Synthesis of activated carbon from biowaste of fir bark for methylene blue removal

Activated carbon (AC) was successfully prepared from low-cost forestry fir bark (FB) waste using KOH activation method. Morphology and texture properties of ACFB were studied by scanning and high-resolution transmission electron microscopies (SEM and HRTEM), respectively. The resulting fir bark-based activated carbon (ACFB) demonstrated high surface area (1552 m2 g−1) and pore volume (0.84 cm3 g−1), both of which reflect excellent potential adsorption properties of ACFB towards methylene blue (MB). The effect of various factors, such as pH, initial concentration, adsorbent content as well as adsorption duration, was studied individually. Adsorption isotherms of MB were fitted using all three nonlinear models (Freundlich, Langmuir and Tempkin). The best fitting of MB adsorption results was obtained using Freundlich and Temkin. Experimental results showed that kinetics of MB adsorption by our ACFB adsorbent followed pseudo-second-order model. The maximum adsorption capacity obtained was 330 mg g−1, which indicated that FB is an excellent raw material for low-cost production of AC suitable for cationic dye removal.


Recommendation?
Major revision is needed (please make suggestions in comments)

Comments to the Author(s)
The manuscript "Synthesis of Activated Carbon from Biowaste of Fir Bark for Methylene Blue Removal" (RSOS-190523) prepared activated carbon from forestry fir bark. The contents fall within the scope of the journal, however, there are some issues need to be addressed properly. this manuscript need revision before publication. Some comments are as below: (1) The adsorption mechanism should be stated clearly, and this part should be added in the manuscript.
(2) The manuscript should add some comparision between AC and other materials, such as graphene, etc.

Review form: Reviewer 2
Is the manuscript scientifically sound in its present form? Yes

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation? Major revision is needed (please make suggestions in comments)
Comments to the Author(s) 1. Heading Summary should be changed to Abstract. 2. For the introduction, a critical comparison of the adsorbents that were used previously for the removal of MB should be discussed to highlight their drawbacks/disadvantages that of new AC needs to be synthesized. 3. All chemicals used should be listed in sub 3.1 including the brand, city and country of origin. 4. Methylene blue should be in small letter unless used at the beginning of a sentence. 5. Sub 3.1 line 31-35 should be included in sub 3.2 as it was part of the AC synthesis procedures. 6. Sub 3.2 line 50: how can you confirm the ACFB synthesized was pure? 7. Sub 4.1: the authors should expand the characterizations to TGA and elemental analysis to prove the purity of ACFB. 8. For each parameter optimized, the author should indicate which optimum condition was chosen for the subsequent analysis. Another way is to indicate the batch adsorption method conditions in figure captions. 9. Sub 4.2.2 line 13: how is it possible to attain 100% removal? 10. For Fig 5, X-axis should be label as mass or amounts of ACFB (mg). 11. Sub 4.2.4: at the mentioned pH, what is the properties of ACFB? In this case, the change in ACFB surface needs to be discussed and correlate with ACFB properties. 12. R2 stands for correlation coefficient or non-linear regression coefficient? 13. The application of ACFB batch adsorption method for the removal of MB should be applied to the real sample to study the matrix effect and efficiency of ACFB in term of recovery.

25-Jun-2019
Dear Dr Zhao: Title: Synthesis of Activated Carbon from Biowaste of Fir Bark for Methylene Blue Removal Manuscript ID: RSOS-190523 Thank you for your submission to Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
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RSC Subject Editor:
Comments to the Author: (There are no comments.) ********************************************** Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) The manuscript "Synthesis of Activated Carbon from Biowaste of Fir Bark for Methylene Blue Removal" (RSOS-190523) prepared activated carbon from forestry fir bark. The contents fall within the scope of the journal, however, there are some issues need to be addressed properly. this manuscript need revision before publication. Some comments are as below: (1) The adsorption mechanism should be stated clearly, and this part should be added in the manuscript.
(2) The manuscript should add some comparision between AC and other materials, such as graphene, etc. Comments to the Author(s) 1. Heading Summary should be changed to Abstract.
2. For the introduction, a critical comparison of the adsorbents that were used previously for the removal of MB should be discussed to highlight their drawbacks/disadvantages that of new AC needs to be synthesized. 3. All chemicals used should be listed in sub 3.1 including the brand, city and country of origin. 4. Methylene blue should be in small letter unless used at the beginning of a sentence. 5. Sub 3.1 line 31-35 should be included in sub 3.2 as it was part of the AC synthesis procedures. 6. Sub 3.2 line 50: how can you confirm the ACFB synthesized was pure? 7. Sub 4.1: the authors should expand the characterizations to TGA and elemental analysis to prove the purity of ACFB. 8. For each parameter optimized, the author should indicate which optimum condition was chosen for the subsequent analysis. Another way is to indicate the batch adsorption method conditions in figure captions. 9. Sub 4.2.2 line 13: how is it possible to attain 100% removal? 10. For Fig 5, X-axis should be label as mass or amounts of ACFB (mg). 11. Sub 4.2.4: at the mentioned pH, what is the properties of ACFB? In this case, the change in ACFB surface needs to be discussed and correlate with ACFB properties. 12. R2 stands for correlation coefficient or non-linear regression coefficient? 13. The application of ACFB batch adsorption method for the removal of MB should be applied to the real sample to study the matrix effect and efficiency of ACFB in term of recovery. The manuscript "Synthesis of Activated Carbon from Biowaste of Fir Bark for Methylene Blue Removal" (RSOS-190523) prepared activated carbon from forestry fir bark. The contents fall within the scope of the journal, however, there are some issues need to be addressed properly. This manuscript need revision before publication.
Some comments are as below: (1) The adsorption mechanism should be stated clearly, and this part should be added in the manuscript.
(2) The manuscript should add some comparision between AC and other materials, such as graphene, etc. (5) Some language and format issues should be revised carefully.

Reply to Reviewer 1:
We thank and totally agree the reviewer for the comments and constructive suggestions concerning our manuscript. We have improved our manuscript taking into account the remarks. Below are the replies for each specific comment: 1、 The adsorption mechanism should be stated clearly, and this part should be added in the manuscript.
We thank reviewer very much and agree with the reviewer. We have tried our best to revise and add a new part of '3.6 Adsorption mechanism' which we hope meet with your approval. The modifications are on yellow background.
2、 The manuscript should add some comparision between AC and other materials, such as graphene, etc.
We thank and agree with the reviewer. We have done the comparision not only in the introduction part, but also in Table 3 We thank reviewer very much for this valuable suggestion. We have tried our best to modify the introduction part and sub 3.4 in order to illuminate the advantages of ACs and also the highlights of this paper. The modifications are on yellow background. 4、 References Bioresource Technology, 2019, 281: 195-201 andBioresource Technology, 2019, 276: 236-243 should be cited in this manuscript.
We thank and agree with the reviewer that there are many related articles published.
We have added the references as follows in the manuscript: The modifications are on yellow background.
5、 Some language and format issues should be revised carefully.
We thank the reviewer. We have improved the English by native speaker for English editing.
At the end, we would like to thank you again for the positive comments and constructive suggestions concerning our manuscript. Best regard to you! Reviewer 2: 1. Heading Summary should be changed to Abstract.
2. For the introduction, a critical comparison of the adsorbents that were used previously for the removal of MB should be discussed to highlight their drawbacks/disadvantages that of new AC needs to be synthesized.
3. All chemicals used should be listed in sub 3.1 including the brand, city and country of origin.
4. Methylene blue should be in small letter unless used at the beginning of a sentence. 11. Sub 4.2.4: at the mentioned pH, what is the properties of ACFB? In this case, the change in ACFB surface needs to be discussed and correlate with ACFB properties.
12. R2 stands for correlation coefficient or non-linear regression coefficient?
13. The application of ACFB batch adsorption method for the removal of MB should be applied to the real sample to study the matrix effect and efficiency of ACFB in term of recovery.

Reply to Reviewer 2:
We thank and totally agree the reviewer for the comments and constructive criticism concerning our manuscript. We have improved our manuscript taking into account the remarks. Below are the replies for each specific comment: 1、 Heading Summary should be changed to Abstract.
We thank reviewer very much. We have changed the headline of 'Summary' to 'Abstract'. The modifications are on yellow background.
2、 For the introduction, a critical comparison of the adsorbents that were used previously for the removal of MB should be discussed to highlight their drawbacks/disadvantages that of new AC needs to be synthesized.
We thank reviewer very much for this valuable suggestion. We have tried our best to discuss a critical comparison of various adsorbents previously using to remove MB and describe their drawbacks in the introduction part. The modifications are on yellow background.
3、 All chemicals used should be listed in sub 3.1 including the brand, city and country of origin.
We thank reviewer very much. We have revised and listed all chemicals we used in new sub 2.1 including their brand, city and country of origin. The modifications are on yellow background.
4、 Methylene blue should be in small letter unless used at the beginning of a sentence.
We thank and agree with the reviewer. We have revised all this mistake in the manuscript.
5、 Sub 3.1 line 31-35 should be included in sub 3.2 as it was part of the AC synthesis procedures.
We thank reviewer very much and agree with the reviewer. We have revised the content in sub 3.1 sub 3.2. The modifications are on yellow background. 6、 Sub 3.2 line 50: how can you confirm the ACFB synthesized was pure?
7、 Sub 4.1: the authors should expand the characterizations to TGA and elemental analysis to prove the purity of ACFB.
We thank reviewer very much for these valuable suggestion. We have modified the synthesis part in order to account for the obtained ACFB is pure, at the same time, the corresponding explanation is also made in sub 4.1, including the TGA, EA and XPS results from our previous studies. We thank the reviewer very much. We have revised the figure caption by adding the batch adsorption method conditions. The modifications are on yellow background. 9、 Sub 4.2.2 line 13: how is it possible to attain 100% removal?
We thank reviewer very much. We have tried our best to revise the manuscript, '~100%' means an approximate value, the actually experimental data is 99.78%. We have revised this value in the paper on yellow background. We thank reviewer very much and agree with the reviewer. We have done the modification, labeling the X-axis of figure 5 as mass of ACFB. The modifications are on yellow background. 11、Sub 4.2.4: at the mentioned pH, what is the properties of ACFB? In this case, the change in ACFB surface needs to be discussed and correlate with ACFB properties.
We thank reviewer very much for this valuable suggestion. We have tried our best to revise and discuss the surface properties change of ACFB in the part of '3.2.4 pH effect'. The modifications are on yellow background.
12、R2 stands for correlation coefficient or non-linear regression coefficient?
We thank the reviewer. R 2 stands for correlation coefficient.
13、The application of ACFB batch adsorption method for the removal of MB should be applied to the real sample to study the matrix effect and efficiency of ACFB in term of recovery.
We thank reviewer very much and agree with the reviewer. We have tried our best to revise, supplement the data and add a new part of '4.4 Regeneration of adsorbent' which we hope meet with your approval. The modifications are on yellow background.
At the end, we would like to thank you again for the positive comments and constructive suggestions concerning our manuscript. Best regard to you.