A Review on Biochar as an Adsorbent for Pb(II) Removal from Water

Round 1

Reviewer 1 Report

1. The sentences in Introduction part, in lines 34-35 and 41-42 are repeated.

2. More information is needed on biocarbons as a material, formation mechanism, and their characteristics with reference to their application as sorbents.

3. Part 1.2 must be supported by adequate literature.

4. Suggestion to the authors to link part 2.3 with concrete examples.

5. Suggestion to add a diagrams in the section 2.6 to illustrate the mechanism and process of the application.

6. Complete Table 1 and 2 with maximum adsorption capacities.

7. Suggestion to the authors to deeply discuss the impact of the modification on the morfological and chemical properties of biochar providing the characterization results from different literature. Although Table 2 summarizes numerous publications, only a few are discussed in the text.

Minor correction of English is necessary.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

In this study the authors revised researches of the last ten years, that involve the use of biochar as a metal adsorbent - Pb(II) for removal from water, highlighting the opportunities and challenges associated to Engineering projects. It was observed that work brings interesting insights for the area; however, need of many adjusts:

Abstract

1) A good abstract must contain a brief contextualization of what will be covered in the study, its general objective, the methodology in a succinct and direct way, the most relevant results, and a closing/concluding sentence. However, not all these items were presented by authors;

2) The authors are invited to use different keywords of the Title to broaden the search for the paper (e.g., biochar and removal).

1. Introduction

1) In Introduction, some very long sentences and with few or no references (e.g., lines 62-73; 74-85; 86-92; 93-105);

2) In the Introduction some older references (e.g.; Glaser et al., 2002 and Laird, 2008), in which should contain many more current references, and others were not included in the references list (e.g., Lehmann & Joseph, 2015; Li et al., 2016; Tomczyk et al., 2020; Ghezzehei et al., 2014; Glaser et al., 2002; Laird, 2008; Singh et al., 2010; U.S. News, n.d.; US EPA, n.d.);

3) lines 35 and 42, separate the numeric value of the unity and also observe the entire text;

4) lines 35, 40, 49, 51-53, 53-55, 59-61, 62-65, - add references;

5) lines 41-43, this information is repeated in lines 30-31 and 34-35, unify;

6) lines 50-51, this information is repeated in lines 35-37, unify;

7) write EPA in full, as it is the first time it appears in the text;

8) Could the authors explain to future readers of this paper, how the articles were selected to compose this research, what inclusion or exclusion criteria were used?

9) The authors did not make clear the novelty or contribution of this study to the frontier of knowledge or for the field.

Items 2 and 3.

1) some citations were not included in the references list (e.g., Mousavi et al., 201; Cao et al., 2011; Uchimiya et al., 2010; Saleh, 2022; Largitte et al., 2016; Lagergren, 1898, Ho & McKay, 1999; Kajjumba et al., 2018; Kalam et al., 2021; Jin et al., 2016; Li et al., 2017; Mohan et al., 2007; Keiluweit & Kleber, 2009; Duku et al., 2011; Granados et al., 2022; Pan et al., 2022; Bian et al., 2022; Cui et al., 2016; Hassan et al., 2020);

2) line 121, could the authors say what low pH values they are referring to?

3) lines 125-128, 134-147, 149-163, 177-185, 219-222, 230-240, 244-250, 253-257, 259-264, 295-307, 328-332, 336-344, 355-358, 364-366 - add references;

4) Figures 1, 2, and 3, Table 1, and all equations (not numbered) were not mentioned in the text;

5) In Figures 1, 2, and 3, the authors percentage values, but it would be interesting if they also presented it in terms of absolute values;

6) For Figures 1, 2, and 3, the authors are invited to plot them in a graphic program, which allows a better presentation and quality for a technoscientific study;

7 line 272, can the authors specify which stronger affinity they are referring to?

8) line 289, how can the authors explain this inner-sphere complexation? What does this mean physically?

9) line 295, would the authors be able to quantify/identify the range of these micro, macro, and mesopores contained in the biochar?

10) In Table 1 (repeated), standardize time - authors must write in hours (h) or minutes (min) format throughout the text;

11) In Table 1, scientific names must be written in italics;

12) In Table 1, in the studies conducted by Cui et al., 2014, Jin et al., 2020, Ho et al., 2017, and Wang et al., 2015 - what were the pyrolysis times or heating rates?

13) In Table 2, in the study performed by Wang et al., 2015, Liu et al., 2021, Han et al., 2015, and Bian et al., 2022 - what was pre- or post-pyrolysis type?

14) In Table 2, in the study of Liang et al., 2017, Wang et al., 2015, and Zhou et al., 2013 - what was the production method of the biochar?

15) In Table 2, in the works of Huang et al., 2020, Mohan et al., 2014, Liu et al., 2018, Pan et al., 2022, Liu et al., 2021, Trakal et al., 2016, Jellali et al., 2016, Mohan et al., 2015, Han et al., 2015, Wang et al., 2015, Inyang et al., 2015, and Wan et al., 2020 - what were the sorption increase?

16) In Table 2, in the study of Liu et al., 2021 - what was the main results of this study?

17) In Table 2, in the study of Wan et al., 2020 - what was the removal mechanism, kinetic model, and isotherm model?

18) line 463, “Several others researchers”, but the authors only presented one reference – add more refences;

19) The article is not very illustrative and attractive; I believe that for a review article the authors could add some figures and/or diagrams that bring better visual understanding to the future reader.

Items 4. and 5.

1) lines 502, 538, and 548, “Various researchers”, “Various studies”, and “Some studies”, but the authors not presented any reference – add more refences;

2) Figure 4 not was mentioned in the text and better presentation and quality for a technoscientific study;

3) lines 549-554 and 558-574, add references;

4) The authors are invited to present more statistical treatment or coefficients that better correlates the main variables demonstrated in this study;

5) How could the authors, of a well-simplified way, highlight the main contributions, innovations, and/or applications of the results presented in this study for use in more practical applications in developing countries?

6. Conclusions and Recommendations

1) The conclusions are good, simple, and direct.

References

1) Observe the correct form (citations and references) in the journal template;

2) include some papers most recent of this important journal;

3) as it is a review paper, the authors used few references;

4) some references that appear in reference list were not cited in text;

5) when citations have the same name of the author and publication year, it is correct to indicate them using alphabet letters, e.g., a, b, c, and d...;

6) 52.08% of the references used in this paper have more than 5 years (high percentage, but understandable for a review paper).

Author Response

please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors corrected their manuscript, so now it can be considered for publication.

Author Response

Thanks a lot to the Reviewer!

Reviewer 2 Report

After a rigorous reading of the new manuscript submitted to the journal by authors, and noting that these answered all the questions and made the changes proposed by me and by other reviewers, corresponding to the reviewers' expectations, I am in favor of accepting and publishing this article in this important journal, and I would also like to thank you for the opportunity to made part of this select team of reviewers. Congratulations to the authors for the excellent work!

Author Response

Thanks a lot to the Reviewer!