Activated Carbon from Selected Wood-Based Waste Materials

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors

I was asked to review the following papers covering fireboards processing towards activated carbons.

Here are some comments to this manuscript:

1. It's entirely well-written with some minor mistakes within the text as  "...obtained during apartament renovation..." (line 106) - I'd suggest to write spent panels or precise it once within the text about this renovation. Is this really the matter whether panels are new or spent - based on this manuscript findings?

2. "unioninzed water"  (line 197)...conductivity data in brackets is enough to specify its purity.

3. please scan the text to find some lack of space between the words as well

Introduction part is written in proper manner with references within the matter.

4. Table 2 - it was not described why decrease in Ni content  in BF was so low after physical and chemical activation (in comparison to HDF). How this nickel is bound that its dissolution/desorption is impossible. similar question can be ascribed to copper. Leaching is effective but not in 100%. Pretty worse results were obtained for Cu in BF.

5. Is the possibility of structure ordering after high temp treatment, having in mind that wihin 1400-1500cm-1 stretching vibrations of aromatic ring may  appear.

6. It would be beneficial in this part to show data of elemental analysis (C,N,O) for materials after physical and chemical activation as well

7. around line 386 this ratio Id/Ig differs in 0.01 units which is pretty small make any far-going thesis.

8. Line 396 - "larger particles size" - how much?

9.  It's a good practice to show the SEM images with the same magnification to sompare data (figure 4b)

Author Response

General Comment:

I was asked to review the following papers covering fireboards processing towards activated carbons.

Answer and Action: Thank you for your thoughtful feedback.

We have carefully considered your suggestions and incorporated them into the main text (yellow color). We trust that these revisions will enhance the clarity and presentation of the manuscript, and we hope they will meet your approval.

 

Comment 1: It's entirely well-written with some minor mistakes within the text as  "...obtained during apartament renovation..." (line 106) - I'd suggest to write spent panels or precise it once within the text about this renovation. Is this really the matter whether panels are new or spent - based on this manuscript findings?

Answer: The floor panels were new post-installation waste.

 

Comment 2: "unioninzed water"  (line 197)...conductivity data in brackets is enough to specify its purity.

Answer: The conductivity was 1.002 µS/cm

Comment 3: please scan the text to find some lack of space between the words as well

Answer: We have checked the text.

Comment 4: Table 2 - it was not described why decrease in Ni content in BF was so low after physical and chemical activation (in comparison to HDF). How this nickel is bound that its dissolution/desorption is impossible. similar question can be ascribed to copper. Leaching is effective but not in 100%. Pretty worse results were obtained for Cu in BF.

Answer: The lower decrease in Ni content in BF after both physical (thermal) and chemical (KOH) activation, compared to HDF, suggests that nickel is bound in a more stable form within the bamboo floor (BF) char matrix. A similar trend is observed for Cu, where leaching was effective but not complete, especially in BF. This could be due to several factors related to metal binding mechanisms and the structural composition of BF-derived char. (1) Nickel may be strongly incorporated into silicate structures within the biomass, forming stable Ni-Si or Ni-O bonds that are resistant to thermal decomposition and chemical leaching [86]. (2) Organic precursors in bamboo, rich in lignin and hemicellulose, may form Ni-organic complexes that are more resistant to desorption, even under alkaline treatment [87]. (3) Ni in BF can form metallic clusters or metal-carbon complexes that are highly stable and less reactive to chemical leaching in contrast, Ni in HDF might be more loosely bound, possibly as surface-adsorbed ions or in a different mineral phase that is more susceptible to volatilization or dissolution. (4) Copper is known to form highly stable oxides (CuO, Cu₂O) during pyrolysis, particularly in biomass-derived chars [88]. (5) In lignocellulosic materials like bamboo, Cu can be bound to functional groups (e.g., car-boxyl, phenolic groups from lignin) that persist after pyrolysis, making it less available for desorption [89]. (6) KOH treatment is known to leach certain metals efficiently, but Cu oxides and Cu-organic complexes might not be fully soluble under these conditions [90].

Comment 5: Is the possibility of structure ordering after high temp treatment, having in mind that wihin 1400-1500cm^-1 stretching vibrations of aromatic ring may appear.

Answer: Higher pyrolysis temperatures (600–1000°C) generally results in a lower I_D/I_G ratio, meaning the carbon material becomes more ordered and graphitic. Although, the trend of a lower I_D/I_G ratio with higher pyrolysis temperatures applies to biomass pyrolysis, but some specific nuances may be observed depending on the biomass type and the nature of the pyrolysis process. Here’s what happens during biomass pyrolysis in the temperature range of 600–1000°C. Lower pyrolysis temperatures (below ~600°C) result in more disordered, amorphous structure due to incomplete carbonization and the retention of functional groups, while the temperature increases, volatile components are more thoroughly removed, leading to a more ordered carbon structure. As mentioned in answer to comment 7, the I_D/I_G ratios range from 0.83 to 0.85 so the impact of temperature in case of our materials was negligible.

Comment 6: It would be beneficial in this part to show data of elemental analysis (C,N,O) for materials after physical and chemical activation as well

Answer: Physically or chemically activated chars exhibit significant differences in carbon (C) and nitrogen (N) content, which result from the impact of the activation process on the elemental composition of the material. The carbon content is significantly higher in carbonized samples before chemical activation. For BF-C700 and HDF-C700, it is 85.40% and 79.20%, respectively, indicating a high degree of carbonization. After chemical activation with KOH, the carbon content drastically decreases to 40.40% (BF-C700KOH) and 39.70% (HDF-C700KOH). The reduction in carbon content is due to intensive oxidation and structural erosion caused by KOH, which leads to the removal of part of the carbon in the form of volatile products. The nitrogen content varies significantly between samples derived from different feedstocks. In the case of BF-C700, the nitrogen content is 0.68%, whereas HDF-C700 exhibits a higher nitrogen content (5.16%), confirming differences in the composition of the raw materials (Table 1). Chemical activation reduces the nitrogen content in BF-C700KOH and HDF-C700KOH, these values decrease to 0.21% and 2.84%, respectively. The KOH activation process leads to the partial degradation of nitrogen-containing groups and their release as gaseous products, resulting in a lower nitrogen content in the final material.

Comment 7: Around line 386 this ratio Id/Ig differs in 0.01 units which is pretty small make any far-going thesis.

Answer: The tested carbon materials exhibited minimal differences in structural disorder, with I_D/I_G ratios consistently ranging from 0.83 to 0.85. This indicates that variations in activation method and pyrolysis temperature had little effect on defect density. Typically, higher pyrolysis temperatures enhance graphitization and lower the I_D/I_G ratio [99], but in this case, the impact was negligible. Additionally, chemical activation with KOH did not significantly alter disorder levels, as HDF-C700KOH and BF-C700KOH displayed the same I_D/I_G ratio as their non-KOH counterparts. While KOH activation generally increases porosity, it does not necessarily enhance carbon ordering. Furthermore, both HDF and BF showed similar graphitization trends, despite their compositional differences, suggesting that precursor type had limited influence on the structural evolution of the carbon matrix under these conditions.

Comment 8: Line 396 - "larger particles size" - how much?

Answer: HDF-C700 3-5 µm and HDF-C700KOH 5-8 µm; BF-C700 8-10 µm and BF-C700KOH 10-15 µm

Comment 9: It's a good practice to show the SEM images with the same magnification to compare data (figure 4b)

Answer: The figures were corrected

 

Reviewer 2 Report

Comments and Suggestions for Authors

There are many studies on the preparation of activated carbon materials using biomass materials as raw materials with high-temperature pyrolysis method. What is the innovation of this article? How are the pyrolysis process parameters determined? What is the performance of the activated carbon material obtained?

Author Response

General Comment:

There are many studies on the preparation of activated carbon materials using biomass materials as raw materials with high-temperature pyrolysis method.

Answer and Action: Thank you for your thoughtful feedback. We have carefully considered your suggestions and incorporated them into the main text (green color). We trust that these revisions will enhance the clarity and presentation of the manuscript, and we hope they will meet your approval.

 

Comment 1: What is the innovation of this article?

Answer: Research demonstrate that it is possible to produce activated carbon from waste substances originating from the wood industry. The article presents the results of research for two waste materials with different properties: bamboo flooring (BF) and high-density fibreboard (HDF). The obtained results allow us to state that it is possible to produce activated carbon from waste substances, which will have acceptable properties for environmental applications. The economic aspect should also be mentioned here - when producing activated carbon from pure wood biomass, the input for production is one of the production costs. For the production of activated carbon from the presented waste, additional fees can be charged for their processing, thanks to which it is possible to offer a final product at a lower price.

 

Comment 2: How are the pyrolysis process parameters determined?

Answer: The method of determining specific parameters of the pyrolysis process has been described in other publications of the authors listed in references: [24] and [54]. It considers both the research using a thermogravimeter [54], own research for various waste substances [24] and the economic aspect (defining the lowest possible process temperature for which the char can be obtained as a substrate for the activation procedure).

 

Comment 3: What is the performance of the activated carbon material obtained?

Answer: For BF, 1000 g yields 346 g of activated carbon, accounting for approximately 35% of the input, while for HDF, it yields 334 g, representing approximately 33% of the input.

 

Reviewer 3 Report

Comments and Suggestions for Authors

Thank the authors for their contribution to the manuscript. This manuscript converts bamboo flooring and high-density fiberboard into activated carbon by pyrolysis and activation technology, and analyzes its chemical composition, surface characteristics and potential environmental application value, which provides a new way for sustainable treatment and resource utilization of wood waste. The manuscript is good as a whole, but there is still room for improvement. The comments are as follows:
1. It is suggested to add in the background: As a widely used material, wood is used in many traditional or new fields of architecture, energy and environmental engineering. To emphasize the importance of wood to human production and life, please refer to 10.1016/j.aej.2022.08.002; 10.3390 In addition, regarding the present situation of wood waste treatment technology, we can briefly mention the limitations of the existing technology in order to better highlight the innovation of this study.
2. Although the pore structure and surface characteristics of activated carbon are characterized by analytical techniques, there is a lack of practical tests on the adsorption performance of activated carbon (such as adsorption experiments on heavy metal ions or organic pollutants). If it is convenient, it is suggested to supplement these tests to verify the practical application potential of activated carbon. If it is not convenient, please refer to comment 6.
3. Thermal activation and chemical activation are compared, but there is no in-depth discussion on the advantages and disadvantages of different activation methods. It is suggested that the differences between the two methods in pore structure, adsorption performance and cost-effectiveness of activated carbon should be further analyzed.
4. It is suggested that the author re-typeset figures, especially Figure 4 and 5. In addition, the letter numbers in each Figure should be in the same font.
5. Some key experimental data (such as carbon content, specific surface area, heavy metal content of activated carbon, etc.) need to be quoted more specifically in the conclusion part to enhance the persuasiveness of the conclusion. For example, it can be pointed out that "after pyrolysis and activation treatment, the carbon content of bamboo flooring (BF) reaches 81%, and the carbon content of high-density fiberboard (HDF) reaches 75%", rather than just "high carbon content".
6. The conclusion part should briefly mention the limitations of the research, such as the lack of practical tests on the adsorption performance of activated carbon (such as adsorption experiments on heavy metal ions or organic pollutants). In addition, it is suggested that the future research direction be put forward in more detail in the conclusion.
7. According to the iThenticate report, the amount of wording duplication in the manuscript is high, so I suggest reducing the repetition rate appropriately.

Best regards.

  Comments on the Quality of English Language

According to the iThenticate report, the amount of wording duplication in the manuscript is high, so I suggest reducing the repetition rate appropriately.

Author Response

General Comment:

Thank the authors for their contribution to the manuscript. This manuscript converts bamboo flooring and high-density fiberboard into activated carbon by pyrolysis and activation technology, and analyzes its chemical composition, surface characteristics and potential environmental application value, which provides a new way for sustainable treatment and resource utilization of wood waste. The manuscript is good as a whole, but there is still room for improvement.

Answer and Action: Thank you for your thoughtful feedback. We have carefully considered your suggestions and incorporated them into the main text (blue color). We trust that these revisions will enhance the clarity and presentation of the manuscript, and we hope they will meet your approval.

 

Comment 1: It is suggested to add in the background: As a widely used material, wood is used in many traditional or new fields of architecture, energy and environmental engineering. To emphasize the importance of wood to human production and life, please refer to 10.1016/j.aej.2022.08.002; 10.3390 In addition, regarding the present situation of wood waste treatment technology, we can briefly mention the limitations of the existing technology in order to better highlight the innovation of this study.

Answer: At the beginning of introduction we have added the following text:

Wood is a widely used raw material in various industries due to its renewable nature, versatility, and unique structural properties. As a natural biomass composite, it exhibits excellent mechanical characteristics, lightweight design, and a porous, anisotropic structure [1]. These properties make wood a valuable resource in construction, furniture production, and energy generation. Additionally, raw wood is commonly utilized for biochar production, offering an environmentally friendly solution for carbon sequestration and pollution mitigation [2]. Given the increasing industrialization and population growth, the sustainable use of wood and its derivatives plays a crucial role in addressing global energy and environmental challenges. However, despite its renewable nature, a significant amount of wood-based materials go to waste each year.

 

Comment 2: Although the pore structure and surface characteristics of activated carbon are characterized by analytical techniques, there is a lack of practical tests on the adsorption performance of activated carbon (such as adsorption experiments on heavy metal ions or organic pollutants). If it is convenient, it is suggested to supplement these tests to verify the practical application potential of activated carbon. If it is not convenient, please refer to comment 6.

Answer: Thank you for your valuable suggestion. In our future research, we plan to conduct practical adsorption experiments to evaluate the performance of the activated carbon, particularly in the removal of dyes. These tests will help verify its practical application potential. However, due to the current scope of our study, we acknowledge this limitation and will address it in our upcoming work.

Comment 3: Thermal activation and chemical activation are compared, but there is no in-depth discussion on the advantages and disadvantages of different activation methods. It is suggested that the differences between the two methods in pore structure, adsorption performance and cost-effectiveness of activated carbon should be further analyzed.

Answer: Both activation methods have their strengths and weaknesses. The physical activation process is much more time consuming than the chemical process. Moreover, the pore size and porosity are very difficult to control in the physical activation process. Therefore, chemical activation becomes the prevailing technique for making activated carbons. Thermal activation is generally more cost-effective for large-scale production because it eliminates the need for expensive chemicals. However, its higher energy requirements can be a drawback. While chemical activation involves significant chemical costs, waste management expenses, and post-treatment costs, making it more expensive overall. Thermal activation is generally more environmentally friendly because it does not require hazardous chemicals and produces less wastewater and solid waste. However, its higher energy consumption can contribute to CO₂ emissions unless renewable energy sources are used.

On the other hand, chemical activation has a higher environmental impact due to chemical residues, water pollution, and waste disposal issues. However, if proper waste treatment and chemical recovery systems are in place, its impact can be reduced [55,57,66].

Comment 4: It is suggested that the author re-typeset figures, especially Figure 4 and 5. In addition, the letter numbers in each Figure should be in the same font.

Answer: In has been corrected.

Comment 5: Some key experimental data (such as carbon content, specific surface area, heavy metal content of activated carbon, etc.) need to be quoted more specifically in the conclusion part to enhance the persuasiveness of the conclusion. For example, it can be pointed out that "after pyrolysis and activation treatment, the carbon content of bamboo flooring (BF) reaches 81%, and the carbon content of high-density fiberboard (HDF) reaches 75%", rather than just "high carbon content".

Answer: The conclusions have been supplemented with values.

Comment 6: The conclusion part should briefly mention the limitations of the research, such as the lack of practical tests on the adsorption performance of activated carbon (such as adsorption experiments on heavy metal ions or organic pollutants). In addition, it is suggested that the future research direction be put forward in more detail in the conclusion.

Answer: The 4^th point, which includes limitations of the study, has been added before conclusions

Comment 7: According to the iThenticate report, the amount of wording duplication in the manuscript is high, so I suggest reducing the repetition rate appropriately.

Answer: The paraphrased sentences have been marked grey.

 

Reviewer 4 Report

Comments and Suggestions for Authors

Journal: Sustainability

Manuscript ID: sustainability-3504172

Type of manuscript: Article

Title: Activated Carbon from Selected Wood-Based Waste Materials

Authors: Małgorzata Kajda-Szcześniak, Anna Mainka *, Waldemar Ścierski, Mirosława Pawlyta, Dariusz Łukowiec, Krzysztof Matus, Kalina Turyła, Daniel Lot, Weronika Barańska, Anna Jabłońska

 

 

In the work, the authors used recycled wood composite materials - bamboo flooring and high-density fiberboard floor panels - to produce e.g. char (by pyrolysis method). To evaluate the produced chars, they used analytical techniques - FTIR, Raman spectroscopy, SEM and TEM.

They used two methods for activation – thermal activation (700 and 850°C), chemical activation with KOH.

 

I have some comments and suggestions outlined below:

In the materials and methods, I would recommend citing the standards in references, e.g. listed in lines 180-187.

I would recommend adding information about the input material - What was the range of density of the waste monitored?

line 365 – “Figure 3. Raman spectra of the BF and HDF samples“ - in the image description, change the order and add the designation (a) and (b). e.g. ..... (a) HDF and (b) BF …

Don't forget to delete the reference writing template from line 686.

 

Reviewer

Author Response

General Comment:

In the work, the authors used recycled wood composite materials - bamboo flooring and high-density fiberboard floor panels - to produce e.g. char (by pyrolysis method). To evaluate the produced chars, they used analytical techniques - FTIR, Raman spectroscopy, SEM and TEM.

They used two methods for activation – thermal activation (700 and 850°C), chemical activation with KOH.

Answer and Action: Thank you for your thoughtful feedback.

We have carefully considered your suggestions and incorporated them into the main text (pink color). We trust that these revisions will enhance the clarity and presentation of the manuscript, and we hope they will meet your approval.

 

Comment 1: In the materials and methods, I would recommend citing the standards in references, e.g. listed in lines 180-187.

Answer: We have followed your recommendation.

Comment 2: I would recommend adding information about the input material - What was the range of density of the waste monitored?

Answer: Unfortunately, we do not have this data available. However, we appreciate your suggestion and will consider it in future research.

Comment 3: line 365 – “Figure 3. Raman spectra of the BF and HDF samples“ - in the image description, change the order and add the designation (a) and (b). e.g. ..... (a) HDF and (b) BF …

Answer:  We have changed the order the figures a) and b)

Comment 4: Don't forget to delete the reference writing template from line 686.

Answer:  Thank you, we have deleted these lines.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

No further comments, all the previous were appropriately corrected.

Author Response

General Comment:

No further comments, all the previous were appropriately corrected.

Dear Reviewer #1,

Thank you for your time and effort in reviewing our manuscript. We appreciate your positive feedback and are glad that our revisions have addressed your previous concerns.

Reviewer 3 Report

Comments and Suggestions for Authors

Thanks to the author's efforts, the manuscript has been greatly improved, and it is recommended to Accept after minor revisions. Comments are as follows:
It is necessary to shorten the sentence of 4. Limitations and merge it into 5. Conclusions (in the form of a paragraph of about 200 words, not many points) to standardize the manuscript structure.

Author Response

General Comment:

It is necessary to shorten the sentence of 4. Limitations and merge it into 5. Conclusions (in the form of a paragraph of about 200 words, not many points) to standardize the manuscript structure.

Dear Reviewer #3,

Thank you for your time and effort in reviewing our manuscript. We followed your comments i.e. have shortened Limitations and merged with Conclusions by adding the text in yellow.

While these findings highlight the promising applications of the chars, some limitations remain. The study is restricted to bamboo flooring and HDF as feedstocks, limiting generalizability to other wood-based waste materials. Additionally, the long-term stability and scalability of the chemical activation process, as well as the potential leaching behavior of heavy metals, require further investigation. A more comprehensive life cycle analysis (LCA) would also help evaluate the environmental impact of the pyrolysis process. Moreover, understanding the influence of additives such as resins, adhesives, and flame retardants on the final composition, structure (BET) and safety of the chars should be a priority.

Despite these limitations, the chars' high …

We appreciate your positive feedback and are glad that our previous revisions have addressed your concerns.

With regards,

Anna Mainka

Author Response File: Author Response.pdf