Development of Antifouling Polyvinylidene Fluoride and Cellulose Acetate Nanocomposite Membranes for Wastewater Treatment Using a Membrane Bioreactor

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This literature focuses on the investigation of a novel PVDF/CA electrospun nanofiber membrane. The study reveals that the hydrophilicity of the composite membrane is crucial for filtering hydrophobic pollutants, and the PVDF/CA blend exhibits superior antifouling performance compared to neat PVDF. The composite membrane demonstrates increased porosity and wastewater flux, a reduced water contact angle, enhanced hydrophilicity, lower overall mass transfer resistance, improved permeability, and a lower transmembrane pressure. The prepared membrane bioreactor shows promising potential in the field of municipal and industrial wastewater treatment. The article is well-structured and exhibits a certain degree of innovation. However, several issues are noted as follows:

1. The labels in Figure 6a are unclear, making it impossible to discern which samples correspond to which curves.
2. For the CA-incorporated membrane, why does the wastewater flux decline so significantly compared to the pure water flux?
3. What about the aging issues and the decline in membrane strength of the electrospun membrane in membrane bioreactor ?
4. Is the higher transmembrane pressure observed for the neat PVDF membrane related to its finer fiber diameter and smaller pore size?
5. What is the removal rate of pollutants passing through the membrane? Does it warrant further investigation?

Author Response

REPORTS OF REVIEWER 1

Thanks for reviewing the article.

 

1. The labels in Figure 6a are unclear, making it impossible to discern which samples correspond to which curves.

ANS: Figure 6a indicates the stress vs strain curve obtained at different concentration of Cellulose acetate added into PVDF membrane. It indicates that the neat PVDF membrane (100:0) has much tensile strength as compare to 90:10, 80:20 and 70:30, by increasing the concentration of cellulose acetate into PVDF membrane the reduction of tensile strength was observed.

 

2. For the CA-incorporated membrane, why does the wastewater flux decline so significantly compared to the pure water flux?

ANS: Pure water contains no any impurities, however wastewater contains total suspended solids and complex nature of impurities, so these impurities can attach on membrane surface and create resistance to push the water and hence decline of flux was observed.

 

3. What about the aging issues and the decline in membrane strength of the electrospun membrane in membrane bioreactor.

ANS: We have operated both neat and composite PVDF/CA membranes in a reactor upto 15 days and observed that no aging issues however neat PVDF required much more physical cleaning by easily deposition of pollutants, However this membrane will be tested in future for long period of time to test its durability and aging.

 

4. Is the higher transmembrane pressure observed for the neat PVDF membrane related to its finer fiber diameter and smaller pore size?
   
   

ANS: The pore size of neat and composite PVDF membrane are almost same but fiber diameter is different, the PVDF membrane material is hydrophobic in nature first hydrophobic pollutant easily attached on membrane surface due to the hydrophobic-hydrophobic interaction so transmembrane pressure is increased to pass water through membrane.

5. What is the removal rate of pollutants passing through the membrane? Does it warrant further investigation?

ANS: The pollutant removal rate is given in Table: 07, However further this membrane can be tested by targeting pollutant removal efficiency in future work.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript “water-3626910” presents results on the antifouling behavior of PVDF/CA composite membranes. While the materials themselves are not novel, the use of a bioreactor-based testing methodology is a positive aspect and could add value to the study with more detailed description and rigorous revisions. However, the manuscript in its current form requires significant improvements in structure, clarity, and content to accept. The following comments are intended to help enhance the overall quality and presentation of the work. Please consider the suggestions below.

1. Please add error bars to the data presented for contact angle, flux, and tensile strength measurements. Kindly ensure that all SI units are used consistently throughout the manuscript—for example, “h” for hours and “°C” for degrees Celsius (not “oC”), flux units. Please review the entire draft for consistency in SI unit usage.
2. Additionally, please provide the full forms of all abbreviations (e.g., EPS, SMP) at their first mention. This is particularly relevant for the content in lines 55–60.
3. The introduction section should be revised to be more concise and coherent. Ensure that there is a logical flow between paragraphs. For instance, the reference to fabric features in lines 69–70 appears disconnected and lacks relevance to the preceding or following discussion on membranes.
4. It is recommended that the authors consider seeking assistance from a native English speaker to improve the overall clarity and fluency of the manuscript.
5. Regarding lines 88–90, could the authors clarify what is meant by "copper porous spinneret"? Was this used in electrospinning? Also, the mention of nanoparticles is unclear—please specify which nanoparticles are being referred to.
6. Please ensure consistent use of the term “electrospinning” or “electrospun” throughout the manuscript and avoid hyphenation of these terms.
7. In lines 107–110, the discussion on piezoelectric materials seems out of context. Instead, the authors are encouraged to focus on prior literature related to PVDF membrane modifications (both chemical and physical) aimed at enhancing hydrophilicity. It would also be beneficial to include more references related to PVDF–cellulose composite membranes. Furthermore, to improve clarity and focus, the introduction could be organized into separate paragraphs, one discussing electrospinning and the other discussing membrane fabrication.
8. The authors may consider including the following relevant references along with their DOIs:

doi.org/10.1016/j.memsci.2016.03.062

doi.org/10.1021/acsaenm.3c00550

doi.org/10.1002/admi.202201550

doi.org/10.1007/s10570-022-04889-9

9. Lines 122–123: The authors refer to “novel materials”; however, PVDF/CA electrospun membranes are well-established and cannot be considered novel. The authors are requested to clearly articulate what is unique or innovative about their study—whether it pertains to material composition, fabrication technique, performance metrics, or application. This clarification will help emphasize the originality and significance of the work.
10. Line 203-208. Correct the sentences. Crystallinity by FTIR?
11. Lines 227–228: Kindly review the sentence for correctness.
12. Line 252: The authors mention membrane roughness. It is recommended to conduct Atomic Force Microscopy (AFM) analysis to support this observation and provide a plausible explanation based on the results. Additionally, please report the viscosities of the neat PVDF solution and the PVDF/CA blend solution.
13. Lines 261–262: Please verify the data reported in the text and ensure it matches the values presented in Table 5.
14. Could the authors specify the average fiber diameter of the neat CA membrane?
15. It is suggested to include SEM images of all membranes at lower magnifications (e.g., 500× or 1,000×) in addition to those shown in Figure 3, in order to assess membrane uniformity and overall morphology.
16. Please include the FTIR spectrum of the neat CA membrane for comparative analysis with the composite membranes shown in Figure 5.
17. The authors are encouraged to provide their interpretation regarding the compatibility between PVDF and CA, particularly in relation to the observed tensile strength. Was the variation in strength solely attributed to differences in fiber diameter? Please provide supporting data such as fiber diameter, pore size, porosity, and water contact angle for each composite membrane prepared with different PVDF/CA ratios.
18. The selection of the 80:20 PVDF/CA composite membrane should be justified, especially given that the 90:10 membrane exhibited higher tensile strength. Please elaborate on the reasoning for this choice in the manuscript.
19. Based on Figure 8a and 8b, it appears that the composite membrane is more susceptible to fouling compared to the neat PVDF membrane. Please provide an explanation for this observation, particularly regarding the sharp decline in flux at 150–200 seconds for the composite membrane, whereas the neat membrane shows a more gradual fouling behavior.
20. Consistency in the naming of membranes is important to avoid confusion. For instance, in Figure 9 the neat membrane is referred to as “non-modified membrane,” while in Figure 10 it is labeled as “conventional PVDF.” Please standardize these terms throughout the draft.
21. Please clarify the procedure used to evaluate membrane fouling in dead-end filtration. Specifically, was the fouling test conducted using wastewater containing proteins, polysaccharides, alginate, or humic acids? If not, the authors are encouraged to assess membrane performance against these common foulants to strengthen the study's relevance.

Author Response

REVIEWER 02

Thanks for reviewing the article.

1. Please add error bars to the data presented for contact angle, flux, and tensile strength measurements. Kindly ensure that all SI units are used consistently throughout the manuscript—for example, “h” for hours and “°C” for degrees Celsius (not “oC”), flux units. Please review the entire draft for consistency in SI unit usage.

ANS: Error bar is added into the manuscript according to reviewer comments, author has corrected the units through out the manuscript.

 

2. Additionally, please provide the full forms of all abbreviations (e.g., EPS, SMP) at their first mention. This is particularly relevant for the content in lines 55–60.

ANS: The author has provided the full forms of SMP and EPS as mentioned for  in lines 55-66.

3. The introduction section should be revised to be more concise and coherent. Ensure that there is a logical flow between paragraphs. For instance, the reference to fabric features in lines 69–70 appears disconnected and lacks relevance to the preceding or following discussion on membranes.

ANS: Author has revised the introduction by adding some more references and removed the lines related to fabric features that was not related to discussion and also author has worked on introduction to make it logical flow between paragraphs.

4. It is recommended that the authors consider seeking assistance from a native English speaker to improve the overall clarity and fluency of the manuscript.

ANS: Author took assistance from USA native speaker improved the English Language  through out manuscript.

 

5. Regarding lines 88–90, could the authors clarify what is meant by "copper porous spinneret"? Was this used in electrospinning? Also, the mention of nanoparticles is unclear—please specify which nanoparticles are being referred to.

 

ANS: A copper porous spinneret in electrospinning is a device that uses a copper material with small pores to guide and distribute the polymer solution (or "spin-dope") during the electrospinning process. Yes this is used in spinning, and no such nanoparticles is used  we have used cellulose acetate polymer to modify the PVDF membrane

 

 

 

6. Please ensure consistent use of the term “electrospinning” or “electrospun” throughout the manuscript and avoid hyphenation of these terms

 

 

ANS: Author has used the word electrospinning through out the manuscript.

 

7. In lines 107–110, the discussion on piezoelectric materials seems out of context. Instead, the authors are encouraged to focus on prior literature related to PVDF membrane modifications (both chemical and physical) aimed at enhancing hydrophilicity. It would also be beneficial to include more references related to PVDF–cellulose composite membranes. Furthermore, to improve clarity and focus, the introduction could be organized into separate paragraphs, one discussing electrospinning and the other discussing membrane fabrication.

 

ANS: Thankyou for your kind suggestions to improve our manuscript. We are agreed with the reviewer, and we have removed the lines 107-110 related to piezoelectric discussion. As suggested by reviewer, now we have added more related references related to PVDF and CA membrane. Introduction is also organized into separate paragraphs and according to reviewer comments.

 

1. The authors may consider including the following relevant references along with their DOIs: The authors may consider including the following relevant references along with their DOIs:

doi.org/10.1016/j.memsci.2016.03.062

doi.org/10.1021/acsaenm.3c00550

doi.org/10.1002/admi.202201550

doi.org/10.1007/s10570-022-04889-9

 

ANS: Thanks for your important and related references suggestion for the improvement of manuscript, Author has added all above 4 references suggested by the reviewer.

 

Lines 122–123: The authors refer to “novel materials”; however, PVDF/CA electrospun membranes are well-established and cannot be considered novel. The authors are requested to clearly articulate what is unique or innovative about their study—whether it pertains to material composition, fabrication technique, performance metrics, or application. This clarification will help emphasize the originality and significance of the work.

 

ANS: Author has removed the word novel and author has also explained that unique of material PVDF/CA electropinning and their use in Membrane bioreactors for their antifouling performance.

 

2. Line 203-208. Correct the sentences. Crystallinity by FTIR?

ANS: The author has corrected the sentence and removed the word crystallinity and added the word molecular  structure.

3. Lines 227–228: Kindly review the sentence for correctness.

ANS: Author has reviewed the sentence and corrected.

 

 

4. The authors mention membrane roughness. It is recommended to conduct Atomic Force Microscopy (AFM) analysis to support this observation and provide a plausible explanation based on the results. Additionally, please report the viscosities of the neat PVDF solution and the PVDF/CA blend solution.

 

ANS: Thankyou for your kind comment. Currently we are working on this, and we will add this AFM in our future work, the work in progress, we apologize for inconvenience.

5. Lines 261–262: Please verify the data reported in the text and ensure it matches the values presented in Table 5.

ANS: Author has verified the data reported in text, Table and corrected the typographical  mistake and highlighted it.

 

6. Could the authors specify the average fiber diameter of the neat CA membrane?

ANS: Thanks, Currently, the author has developed only two membrane such as neat PVDF membrane and composite PVDF/CA membrane and specify their average fiber diameter in Figure 3. However, the author has not developed neat CA membrane, because our focus was to modify the PVDF membrane with CA and to check its efficiency.

 

7. It is suggested to include SEM images of all membranes at lower magnifications (e.g., 500× or 1,000×) in addition to those shown in Figure 3, in order to assess membrane uniformity and overall morphology.

 

ANS: Thank you for your kind suggestion. Now we have provided the SEM images of lower resolution (1000x) also in Figure 3.

 

8. Please include the FTIR spectrum of the neat CA membrane for comparative analysis with the composite membranes shown in Figure 5.

ANS. Thank you again for your kind suggestion. Currently, the author has developed only two membrane such as neat PVDF membrane and composite PVDF/CA membrane and performed the FTIR in Figure 5. However, the author has not developed neat CA membrane, because our focus was to modify the PVDF membrane with CA and to check its efficiency.

 

9. The authors are encouraged to provide their interpretation regarding the compatibility between PVDF and CA, particularly in relation to the observed tensile strength. Was the variation in strength solely attributed to differences in fiber diameter? Please provide supporting data such as fiber diameter, pore size, porosity, and water contact angle for each composite membrane prepared with different PVDF/CA ratios.

 

ANS: The blending of PVDF with cellulose acetate (CA) increased the enthalpy of mixing, decreased the thermodynamic compatibility and increase both amorphous structure. Yes variation in strength was observed with difference in fibers diameter which is also mentioned in manuscript. Porosity, pore size and fiber diameter is also mentioned in manuscript.

 

10. The selection of the 80:20 PVDF/CA composite membrane should be justified, especially given that the 90:10 membrane exhibited higher tensile strength. Please elaborate on the reasoning for this choice in the manuscript.

ANS: The author has focused the antifouling performance of membrane and tested the  80:20 and 90:10 membranes so it was showed that 80:20 has better antifouling performance as compared to 90:10 but little decrease in  tensile strength was observed   secondly 90:10 membrane required much more physical cleaning due to foulant attachment during wastewater treatment as compared to 80:20 membrane.

11. Based on Figure 8a and 8b, it appears that the composite membrane is more susceptible to fouling compared to the neat PVDF membrane. Please provide an explanation for this observation, particularly regarding the sharp decline in flux at 150–200 seconds for the composite membrane, whereas the neat membrane shows a more gradual fouling behavior

ANS: Initially A rougher surface on composite PVDF/CA membrane provides more nucleation sites for foulants to attach, promoting faster cake layer formation or pore blocking, especially early in the filtration process at 150-200 after some times the overall attachment of foulants on neat PVDF membrane is greater than composite PVDF membrane due to its hydrophobic attachment of pollutants.

 

12. Consistency in the naming of membranes is important to avoid confusion. For instance, in Figure 9 the neat membrane is referred to as “non-modified membrane,” while in Figure 10 it is labeled as “conventional PVDF.” Please standardize these terms throughout the draft.

ANS: Author has made consistency through out the manuscript as suggested by reviewers.

 

13. Please clarify the procedure used to evaluate membrane fouling in dead-end filtration. Specifically, was the fouling test conducted using wastewater containing proteins, polysaccharides, alginate, or humic acids? If not, the authors are encouraged to assess membrane performance against these common foulants to strengthen the study's relevance.

ANS: Author has provided the procedure to evaluate the membrane fouling through dead end filtration setup. Secondly the  only wastewater was used but not specific pollutants such as proteins, polysaccharides, alginates or humic acid. And author has removed the terms such as proteins, polysaccharides, alginates or humic acid according to reviewer comments

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Please see attached 

Comments for author File: Comments.pdf

Author Response

Reviewer 3.

Thanks for reviewing the article.

 

General Comments:

The manuscript requires major revision before it can be considered for publication in a scientific journal. The research topic is quite interesting and thanks for your hard work on this topic. Thank you for your effort and contribution to this area of study. Please see the detailed comments below:

Specific Comments:

 

 Lines 33–34 (Abstract): These lines are overly broad. Please provide specific results to support your statements

Ans: Author has modified the sentence to support the statement

 

 Line 44: Verify and correct the abbreviation for "AOPs."

Ans: Author has verified and corrected the abbreviations and highlighted in manuscript

 

Line 46: Include the pore size range of the membrane.

Ans. Author has explained the properties of nanofibers from literature as reference according to it nanofibers have large interconnected pores.

 

Line 53: You have not addressed particulate fouling. Is this not a concern in your study?

Ans. We have used the general wastewater and was not targeted to a particulate fouling

 

Line 55: Define the abbreviations for EPS and SMP upon first use.

ANS: The abbreviation EPS is Extra Cellular Polymeric substance and  SMP is the soluble Microbial Product

 

Line 127: Confirm whether the molecular weight is 534,000 Daltons. If so, please specify this clearly.

ANS: Yes, Poly(vinylidene fluoride) (PVDF) with an average molecular weight of 534,000 Daltons is a common form of this polymer, particularly used in nanopowder and powder forms for various applications. 

 

Line 145: The rationale behind selecting an 80:20 ratio is not explained. Please provide justification for this choice.

 

ANS: The author has focused the antifouling performance of membrane and tested the  80:20 and 90:10 membranes so it was showed that 80:20 has better antifouling performance as compared to 90:10 but little decrease in tensile strength was observed   secondly 90:10 membrane required much more physical cleaning due to foulant attachment during wastewater treatment as compared to 80:20 membrane.

 

 Line 153: You mention soaking the membrane in "pure water." Please clarify what is meant by “pure water.” Additionally, how did you ensure removal of membrane coatings or chemicals during soaking? Did you measure DOC (Dissolved Organic Carbon)?

 

ANS: We have not measured the DOC (Dissolved Organic Carbon) and pure water indicates the Distilled  wate/Clean water, Distilled  water/Clean water  was used to clean the membrane because after membrane synthesize the small amount of powder like substance is formed on membrane surface,  by washing with distilled  water the,  powder type material on the surface of membrane was washed.

 

Line 360: The reported clean water flux for the composite membrane is 650, yet the graph shows a consistent decline. How was this value calculated? Why is the clean water flux decreasing? Does this suggest incomplete membrane cleaning, or fouling even with clean water? Please address and discuss this.

 

ANS: Even with pure or distilled water, the water flux through a membrane can decline due to factors such as concentration polarization and osmotic pressure. When pure water is used for membrane testing, a reduction in water flux is often observed over time. This decline occurs because osmotic pressure is generated, which reduces the pure water flux, even if the membrane has been properly cleaned.

 

 Figures 8b and 8c: The initial flux for clean water stops at 50, whereas the wastewater flux at t= 0 is 160. This discrepancy (almost three times higher) raises questions—did you use different membranes?

Ans. Thanks for comments, We have used only 2 membranes i.e. neat PVDF and composite PVDF/CA membrane for wastewater and clean water flux as shown in Figure 8. Author has explained in Figure that the clean water flux of composite membrane was 650 L/m².hr, and its wastewater flux was 190 L/m².hr whereas the in pure PVDF membrane, the clean water flux was 350 L/m².hr  and wastewater flux was 160 L/m².hr as shown in Figure.8

 

Figure 8: Since the initial flux values differ, direct comparison might be an issue. Please normalize the data before comparing.

 

Ans: The data of Flux is normalized and compared according to reviewer comments in Figure.8

 

 Figure 9: The total resistance at the start is not same. Normalize the data to allow proper comparison. It is recommended to calculate the percentage increase in resistance.

 

Ans: Thanks for precious comments, Author has normalized the data of total resistance for comparison.

 Figure 9: Why is total resistance increasing during filtration with clean water? Is clean water and pure water same? If so use the same terminology.

Ans: Clean water flux through a membrane can decline due to factors like concentration polarization, osmotic pressure between membrane and water. Clean water and pure water are same, therefore, we have updated in manuscript and used only word clean water in all manuscript.

2. Under applied pressure, membranes can undergo structural compaction, leading to reduced pore sizes and decreased permeability. This compaction increases resistance over time, even in the absence of particulate foulants.

 

 Line 407: Please review and revise this sentence for clarity.

 

 Ans: Thanks for your comments, Author has revised the sentence for more clarity.

 Figure 10: The TMT for the modified PVDF membrane is significantly higher than for the conventional PVDF, which suggests greater fouling—contradicting your conclusion. Please explain.

ANS: Author wants to further clarify about given statement that  the transmembrane pressure TMP of composite PVDF/CA membrane was 55±3 Kpa and neat PVDF membrane was 68±5  so composite PVDF/CA membrane has less TMP as compared to neat PVDF membrane However, negative sign indicates in graph as a direction of water but not value.

 

Figure 10: TMT values are reported only after 20 hours. Consider reporting from the beginning to capture the full trend.

ANS: Thanks for your precious comments, Author has reported the data from beginning as given in Figure.10

Figure 12: Define the terms J and Jo, and explain the method used to calculate normalized flux.

ANS: Flux (J): This represents the volume of permeate (filtered liquid) that passes through a unit area of the membrane per unit time. It's typically expressed in liters per square meter per hour (L·m⁻²·h⁻¹).

Initial Flux (J₀): This is the flux measured at the very beginning of the filtration process, often using purified water. It serves as a baseline to assess the membrane's performance before any fouling or degradation occurs.

Normalized Flux (J/J₀): This is a dimensionless ratio that compares the current flux (J) to the initial flux (J₀). It provides a standardized way to monitor changes in membrane performance over time, independent of the absolute flux values. And normalized flux is calculated by using formula J/Jo with change of time

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Agreed

Author Response

Dear Reviewer, 

Thanks for agreeing to our comments, and consider the manuscript for publication. 

 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed most of the comments satisfactorily. However, a few points still require clarification. Please consider following comments.

1. Please check the SI units in Table 2, the correct unit is "kV" (kilovolt), not "Kv".
2. The terms “electrospinning” and “electrospun” are still found with hyphenation in several places. Kindly revise “Electro-spinning” to “electrospinning”, and “Electro-spun” to “electrospun” throughout the manuscript. Avoid using hyphenation for these standard terms.
3. Please measure and report the viscosity of the electrospinning solutions in Section 3.1. This data is essential to fully support the discussion and conclusions in the manuscript.
4. In response to Comment No. 6, the authors mentioned that a CA membrane was not developed. However, Table 2 includes CA solution and its electrospinning parameters. Provide SEM images of the CA membrane along with its fibre diameter. Including this data would greatly improve the readability and completeness of the manuscript.
5. While the manuscript emphasizes the modification of PVDF, a comparison with a neat CA membrane is also relevant, since CA was used to modify PVDF. Please consider adding FTIR, contact angle data for the CA membrane and include a brief discussion to enhance the interpretation of composite membrane results.
6. Fibre diameters for membranes with various blend ratios have not been reported in Section 3.4. Including this data would strengthen the analysis.
7. Replace Figure 6A (tensile strength) with an updated version where each tensile curve is shown in a distinct color. The current figure format makes it difficult to differentiate the curves and interpret the data effectively.

 

Author Response

REVIEWER 2. SECOND ROUND.

Thanks again for making the valuable comments/suggestions and providing us the opportunity for further refinement of the manuscript.

1. Please check the SI units in Table 2, the correct unit is "kV" (kilovolt), not "Kv".

ANS: Author has checked the SI units in Table 2, corrected and highlighted in the manuscript.

 

2. The terms “electrospinning” and “electrospun” are still found with hyphenation in several places. Kindly revise “Electro-spinning” to “electrospinning”, and “Electro-spun” to “electrospun” throughout the manuscript. Avoid using hyphenation for these standard terms.

ANS: The Author has avoided the hyphenation of electrospinning and electrospun throughout the manuscript and highlighted.

3. Please measure and report the viscosity of the electrospinning solutions in Section 3.1. In response to Comment No. 6, the authors mentioned that a CA membrane was not developed. However, Table 2 includes CA solution and its electrospinning parameters. Provide SEM images of the CA membrane along with its fibre diameter. Including this data would greatly improve the readability and completeness of the manuscript. While the manuscript emphasizes the modification of PVDF, a comparison with a neat CA membrane is also relevant, since CA was used to modify PVDF. Please consider adding FTIR, contact angle data for the CA membrane and include a brief discussion to enhance the interpretation of composite membrane results. Replace Figure 6A (tensile strength) with an updated version where each tensile curve is shown in a distinct color. The current figure format makes it difficult to differentiate the curves and interpret the data effectively.

ANS:  Thanks for comments, Author has not mentioned the viscosity of solution during solution preparation and Cellulose acetate characterization but author has focused the blending of PVDF/CA and their characterization which is crucial for composite PVDF/CA membrane, However the neat Cellulose acetate characterization and their solution viscosity is under process, after characterization it will be given in future work. The author has replaced Figure 6a and updated it; each curve is now shown in a distinct color, as illustrated in the revised Figure 6. Please kindly consider for publication at your best convenience.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Please see attached comments (in red) based on the response provided by the author.

Comments for author File: Comments.pdf

Author Response

REVIEWER 3. SECOND ROUND.

Thanks again for making the valuable comments/suggestions and providing us the opportunity for further refinement of the manuscript.

 Verify and correct the abbreviation for "AOPs

ANS: The Author has verified and corrected the abbreviation of AOP in the manuscript

 You have not addressed particulate fouling. Is this not a concern in your study?

ANS: The Author has not specifically targeted particulate fouling, but the author has focused on overall fouling that occurs during wastewater treatment, which can be biofouling, organic fouling, Inorganic fouling, and so on.

 

 The rationale behind selecting an 80:20 ratio is not explained. Please provide justification for this choice.

ANS: Thanks for your comments. The author has focused on the Blend ratio of PVDF/CA, which is  80:20, because it is the stage where the antifouling performance of the membrane is better, and a slight change in tensile strength was observed. However the author has also tested the 90:10 and 70:30, but blending of 90:10 has more strength as shown in Figure.06 but little antifouling performance and blending of 70:30 has higher antifouling performance but greater decrease of tensile strength was observed that is why for optimization, the author has focused the PVDF/CA that is 80:20. The results are given in Figure.6

 

The reported clean water flux for the composite membrane is 650, yet the graph shows a consistent decline. How was this value calculated? Why is the clean water flux decreasing? Does this suggest incomplete membrane cleaning, or fouling even with clean water? Please address and discuss this.

 

ANS:    Even with pure or distilled water, the water flux through a membrane can decline due to factors such as concentration polarization and osmotic pressure; thus, the pores might collapse due to these factors, which can also reduce the flux. Perhaps the membrane may not be 100% cleaned during physical cleaning. When pure water is used for membrane testing, a reduction in water flux is often observed over time. Secondly the decline occurs because osmotic pressure is generated, which reduces the pure water flux, even if the membrane has been properly cleaned.

 

 

Figures 8b and 8c: The initial flux for clean water stops at 50, whereas the wastewater flux at t= 0 is 160. This discrepancy (almost three times higher) raises questions—did you use different membranes?

 

Ans. Thanks for the comments, the Author has used two membranes, i.e., neat PVDF and composite PVDF/CA membrane, for wastewater and clean water flux as shown in Figure 8. The author has explained in the Figure that the clean water flux of the composite membrane was 650 L/m2.hr, and its wastewater flux was 190 L/m2.hr whereas in the pure PVDF membrane, the clean water flux was 350 L/m2.hr  and the wastewater flux was 160 L/m2.hr as shown in the Figure.8, Overall, it is found that the composite PVDF/CA membrane has a higher water flux compared to the neat membrane.

 

Why is total resistance increasing during filtration with clean water? Is clean water and pure water same?

 

Ans: Yes, clean water and pure water are the same, and the author has used clean water throughout the manuscript. Clean water flux through a membrane can decline due to factors like concentration polarization, osmotic pressure between the membrane and water.

 

2. Under applied pressure, membranes can undergo structural compaction, leading to reduced pore sizes and decreased permeability. This compaction increases resistance over time, even in the absence of particulate foulants.

 

Thank you again; please consider this for publication at your convenience.

 

Author Response File: Author Response.pdf