Arsenic Biosorption by the Macroalgae Chondracanthus chamissoi and Cladophora sp.

Round 1

Reviewer 1 Report

1

1.       Refer to arsenic as a metalloid and not as a mineral

2.       Changing the term bioadsorption to biosorption since the latter implies different mechanisms of association between the biological material and the sorbate not only physical sorption.

3.       It is important that the authors mention that arsenic in aqueous solution is in the form of oxyanions (arsenite and arsenate), which affects the optimal pH of biosorption and the mechanism of the process and cannot be compared to the phenomenon of biosorption of metals that occur in solution in cationic form.

4.       Write all the scientific names in italics

5.       Specify if the As solution used came from arsenite or arsenate.

6.       Change the title of section 3.1 since results are not only presented for 0.25 ppm As solutions.

7.       The authors report removal percentages of As not biosorption capacities, it is essential to correct the term biadsorption capacities that they use inappropriately.

8.       According to figures 1 and 2, a greater amount of arsenic is removed between 3 and 6 h than between 0 and 3 h. Could it be that the decrease in pH observed favored the biosorption of As oxyanions?

9.       Write the title of figure 4 in English.

10.   Verify that all the text of the micrographs is in English.

11.   It is desirable to present FTIR spectra of the biosorbents before and after the As removal process to establish the functional groups that participate in the interaction with As.

12.   Improve the text of the discussion on the effect of pH, the authors should focus more on their observations.

 

Author Response

Dear colleague, I hope you are in good health. I am sending the answers to each of your suggestions.

• Refer to arsenic as a metalloid and not as a mineral

Ans.The term metalloid was included instead of mineral.

• Changing the term bioadsorption to biosorption since the latter implies different mechanisms of association between the biological material and the sorbate not only physical sorption.

Ans. The term bioadsorption was changed to biosorption.

• It is important that the authors mention that arsenic in aqueous solution is in the form of oxyanions (arsenite and arsenate), which affects the optimal pH of biosorption and the mechanism of the process and cannot be compared to the phenomenon of biosorption of metals that occur in solution in cationic form.

Ans. Information on the oxyanion forms arsenite and arsenate was included.

• Write all the scientific names in italics

Ans.  All scientific names are written in italics.

• Specify if the As solution used came from arsenite or arsenate.

Ans. It is indicated that the solution used came from arsenite.

• Change the title of section 3.1 since results are not only presented for 0.25 ppm As solutions.

Ans.The concentration of 1.50 ppm was included in the title of section 3.1.

• The authors report removal percentages of As not biosorption capacities, it is essential to correct the term biadsorption capacities that they use inappropriately.

Ans.The word capacity was changed to percentage of biosorption.

• According to figures 1 and 2, a greater amount of arsenic is removed between 3 and 6 h than between 0 and 3 h. Could it be that the decrease in pH observed favored the biosorption of As oxyanions?

Ans.The discussion justifies the lower percentage of biosorption between 0 and 3 hours.

• Write the title of figure 4 in English.

Ans.Corrected the title of figure 4.

• Verify that all the text of the micrographs is in English.

Ans.All the text of the micrographs was placed in English.

• It is desirable to present FTIR spectra of the biosorbents before and after the As removal process to establish the functional groups that participate in the interaction with As.

Ans.One of the limitations was not having a lot of resources to do the FTIR test before and after

• Improve the text of the discussion on the effect of pH, the authors should focus more on their observations.

Ans.The discussion on the effect of pH was improved.

Best regards

 

Author Response File: Author Response.docx

Reviewer 2 Report

This paper's experiment details have serious flows. It is crucial for the reader to understand what species of As were adsorbed in the experiments, however the authors neglected to mention this. The removal percentage is not a reliable indicator of the material's adsorption performance. Also, it is recommended use As concentrations close to background ppb levels found in drinking waters and demonstrate the materials ability to reduce the As contents below EPA 10 ppb limits. In addition, the adsorption mechanisms with pertinent chemistry information must be presented. SEM cannot be used to interpret sorption mechanistic. Please includes EDX data to support the claims. Most of these specifics are understood incorrectly. This manuscript is unacceptable at the current state. Substantial changes are advised before resubmission to any journal.

Author Response

Best regardsDear colleague, I hope you are in good health.
I will send the comment to your suggestion:
To address your recommendations the following changes were made:
You are indicating that in the working solution you have the form of arsenite.
The removal percentage indicates the potential of the sorbent to carry out As removal processes.
In this case we are not using As concentrations close to the As ppb levels of drinking water because we want to work in water bodies contaminated with As, which have higher amounts than those tolerated in drinking water, and we are comparing the final As concentrations with the concentrations allowed by EPA and WHO.
SEM is being used to look at changes in the sorbent surface.
One of the limitations was the lack of resource to perform EDX to confirm that the metalloid has bound to the sorbent, however, this is being noted as a limitation of the research and will be taken into account for future research.

Best regards

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I still have a few concerns about recommending this manuscript for publication.

1. What was the detection limit of As in AA spectroscopy? Did you use hydride generation or graphite furnace accessories? This information must be included.

2. Why not use sodium arsenate salt instead of oxide for solution preparation?

3. Please change ppm to mg/L, and also, units can be introduced on table fields

 

Author Response

Dear Editor, I hope you are in good health.
Enclosed are the responses to your comment:

1. What was the detection limit of As in AA spectroscopy? Did you use hydride generation or graphite furnace accessories? This information must be included.

Ans. In this case, flame atomic absorption spectrophotometry was used, the detection limit of which is 0.01 mg/L.
This detail had been unintentionally omitted, but it is already indicated in the methodology.

2. Why not use sodium arsenate salt instead of oxide for solution preparation?

Ans. We did not use the arsenate salt because a certified standard solution of As2O3 was available. On the other hand, arsenite is much more toxic than arsenate, so we wanted to know the removal capacity of arsenate by algae.

3. Please change ppm to mg/L, and also, units can be introduced on table fields

Ans. The changes indicated in the article were made.

Best regards.

Author Response File: Author Response.docx