Investigation of Efficient Adsorption of Toxic Heavy Metals (Chromium, Lead, Cadmium) from Aquatic Environment Using Orange Peel Cellulose as Adsorbent
Round 1
Reviewer 1 Report
Removing heavy metal ions from wastewater is of considerable interest and great significance for sustainable development. Orange peel cellulose (OPC) has considered as the adsorbent to remove heavy metal ions from wastewater attributed to low-cost, environmentally friendly, and greater adsorption featured functional groups. At neutral pH, the OPC exhibited stronger absorption capacity for Pb2+ solution superior to Cd2+ solution and Cr6+ solution. The research of this manuscript is interesting and results are reliable. However, major revision is required and the comments are given below.
1. “bioremediation of toxic heavy metals”? It should be “bioremediation of waste water” or “absorption of toxic heavy metals”. Please go through the whole manuscript to revise such statements.
2. Scale bars are suggested to be added in the Figure 1 to show the size of beads.
3. In Figure 2, FT-IR analysis about the peaks at 2850 and 2355 cm-1 is suggested to be provided.
4. I cannot understand the sentence of “For Co2+, the maximum bioadsorption was observed at pH 4 and 8 (line 343).
5. Could orange peel cellulose (OPC) be recycled and reused? How about the absorption capacity for the OPC after several times of recycles?
6. Please pay attention to the writing of units. All the units should be written in the same style. “mg g-1 (line 398, 406, 408, etc.)”, “g/L” and other units should be revised. Please double check the manuscript.
7. Please pay attention to the placement of text references ([62, line 464]).
8. The “orange peel cellulose” is suggested to be added as a keyword.
9. In introduction, other adsorbents for the elimination of heavy metal ions are suggested to be introduced, such as activated carbon. Some typical references are suggested to be cited, e.g. Journal of Bioresources and Bioproducts 2022, 7 (2), 109-115; Journal of Bioresources and Bioproducts 2021, 6 (4), 292-322.
10. Please add some comparisons on the adsorption capacity of heavy metal ions to adsorbents reported in other papers.
11. Please pay attention to some spellings and formatting errors in the References. Such as Ref. 46, please double check all references.
Author Response
Dear Reviewer,
Thank you for reviewing our manuscript. Attached, please find the author's responses.
With best regards
Aminur Rahman, Ph.D. Assistant Professor Dept. Biomedical Sciences College of Clinical Pharmacy King Faisal University
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The present paper entitled “Investigation of efficient bioremediation of toxic heavy metals (chromium, lead, cadmium) from aquatic environment using orange peel cellulose as adsorbent” reports an interesting work on the very important topics of adsorption properties of biowaste material. The article is well written, summarizes a lot of valuable information in its figures and tables, and contains a lot of work. The manuscript needs several revisions before it can be published. Therefore, please improve or clarify the following points:
1. The authors did not provide sufficient background in the introduction to judge the novelty of their material, in comparison with natural products, other materials that act as absorbents for Pd, Cd and Cr should be mentioned. For example: chitosan https://doi.org/10.3390/ma14247894, MOFs https://doi.org/10.1080/01496395.2017.1340953, https://doi.org/10.1016/j.jece.2022.109131; powder activated carbon: https://doi.org/10.1007/s10661-020-8162-0, etc.
2. In addition, as stated in the introduction, heavy metal toxicity can be linked to Sustainable Development Goals and Planetary Boundaries (see: https://doi.org/10.1021/acs.jchemed.1c00284).
3. What is the maximum number of cycles that the adsorbent can be used without losing its activity? Please indicate the reusability of the adsorbent material.
4. How did you perform the desorption of the adsorbed material?
5. Could you explain why the temperature of room temperature was used? Did you investigate how temperature affects adsorption capacities?
6. The point of zero charge should be calculated in order to better understand the adsorption process.
7. Please compare the adsorption capacities with those presented in the research literature for similar adsorbents, and present this information as a table.
8. How about the practical application value on an industrial scale?
Based on these, I advise the authors to rectify the above-mentioned issues, and I hope to re-evaluate the revised manuscript.
Author Response
Dear Reviewer,
Thank you for reviewing our manuscript. Attached, please find the author's responses.
With best regards
Aminur Rahman, Ph.D. Assistant Professor Dept. Biomedical Sciences College of Clinical Pharmacy King Faisal University
Author Response File: Author Response.pdf
Reviewer 3 Report
General: "reduction" in chemistry means to achieve a lower oxidation number. Pb and Cd can only be reduced to the metal, which is not the case under ambient conditions!
Line 50/51: please skip the sentence "Meanwhile , cadmium accumulates in animals and plants with a long half-life of 25-30 years" - many organisms do not live as long as 25 years!
Line 55: add "hexavalent chromium" ..... trivalent chromium is much less toxic, and reference 15 refers to hexavalent chromium only
Line 73: improve stile .... "... use and disposal as bioadsorbents contribute to the enrichment and isolation of environmental pollutants" : Metals as pollutants still exist, and organics are not necessarily degraded during adsorption !
Lines 337/342/344: replace Cr6+ by Cr042- ... at this pH, hexavalent chromium is anionic, and this explains why it is not completely adsorbed. In fact, it is partially reduced at the surface and adsorbed as Cr3+ . In fact, chromate is rapidly reduced at pH<6 by humics
Line 361: which buffer to reach pH 7 was used ? Phosphate? This may be important for phosphate precipitates or chromate reductions
Line 456: please skip the sentence (it is unnecessary) "The percentage reduction values obtained for lead and arsesnic ..... " Arsenic is not within the scope of this article; arsenate may be reduced to arsenite which may be more mobile
Line 461: please skip the sentence "In a study by Olaye ..." and reference [67], because arsenic is not within the scope of this article
Line 476: you surely mean "The adsorption of chromate from the aqueous phase was observed by 33.5 %, which is relatively low." In fact, chromate as such can be reversibly adsorbed at clays within a few percent, but at an organic surface it is probably reduced. Can you conclude this from the IR-spectra?
Lack of quantitative adsorption of chromate is due to the anionic status of hexavalent chromium. At a more acid pH, this would be improved
Author Response
Dear Reviewer,
Thank you for reviewing our manuscript. Attached, please find the author's responses.
With best regards
Aminur Rahman, Ph.D. Assistant Professor Dept. Biomedical Sciences College of Clinical Pharmacy King Faisal University
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript has been revised according to the comments and suggest to be accepted.
Reviewer 2 Report
The authors have spent a lot of effort to further improve the manuscript, and they answered almost all of my questions well. Thus, I would recommend the Editor to consider an acceptance for publication in Sustainability.
