Computational Simulation of Filters Used in the Removal of Heavy Metals Using Rice Husks
Round 1
Reviewer 1 Report
The paper entitled “Computational simulation of filters used in the removal of heavy metals using rice husks” was submitted for review for possible publication. So here are my comments and suggestions:
- The abstract does not represent the”actual” findings of the study. The authors need to fix this to make it more a clearer picture of what was actually done and obtained.
- The introduction must also discuss how rice husks was used to filter Cu, Cd and Cr. If scarce, present related literature in the purpose of establishing the need to use it.
- Figure 1 is confusing. The arrows and arrow heads must in the basic manner indicate incoming and outgoing streams. The authors must use separate symbols to delineate incoming and outgoing streams from the filter media parts. Replace the incoming stream as “influent” or “contaminated Feed stream (Cu, Cr, Cd) and replace the outgoing stream as “effluent” or “treated water”.
- What is the basis for Figure 2. From its caption, it is a forecast of the adsorption mechanism so it should have some theoretical basis. The same figure illustrates no adsorption of Cr on the rice husk so where will you attribute the %adsorption capacity if Cr reported?. Fix this.
- Line 212. The statement “those of Langmuir was better” must he explained further in the context of the result. Mention that the predicted and experimental resulta agrees better with the Langmuir isotherm. These is supported further by the r-squared values in Table 3 which was greater than 0.99 and is agains supported by Figure 4 abc.
- Line 218-219. “.. no interaction between the molecules adsorbed on surface of the rice husk” is confusing since you have mentioned after figure 2 in the paper that “ to be adsorbed by the rice husk, process such as redox and ion exchange must take place”. These are contrasting statements. Fix this.
- Line 219-221. ...”adsorption occurs at specific binding sites that are located on the surface of the rice husk” but Figure 2 does not say so. Fix this.
- Line 224-227. “ ... q max is the max capacity of adsorption which increases with temp up to 303.15 K means that the biofilter works correctly because temp like these are present in real life”... provide a more scientific explanation on these. There is no discussion in the background or in the results how a filter works correctly with reference to temperature. Fix this.
- The breaking curve is presented as for Cu and Cd: pH=9; T=303.15 K while Cr is at pH=4;T=298 K. Explain why the conditions for Cr is different. Also, separate the discussion on Cu and Cd from Cr. They might confuse the readers on your result.
- The conclusion mentioned that Cr 6+ behavior is the same as that of Cr3+ behavior but there is no mention of the behavior of Cr3+ in the background and even in the results and discussion. Fix this.
Author Response
The paper entitled “Computational simulation of filters used in the removal of heavy metals using rice husks” was submitted for review for possible publication. So here are my comments and suggestions:
Reviewer comment 1
1. The abstract does not represent the”actual” findings f the study. The authors need to fix this to make it more a clearer picture of what was actually done and obtained
Answer to comment 1
Changes were made in the summary showing the results obtained in the work and highlighting the most important data according to the suggestions presented.
2. Figure 1 is confusing. The arrows and arrow heads must in the basic manner indicate incoming and outgoing streams. The authors must use separate symbols to delineate incoming and outgoing streams from the filter media parts. Replace the incoming stream as “influent” or “contaminated Feed stream (Cu, Cr, Cd) and replace the outgoing stream as “effluent” or “treated water”.
Answer to comment 2
In Figure 1 the corresponding changes were made, listing the parts of the filter and indicating with other symbols the treated and contaminated water according to the suggestions made.
3. What is the basis for Figure 2. From its caption, it is a forecast of the adsorption mechanism so it should have some theoretical basis. The same figure illustrates no adsorption of Cr on the rice husk so where will you attribute the %adsorption capacity if Cr reported?. Fix this Given the authors take care of above points, the manuscript may be accepted for publication after review.
Answer to comment 3
The mechanism shown in Figure 2 was modified, where it is shown that there is absorption of Cr, Cu and Cd, leaving a few free atoms, but in a smaller proportion than those absorbed, indicating that there is absorption of the three heavy metals.
4. Line 212. The statement “those of Langmuir was better” must he explained further in the context of the result. Mention that the predicted and experimental result agrees better with the Langmuir isotherm. These is supported further by the r-squared values in Table 3 which was greater than 0.99 and is agains supported by Figure 4 abc.
Answer to comment 4
The explanation of the correlation coefficients and the support of Figure 4 were added to this paragraph, which shows that the process is better described using the Langmuir isotherm according to the suggestions made.
5. Line 218-219. “.. no interaction between the molecules adsorbed on surface of the rice husk” is confusing since you have mentioned after figure 2 in the paper that “ to be adsorbed by the rice husk, process such as redox and ion exchange must take place”. These are contrasting statements. Fix this
Answer to comment 5
It is indicated that for the heavy metal removal process to exist, there must be an interaction between the adsorbed molecules on the surface of the rice husk. Showing that they are interactions occur by mechanisms such as ion exchange
6.Line 219-221. ...”adsorption occurs at specific binding sites that are located on the surface of the rice husk” but Figure 2 does not say so. Fix this.
Answer to comment 6
It was clarified that the absorption process occurs in the active sites as indicated in Figure 2
7. Line 224-227. “ ... q max is the max capacity of adsorption which increases with temp up to 303.15 K means that the biofilter works correctly because temp like these are present in real life”... provide a more scientific explanation on these. There is no discussion in the background or in the results how a filter works correctly with reference to temperature. Fix this.
Answer to comment 7
The explanation about the operation of the filter at temperatures such as 303.15 K was changed, indicating that for the modeled temperatures 293.15 K, 298.15 K and 303.15 K, the lignocellulosic material does not deteriorate, maintaining its capacity to absorb heavy metals.
8. The breaking curve is presented as for Cu and Cd: pH=9; T=303.15 K while Cr is at pH=4;T=298 K. Explain why the conditions for Cr is different. Also, separate the discussion on Cu and Cd from Cr. They might confuse the readers on your result.
Answer to comment 8
The temperatures were reviewed and it was verified that the same temperature is used for Cr (VI) as for Cd (II) and Cu (II), the variation is in the pH value. The discussions of Cd (II) and Cu (II) were separated from that of Cr (VI). In addition, it was explained that chromium can be retained in the following ways: adsorbed (Cr (VI) and Cr (III)), precipitated and bioaccumulated on the support, in the cell membrane and in the metabolites produced by microorganisms.
9. The conclusion mentioned that Cr 6+ behavior is the same as that of Cr3+ behavior but there is no mention of the behavior of Cr3+ in the background and even in the results and discussion. Fix this
Answer to comment 9
In the conclusions and in the explanation of the breakdown curves, it is explained that Cr 6+ can be decomposed into Cr 3+ and this is what makes its behavior different, since it affects the removal processes.
Reviewer 2 Report
The authors present in their manuscript the use of rice husks for removing heavy metals, Although the idea is not new, in these, lasts years the use of different bioproducts for agriculture have been used with this purpose, the characterization of the performance of this specific bioproduct is interesting. The topic fits with the journal scope. Nonetheless, there are some issues which must be solved to enhance the quality of the paper:
I suggest avoiding using the same words in the title and the keywords. Therefore, please delete the keywords already used in the title and include new ones.
In the abstract, authors must include more information about the conditions in which they have obtained their results, duration, pH, temperature, etc …
At the end of the introduction, the authors include a short paragraph in which they detail the aim of the paper and the structure of the paper. I would recommend to split it into two paragraphs and extend the information included about the aim of the paper.
Authors must detail if the rice husk has been modified somehow. Does it have been ground? Does any compound have been added to maximize its specific area and pores?
A section in which authors compare their results with the results of related work must be added. In this new section, authors have to detail if the performance of rice husks are similar to the performance of other biomaterials regarding the sorption rates and regarding the effects of temperature and pH in these rates.
At the end of the conclusions, authors have to describe the future work linked to their results, as well as the possible real and scale-up application of the proposed solution.
Author Response
The authors present in their manuscript the use of rice husks for removing heavy metals, Although the idea is not new, in these, lasts years the use of different bioproducts for agriculture have been used with this purpose, the characterization of the performance of this specific bioproduct is interesting. The topic fits with the journal scope. Nonetheless, there are some issues which must be solved to enhance the quality of the paper:
1.I suggest avoiding using the same words in the title and the keywords. Therefore, please delete the keywords already used in the title and include new ones.
Answer to comment 1
The following words are added to the keywords as shown in the abstract: pH, Langmuir, Freundlich.
2. In the abstract, authors must include more information about the conditions in which they have obtained their results, duration, pH, temperature, etc …
Answer to comment 2
Outstanding results filter operating temperature, pH values, and lock-in time to remove heavy metals were included in the summary.
3. At the end of the introduction, the authors include a short paragraph in which they detail the aim of the paper and the structure of the paper. I would recommend to split it into two paragraphs and extend the information included about the aim of the paper.
Answer to comment 3
The objective of the paper was added in the introduction part, which is based on the fact that due to the great presence of heavy metals in both water and food, the need arises to propose alternatives for the removal of heavy metals. The alternative that arises in this case is a bio-filter made from easily accessible materials that contribute to a circular economy, such as rice husk, which allows the removal of metals such as Cr (VI), Cd ( II) and Cu (II) from water.
4.Authors must detail if the rice husk has been modified somehow. Does it have been ground? Does any compound have been added to maximize its specific area and pores?
Answer to comment 4
In the Selection of lignocellulosic material part the explanation is added that the rice husk does not require any additional process, only with a simple washing it can be used. Additionally, no component was used to maximize specific area and pores.
5.A section in which authors compare their results with the results of related work must be added. In this new section, authors have to detail if the performance of rice husks are similar to the performance of other biomaterials regarding the sorption rates and regarding the effects of temperature and pH in these rates.
Answer to comment 5
Table 8 was added in which the efficiencies obtained with rice husks are compared with other materials such as coffee, orange peel, sheep wool and banana peel. Showing that in some cases the removal process is less efficient using rice husks, which is due to the fact that other materials require an activation process to be used, while the rice husks only require washing.
6.At the end of the conclusions, authors have to describe the future work linked to their results, as well as the possible real and scale-up application of the proposed solution.
Answer to comment 6
A section called Perspectives was added in which it talks about a possible future job that consists of a shared study between the Thomas model, Bohart-Adams model and Yoon-Nelson model and Wolborska who is the employee in this job. Additionally, a possible real application of this filter is proposed in tributaries close to mining areas in Colombia in order to reduce heavy metal concentrations.
Reviewer 3 Report
I have the following comments and suggestions:
- The aim is not clearly defined in the abstract.
- The following reference can be used in the Introduction part since it is dealing with the issue of heavy metals found in food: Kulawik, P., Dordevic, D., Gambuś, F., Szczurowska, K., & Zając, M. (2018). Heavy metal contamination, microbiological spoilage and biogenic amine content in sushi available on the Polish market. Journal of the Science of Food and Agriculture, 98(7), 2809-2815.
- Please define the aim of the work more clearly at the end of the Introduction part.
- Lines 83-125: this part should be shorten.
- Lines 158-191: this part belongs to the results and discussion part.
- The determination of heavy metals' concentrations after filtering has not been done, and that is the main obstacle for the research.
Author Response
I have the following comments and suggestions:
1. The aim is not clearly defined in the abstract.
Answer to comment 1
In the abstract, the objective of the work was added, which is the modeling of a biofilter using the Wolborska model in order to obtain the operating parameters of the filter.
2. The following reference can be used in the Introduction part since it is dealing with the issue of heavy metals found in food: Kulawik, P., Dordevic, D., Gambuś, F., Szczurowska, K., & Zając, M. (2018). Heavy metal contamination, microbiological spoilage and biogenic amine content in sushi available on the Polish market. Journal of the Science of Food and Agriculture, 98(7), 2809-2815.
Answer to comment 2
The reference suggested in the introduction in the fourth paragraph of the introduction was added, also adding other types of foods that present heavy metals.
3. Please define the aim of the work more clearly at the end of the Introduction part.
Answer to The objective of the work was specified in the introduction, which is based on the fact that Due to the great presence of heavy metals both in water and in food, the need arises to propose alternatives for the removal of heavy metals. The alternative that arises in this case is a bio-filter made from easily accessible materials that contribute to a circular economy, such as rice husk, which allows the removal of metals such as Cr (VI), Cd ( II) and Cu (II) from water. comment 3
4. Lines 83-125: this part should be shorten.
Answer to comment 4
Some lines were removed as noted in the document with track changes
5. Lines 158-191: this part belongs to the results and discussion part.
Answer to comment 5
Selection of lignocellulosic material part added to results and discussion
6. The determination of heavy metals' concentrations after filtering has not been done, and that is the main obstacle for the research.
Answer to comment 6
The initial concentration values taken for the modeling were added, which exceed the allowed values with the intention of proposing an alternative to remove the excesses of heavy metals in the tributaries. And a table with the final concentration values was added after choosing an operating temperature and varying the pH as shown in Table 7
Round 2
Reviewer 1 Report
Dear Authors,
congratulations for a job well done in revising this paper. All it needs now is a thorough spell check and minor grammar check, and its good to go.
Author Response
- Please reconsider the main paragraph titles such as:
- Introduction
- Materials and Methods
- Results
- Discussion
- Conclusions
Please revise. Thank you.
Answer to comment 1
The change of title of the sections is considered according to the comment
- There is no reference 25 quoted in main text. Please revise. Please make sure references are quoted in numerical order.
Answer to comment 2
A review of the bibliography was made and the citations are listed in numerical order as shown in the text and in the bibliography.
- The figures or tables are required to be put after its first citation. Please check all Figure and Table quotes numerical order and quote order as written is this comment. Please revise. Thank you.
Answer to comment 3
It was verified that the graphs and tables will be shown after their first citation as indicated in the suggestion.
- Figures should be after theire quotes in the main text. In the paragraph before (Figure 3 and Figure 4), after that the images are put. Please revise.
Answer to comment 4
Figure 3 and 4 are shown after the paragraph as shown in the text.
- Table 4 not quoted in main text please revise.
Answer to comment 5
Table 4 was cited in the previous paragraph “The efficiencies for each metal at different temperatures are presented below in Table 4:”
- Quote first and then the image. Please revise. Thank you.
Answer to comment 6
Figure 5 was cited first and then shown.
- Table 6 not quoted in main text please revise.
Answer to comment 7
Table 6 was cited in the previous paragraph “The Table 6 shows the efficiencies are obtained:”
- There are 2 table & in the manuscript, please revise, renumber and quote in the paragraph before, and then insert the quoted table. Please revise thru the whole main text. And also Table 7 is not quoted in main text, please add;
Answer to comment 8
The names of the Tables were corrected, and none were repeated. Also, Table 7 is presented before being shown.
- Add information additional
Answer to comment 9
The required information was added to the end of the document corresponding to Author Contributions, Funding, Institutional Review Board Statement, Informed Consent Statement, Data Availability Statement, Conflicts of interest and Acknowledgments
- The references should be cited with the reference number in an “[]”, such as [1], [1,2], and [2–4]. Addi-tionally, they must be cited in ascending order of appearance in the text . All references must be cited with Arabic numbers. Citations with more than two consecutive references should be replaced with an en dash (–) in between: [1], [1,2], [3–5], and [1,3–5,7]
Answer to comment 10
References are cited as suggested. They were cited in ascending form and in Arabic numbers and the format was changed when there are several citations as shown in the bibliography.
Reviewer 3 Report
The manuscript can be accepted.
