Sorption-Desorption of Phosphorus on Manure- and Plant-Derived Biochars at Different Pyrolysis Temperatures

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The goal of this work was to increase phosphorus efficiency in soil by utilizing agricultural and farm derived wastes based biochars. Authors tried to find out the effect of pyrolysis temperatures on phosphorus sorption efficiency of biochars by studying properties and structures of biochars generated at two diffident temperatures. Moreover, authors also tried to establish a mechanism of phosphorus sorption on biochars.

The subject of this work is important but not very novel.  There are a few issues for which the manuscript in its current form might not be suitable for publication.

1)      For any application employing activated carbons or biochars, porosity is very important. As authors have reported, increase of temperature a lot of times decreases specific surface area as micropores get converted to macropores. It will be important to find out if a similar conversion is occurring here. This may help to find out the real mechanism involved in this process.

2)      In the line # 347, authors stated. ‘the materials with a high SSA have a larger surface area available for interaction with their surroundings, which can result in higher sorption capacities’. However, earlier (line # 328) authors wrote, ‘phosphorus sorption capacity and the SSA of biochar were found to be negatively correlated in the study, suggesting that higher P sorption is correlated with lower SSA’. Authors need to justify these self-contradictory statements.

3)      In the line # 353, authors stated, ‘Surprisingly the value of Qmax for PB at 600°C is even greater than both manure biochars at the same temperature’. This is not correct as Q_max  of FYMB at 600˚C is 3.18 and Q_max of PB at the same temperature is 2.82.

Author Response

Response to Reviewer 1 Comments
1. Summary
Thank you for dedicating time to review the manuscript. Please find detailed responses below, along with corresponding revisions highlighted /presented in track changes in the resubmitted file. The revisions have been indicated using red-colored text in manuscript file.     2. Questions for General Evaluation Reviewer’s Evaluation Response and Revisions Does the introduction provide sufficient background and include all relevant references? Yes/Can be improved/Must be improved/Not applicable We have ensured that the background information has been thoroughly updated, and have verified the relevance of all references cited in the manuscript. Are all the cited references relevant to the research? Yes/Can be improved/Must be improved/Not applicable We have verified the relevance of all references cited in the manuscript Is the research design appropriate? Yes/Can be improved/Must be improved/Not applicable   Are the methods adequately described? Yes/Can be improved/Must be improved/Not applicable   Are the results clearly presented? Yes/Can be improved/Must be improved/Not applicable   Are the conclusions supported by the results? Yes/Can be improved/Must be improved/Not applicable Conclusion section has been updated.
3. Point-by-point response to Comments and Suggestions
Comments 1: For any application employing activated carbons or biochars, porosity is very important. As authors have reported, increase of temperature a lot of times decreases specific surface area as micropores get converted to macropores. It will be important to find out if a similar conversion is occurring here. This may help to find out the real mechanism involved in this process.
Response 1: Thank you for bringing this to our attention. We acknowledge and agree with this comment. The required information has been incorporated in the manuscript (Page 6, Line 202-206 and Table 1)
Comments 2 In the line # 353, authors stated, ‘Surprisingly the value of Qmax for PB at 600°C is even greater than both manure biochars at the same temperature’. This is not correct as Qmax of FYMB at 600˚C is 3.18 and Qmax of PB at the same temperature is 2.82. Response 2: The mistake has been addressed and rectified.

Reviewer 2 Report

Comments and Suggestions for Authors

The article is devoted to the current topic of studying the physicochemical properties of various biochars. The authors used modern research methods to study biochars. The data obtained are described using various adsorption models.

Author Response

Thank you for your positive feedback on our research article. We greatly appreciate your support and encouragement.

Reviewer 3 Report

Comments and Suggestions for Authors

This paper examines P sorption-desorption in plant-based (parthenium, corn cobs) and animal-based (farmyard manure, poultry manure) biochars prepared at 400°C and 600°C separately. Animal-based biochars demonstrated higher P sorption at 400°C, diminishing at 600°C, while plant-based counterparts exhibited lower sorption capacities. Phosphorus desorption increased at 600°C, particularly in manure-based biochars. This work can give some guidance for the adsorbent preparation. However, before considering publication, there are some issues that need to be clarified. The detailed comments are as follows:

1. At the beginning of the abstract, a brief background Phosphorus (P) should be provided.

2. The abstract is not well focused on the purpose of the paper and jumps from topic to topic from sentence to sentence, rendering the narrative unconnected.

3. Please describe the hazards of Phosphorus (P) in more detail.

4. Please compare the current main methods for treating phosphorus in water and indicate the main advantages of biochar?

5. How do you recycle the adsorbent? What is the approximate adsorbent recovery rate per cycle? Have you considered more efficient recycling methods?

6. Specific surface area is important for materials. Please give N2 adsorption isotherm and pore size distribution curve. The isotherm and hysteresis loop need be explained. BJH adsorption or desorption are selected for mesoporous ones. DFT is selected for microporous ones. Please refer to and cite the literature for drawings and explanations. Chemical Engineering Journal (2024), doi: https://doi.org/10.1016/j.cej.2024.149776; Surfaces and Interfaces https://doi.org/10.1016/j.surfin.2024.103885

7. Some tense problems, grammatical problems and the beauty of pictures in the article need to be further improve.

Comments on the Quality of English Language

Some tense problems, grammatical problems and the beauty of pictures in the article need to be further improve.

Author Response

1. Summary
Thank you for dedicating time to review our manuscript. Below, you will find detailed responses along with corresponding revisions and corrections, highlighted in red text within the resubmitted files. We have tried to improve background information, reference relevancy, discussion and English language as per your suggestion. Further point by point responses are given as follows:
2. Point-by-point response to Comments and Suggestions for Authors
Comments 1: At the beginning of the abstract, a brief background Phosphorus (P) should be provided.
Response 1:  A background of P has been added (page 1, line 18-19).
Comments 2: The abstract is not well focused on the purpose of the paper and jumps from topic to topic from sentence to sentence, rendering the narrative unconnected.
Response 2: The abstract has been revised accordingly (page 1, line 18-34).
Comments 3: Please describe the hazards of Phosphorus (P) in more detail. Response 3: The required information has been incorporated in the manuscript (page,2 lines 47-51)
Comments 4: Please compare the current main methods for treating phosphorus in water and indicate the main advantages of biochar? Response 4: The required information has been incorporated into the manuscript (page,2 lines 55-61)
Comments 5: Specific surface area is important for materials. Please give N2 adsorption isotherm and pore size distribution curve. The isotherm and hysteresis loop need be explained. BJH adsorption or desorption are selected for mesoporous ones. DFT is selected for microporous ones. Please refer to and cite the literature for drawings and explanations. Chemical Engineering Journal (2024), doi: https://doi.org/10.1016/j.cej.2024.149776; Surfaces and Interfaces https://doi.org/10.1016/j.surfin.2024.103885   Response 5: I appreciate your insightful suggestion. We selected the EGME method to assess the specific surface area (SSA) of the biochar as it is the only available technique in our institute. Unfortunately, the BET-N2 method is currently inaccessible here. Time constraints are a significant factor for us, and while we would be willing to explore the BET-N2 method in other institutes, a timeframe of 3-4 months would be needed. This option is challenging due to the limited availability of such facilities in Pakistan, leading to extended processing times caused by high demand.   Nevertheless, this method holds equal recognition in the scientific community for analyzing specific surface area (SSA). A study conducted by Bakshi, Aller, Laird, and Chintala (2016) compared the EGME and BET-N2 methods, revealing equivalent SSA results. Additionally, several other studies, including those by Günal et al. (2018), Laird et al. (2010), Arthur et al. (2015), and Wang, Sedighi, and Lea-Langton (2020), have successfully employed the EGME method for SSA computations.
Comments 6: Some tense problems, grammatical problems and the beauty of pictures in the article need to be further improve.
Response 6: The quality of English level has been improved by co-author Joseph C. Blankinship who is a native English speaker. The revisions made for language enhancement are indicated by the use of blue text color in the manuscript. Improvements have been made to the figures to enhance their clarity and beauty (Page 5,7,8,10).

Reviewer 4 Report

Comments and Suggestions for Authors

7

The article presents very important topics about Sorption-Desorption of Phosphorus on Manure- and Plant-Derived Biochars at Different Pyrolysis Temperatures. The article is very interesting, the methodology planned correctly. Unfortunately the authors did not avoid mistakes. Below is a list of things to fix:

the article lacks an assessment of the produced biochars as sorbnets. I suggest using the proposed methodology:

DOI: 10.12911/22998993/63480

in the part regarding sorption and desorption, an implementation diagram would be useful.

In the introduction, there was no information on the use of agricultural waste as potential sorbents, t

A list of abbreviations should be at the beginning of the article.

The Discussion of results section should be added, where the results will be compared with the other region.

Author Response

We are grateful that you took the time to read the submission. The accompanying revisions/corrections that have been noted or tracked in the resubmitted files are marked by red coloured text.

We've thoroughly improved the background information, ensured reference relevancy, and refined the discussion as per your guidance. Additionally, we've provided detailed point-by-point responses to address your feedback .

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

accepted

Comments on the Quality of English Language

accepted

Reviewer 4 Report

Comments and Suggestions for Authors

All corrections have been included. In its current state, I recommend the article for publication in the journal.