Modelling Arsenic-Removal Efficiency from Water Through Adsorption Using Modified Saxaul Ash as Adsorbent

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 My comments on the individual sections are summarized in the attached file. 

Comments for author File: Comments.pdf

Author Response

In the present study, the researchers explored the modelling approach and validated the model through selected arsenic removal experimental datasets using synthesized adsorbent. Research like these may provide crucial insights into the factors affecting fate and transport of heavy metal and might help in designing remediation strategies. However, in this study only few datasets are presented. Some concerns which should be addressed before further processing of this manuscript.

Some critical issues to be focused earlier acceptance

1. The first line of the abstract section starts with the methodology part. The author must include one broad sentence about the Arsenic problem thereby giving some clue to the reader why this work is needed.

Authors’ response: A new first line has been introduced with a broad Arsenic problem.

1. The abstract section needs to include few more results of modeling

Authors’ response: Few more results are incorporated in the abstract of revised version

• Line 38-53 Could the author provide a few lines different forms of the arsenic

As well as any detected arsenic concentration in the local region?

Authors’ response: Description on different forms of arsenic is discussed in the revised manuscript.

1. The 2nd half of the introduction Line 54-73 does not provide satisfactory knowledge related to the present research Such as any background about the parameters selected.

Authors’ response: More background on the current research area are appended in the revised manuscript.

1. The aims and objective of the current study are not clearly The work presented in the subsequent sections is not stated in the objective of the study.

Authors’ response: Aims and objectives are more clearly defined in the revised manuscript.

1. Line 116 to 188, There is no information provided that how adsorbent was prepared from selected plant. Moreover, what was the final composition of adsorbent prepared and proximate or ultimate analysis was done.

Authors’ response: Sample preparation details are provided in the revised manuscript. Chemical composition of the final adsorbent was not determined. Also, was not a focus of current study.

• Line 260-261. How was the dataset of input variable selected? Which statistical tool used?.

Authors’ response: Dataset of the input variable was selected by the authors of the original experimental study, Rahdar et al. (2019). No information on any use of statistical was provided in the original study. 

• Methodology part needs significant improvement, as no information about some equation is provided.

Authors’ response: Methodology part is improved in the revised manuscript. Information on equations 2-4 is provided in one paragraph (immediately after Equation 4). Similarly, information on equations 5-7 is provided in one paragraph (immediately after Equation 7). As Equations 8-10 used the same variables, the description of the variables are only provided after first appearance (i.e. Equation 8).

1. Why was only the pH selected. It should be noted that groundwater contains some mono and divalent cations are also present. There is no background knowledge about this parameter in the introduction part.

Authors’ response: Current study had no influence on the selection of variables, all the variables were selected by the authors of original experimental study, Rahdar et al. (2019). It is to be noted that many researchers used the factor pH alone and investigated the effect of pH on arsenic removal efficiency. Imteaz et al. (2021) described details of effect of pH on arsenic removal efficiency.

73. Line 54-73. Please provide the few removal results in the numbers of previous

Authors’ response: Provided in the revised manuscript.

175. Line 151-175. What modification was done in present study for the selected

Authors’ response: In the current study no experiment was conducted, as such there was no modification of the selected contaminant. In the revised manuscript, the details of contaminant preparation is appended.

• The results section needs significant improvement. I recommend that it should be rewritten. The result justification is missing as no reference is provided in whole part of the results.

Authors’ response: There is no other study available, which can be compared with the current modelling results. However, model results are compared with the original experimental results and presented in Table 1.

• The conclusion must talk about the significance and broader scope of this study and how these observations can help in better understanding of water Moreover, the conclusion needs to present the final words of this study.

Authors’ response: The ‘Conclusion’ section has been improved as suggested.

• Please review the entire manuscript for grammar and avoid using large

There are many typos in different sections of the text, e.g., a capital letter instead of small one, or dot instead of a comma. Use of free tools like "Grammarly" for rapid revision is recommended.

Authors’ response: Thoroughly checked in the revised manuscript.

Ref.: Imteaz, M.A., Khan, S.A. and Kaur, P. (2021) Generalised equation for the effect of pH on Arsenic removal efficiency using natural adsorbents, Water, Air, & Soil Pollution, Vol. 232(444), DOI: 10.1007/s11270-021-05398-4.

Reviewer 2 Report

Comments and Suggestions for Authors

1) The model is valid only for saxaul ash. How confident are you that the core methodology (integrating pH, initial arsenic concentration, and adsorbent dose effects) couldn’t be adapted for other adsorbents with modifications to f(p), f(IC), and f(D)? What are the key challenges?

2) The MRE was assumed to be 100%. How would the model’s accuracy change if the actual MRE of saxaul ash under optimal conditions were lower (e.g., 80-90%)?

3) The model predicts arsenic removal at equilibrium. How is equilibrium time determined, and how sensitive is the model's accuracy to variations in actual equilibrium time under different conditions?

4) The relationships between the variables and arsenic removal are based on best-fit equations. How was overfitting addressed, given the limited data points from Rahdar et al.?

5) The model assumes constant temperature and contact time. How could it be extended to account for fluctuations in these parameters on arsenic removal efficiency?

6) The title mentions "modified" saxaul ash, but the modification process isn't detailed. How does the modification affect adsorption, and how would changes in the process impact the model’s predictions?

7) The paper cites discrepancies in predicted values due to non-adherence to measured values. How can the model be improved to address this and enhance accuracy?

8) Cite the following paper in the introduction section: doi.org/10.1016/j.dwt.2024.100446.

9) Please double-check all the references for accuracy and style, as I have found discrepancies. Also, check the manuscript for any typographical, syntactical, and grammatical errors.

Author Response

Comments and Suggestions for Authors

• The model is valid only for saxaul ash. How confident are you that the core methodology (integrating pH, initial arsenic concentration, and adsorbent dose effects) couldn’t be adapted for other adsorbents with modifications to f(p), f(IC), and f(D)? What are the key challenges?

Authors’ reply: Core methodology could be used for other adsorbents, however, a detailed experimental data would be required to establish new relationships. Key challenge here is the establishment of experimentally valid relationships for each adsorbent or contributing factor. Comment on this appended in the revised manuscript.

• The MRE was assumed to be 100%. How would the model’s accuracy change if the actual MRE of saxaul ash under optimal conditions were lower (e.g., 80-90%)?

Authors’ reply: Ideally, the MRE should be 100% given the fact that mentioned adsorbent has very high capacity of adsorbing arsenic. For the current modelling effort, the good accuracy was observed with an MRE value of 100%. However, consideration of lower MRE values would affect the model’s accuracy. Comment on this appended in the ‘Conclusion’ section of the revised manuscript.

• The model predicts arsenic removal at equilibrium. How is equilibrium time determined, and how sensitive is the model's accuracy to variations in actual equilibrium time under different conditions?

Authors’ reply: From the original experimental study the equilibrium time was found to be 60 minutes. As such, the model is valid for an equilibrium time of 60 minutes, this fact is now mentioned in the revised manuscript. Model’s accuracy will vary for a lower equilibrium time, which was not a part of current modelling effort.

• The relationships between the variables and arsenic removal are based on best-fit equations. How was overfitting addressed, given the limited data points from Rahdar et al.?

Authors’ reply: Although, data points were limited, however, experimental measurements captured the actual peak removal efficiency. As such, covered the effective ranges of arsenic removals and overfitting is not an issue for this modelling task. Comment on this now appended in the ‘Conclusion’ of revised manuscript.

• The model assumes constant temperature and contact time. How could it be extended to account for fluctuations in these parameters on arsenic removal efficiency?

Authors’ reply: The original study conducted measurements with varying contact time and temperature. It is possible to include those factors in the developed equation. Authors are in the process of improving current developed model with the addition of two more factors (contact time and temperature). It is mentioned in the revised manuscript.

• The title mentions "modified" saxaul ash, but the modification process isn't detailed. How does the modification affect adsorption, and how would changes in the process impact the model’s predictions?

Authors’ reply: The modification process is now appended in the revised manuscript. Changes in the process is likely to impact the arsenic removal efficiency, as the process was derived based on some earlier studies and successes.

• The paper cites discrepancies in predicted values due to non-adherence to measured values. How can the model be improved to address this and enhance accuracy?

Authors’ reply: It is recommended that another study be conducted with more measured data having high quality control on experimental measurements. This would validate the current modelling results.

• Cite the following paper in the introduction section: doi.org/10.1016/j.dwt.2024.100446.

Authors’ reply: The recommended paper cited in the revised manuscript

• Please double-check all the references for accuracy and style, as I have found discrepancies. Also, check the manuscript for any typographical, syntactical, and grammatical errors.

Authors’ reply: The revised manuscript has been thoroughly checked for references, grammar and typographical errors.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed all the major concerns related to the review. I believe that the manuscript quality is now up to an acceptable level. 

Reviewer 2 Report

Comments and Suggestions for Authors

The revised version is acceptable for publication.