Characterizing Aqueous Cd2+ Removal by Plant Biochars from Qinghai–Tibet Plateau
Round 1
Reviewer 1 Report (Previous Reviewer 1)
I recommended this manuscript to publication
Author Response
Thank you for your recognition of our work.
Reviewer 2 Report (New Reviewer)
The paper presents an interesting comparison of different biochar types, prepared from different feedstocks and at various condition, testing the affinity towards Cd adsorption in water solutions.
The trends observed in the paper are potentially interesting for a broad audience and some insights given from the results can worth the publication, however there are several experimental details which should better be described and results which need a more detailed description before considering this paper for publication in my opinion.
Regarding methods, authors should more clearly state experimental details and the reasons behind some choices made.
For example, which was the adsorption time used in the experiments in sections 2.2 and was it validated after kinetics analysis?
Then, why experimental temperature was chosen as a variable to test? And on which base the adsorption concentration of Cd was selected? Authors should better justify these assumptions made to set up the experimental design. Temperature is in fact observed to poorly affect adsorption efficiency.
Moreover, to which value was the pH adjusted? This is extremely important since it is known to affect adsorption phenomena and metal speciation (see e.g., Huang et al, 2022 https://doi.org/10.1016/j.chemosphere.2022.135471 )
Similar lack of details is observed in results and Discussion section. In section 3.2, for example, which biochar are showed in figure 1? At which temperature? This should be stated.
Then, why authors tested the adsorption process from SEM images? It should be better to corroborate their hypothesis after the discussion of the BET surface area and the actual adsorption data.
Then, why only SBB biochar is listed in figure 3 and table 2?
Moving to adsorption results, I suggest to the authors to preliminary analyze adsorption kinetics and then indicate how other factors affect adsorption capacity. Authors should also stress how the different biochar source can affect the adsorption process, since this variable is known to strongly affect the final chemical composition of biochar and adsorption processes. They should analyze in more detail which chemical features highlight the evident differences in adsorption properties. See for example in Binda et al. 2022 https://doi.org/10.3390/chemosensors10050168
Then, to which biochar type do the author refer in the discussion of section 3.2.2? Are they considering a single output of all biochars? This is not clear and in poor connection with the previous section.
There are then some other minor issues to fix in my opinion:
-line 46: 2+ in uppercase
-line 61-97: This section can be shortened and only the main trends should be highlighted in adsoprtion processes.
-line 113-117: Rephrase to avoid repetitions;
-line 127: Was the TGA performed in air or in N2? This can affect the results.
- lines 159-160: unclear sentence, please rephrase;
-section 3.1: Authors should compare their data with the abundant literature on biochar physicochemical features to better support their hypothesis of processes (such as Liu et al., 2017 https://doi.org/10.1021/acs.chemrev.6b00647 )
-I suggest to revise figure 4 and 5 graphically. As they are, axis values and titles are not readable.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Round 2
Reviewer 2 Report (New Reviewer)
The revised version of the paper improved the overall quality to some extent. There are still some issues which need to be resolved in my opinion.
Firstly, I still suggest to the authors to better justify in the manuscript text why they selected the adsorption temperature as a variable, since the references suggested in their response letter analyzed the effects of pH and ionic strength.
Considering then the results, it is still not clear to me why do the authors present only IR data of one biochar type. Moreover, this is listed as SBB in figure but referred as GBB in caption and in text. If the authors want to discuss only the detail in characterization of GBB because is the one showing higher performance, I suggest to move the section of adsorption kinetics above and then to present the characterization results, finally moving on the effects of other factors with the model. Otherwise, authors should anyway consider the characterization of all materials.
There are finally some misspellings and unclear sentence to revise:
-please rephrase the sentences in lines 12-14 and 33-35;
-line 58: "The properties such as surface properties and..." rephrase to avoid the repetition of "properties";
-line 97: please remove the dot;
-lines 153-154: please rephrase as "About 0.1g of all biochar samples were accurately weighted and placed in a 50 ml corkscrew conical flask..."
-line 180: "The" with capital T;
-line 182: "the" with lowercase t;
-line 294: remove "It can be seen from Figure 106 (a), (b) and (c) that" to avoid repetitions with the previous sentence.
Author Response
Thank you for your letter comments concerning our manuscript. Those comments are all valuable and very helpful for revising and improving our paper. We made a careful revision according to all the comments raised by the referees. We hope this revision meet the high requirement of your reputation journal. The main revision in the paper has marked up using the“Track Changes” function and the responds to the comments are as following:
Author Response File: Author Response.pdf
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Dear Authors, after reading your work, I had the following comments:
1. The title of the article is difficult to read. There is no such thing as a sorption effect... You may be writing sorption capacity.
2. The topic of your work is very popular, therefore, in my opinion, the Authors have read a little literature.
3. The Authors must improve the quality of the Figures!
4. The Authors need to think about Fig. 9.
4.1 The graph of sorption kinetics should start from 0 min. The y-axis must have a different unit of measurement (must be mg/g)
4.2 I do not understand what means the quality of adsorption ... It is traditional using the adsorption capacity and units of measurement mg/g.
In my opinion, the Authors did not correctly present the results of experimental studies
5. Fig. 10 should be in the Results section!
6. In the Abstraction, the Authors should write about their of the obtained specific results. In the Abstraction, there is no need to talk about comparing the obtained results with others.
7. Line 55-65: In my opinion, this information should be shortened and leave maybe one sentence! It does not provide the reader with any information related to the topic of the article.
8. Line 65-68: Authors need to think and write correctly. Firstly, it is necessary to write that one of the many factors!!!! I do not understand what means of pH value?
9. Line 86: in this sentence, but also throughout the text of the manuscript, the authors write about static adsorption experiments! It is necessary to use the following words: adsorption capacity, static conditions. Such write it is wrong!!! I advise you to read articles that are devoted to the sorption of heavy metals by different adsorbents!!!!! The Authors using non-professional terms.
10. Give answer, please, how did the Authors determine the pH of coal with the specified pH meter???? Scientists determinating pHpzc of adsorbent. For this, using a special method with different solutions. Also, it begs the question, what information can the pH of coal give in your research? How using it?
11. Line 136-153: the Authors did not write at which pH solution the experiments were carried out. In addition, the authors studied the adsorption capacity in static conditions at three different temperatures, and in dynamic conditions - at one (25 C)
12. Line 99: it is not clear, why the authors write about the feasibility of using it to optimize biological processes????
13. Line 251-252: the numerical values ​​of the parameters should be rounded off in the same way, for example to a thousand
14. The Authors did not write the purpose of the work, then it is impossible to evaluate this manuscript as a whole!
Conclusions are very poorly connected to the introduction, purpose and aim!
To sum up the all manuscript, I want to say that it needs to be redone!!!! It contains many professional errors. Since the purpose of the work is not formed, the conclusions cannot be evaluated!
I suggest the authors find authoritative articles devoted to adsorption research and take them as a prototype. After that, I'm ready to read your manuscript again. In this form, unfortunately, it is unfit for publication
With best regards
Reviewer 2 Report
1. Abstract section should be revised and rewritten. Focus on your aim and finding important results. It seems introduction of “Material and Method”.
2. Line 106 should be rewritten.
3. The temperature was controlled or set at 350 ℃, 500 ℃, and 650 ℃? And check the commas and punctuation marks carefully.
4. Line 124-126 should be rewritten.
5. How did you determine the experimental parameters (e.g. 0.1 to 0.5g) in the 2.2 Section?
6. There is no discussion in the “Results and Discussion” part. It is unacceptable.
7. Manuscript should be revised, and all typos and grammatical errors should be checked.
Reviewer 3 Report
Dear authors
very interesting job,
I have no comments
