Biochar from A Freshwater Macroalga as A Potential Biosorbent for Wastewater Treatment

Round 1

Reviewer 1 Report

Comments:1.     Title: it needs a little modification. Replace “biosorbent in wastewater treatment” with “biosorbent for wastewater treatment”.2.     Abstract: include a couple of lines on the functional element of the biochar obtained from FTIR analysis.3.     L32: “In the recent years” should be removed. The work and interest on the exploitation of macroalgae has long history and its not a recent case.4.     Throughout the manuscript, consistency is required, avoid the use of repetitive or unnecessary introductory words, e.g., L33 - On the one hand, L35 - On the other hand, L43 - So far, L44 - Nowadays, L49 - As can be seen, L80 - According to our knowledge, and so on. It is not necessary to start each sentence with an introductory term. This should be avoided for a concise and refined writing.5.     Throughout, the level of English used needs to be improved substantially. The sentences are badly worded with repetitive words. Most of the part is badly worded with long sentences. Please consider breaking longer sentences into smaller fragments for easy understanding. Authors are advised to seek help from a native English speaker. There are several grammatical, typo errors, and contextual errors.6.     L56 - This paper focuses, L75 - In this paper, we propose to apply… Avoid the scatteredness, overall aim and focus of the study should be clearly mentioned at the end of Introduction in a single paragraph rather than with scattered lines throughout.7.     L80 – “there are limited literature data” Gramatical attention required.8.     L200 -  Table 1: What was the sample size? It needs to be clearly mentioned. Add a footnote explaining the coated values were taken from the duplicate/triplicate samples.9.     L250 - Table 2: same comment as above for Table 1.10.  L254 - Figure 2 lacks error bars. Reconstruct.11.  L302 - Figure 3 is incomplete and suffers from inconsistent sample trial. Why authors have only given the SEM for biochar obtained at 450°C? How about other biochar samples prepared at 300, 350 and 400 oC? For clear comparison purposes, SEM images for all samples should be included.12.  L302 - Figure 3 b) shows agglomeration behavior, this needs to be discussed in the results with justification and supporting literature.13.  L328 - Figure 4: FTIR spectra, most of the peak numbers are missing. What authors can explain about the peaks between 400 and 2000 wavenumbers.? Characteristic peak numbers should be assigned in the Figure.14.  L328 - Figure 4 All sample lines are overlapping and make the graph difficult to compare. The overlapping should be avoided by using larger difference at Y-axis. Important: I don’t see any change or appearance of new peaks to confirm any chemical interaction happen. How authors can justify the chemical interaction at different temperatures?15.  L369 - Figure 6. Legends needs attention.16.  374 - Table 4: same comment as above for Table 1.17.  The conclusion section is simply a repetition and present redundancy with the abstract. This needs a complete rewrite. Herein, I would like to see the major findings and how they are addressing the left behind research gaps and covering current challenges.18.  Editorial issues: The Latin names and Greek letters should be presented in italic in whole manuscript, units presentation should be unified in the whole manuscript, abbreviations presentation should be unified.19.  Referencing is not right and consistent. Above points are some highlighted areas. This should be improved as there are many reports available from the year 2018-2019. Reference list is too short and should be extended with recent studies.

Author Response

In the attached file

Author Response File: Author Response.docx

Reviewer 2 Report

This paper reports the potential application of biochar, from a freshwater microalga, as an adsorbent in wastewater treatment. Furthermore, this manuscript fits well with the scope of the journal, therefore this work should be published in Water after minor revisions. Please see some of theses suggestions below: 

Introduction: authors should add the multi-adsorption process in the aim of the manuscript. 

Material and Methods: authors should explain in more detail the sections 2.4.1; 2.4.2; 2.4.3 and 2.4.5. Moreover, in line 180, the sample was not filtered?

Results and Discussion:

· Authors should add the standard deviation in Table 1 and Table 2.

· In line 207, this information should be referenced.

· Authors should add the “yield of biochars” formula in M&M section.

· Authors should remove the Figure 2. This information it is already in Table 2.

· Authors should eliminate “e.g.,” in line 295.

· Authors should explain in more detail and discuss this the literature the information between lines 296 to 299. Also, they should compare the raw material and the biochar.

·  In Figure 6, the A450 does not appear in the legend of the figure.

· Equation 5 (line 405) should write by editor of equations.

· In line 407, where it says “efficiency of (III)” it should be said “efficiency of Cr (III)”.

· Authors should explain the mechanisms of ions adsorption on biochar because the journal is about “Water” not only “Materials”. For that, these references (J Env Sci 38 (2015) 158-167; Water Air Soil Pollut 226 (2015) 133; Ecotoxicology and Environmental Safety 131 (2016) 118-126) can help for the explanation and therefore they should be referenced in the manuscript.

Author Response

In the attached file

Author Response File: Author Response.docx

Reviewer 3 Report

The authors of water-528096 presents an interesting material in the prepared manuscript. The goal of the research has been clearly defined and the presented results are interesting for the readers of the Journal. The introduction places the research in a broad context and determines the purpose of the work and its significance. The figures and tables included in the work help in explanations of the concepts in the paper.

However the some elements must be improved. In this regard, my comments include:

1.      Follow the IUPAC guideline on formatting units, i.e. avoid x/y and use x y^-1 consist

ently throughout the manuscript.

2.      Line 125, 131, 166: “POCh S.A.” is now “Avantor Performance Materials Poland S.A.”

3.      Give more details about the SEM analysis.

4.      Table 3 and 5. Give all wavelength values to two decimal places.

5.      Figure 4. All transmittance values should be given to one decimal place.

Author Response

In the attached file

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The revised version reads well. Though, authors have addressed all the comments raised in the last review. However, still, there are editorial irregularities which I believe can be corrected at the proof stage. Thus, this manuscript can now be accepted for publication.

Reviewer 2 Report

The authors have taken into account all the comments suggested by the reviewer, therefore the article should be published in this form.

Reviewer 3 Report

I accept all corrections made by the authors.