Organoclay Microparticle-Enhanced Microfiltration for the Removal of Acid Red 27 in Aqueous Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The submitted manuscript presents experimental work on the removal of AR27 using bentonite-based adsorbents. Both natural and modified forms of bentonite were employed in a microparticle-enhanced microfiltration process. Two synthesized samples were characterized using various analytical techniques (ATR, SEM-EDS, DLS, and thermal analysis). Equilibrium adsorption (Langmuir, Freundlich, and Temkin) and kinetic models (pseudo-first-order and pseudo-second-order) were evaluated for AR27 removal from aqueous solution. Moreover, desorption studies of AR27 from the bentonite samples were performed.

The manuscript presents a substantial body of experimental data, including synthesis, characterization, and application results. The authors report that the modified sample (BAPTES) exhibits a significantly higher adsorption capacity than bentonite, attributed to its positive zeta potential. However, the adsorption capacity of the BAPTES remains modest compared with values reported for cationic-modified bentonites, and the adsorption kinetics are relatively slow. The Introduction section is well structured.

However, the presentation of the results is somewhat verbose, and the discussion could be more concise and focused. In addition, certain sections contain scientific inconsistencies (e.g., Fig. 2, Fig. 3, Table 1, and Fig. 4).

Regarding novelty, the topic does not convey an original concept, and there are similar works in the field.

Despite these limitations, the work has merit and could be of interest to the readership after significant improvements. I recommend a major revision to address issues of scientific clarity, conciseness, and overall language quality. Detailed comments have been provided to assist the authors in enhancing the manuscript.

1. A graphical abstract is recommended.
2. The authors should clearly articulate the novelty of this work in comparison to existing studies on AR27 removal using bentonite-based adsorbents and microparticle-enhanced microfiltration.
3. Key process variables such as pH, adsorbent dosage, and the presence of interfering ions were not investigated on the AR27 adsorption. These factors can significantly influence adsorption performance and should be addressed experimentally.
4. In the Experimental section, describe the functionalization process in detail.
5. The authors should clarify that utilized AR27 solution is synthetic or derived from real wastewater and comment on whether the method is sufficiently efficient for the treatment of natural wastewater containing complex matrices.
6. The time to reach adsorption equilibrium is approximately 960 min, indicating very slow kinetics. The suitability of the adsorbent and the process for practical applications should be critically assessed considering this limitation.
7. Figure 1 is overly large; it is recommended to reduce its size and present the chemical structures more compactly.
8. In Figure 3, since color distribution images are already presented, the SEM image should not be colorized.
9. In Figure 3, bentonite contains Al, but BAPTES shows no Al content. Discuss why the Al content appears to have disappeared during functionalization with APTES. Also, indicate the Al–O peak in the IR-ATR spectra (Fig. 2A).
10. The observed increase in particle size, which is unfavorable for adsorption surface area, could potentially be mitigated through strong mixing and ultrasonication.
11. The elemental composition reported in Table 1 contains inconsistencies and errors.
12. In Figure 4b, the reported weight loss of 4.6% appears to be incorrect. Please recheck the data.
13. The term sorption has been used inappropriately in several places. Since adsorption refers to the adhesion of molecules onto the surface of a solid, and sorption is a broader term encompassing both adsorption and absorption (or when the exact mechanism is unknown), the correct term should be used consistently throughout the manuscript.
14. Some parameters in the text are not clearly defined (e.g., R_sys and R_Baptes). It is recommended that all symbols be properly defined.
15. It is advised to include a table comparing the main results of this work with similar adsorbents reported in other references.
16. Abbreviations should be standardized and used consistently throughout the text (e.g., BAPTES, APTES).
17. The keywords could be revised to improve discoverability and relevance.
18. The arrangement of author affiliations should be corrected.
19. The entire manuscript should undergo thorough English language editing to improve clarity, grammar, and fluency. For example, certain phrases such as “bacht”, “line 255”, and “line 669” appear to be typographical errors and should be corrected.
20. The presentation of results is somewhat verbose, and the discussion could be more concise. It is recommended to focus on explaining the adsorption mechanism and the adsorption–desorption pathway.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The entire manuscript should undergo thorough English language editing to improve clarity, grammar, and fluency.

For example, certain phrases such as bacht appear to be typographical errors and should be corrected.

Author Response

The submitted manuscript presents experimental work on the removal of AR27 using bentonite-based adsorbents. Both natural and modified forms of bentonite were employed in a microparticle-enhanced microfiltration process. Two synthesized samples were characterized using various analytical techniques (ATR, SEM-EDS, DLS, and thermal analysis). Equilibrium adsorption (Langmuir, Freundlich, and Temkin) and kinetic models (pseudo-first-order and pseudo-second-order) were evaluated for AR27 removal from aqueous solution. Moreover, desorption studies of AR27 from the bentonite samples were performed.

The manuscript presents a substantial body of experimental data, including synthesis, characterization, and application results. The authors report that the modified sample (BAPTES) exhibits a significantly higher adsorption capacity than bentonite, attributed to its positive zeta potential. However, the adsorption capacity of the BAPTES remains modest compared with values reported for cationic-modified bentonites, and the adsorption kinetics are relatively slow. The Introduction section is well structured.

However, the presentation of the results is somewhat verbose, and the discussion could be more concise and focused. In addition, certain sections contain scientific inconsistencies (e.g., Fig. 2, Fig. 3, Table 1, and Fig. 4).

Regarding novelty, the topic does not convey an original concept, and there are similar works in the field.

Despite these limitations, the work has merit and could be of interest to the readership after significant improvements. I recommend a major revision to address issues of scientific clarity, conciseness, and overall language quality. Detailed comments have been provided to assist the authors in enhancing the manuscript.

1. A graphical abstract is recommended.

Ans. The graphical abstract was adjusted and included in the paper.

 

1. The authors should clearly articulate the novelty of this work in comparison to existing studies on AR27 removal using bentonite-based adsorbents and microparticle-enhanced microfiltration.

Ans. Thank you for your comments. Table 1 was included in the introductory section, highlighting reported studies using functionalized bentonite and hybrid adsorption-microfiltration-based separation systems.

 

1. Key process variables such as pH, adsorbent dosage, and the presence of interfering ions were not investigated on the AR27 adsorption. These factors can significantly influence adsorption performance and should be addressed experimentally.

Ans. Thank you for your comment. Indeed, factors such as pH and the presence of interfering species can play a role in the adsorption process. The kinetic and isotherm experiments were not subjected to these variables; however, in the "Study of the desorption capacity of dye" section, it can be observed how pH variation and the presence of interfering ions, Na⁺ and Cl^-, modify the strength of the interaction between the analyte and the adsorbent.

 

1. In the Experimental section, describe the functionalization process in detail.

Ans. Section 2.2 was reviewed, and the methodology is detailed in the paper.

 

1. The authors should clarify that utilized AR27 solution is synthetic or derived from real wastewater and comment on whether the method is sufficiently efficient for the treatment of natural wastewater containing complex matrices.

Ans. In section 2.11 of the methodology, it is clarified that a model AR27 solution was used for the microparticle-enhanced microfiltration experiments. It is important to clarify that this work seeks to obtain a first approximation of the use of a hybrid adsorption-microfiltration technique for the removal of AR27 specifically. The perspectives of the work conclude that it is necessary to analyze complex matrices containing other contaminants and even to evaluate the effect of the presence of different types of dyes in the same sample.

 

1. The time to reach adsorption equilibrium is approximately 960 min, indicating very slow kinetics. The suitability of the adsorbent and the process for practical applications should be critically assessed considering this limitation.

Ans. Thank you for your observation. Indeed, according to the adsorption kinetics studies, equilibrium is reached after 16 hours of contact, and for practical purposes, the kinetics can be considered slow. However, it is important to highlight that these experiments were conducted in a steady state. In contrast, when the Microparticle-Enhanced Microfiltration system was used, steady-state experiments were not performed, and the adsorbent-analyte contact time was much shorter than required to reach equilibrium. Table 6 shows the experimental times, t_exp (h), which did not exceed 5 hours of contact, yet retentions of up to 85% were achieved relative to the capacity reached at equilibrium.

 

1. Figure 1 is overly large; it is recommended to reduce its size and present the chemical structures more compactly.

Ans. The figure has been resized and reduced in size. Thank you for your comment.

 

1. In Figure 3, since color distribution images are already presented, the SEM image should not be colorized.

Ans. Thank you for your comment. The SEM image was replaced by the original, which does not show the element distribution.

 

1. In Figure 3, bentonite contains Al, but BAPTES shows no Al content. Discuss why the Al content appears to have disappeared during functionalization with APTES. Also, indicate the Al–O peak in the IR-ATR spectra (Fig. 2A).

Ans. Figure 3 shows the results obtained from the identification of elements using the EDS technique during the SEM analysis. It is important to remember that this analysis technique is quantitative, surface-specific, and limited to the surface of the selected analysis area. Therefore, its results should be interpreted with caution and should not be considered qualitative. Therefore, the lack of identification of Al in the functionalized bentonite sample does not mean that Al has disappeared from the sample; it only indicates that the element was not observed on the analysis surface. Likewise, in the discussion session on the IR-ATR spectrum, it was stated that "Likewise, the typical signals observed for bentonite associated with the deformation vibration of the Si-O-Si groups, strain vibrations of the Si-OH and Si-O-Al groups, and out-of-plane strain vibration of the Al-O and Si-O groups in the region between 600 and 1200 cm^-1 were also observed for the BAPTES organoclay."

 

1. The observed increase in particle size, which is unfavorable for adsorption surface area, could potentially be mitigated through strong mixing and ultrasonication.

Ans. Thank you for your observation. It is important to note that due to the use of microfiltration membranes with a pore size of 0.45 micrometers (450 nm), the implementation of ultrasonication techniques can cause clay exfoliation and a decrease in particle size. This would be detrimental to the retention process of suspended particles by the membrane.

 

1. The elemental composition reported in Table 1 contains inconsistencies and errors.

Ans. The values ​​were verified and adjusted. It was clarified in the table footnote that "---" means the "Unidentified chemical element" to avoid misleading the reader.

 

1. In Figure 4b, the reported weight loss of 4.6% appears to be incorrect. Please recheck the data.

Ans. The values ​​in Figures 4A and 4B were verified and adjusted as described in the text.

 

1. The term sorption has been used inappropriately in several places. Since adsorption refers to the adhesion of molecules onto the surface of a solid, and sorption is a broader term encompassing both adsorption and absorption (or when the exact mechanism is unknown), the correct term should be used consistently throughout the manuscript.

Ans. Thank you for your feedback. The document has been adjusted to use the correct term for adsorption.

 

1. Some parameters in the text are not clearly defined (e.g., R_sys and R_Baptes). It is recommended that all symbols be properly defined.

Ans. All symbols and formulas were correctly defined in section 2.11 of the methodology.

 

1. It is advised to include a table comparing the main results of this work with similar adsorbents reported in other references.

Ans. Thank you for your comment. The suggested table was included in the introductory section, "Table 1. Summary of dye removal methods using functionalized bentonite and microfiltration systems."

 

1. Abbreviations should be standardized and used consistently throughout the text (e.g., BAPTES, APTES).

Ans. The abbreviations were reviewed and corrected.

The abbreviations are defined below:

APTES: (3-aminopropyl)triethoxysilane

BAPTES: Organoclay based on APTES-functionalized bentonite

 

1. The keywords could be revised to improve discoverability and relevance.

Ans. The keywords were revised and the following were included: bentonite, APTES, amaranth, hybrid separation methods, FEDS, microfiltration, microparticles.

 

1. The arrangement of author affiliations should be corrected.

Ans. The affiliations were arranged in the order of presentation.

 

1. The entire manuscript should undergo thorough English language editing to improve clarity, grammar, and fluency. For example, certain phrases such as “bacht”, “line 255”, and “line 669” appear to be typographical errors and should be corrected.

Ans. The document was reviewed and typographical errors were corrected.

 

1. The presentation of results is somewhat verbose, and the discussion could be more concise. It is recommended to focus on explaining the adsorption mechanism and the adsorption–desorption pathway.

Ans. Thank you for your observation. Discussion sessions have been adjusted to be more concise.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Major Revision

1. Abstract section: The mechanism involved in using an organoclay, BAPTES for use as a semi-synthetic adsorbent material in the microparticle-enhanced MF process must be well explained.
2. Introduction section: First paragraph is too generalised. The authors can come up with problem statement instead of discussing the negative impacts of various dyes.
3. Figure 1 (a) and (b): Are we gaining any scientific insights? It is well known chemical structure and available in other literature.
4. State-of-art discussion table must be included by comparing the various microparticle enhanced MF processes (microparticle type/ membrane/ modification/ target pollutant/ performance metrics/ reference) to show the effectiveness of the present research study.
5. Where was the ‘propylene microfiltration membrane’ acquired from? Please update the information in materials and methods.
6. Membrane modification part seems to be missing from “Materials and Methods” section.
7. Figure 3 is difficult to assess. Resolution is poor as well.
8. Some important data are missing from the manuscript which are as follows:

• Hydrophobicity/ hydrophilicity of pristine and modified membrane
• Membrane thickness of fabricated membrane.

Author Response

1. Abstract section: The mechanism involved in using an organoclay, BAPTES for use as a semi-synthetic adsorbent material in the microparticle-enhanced MF process must be well explained.

Ans. Thank you for your comment. The abstract was revised and indicates that the interaction is electrostatic between the organoclay and the dye. "The results showed a significant increase in the adsorption capacity of AR27 by organoclay (86.06%) compared to natural bentonite (2.10%), due to the presence of ionizable amino groups in the organoclay structure that promote electrostatic interactions with the dye."

 

1. Introduction section: First paragraph is too generalised. The authors can come up with problem statement instead of discussing the negative impacts of various dyes.

Ans. Thank you for the comment. The introduction was adjusted and studies related to functionalized bentonite-based materials were described.

 

1. Figure 1 (a) and (b): Are we gaining any scientific insights? It is well known chemical structure and available in other literature.

Ans. Figure 1 is intended to help the reader identify the structures of the organosilane used in the bentonite modification and the structure of the dye evaluated. This allows the reader to identify the functional groups involved in the process. Additionally, Figure 1B shows the configuration of the microparticle-enhanced microfiltration system used in this study. Similar systems are reported in the literature, but with some configuration variables. The image has been scaled down to a smaller size.

 

1. State-of-art discussion table must be included by comparing the various microparticle enhanced MF processes (microparticle type/ membrane/ modification/ target pollutant/ performance metrics/ reference) to show the effectiveness of the present research study.

Ans. The introduction discusses published work associated with the use of clay-based adsorbent materials and hybrid adsorption/microfiltration systems. Table 1 is included as a compendium of the aforementioned work.

 

1. Where was the ‘propylene microfiltration membrane’ acquired from? Please update the information in materials and methods.

Ans. The microfiltration membrane supplier information in the methodology session has been updated. "A hydrophobic polypropylene microfiltration membrane (Merck, USA) with a pore size of 0.45 µm, a diameter of 47 mm, and an effective filtration area of ​​0.001257 m² was used."

 

1. Membrane modification part seems to be missing from “Materials and Methods” section.

Ans. No modification process was performed on the membrane in the microfiltration experiments. The APTES-modified bentonite-based adsorbent material was the only material obtained through chemical modification. The membrane was used as purchased from the supplier described in the methodology session.

 

1. Figure 3 is difficult to assess. Resolution is poor as well.

Ans. Thank you for your comment. The figure has been adjusted to include its original SEM image. It is also noted that the image uploaded to the publisher's system has adequate resolution.

 

1. Some important data are missing from the manuscript which are as follows:

• Hydrophobicity/ hydrophilicity of pristine and modified membrane
• Membrane thickness of fabricated membrane.

Ans. Thank you for your comments. However, it is important to clarify that the experiments described did not involve modifying the microfiltration membrane used. The methodology indicates that it is a hydrophobic polypropylene membrane.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors investigated the synthesize of an organoclay, BAPTES, based on bentonite and (3-aminopropyl)triethoxysilane for use as a semi-synthetic adsorbent material in the microparticle-enhanced microfiltration process for the removal of AR27 in aqueous systems. I have included several comments in this work, which may enhance its quality and support my decision to submit it for publication.

- The abstract must cover the whole study and the results of this research.

- Microfiltration is generally not so effective for dye removal from wastewater. Why did the authors think to improve this process instead of using the ultrafiltration process?

- The authors must mention the type of membrane used in this study and its source. Also, they should mention if the filtration process was crossflow or dead-end.

- Figure 1c is ambiguous and the operation mechanism must be clarified. Also, the typo must be corrected, such as Presure source N2. The role of the magnetic stirrer and reservoir is not understood.

- Please correct this typo in the whole manuscript "bacht", Pages 5, 7, 8.

- Please assign the equations to references. Some of them are mentioned in the following reference, which can be useful for this purpose.

DOI: 10.1002/apj.2967

- For the study mentioned in section 2.10, why did the authors use a solution volume of different sizes in each study? If the volume is not variable, then it must be kept constant.

- The pH of the solution containing the dye is an important factor, and it must be studied.

- The operation procedures mentioned in section 2.11 are not understood and must be clarified. The units of the given variables and symbols must be given. The symbols of concentration must be put in Figure 1C to be clarified. Figure 1C must come after section 2.11 for clarity.

- The authors showed very excessive use of the phrase "on the other hand"! about 11 times!

- Please check if this sentence is complete "On the other hand, for APTES organoclay, the elements 416 present in bentonite were identified.".

- Table 1: The authors must explain why Al disappeared in the BAPTES.

- Section 3.3: I think the authors meant "To determine the adsorption kinetics of AR27", not "To determine the adsorption dynamics of AR27". The authors must express the time in h units as used in Figure 5, or present the time in this figure in min units.

- Section 3.5: Equilibrium constants- Kd=qe/Ce or KC=(Co-Ce)/(Co), or Kd=(V/m)*(Co-Ce)/Co, or Kc= Cs/Ce., or K= Ln(qe/Ce), or Kd= qexdensity/ce. Although several papers reported in the literature use these relationships as the equilibrium constant for obtaining thermodynamic parameters such as enthalpy changes, entropy changes, and free Gibbs energy, the thermodynamic parameters obtained by these Kc or KD are not correct. Please read the following paper: DOI: 10.1002/apj.2967, which reports the use of the above equation in adsorption studies. This is not just multiplying it by any factor to make it dimensionless but using the activity.

• Moreover, activity is the molar concentration (mol/L) when the activity coefficient equals 1.00.

- Please mention the condition of experiments E1-E5.

- Table 5: correct "Baptes" to "BAPTES".

- The conclusion sections must be rewritten based on the previous comments.

Comments for author File: Comments.pdf

Author Response

The authors investigated the synthesize of an organoclay, BAPTES, based on bentonite and (3-aminopropyl)triethoxysilane for use as a semi-synthetic adsorbent material in the microparticle-enhanced microfiltration process for the removal of AR27 in aqueous systems. I have included several comments in this work, which may enhance its quality and support my decision to submit it for publication.

 

- The abstract must cover the whole study and the results of this research.

Ans. Thank you for your comment. The abstract was adjusted to highlight the most important results.

 

- Microfiltration is generally not so effective for dye removal from wastewater. Why did the authors think to improve this process instead of using the ultrafiltration process?

Ans. Thank you for your comment. The proposed hybrid separation method, based on suspended microparticles and the use of microfiltration membranes, is based on the principle that the microparticulate adsorbent material has a particle size larger than the pore size of the membrane used and acts as the separation component. Microfiltration is used to retain suspended microparticulate material in the aqueous effluent, acting as a physical barrier to prevent its passage. Therefore, the microfiltration membrane can be considered a passive component in the adsorption process. Furthermore, the process's energy consumption is intended to be low, which, through the use of microfiltration, is possible by reducing the operating pressure of the system; the system can even operate under gravity.

 

- The authors must mention the type of membrane used in this study and its source. Also, they should mention if the filtration process was crossflow or dead-end.

And. The characteristics of the membrane used are defined in the materials section. Figure 1C also represents the equipment used, which corresponds to a dead-end filtration system.

 

- Figure 1c is ambiguous and the operation mechanism must be clarified. Also, the typo must be corrected, such as Presure source N2. The role of the magnetic stirrer and reservoir is not understood.

Ans. Thank you for your comments. The typos have been corrected. The stirrer's function is to generate turbulence in the system to keep the BAPTES microparticles suspended and prevent their precipitation and fouling on the membrane. The reservoir was used to supply water for the continuous microfiltration experiment.

 

- Please correct this typo in the whole manuscript "bacht", Pages 5, 7, 8.

Ans. The error has been corrected. Thank you.

 

- Please assign the equations to references. Some of them are mentioned in the following reference, which can be useful for this purpose.

DOI: 10.1002/apj.2967

Ans. Thank you for the comment. The equations have been referenced.

 

- For the study mentioned in section 2.10, why did the authors use a solution volume of different sizes in each study? If the volume is not variable, then it must be kept constant.

Ans. For the experiment in section 2.10, the contact solution volumes were constant at 10.0 mL and the concentration was 500 ppm AR27. In particular, the experiment sought to evaluate the effect of varying temperature, between 298.15 and 328.15 K, on ​​dye adsorption.

 

- The pH of the solution containing the dye is an important factor, and it must be studied.

Ans. Thank you for your comment. Indeed, factors such as pH and the presence of interfering species can play a role in the adsorption process. The kinetic and isotherm experiments were not subjected to these variables; however, in the "Study of the desorption capacity of dye" section, it can be observed how pH variation and the presence of interfering ions, Na⁺ and Cl^-, modify the strength of the interaction between the analyte and the adsorbent.

 

- The operation procedures mentioned in section 2.11 are not understood and must be clarified. The units of the given variables and symbols must be given. The symbols of concentration must be put in Figure 1C to be clarified. Figure 1C must come after section 2.11 for clarity.

Ans. Thank you for the comments. The session was described in more detail, and the equations and their variables were included. The figure was relocated in the document.

 

- The authors showed very excessive use of the phrase "on the other hand"! about 11 times!

Ans. Thank you for the observation. The use of the indicated connector has been reduced in the document.

 

- Please check if this sentence is complete "On the other hand, for APTES organoclay, the elements 416 present in bentonite were identified.".

Ans. Thank you for your comment. The sentence was edited.

 

- Table 1: The authors must explain why Al disappeared in the BAPTES.

Ans. Thank you for your comment. Figure 3 shows the results obtained from the EDS element identification technique during the SEM analysis. It is important to remember that this analytical technique is quantitative, surface-specific, and limited to the surface of the selected analysis area. Therefore, its results should be interpreted with caution and should not be considered qualitative. Therefore, the lack of identification of Al in the functionalized bentonite sample does not mean that the Al has disappeared from the sample; it only indicates that the element was not observed on the selected analysis surface. The requested clarification was provided in the discussion.

 

- Section 3.3: I think the authors meant "To determine the adsorption kinetics of AR27", not "To determine the adsorption dynamics of AR27". The authors must express the time in h units as used in Figure 5, or present the time in this figure in min units.

Ans. Thank you for the comment. The expression has been corrected, and the correct use of time units is in hours.

 

- Section 3.5: Equilibrium constants- Kd=qe/Ce or KC=(Co-Ce)/(Co), or Kd=(V/m)*(Co-Ce)/Co, or Kc= Cs/Ce., or K= Ln(qe/Ce), or Kd= qexdensity/ce. Although several papers reported in the literature use these relationships as the equilibrium constant for obtaining thermodynamic parameters such as enthalpy changes, entropy changes, and free Gibbs energy, the thermodynamic parameters obtained by these Kc or KD are not correct. Please read the following paper: DOI: 10.1002/apj.2967, which reports the use of the above equation in adsorption studies. This is not just multiplying it by any factor to make it dimensionless but using the activity.

• Moreover, activity is the molar concentration (mol/L) when the activity coefficient equals 1.00.

Ans. Thank you for your valuable feedback. Equations were adjusted in the methodology. The work was referenced. Additionally, the enthalpy, entropy, and Gibbs free energy parameters were recalculated. The values ​​were adjusted in the text, and the discussion was corrected.

 

- Please mention the condition of experiments E1-E5.

Ans. Table 6 shows the initial concentration of the AR27 solution (Ci) and the mass of BAPTES used.

 

- Table 5: correct "Baptes" to "BAPTES".

Ans. Thank you. The abbreviation has been corrected.

 

- The conclusion sections must be rewritten based on the previous comments.

Ans. Thank you for the comments. The conclusions were adjusted based on the results obtained.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Lerma et al., presented a research article where was studied the removal of acid RED 27 in aqueous systems using the microparticle-enhanced microfiltration technique. For that purpose the authors synthesized, characterized and tested an Organoclay (BAPTES) as semi-synthetic adsorbent material.  The paper in general was well written, and organized, but the authors must address the following recommendations:

• Please add at the end of the abstract the implication or relevance of this study to the scientific community or stakeholders.
• Line 143: Figure 1(C). This figure can be moved close to section 2.11, where was introduced and explained in detail.
• Lines 277-278. The authors defined the variables “R” and “T”, but those variables should be defined earlier for the equation #8 at some point between line 255 and 258. Please make the respective modification.
• Lines 480-482: “…the BAPTES organoclay showed a dye retention capacity of 86.06%, 35.52mg g^-1, being 41 times higher than the adsorption capacity recorded by bentonite”. The authors showed the enhancement of the retention capacity by the BAPTES organoclay in comparison with bentonite. However, it was not included the total cost of that enhancement per functional unit (i.e. area, or volume, etc.). The previous is relevant for implementation purposes and quantification of the ratio benefit/cost.
• Line 496: “… it was observed that after 960 min of contact, …” and the “x” units on figure 5a are in hours. Please be consistent with the units. Either way keep the units in minutes or hours for comparison purposes. Please make the respective modification.
• Lines 552-553: “… at different initial concentrations of AR27 25-1000”. Can the authors justify or provide the reasons to select that range of concentrations? i.e., Mimic commercial concentrations, typical environmental concentrations, etc.
• Line 621-Figure 6. Please add the units to the “x” axis
• Lines 626-681. Just one reference was included in this section to compare or discuss the results. Please improve this section and expand the comparison and discussion of your results using additional references.
• Line 640; “ .. experiments E1 to E5…”. Please specify each experiment in detail. i.e. the “amount or concentration” of BAPTES that was incorporated for each condition, etc.
• The authors did a great job highlighting the pros of the BAPTES organoclay but there were not mentioned the limitations or cons of this technique. Please provide the respective information and/or justification and add the respective information to the manuscript.

Author Response

Lerma et al., presented a research article where was studied the removal of acid RED 27 in aqueous systems using the microparticle-enhanced microfiltration technique. For that purpose the authors synthesized, characterized and tested an Organoclay (BAPTES) as semi-synthetic adsorbent material.  The paper in general was well written, and organized, but the authors must address the following recommendations:

• Please add at the end of the abstract the implication or relevance of this study to the scientific community or stakeholders.

Ans. Thank you for your comments. The abstract has been adjusted.

 

• Line 143: Figure 1(C). This figure can be moved close to section 2.11, where was introduced and explained in detail.

Ans. Thank you for your observation. The figure has been adjusted and relocated in the document.

 

• Lines 277-278. The authors defined the variables “R” and “T”, but those variables should be defined earlier for the equation #8 at some point between line 255 and 258. Please make the respective modification.

Ans. Thank you for your observation. The indicated adjustments have been made.

 

• Lines 480-482: “…the BAPTES organoclay showed a dye retention capacity of 86.06%, 35.52mg g^-1, being 41 times higher than the adsorption capacity recorded by bentonite”. The authors showed the enhancement of the retention capacity by the BAPTES organoclay in comparison with bentonite. However, it was not included the total cost of that enhancement per functional unit (i.e. area, or volume, etc.). The previous is relevant for implementation purposes and quantification of the ratio benefit/cost.

Ans. Thank you for your comments. An analysis of the production price of the material was included in the discussion session.

 

• Line 496: “… it was observed that after 960 min of contact, …” and the “x” units on figure 5a are in hours. Please be consistent with the units. Either way keep the units in minutes or hours for comparison purposes. Please make the respective modification.

Ans. Thank you for the observation. The units have been corrected.

 

• Lines 552-553: “… at different initial concentrations of AR27 25-1000”. Can the authors justify or provide the reasons to select that range of concentrations? i.e., Mimic commercial concentrations, typical environmental concentrations, etc.

Ans. Thank you for your comment. It is important to highlight that the methodology described corresponds to steady-state experiments to study behavior through Langmuir, Freundlich, and Temkin adsorption isotherms. To accomplish this study and apply equations 6, 7, and 8, respectively, the experiments must be designed based on variations in the initial concentration of the dye solution used.

 

• Line 621-Figure 6. Please add the units to the “x” axis

Ans. The x-axis units have been added. Thank you.

 

• Lines 626-681. Just one reference was included in this section to compare or discuss the results. Please improve this section and expand the comparison and discussion of your results using additional references.

Ans. Thank you for your comment. Table 1 was included in the document, describing work associated with the use of adsorbent material and hybrid microfiltration separation systems. The discussion session was also expanded.

 

• Line 640; “ .. experiments E1 to E5…”. Please specify each experiment in detail. i.e. the “amount or concentration” of BAPTES that was incorporated for each condition, etc.

Ans. Thank you for your comment. Table 6 includes a description of the concentration of the AR27 solution used and the amount of adsorbent material.

 

• The authors did a great job highlighting the pros of the BAPTES organoclay but there were not mentioned the limitations or cons of this technique. Please provide the respective information and/or justification and add the respective information to the manuscript.

Ans. Thank you for your comment. At the end of section 3.1, where the material cost analysis is conducted, the main disadvantage associated with the use of organoclay is highlighted: its production cost associated with the organosilane used.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The author's have addressed all my queries with scientific explanation. Therefore, the revised mansucript can be accepted in the present format. 

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have done the corrections