Optimization of the Preparation of Activated Carbon from Prickly Pear Seed Cake for the Removal of Lead and Cadmium Ions from Aqueous Solution

Round 1

Reviewer 1 Report

The paper is precisely written. The layout of the present paper is well-organized. The introduction presents the goal of the paper in detail. Experimental design and analysis are described in the section Material and methods. The results are clearly presented with the relevant accompanying literature. The most important results are highlighted in the conclusion. 

 

Comments for author File: Comments.docx

Author Response

I would like to thank you for the time you are spending to review our paper. Thank you for this positive evaluation and for your nice words.

Reviewer 2 Report

Dear Authors,

Please find attached my comments and suggestions.

Comments for author File: Comments.pdf

Author Response

First of all, I would like to thank you for the time you are spending to review our paper. We tried to take into account all the remarks. The corresponding corrections in the revised manuscript are highlighted with a yellow background, and the replies to your queries are listed below.

 

Dear Authors,

The manuscript presents a study about the properties of a byproduct of prickly pear seed oil extraction activated carbon based on response surface methodology with respect to optimize preparation conditions and achieve the best removal capacity of Cd and Pb.

The topic of the study is interesting. However, the content of the manuscript is not rigorously presented and represented, and it needs a revision. The experimental design needs to be described more carefully. The experiments seem to be performed as single shot, which is not enough to provide reliable results.

Reply:

Thank you for your comments. You have raised an important point. Experiments were performed in single content and currently we are carrying out tests on binary systems and we are moving on to applications on real effluents. As you know the health situation relating to COVID-19, we could not complete our work and this will be the subject of the rest of this work in the future.

 

Therefore, I suggest the following general comments and questions related to the part of material and methods:

Introduction: It is important to motivate the novelty of the study. In the introduction should be valuable to discuss some relevant scientific work, useful to highlight the further step provided by your work as compared to the state of art.

Reply:

Thank you, Agree. We have, accordingly, revised the introduction to emphasize this point.

 

Material and methods: which were the physico-chemical characteristics of the raw material are useful informations, try to put it.

Reply:

Indeed. You are right. The characteristics of the precursor were added in the revised manuscript.

 

You didn’t specify the quantity of raw material used for activation, the concentration of H₃PO₄

Reply:

Thank you for your comment. The phosphoric acid used for the activation was 85% wt., and the activation ration was 2:1 (g H₃PO₄/g carbon), which is the mass of the (H₃PO₄) / mass of the carbonized material. For each test 20g of carbon were used.

 

What you want to say by hermetic bottle?

Reply:

Thank you, a hermetic bottle is a container that is useful for the storage and preserving of the adsorbent under a dry environment.

 

Line 107, temperature of carbonization

Line 127 – the quantity of activated carbon

Reply:

Thank you; we have corrected the mistakes accordingly.

 

What stirrer did you used?

Reply:

The stirrer used was a tilting shaker.

 

140 – Put the specific wavelength, not a general one

Reply:

Thank you; the wavelength use d was 664 nm for the determination of the concentration of methylene blue.

 

For your measures, you used AAS? Put the type of AAS, LOD, LOQ, calibration curves, wavelength, you used the flame technique or furnace, etc..

Reply:

Thank you. In this study, (AAS, Thermo Fisher Scientific instrument, iCE 3500) with Air-acetylene flame was used for the determination of Pb (II) ions and Cd (II) ions concentration. More details were added in the revised manuscript.

 

For my point of view, you have to reformulate the paragraph of methods, which is heavy to read and understand.

Reply:

Thank you for your suggestion. More details were added in the experimental section.

Reviewer 3 Report

This is an interesting article that deals with a practical issue of interest and worth’s publication. However, the authors should perform several amendments to the manuscript before publication.

 

1. The authors should include some additional references in the introduction
   2019. El Maguana, N. Elhadiri, M. Bouchdoug, M. Benchanaa, A. Jaouad, "Activated Carbon from Prickly Pear Seed Cake: Optimization of Preparation Conditions Using Experimental Design and Its Application in Dye Removal", International Journal of Chemical Engineering, vol. 2019, Article ID 8621951, 12 pages, 2019.
   2020. Amari, A., Alalwan, B., Eldirderi, M. M., Mnif, W., & Rebah, F. B. (2019). Cactus material-based adsorbents for the removal of heavy metals and dyes: a review. Materials Research Express, 7(1), 012002.
   2021. Liosis, C.; Papadopoulou, A.; Karvelas, E.; Karakasidis, T.E.; Sarris, I.E. Heavy Metal Adsorption Using Magnetic Nanoparticles for Water Purification: A Critical Review. Materials 2021, 14, 7500. https://doi.org/10.3390/ma14247500
2. The increase of adsorption dose causes higher adsorption capacity due to the availability of active sites (lines 336-337). If the adsorption dose increases further, the actives sites availability will increase for ever? Thus, all we need to success optimum adsorption (100% efficiency) is just to increase adsorption dose. Probably a saturation point exist, where a further increase of adsorption dose will not affect adsorption capacity. Have authors found this saturation point of adsorption dose?
3. In the majority of articles adsorption/desorption cycles are characterized by efficiency. In order the results of the present manuscript to be comparable to previous articles should add the efficiency of the 1^st and last cycle at the regeneration study (Figure 6 is fine).
4. At references section number 29 appears twice.
5. At references section: the instruction (include the digital object identifier (DOI) for all references where available) that have been provided to the authors are not satisfied. Only 1/44 cited articles have DOI.
6. At lines 54 and 55 some words have different style.
7. A space is needed (line 59), at the end of the sentence.
8. In whole manuscript parenthesis at Figure should be avoided. For example (Figure 5(d)) to (Figure 5d).
9. In abstract iodine number and methylene blue index need units as used at lines 184 and 185.
10. At lines 64 and 85 the definition raw material should be changed.
11. At line 78 authors are referred generally to optimal conditions, don’t mention any condition. If are the same conditions which are explained in paragraph 2.2 what makes them optimal? Do authors have any reference or previous experimental data to support their statement?
12. At lines 107-108 both temperatures are for the activation? Probably Tc is carbonization temperature.
13. At line 166 “the contact time was varied between 0 and 720 min” should be changed to the contact time up to 720 min.
14. The caption of Figure 4 must be changed. The word species should be replaced either by ions or group. For example “Distribution of ions in the aqueous system as a function of pH: (a) cadmium groups, (b) lead groups”.

 

Author Response

First of all, I would like to thank you for the time you are spending to review our paper. We tried to take into account all the remarks. The corresponding corrections in the revised manuscript are highlighted with a yellow background, and the replies to your queries are listed below.

This is an interesting article that deals with a practical issue of interest and worth’s publication. However, the authors should perform several amendments to the manuscript before publication.

1. The authors should include some additional references in the introduction
   2019. El Maguana, N. Elhadiri, M. Bouchdoug, M. Benchanaa, A. Jaouad, "Activated Carbon from Prickly Pear Seed Cake: Optimization of Preparation Conditions Using Experimental Design and Its Application in Dye Removal", International Journal of Chemical Engineering, vol. 2019, Article ID 8621951, 12 pages, 2019.
   2020. Amari, A., Alalwan, B., Eldirderi, M. M., Mnif, W., &Rebah, F. B. (2019). Cactus material-based adsorbents for the removal of heavy metals and dyes: a review. MaterialsResearch Express, 7(1), 012002.
   2021. Liosis, C.; Papadopoulou, A.; Karvelas, E.; Karakasidis, T.E.; Sarris, I.E. Heavy Metal Adsorption Using Magnetic Nanoparticles for Water Purification: A Critical Review. Materials 2021, 14, 7500. https://doi.org/10.3390/ma14247500

Reply:

Thank you for your kind comments. We have included the proposed articles in the revised manuscript and summarized its main finding relevant to our investigation.

 

2. The increase of adsorption dose causes higher adsorption capacity due to the availability of active sites (lines 336-337). If the adsorption dose increases further, the actives sites availability will increase forever? Thus, all we need to success optimum adsorption (100% efficiency) is just to increase adsorption dose. Probably a saturation point exists, where a further increase of adsorption dose will not affect adsorption capacity. Have authors found this saturation point of adsorption dose?

Reply:

Thank you. You have raised an important point here. We have added corresponding in formation and we have modified the corresponding figure to illustrate the saturation point of adsorption dose.

 

3. In the majority of articles adsorption/desorption cycles are characterized by efficiency. In order the results of the present manuscript to be comparable to previous articles should add the efficiency of the 1^st and last cycle at the regeneration study (Figure 6 is fine).

Reply:

Thank you for your suggestion. As it is proved by the follow-up of adsorption performance of the obtained activated carbon during the 5 cycles of regeneration, the adsorption efficiency was decreased from 180.5 mg g^-1 to 166.3 mg g^-1 for cadmium and from 163.3 mg g^-1 to 147.8 mg g^-1 for lead, (decrease of 7 and 9% of efficiency between the 1^st and the 5^th cycle, respectively for Cd and Pb), therefore it is considered that after 5 cycles of regeneration the adsorbent is still efficient for the elimination of heavy metals.

 

4. At references section number 29 appears twice.

Reply:

Thank you. Sorry for this mistake. This was corrected in the revised manuscript.

 

5. At references section: the instruction (include the digital object identifier (DOI) for all references where available) that have been provided to the authors are not satisfied. Only 1/44 cited articles have DOI.

Reply:

Thank you. We have added DOI for all references.

 

6. At lines 54 and 55 some words have different style.

Reply:

Thank you. This was corrected in the revised manuscript.

 

7. A space is needed (line 59), at the end of the sentence.

Reply:

Thank you. Sorry for this mistake. We have corrected the mistake in the revised manuscript.

 

8. In whole manuscript parenthesis at Figure should be avoided. For example (Figure 5(d)) to (Figure 5d).

Reply:

Thank you, we have verified the whole manuscript and we have deleted parentheses for all figures.

 

9. In abstract iodine number and methylene blue index need units as used at lines 184 and 185.

Reply:

Thank you, we have added units to iodine number and methylene blue index in abstract.

 

10. At lines 64 and 85 the definition raw material should be changed.

Reply:

Thank you, we have changed “raw material” by “carbon precursor”. Raw material was the carbon precursor in this study (Prickly pear seed cake).

 

11. At line 78 authors are referred generally to optimal conditions, don’t mention any condition. If are the same conditions which are explained in paragraph 2.2 what makes them optimal? Do authors have any reference or previous experimental data to support their statement?

Reply:

Thank you for your comment. The optimal conditions for the preparation of activated carbons were obtained by using an experimental design, these conditions are specific to this study, and the selection of parameters was based on the literature and preliminary tests.

 

12. At lines 107-108 both temperatures are for the activation? Probably Tc is carbonization temperature.

Reply:

Thank you; we have corrected the mistakes in the revised manuscript.

 

13. At line 166 “the contact time was varied between 0 and 720 min” should be changed to the contact time up to 720 min.

Reply:

Thank you; this was modified.

 

14. The caption of Figure 4 must be changed. The word species should be replaced either by ions or group. For example “Distribution of ions in the aqueous system as a function of pH: (a) cadmium groups, (b) lead groups”.

Reply:

Thank you, we have modified it accordingly.

Reviewer 4 Report

1. The given title is not clear, need to modify the title in correct way.
2. In the section of introduction, the given content is not enough, it must be add the more content with citing recent literature.
3. In the section of abstract, it must be given more experimental conditions with optimized results.
4. Check the given table.2 it having correction.
5. In fig. 6 what is meaning of x-axis, it should be include.
6. 7 give the subsection like (a), (b), etc.,
7. The citied reference is not enough, please add the more reference with recent research article.

Author Response

First of all, I would like to thank you for the time you are spending to review our paper. We tried to take into account all the remarks. The corresponding corrections in the revised manuscript are highlighted with a yellow background, and the replies to your queries are listed below.

1. The given title is not clear, need to modify the title in correct way.

Reply:

Thank you for pointing this out. We have modified the title to “Optimization of the Preparation of Activated Carbon from Prickly Pear Seed Cake for the Removal of lead and cadmium ions from Aqueous Solution”

 

2. In the section of introduction, the given content is not enough; it must be add the more content with citing recent literature.

Reply:

Thank you for your comment. We have revised the introduction and we have added other recent references.

 

3. In the section of abstract, it must be given more experimental conditions with optimized results.

Reply:

Thank you. The abstract was modified and we have added optimized results in the revised manuscript.

 

4. Check the given table.2 it having correction.

Reply:

Thank you for your comment. This Table is based on the results generated by the experimental design software. We have revised the table to avoid any mistakes.

 

5. In fig. 6 what is meaning of x-axis, it should be include.

Reply:

Thank you. X-axis in figure 6 correspond to Regeneration cycle number, it was added in the figure.

 

6. 7 give the subsection like (a), (b), etc.,

Reply:

Thank you, we have modified the figure 7 in the revised manuscript.

 

7. The citied reference is not enough; please add the more reference with recent research article.

Reply:

Thank you for this remark. We have updated the literature and added the appropriate papers, where needed.

Round 2

Reviewer 2 Report

Dear Authors,

Thank you for addressing most of my comments and suggestions. I find the readability of the paper has improved by consolidating the material and method section, with the additional information about sample preparation and method validation.