show surfacarea or exchange equivalents.

Response 10: Thank you very much for your comment. We have adjusted the formats of Table 1 and Table 2. We have also shown the surface area of the material in Section 3.2. as in highlighted (turqoise) text in the revised manuscript.

 

Comments 11: L. 132: be more precise, don't only write "predetermined time intervals"

Response 11: Thank you very much for your comment. We have revised the sentence into “At predetermined time intervals (1, 2, 3, 4, 5, 6, 7, 10, 11, 15, 18, and 24 h), the supernatant was collected….” Kindly refer to the highlighted (turquoise) text in the revised manuscript.

 

Comments 12: L. 168: What kind of soil did you use? Please provide information and characteristics.

Response 12: Thank you very much for your comment. We used the type of soil known as andosol. We have provided some information on the characteristics of this soil as well such as “Andosol-type soil, with an average pH of 5.650.07 and a C/N ratio of 15.59 was used in this study”. Kindly refer to the highlighted (turquoise) text in the revised manuscript.

 

Comments 13: Results and Discussion: You did not mention FTIR analysis and Boehm titration in the materials and methods section. All the details regarding the methods need to be moved to the respective section. Otherwise it is mixed up and the structure hardly can be followed.

Response 13: Thank you very much for pointing out this matter. We agree with this matter. We have provided and adding information regarding FTIR and Boehm titration in the materials and method (Section 2.3) for easier understanding. Kindly refer to the highlighted (turquoise) text in the revised manuscript.

 

Comments 14: You find pH 2 being the condition with highest adsorption capacity (not rate that would refer to a time dependend value, but you are in equilibrium). However, pH 2 is no value we could expect in soil or any other envorinmentally realistic condition. It would be more interesting analyzing pH ranges of 6-8.

Response 14: Thank you very much for this valuable comment. We really appreciate it. Based on the finding in our research, pH 2 has shown the best removal of nitrate by the bamboo charcoal. The pH 2 condition used was solely to evaluate the equilibrium adsorption capacity of the adsorbent under controlled aqueous conditions. Based on our reference also, there are many studies showed better removal of nitrate between pH 3. However, we agree that this pH is not environmentally suitable and realistic for soil application. In the soil column experiments, we did not adjust the pH into 2 and instead used the natural pH of the Andosol soil (pH 5.65). Despite without pH adjustment, the Gel-Mg-BC still demonstrated excellent nitrate adsorption performance in soil, indicating its practical functionality at natural soil conditions. We hope this can clarify the matter regarding the pH relevance in the environment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript titled: "Basic research on the adsorption capacity and enhancement of bamboo charcoal for the prevention of nitrate groundwater pollution” The research presented in this manuscript is interesting and addresses a relevant topic. The explanation (except the introduction part) is not entirely clear and may be difficult for readers to follow. However, there are several aspects of the manuscript that require improvement before it can be considered for publication:

 

1. To meet the journal’s submission standards, the manuscript should be revised to strictly follow the required formatting and structural guidelines.
2. Figures 1 and 8 could be improved in terms of clarity and visual quality.
3. The references section needs careful revision. Some references do not follow the proper formatting style, and a few lack correctly hyperlinked DOIs.
4. I recommend that the authors revise the conclusion part to summarize the key findings and highlight the broader significance of their work.
5. The authors should ensure that figures and tables are positioned immediately after the corresponding text that describes them, to enhance clarity and facilitate reader understanding.
6. What was the role of calcium chloride in forming beads?
7. It would be better to include a brief definition of the hydrogel, along with a short explanation of selecting alginate as the hydrogel matrix.

Comments for author File: Comments.pdf

Author Response

For research article

Response to Reviewer 4 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. I would like to thank you also for giving suggestions and examples. Please find detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

 

2. Point-by-point response to Comments and Suggestions for Authors

Comments 1: To meet the journal’s submission standards, the manuscript should be revised to strictly follow the required formatting and structural guidelines.

Response 1: Thank you very much for your comment. We have tried to revise the overall manuscript according to the required formatting and structural guidelines. Kindly refer to the revised manuscript.

 

Comments 2: Figures 1 and 8 could be improved in terms of clarity and visual quality.

Response 2: Thank you very much for pointing out this matter. We agree with this matter. We have tried to improve the figure to better quality as in the revised manuscript.

 

Comments 3: The references section needs careful revision. Some references do not follow the proper formatting style, and a few lack correctly hyperlinked DOIs.

Response 3: Thank you very much for your comment. We have reviewed and revised the reference sections according to the required formats.

 

Comments 4: I recommend that the authors revise the conclusion part to summarize the key findings and highlight the broader significance of their work.

Response 4: Thank you very much for your comment. We agree with this comment. We have improved the conclusion section by adding the main findings and significance of this work. Kindly refer to the highlighted (yellow) text in the revised manuscript.

 

Comments 5: The authors should ensure that figures and tables are positioned immediately after the corresponding text that describes them, to enhance clarity and facilitate reader understanding.

Response 5: Thank you very much for your comment. We totally agree on this matter. We have moved the figures and tables immediately after the corresponding text as in revised manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

 

Comment 1: Page 4: Effet of temperature on nitrate adsorption section: Was the stirring speed of 500 rpm previously optimized?.

Comment 2 : Although the authors responded to comment 6, it should be noted that they did not provide, either in their response or in the manuscript, the reference as well as the data relating to the size of the hydrogels formed.

 ‘’Response 6: Thank you very much for your comments and suggestions. The preparation of Mg-bamboo biochar hydrogel was produced according to the procedure reported by???? We have included the reference in the revised text. In addition, we also have measured the size of the hydrogel ( ) and provide the information in the manuscript.  Kindly refer to the highlighted text (yellow)…………….’’

 

Comment 3 : 2.5 evaluation parameter section

• Line 204 : Leave a space between capacity and (mg/L)
• Line 208 : Add % after d:    d(%) = ...     2

Line 214 : The constant K differs depending on whether the Langmuir or Freundlich model is used. It would therefore be more rigorous to denote it as K_L​ in the Langmuir model equation and K_F in the Freundlich model equation, and to specify the respective units of these two constants within the parentheses that have been left empty.

Comment 4:

Page 4, Line 234: 3.1.1. Effect of pH, mixing time and temperature section

You previously stated that the adsorption rate is given by Equation (2). However, in this section, you mention that the same equation describes the adsorption capacity, which represents an inconsistency and immediately afterwards, you refer to the adsorption rate.

Comment 5 : page 5, line 193:

The nitrate concentration is 22 or 22.5 mg/L

Comment 6: Page 7

• Line 259: Replace Figure 3 with Figure 5
• Line 264: Move ''Figure 6'' to the end of the sentence after the Langmuir equation.

Comment 7 : Page 9 : Lines 320-322

In this section, you state that the Langmuir model describes the nitrate adsorption process, which leads you to conclude that adsorption occurs in multilayers. However, on page 7, line 268, the same Langmuir model is used to describe adsorption, but this time you conclude that adsorption occurs in a monolayer. This contradiction calls for clarification: is it a monolayer or multilayer adsorption?

Comment 8 :

Figures 9 and 10 : In the figure captions, specify that it is 0.1 g/50 mL

Ensure consistency in the notation of units throughout the text. For example :

 page 3,  50 ml      (50 mL)

 Page 4 : 150mm    (150 mm)

Author Response

For research article

Response to Reviewer 2 Comments

Thank you very much for taking the time to review this manuscript. I would like to thank you also for giving suggestions and examples. Please find detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

 

Comments 1: Effet of temperature on nitrate adsorption section: Was the stirring speed of 500 rpm previously optimized?.

Response 1: Thank you very much for your comment. Yes, 500 rpm is the stirring speed that we have optimized during the adsorption process. The suitable stirring speed is between 400-600 rpm. Higher stirring speed above than 600 rpm caused the beads structure to be unstable over long time, while too slow speed might cause inefficient mixing with the adsorbate solution. 

 

Comments 2: Although the authors responded to comment 6, it should be noted that they did not provide, either in their response or in the manuscript, the reference as well as the data relating to the size of the hydrogels formed.

Response 2: Thank you very much for your comment. We really apologize for the mistake. We have mentioned the reference in the manuscript regarding preparation of the sample as follow "The Mg-BC treatment procedure was performed according to the method from [23] with slight modification by mixing a total of 101.65 g of magnesium chloride hexahydrate with 1 L of distilled water in a 1 L beaker." (Hidayat, E., Sarbani, N. M. M., Samitsu, S., Nugroho, F. A. A., Lahiri, S. K., Aoyagi, M., ... & Harada, H. Evaluation of slow-release fertilizers derived from hydrogel beads: Sodium alginate-poly (acrylic acid) and humic acid-encapsulated struvite for soil salinity amelioration. Arabian Journal of Chemistry 2024,17(9), 105877. https://doi.org/10.1016/j.arabjc.2024.105877). 

The size particle of the hydrogel was also provided in the manuscript in Section 3.2, "The average particle diameter of the Gel-Mg-BC was determined to be 1.74 mm."

 

Comments 3: 

• Line 204 : Leave a space between capacity and (mg/L)
• Line 208 : Add % after d:    d(%) = ...     2

Line 214 : The constant K differs depending on whether the Langmuir or Freundlich model is used. It would therefore be more rigorous to denote it as K_L​ in the Langmuir model equation and K_F in the Freundlich model equation, and to specify the respective units of these two constants within the parentheses that have been left empty.

Response 3: Thank you very much for your thoughtful comment and suggestions. We have corrected the section accordingly as suggested, kindly refer to the revised manuscript, Section 2.5.

 

Comments 4: 3.1.1. Effect of pH, mixing time and temperature section. You previously stated that the adsorption rate is given by Equation (2). However, in this section, you mention that the same equation describes the adsorption capacity, which represents an inconsistency and immediately afterwards, you refer to the adsorption rate.

Response 4: Thank you very much for pointing this out. We apologized for our mistake. We have revised thoroughly and changed it into adsorption rate in the Section 3.1.1. (pink highlight) in the revised manuscript. 

 

Comments 5: page 5, line 193: The nitrate concentration is 22 or 22.5 mg/L

Response 5: Thank you very much for your comment. The nitrate concentration is 22 mg/L for the soil column test and the results can be refer to Figure 13. While, the nitrate concentration of 22.5 mg/L was used for initial experiment in aqueous solution to investigate the effect of pH, time, and temperature during the adsorption process.

 

Comments 6: Page 7

• Line 259: Replace Figure 3 with Figure 5
• Line 264: Move ''Figure 6'' to the end of the sentence after the Langmuir equation.

Response 6: Thank you very much for your thoughtful comment and suggestion. We have revised it accordingly for the text in line 259 and line 264 "Figure 5 shows a comparison of the experimental data ​with the theoretical isothermal adsorption curve ​​calculated from the constants in the Langmuir equation (Figure 6)". Kindly refer to the highlighted text (pink) in the revised manuscript. 

 

Comments 7: Page 9 : Lines 320-322

In this section, you state that the Langmuir model describes the nitrate adsorption process, which leads you to conclude that adsorption occurs in multilayers. However, on page 7, line 268, the same Langmuir model is used to describe adsorption, but this time you conclude that adsorption occurs in a monolayer. This contradiction calls for clarification: is it a monolayer or multilayer adsorption?

Response 7: Thank you very much for your detailed comment. We apologized for our mistake that causing confusion. It was supposed to be monolayer adsorption for Langmuir, while Freundlich model describes multilayer adsorption. We have changed the sentence accordingly on page 9 "This suggests that nitrate adsorption occurred via monolayer adsorption on the homogenous surface of adsorption sites".

 

Comments 8: 

Figures 9 and 10 : In the figure captions, specify that it is 0.1 g/50 mL

Ensure consistency in the notation of units throughout the text. For example :

 page 3,  50 ml      (50 mL)

 Page 4 : 150mm    (150 mm)

Response 8: Thank you very much for your kind and thoughtful comments. We apologized for the mistake and we have corrected the text as suggested. Kindly refer to the highlighted text (pink) in the revised manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for your efforts to substantially improve the quality of your manuscript.

Just one last suggest, do not use BJH for calculating surface area. For porous charcoals BET would be the recommended method.

Author Response

For research article

Response to Reviewer 3 Comments

Thank you very much for taking the time to review this manuscript. I would like to thank you also for giving suggestions and advice.

Suggestion/comment: Just one last suggest, do not use BJH for calculating surface area. For porous charcoals BET would be the recommended method.

Response: Thank you very much for your great suggestion. Yes, we are totally agree with this because BET analysis is the acknowledged and recommended method for determining the surface area of porous material. Therefore, we have revised the result for the specific surface area of the charcoal by using BET analysis. Kindly refer to the highlighted text (pink) in the revised manuscript. Thank you.

Reviewer 4 Report

Comments and Suggestions for Authors

 

Most of the suggested improvements have been addressed, and the paper is now ready for acceptance. Regarding the references, please note that references (6, 19, and 30) do not have DOI numbers available.

Author Response

For research article

Response to Reviewer 4 Comments

Thank you very much for taking the time to review this manuscript. I would like to thank you also for giving suggestions and comments.

Comments: please note that references (6, 19, and 30) do not have DOI numbers available.

Response 1: Thank you very much for pointing this out. We apologized for this. We have revised the reference information accordingly in the revised manuscript. However, for reference 6, we could not provide the DOI number since this information is not available, as it found in the database, therefore we include the URL of the database in the reference part. For reference 19, it was a department bulletin paper published by Soka University Plankton Engineering Institute, therefore we could not provide the DOI number, instead we provided the URL of the paper in the revised manuscript. Thank you very much.