Untreated Opuntia ficus indica for the Efficient Adsorption of Ni(II), Pb(II), Cu(II) and Cd(II) Ions from Water
, Serena Indelicato 2, David Bongiorno 2, Valentina Censi 1, Filippo Saiano 3 and Daniela Piazzese 1,*Round 1
Reviewer 1 Report
Recommendation: Major Revision
Comments: The writing logic is confused, the graphics are not beautiful, and it is not clear what scientific problem the author is trying to solve. Until the author makes Major Revision to the manuscript, I don't think the manuscript meets the journal publication requirements. Some comments are as follows:
1. The picture processing is too rough, the format is not uniform, the lack of horizontal and vertical coordinates.
2. What is the active ingredient that plays a major role in OFI?
3. What is the basis for screening 65-250 μm particle size?
4. Please improve the reasonable metal ion adsorption mechanism.
5. The drawing and processing of tables are too bad. The width of Table 4 is inconsistent, and the representation of values in Table 1 is inconsistent.
6. What does Cd2 stand for in the conclusion?
7. The number of experimental values selected for pH is too small.
8. Biomass derived adsorbents are widely applied in waste water treatment. Some typical references are suggested to be cited to enhance the background, e.g. Journal of Bioresources and Bioproducts 2021, 6 (3), 223-242; Journal of Bioresources and Bioproducts 2022, 7 (2), 109-115.
9. Please pay attention to the writing of units. They should be written in the same way.
10. Most of the references are quite old. Some newly published references since 2022 are suggested to be added.
The quality of English language is fine.
Author Response
Thank you for your comment. Please, enclosed find the answers' authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
1) Increase image quality for figures 1,2,3
2) Check throughout the text for pH values and make the writing consistent
3) Line 363 use capitol for the word "figure"
Author Response
Thank you for your comments. Please, enclosed find the authors' answers
Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript entitled "Untreated Opuntia ficus indica for the efficient adsorption of Ni(II), Pb(II), Cu(II) and Cd(II) ions from water" present original results in the wastewater treatment field. I present my suggestions and comments.
I kindly suggest the authors review the writing as there are some simple formatting and writing errors to correct. I also recommend adding statistical analysis to the results because they lack such analysis.
Line 284
% abs is % ads?
Line 296
Scientific names (such as Phomopsis) are in italics.
Lines 333 and 371
Blue line=blue line?
Figure 4
mmoli=mmol?
mg in solution means mg/L?
Table 1
umoli=umol?
There is no consistency in the units. In material and methods, the authors mention that qe and ce will be in mg/g and mg/L, respectively. However, in the graphs (Fig. 4), the units are in mmol/g and mg.
If the authors handle the units of mmol/g, please describe it in the methodology where the equations are. On the other hand, if qe has units of mmol/g, Ce should be in mM.
Something similar occurs in the kinetic study where the non-adsorption capacity at different times appears in mmol/g (Fig. 5).
Figure 5
mmols = mmol?
The caption of this figure refers to the kinetics of metals biosorption, but it should be: non-biosorbed metals.
Section 3.4
The supplementary material shows the initial concentrations used for the experiments with a single metal at different pH.
Why didn't the authors use the same initial concentrations for all metals?
On the other hand, the table shows the different concentrations of metals at pH 4 and 5 (Table S2). On what basis do the authors propose different concentrations for each metal?
e.g., for pH 4, there is an initial concentration of 352 ug Ni/mL and 1249 ug Pb/mL. Do these concentrations belong to the same umol or uM?
Would the % adsorption be comparable when starting with different metal concentrations? Could table S2 be made with the initial concentrations in umol or uM?
Perhaps it would be convenient to write the manuscript in the same units. Since the manuscript makes comparisons in multi-component systems, it would be best to use mmol/g and mM (umol or uM).
Figures 4-6
There are no standard error lines.
Tables 1-3-
There are no standard deviations.
Table 5
Please, only write the scientific names of the biosorbents in italics.
Line 537
The authors mention that 0.5 g of OFI can adsorb a certain quantity of the tested metals.
However, the biosorbent concentration in mg/L would be better since 0.5 g can be in 10 mL or 1 L.
Author Response
Thank you for your comments. Please, enclosed find the authors' answers
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript could be accepted now.
Reviewer 3 Report
I appreciate the attention that the authors paid to my previous recommendations, which I consider fulfilled.
I would suggest that authors have consistency in the units they use during the manuscript because the kind of units are described during material and methods and other units appear during the manuscript.
