Antifouling Properties of Silver-Zinc Oxide Polyamide Thin Film Composite Membrane and Rejection of 2-Chlorophenol and 2,4-Dichlorophenol
Round 1
Reviewer 1 Report
The manuscript certainly contains interesting information that fully corresponds to the topic of the journal.
The work was done thoroughly and was written qualitatively. However, it is necessary in all parts of the article, including the abstract, to enter information, how polyamide and a composite based on it appear. It is impossible to prove the presence of an amide bond without explaining in which reaction and from which reagents it appears.
Why did the authors choose polyamide? How does it affect the filtration process and does it change the antimicrobial activity of the nanocomposite? In addition, in the experimental part, the membrane separation method is not described in detail. Why was this method chosen? What happens as a result with the membrane, if known?
From small remarks - a typo in the inscription on the Fig. 13
Author Response
Reviewer 1:
Comments and Suggestions for Authors
The manuscript certainly contains interesting information that fully
corresponds to the topic of the journal.
The work was done thoroughly and was written qualitatively. However, it
is necessary in all parts of the article, including the abstract, to
enter information, how polyamide and a composite based on it appear.
We have included the schematic chemical equation for the condensation polymerization reaction between trimesoyl chloride and piperazine.
This information has been included in the abstract, methodology, results and conclusion sections
It is impossible to prove the presence of an amide bond without explaining
in which reaction and from which reagents it appears.
The information has been included ( as in the above comment). Trimesoyl chloride and piperizane
Explanation given
Why did the authors choose polyamide?
Explained- line 90-94
How does it affect the filtration process and does it change the antimicrobial activity of the nanocomposite?
Section on antibacterial activity has been removed based on the comment by another reviewer, so explanation on effect of polyamide on antibacterial activity is not provided
In addition, in the experimental part, the membrane
separation method is not described in detail. Why was this method
chosen?
We understand Membrane separation method to be the rejection method. More explanation of the rejection method has been added
What happens as a result with the membrane, if known?
The explanation of what happens with membrane was discussed in terms of fouling properties. That is reversible fouling and irreversible fouling.
However, further SEM analysis on fouled membranes was not performed
From small remarks - a typo in the inscription on the Fig. 13
Now Figure 13 is now Figure 12.
Typo noticed was: (mg/l with one bracket – we have included another bracket
X-axis label – Time ( hrs) changed to Time (hr)
Reviewer 2 Report
The focus of the study, i.e removal of chlorophenol compounds from water, is clearly important and the authors have shown some encouraging results using a simple modification of polyamide membranes. The results and the coressponding calculations are well presented in the paper. I believe the paper can be accepted in its current form.
Author Response
Reviewer 2:
Comments and Suggestions for Authors
Comments and Suggestions for Authors
The focus of the study, i.e removal of chlorophenol compounds from water, is clearly important and the authors have shown some encouraging results using a simple modification of polyamide membranes. The results and the coressponding calculations are well presented in the paper. I believe the paper can be accepted in its current form.
Thank you
Reviewer 3 Report
The manuscript entitled "Antifouling properties of Ag-ZnO/PA-TFC membrane and rejection of 2-CP and 2,4 -DCP" describes the improvements of the antifouling and antibacterial properties of polymeric membranes. The findings are interesting, and the extensive characterizations are performed to support the conclusions. The topic quite fits the scope of the journal.The referee suggests a minor revision regarding the following concerns. 1- Introduction, the following references are suggested to discuss the antibacterial and antifoulong properties of silver nanoparticles.Design of Antibacterial Poly(ether sulfone) Membranes via Covalently Attaching Hydrogel Thin Layers Loaded with Ag Nanoparticles;A facile approach toward multi-functional polyurethane/polyethersulfone composite membranes for versatile applications;Mussel-inspired chitosan-polyurethane coatings for improving the antifouling and antibacterial properties of polyethersulfone membranes. 2- Figure 5. The authors should indicate the MIC and disc diffusion for the materials against Staphylococcus aureus (S. aureus, Gram positive). 3- Figure 1. The curves of FTIR are overlapped. 4- Some grammar mistakes. For instance, Page 2 line 78. "Sodium dodecyl Sulphate (98.5%), Pepirazine (99%), trimesoylchloride (98%), anhydrous hexane (95%), Poly (vinyl..." should read "Sodium dodecyl sulphate (98.5%), pepirazine (99%), trimesoylchloride (98%), anhydrous hexane (95%), poly (vinyl..."
Author Response
Reviewer 3:
Comments and Suggestions for Authors
The manuscript entitled "Antifouling properties of Ag-ZnO/PA-TFC membrane and rejection of 2-CP and 2,4 -DCP" describes the improvements of the antifouling and antibacterial properties of polymeric membranes. The findings are interesting, and the extensive characterizations are performed to support the conclusions. The topic quite fits the scope of the journal.The referee suggests a minor revision regarding the following concerns.
1- Introduction, the following references are suggested to discuss the antibacterial and antifoulong properties of silver nanoparticles.Design of Antibacterial Poly(ether sulfone) Membranes via Covalently Attaching Hydrogel Thin Layers Loaded with Ag Nanoparticles;A facile approach toward multi-functional polyurethane/polyethersulfone composite membranes for versatile applications;Mussel-inspired chitosan-polyurethane coatings for improving the antifouling and antibacterial properties of polyethersulfone membranes.
Response – The section on antibacterial activity was removed as suggested by another reviewer. Hence only one relevant reference was included. Ref [30]
2- Figure 5. The authors should indicate the MIC and disc diffusion for the materials against Staphylococcus aureus (S. aureus, Gram positive).
Response – The section on antibacterial activity was removed as suggested by another reviewer hence Figure 5 was removed from the article.
3- Figure 1. The curves of FTIR are overlapped.
Response – FITR has been replotted
4- Some grammar mistakes. For instance, Page 2 line 78. "Sodium dodecyl Sulphate (98.5%), Pepirazine (99%), trimesoylchloride (98%), anhydrous hexane (95%), Poly (vinyl..." should read "Sodium dodecyl sulphate (98.5%), pepirazine (99%), trimesoylchloride (98%), anhydrous hexane (95%), poly (vinyl..."
Response – corrected has suggested.
Reviewer 4 Report
This work studies membrane modification by using Ag-ZnO nanoparticles. It is concluded that the incorporation of Ag-ZnO into PA-TFC membranes improves membrane hydrophilicity, permeation, rejection and fouling resistance. However, there is no much new finding in this work. The data and claims are not well explained and supported. It is not recommended for publication.
1. Both Ag and ZnO have been used as nanoparticles in membrane fabrication. What is the new ideal of adding them in together? Is there any new improvement from the combination?
2. What is the structure of the new Ag-ZnO nanoparticle? The characterization from FTIR and XRD only show the existence of both particles, but not the structure of Ag-ZnO.
3. What is the size of Ag-ZnO?
4. From Fig 5, does it mean Ag-ZnO has better antimicrobial properties than Ag?
5. Fig 6, the broad band at 3336 cm-1 is explained by the increase in hydrophilicity due to the addition of Ag-ZnO. How does it increase the –OH stretch?
6. Fig 8, why does the contact angle increase after 1 wt% of Ag-ZnO addition?
7. The better rejection of Ag-ZnO/PA-TFC membrane is not clearly explained.
8. From Fig 10(a), the claimed better antifouling property of Ag-ZnO/PA-TFC membrane is not seen.
Author Response
Reviewer 4:
Comments and Suggestions for Authors
This work studies membrane modification by using Ag-ZnO nanoparticles. It is concluded that the incorporation of Ag-ZnO into PA-TFC membranes improves membrane hydrophilicity, permeation, rejection and fouling resistance. However, there is no much new finding in this work. The data and claims are not well explained and supported. It is not recommended for publication.
1. Both Ag and ZnO have been used as nanoparticles in membrane fabrication. What is the new ideal of adding them in together? Is there any new improvement from the combination?
Response – Silver and ZnO have been used independently for improving the antifouling properties of the membranes with silver usually used for antibiofouling. There are very few publications if not none on Ag-ZnO modified PA-TFC membranes. As a result this area has not been adequately researched. It has been shown that Ag modified membranes suffer problems of leaching from the membranes hence unsustainable as an antibiofouling membrane depending on the method used. Our research initially showed some antibacterial property of the nanoparticles against E.coli. However, We have since removed that section to concentrate on the effect of Ag-ZnO on PA-TFC for enhancing antifouling of the membrane and rejection of 2-CP and 2,4-DCP. So before engaging on the antibiofouling achievements of the silver component in the membrane. We discussed the effectiveness of the Ag-ZnO incorporation on the PA-TFC membrane then its performance for rejection of target pollutants.
2. What is the structure of the new Ag-ZnO nanoparticle? The characterization from FTIR and XRD only show the existence of both particles, but not the structure of Ag-ZnO.
Response – the FTIR and XRD discussion has been rephrased to give more meaningful explanation.
3. What is the size of Ag-ZnO?
Response –The estimated length of the rods was 603 nm ± 50.4 with diameter of 82.92 ±5.4. The mean sizes for the spherical particles around the rods in Ag-ZnO (3%) was 36.7 ± 6.9 nm.
Response has been added in the article.
4. From Fig 5, does it mean Ag-ZnO has better antimicrobial properties than Ag?
Response – section removed
5. Fig 6, the broad band at 3336 cm-1 is explained by the increase in hydrophilicity due to the addition of Ag-ZnO. How does it increase the –OH stretch?
Response – Explanation provided
6. Fig 8, why does the contact angle increase after 1 wt% of Ag-ZnO addition?
Response – beyond 1.5 wt% of Ag-ZnO nanocomposites contact angle increased. This is because with high concentration of nanomaterials in the aqueous solution particles tend to agglomerate and affect the hydrophilicity [52]. The sudden increase in contact angle may also be explained in terms of viscosity effect. That is, the high amount of the nanoparticles in the aqueous solution increases the viscosity. Viscosity effect dominates and hinders interfacial polymerization between the aqueous and the organic phase and affect hydrophilicity
Explanation added in the artiocle
7. The better rejection of Ag-ZnO/PA-TFC membrane is not clearly explained.
Response – more explanation included
8. From Fig 10(a), the claimed better antifouling property of Ag-ZnO/PA-TFC membrane is not seen.
Response – More explanation given
Reviewer 5 Report
1. Abstract: The abstract should be shortened to only emphasize the gist of the article.
2. Better to use L m-2h-1bar-1 as a unit of flux.
3. Line 104, the spelling of “pepirazine” is wrong.
4. Page 4 (and throughout the text), the size and format of texts in the equations must be unified.
5. Figure 2 is blurring and unpleasant, please increase resolution.
6. Figure 9. The standardized curve between absorbance and concentration should be moved to supporting information.
7. What is the mechanism behind the enhanced anti-fouling properties of Ag-ZnO composite membrane against 2-CP and 2-DCP?
8. The addition of Ag to ZnO is not directly related to the antifouling or rejection properties (as suggested by the title), hence it seems a little off the topic that the authors include the antibacterial properties of the Ag/ZnO materials (but not the membrane) in the manuscript. The authors can consider remove the antibacterial part, or include new information regarding the antibacterial test for the Ag/ZnO composite membrane.
9. There is no comparison to other piperazine based nanocomposite membranes.
10. Figure 7. The FESEM image of the Ag-ZnO does not seem to show successful blending of Ag/ZnO.
11. There seems to be a contradiction as to where the author blended the Ag-ZnO. Was it bended in the PSF support or in the piperazine aqueous solution?
Line 14-Line 17:
“The Ag-ZnO NCs were characterized using UV-Vis, XRD, SEM and EDX. They were investigated for antimicrobial activity using MIC and disc diffusion against E.coli. The composites (varied amounts from 0.0 wt % -2.0 wt%) were blended into a polyether sulfone membrane (support) to fabricate”
Line 103-105: “Aqueous solutions of pepirazine and nanocomposites of Ag-ZnO (0 to 2 wt%), and…”
The grammar needs to be re-checked as there are some casual mistakes.
Author Response
Reviewer 4:
Comments and Suggestions for Authors
1. Abstract: The abstract should be shortened to only emphasize the gist of the article.
Response – the abstract has been shortened, aspects on antimicrobial activity removed. It now focused on antifouling performance of the modified membrane and rejection of chlorophenols.
2. Better to use L m-2h-1bar-1 as a unit of flux.
Response- Amended as per comment
3. Line 104, the spelling of “pepirazine” is wrong.
Response – pepirazine has been changed to piperazine
4. Page 4 (and throughout the text), the size and format of texts in the equations must be unified.
Response – the text and the equation has been unified as suggested.
5. Figure 2 is blurring and unpleasant, please increase resolution.
Response – figure 2 has been adjusted
6. Figure 9. The standardized curve between absorbance and concentration should be moved to supporting information.
Response - The standardized curve between absorbance and concentration has been removed.
7. What is the mechanism behind the enhanced anti-fouling properties of Ag-ZnO composite membrane against 2-CP and 2-DCP?
Response – Explanation given
8. The addition of Ag to ZnO is not directly related to the antifouling or rejection properties (as suggested by the title), hence it seems a little off the topic that the authors include the antibacterial properties of the Ag/ZnO materials (but not the membrane) in the manuscript. The authors can consider remove the antibacterial part, or include new information regarding the antibacterial test for the Ag/ZnO composite membrane.
Response – Section on antibacterial activity has been removed
9. There is no comparison to other piperazine based nanocomposite membranes.
Response – literature not available
10. Figure 7. The FESEM image of the Ag-ZnO does not seem to show successful blending of Ag/ZnO.
Response – we explained this as silver being distributed around the ZnO rods
11. There seems to be a contradiction as to where the author blended the Ag-ZnO. Was it bended in the PSF support or in the piperazine aqueous solution?
Line 14-Line 17:
“The Ag-ZnO NCs were characterized using UV-Vis, XRD, SEM and EDX. They were investigated for antimicrobial activity using MIC and disc diffusion against E.coli. The composites (varied amounts from 0.0 wt % -2.0 wt%) were blended into a polyether sulfone membrane (support) to fabricate”
Line 103-105: “Aqueous solutions of pepirazine and nanocomposites of Ag-ZnO (0 to 2 wt%), and…”
Response – Corrected. Sentence removed in line 14
The grammar needs to be re-checked as there are some casual mistakes.
Response – the grammar has been checked and correction make where necessary.
Round 2
Reviewer 4 Report
The revised work still fails to address the issue of innovation. Both Ag and ZnO have been used as nanoparticles in membrane fabrication. Their effects on membrane hydrophilicity and anti-fouling properties have also been largely studied. What is the main difference between this work and previous studies? What is the advantage of adding the combined Ag-ZnO nanoparticle? Is there any new improvement and observation?
Author Response
The revised work still fails to address the issue of innovation. Both Ag and ZnO have been used as nanoparticles in membrane fabrication. Their effects on membrane hydrophilicity and anti-fouling properties have also been largely studied.
What is the main difference between this work and previous studies?
Response
It has never been done following the same procedure
What is the advantage of adding the combined Ag-ZnO nanoparticle?
Response:
To find out if the two will still show antifouling properties. We will then study both the anti biofouling and anti organic fouling properties
Is there any new improvement and observations?
Response
Addition of Ag-ZnO has shown improved antifouling properties using 2-CP and 2,4 -DCP
Response
There has never been a report on incorporation of Ag-ZnO nanoparticles on PA-TFC for rejection of 2-CP and 2,4 DCP following the same procedure
Reviewer 5 Report
improved.
Author Response
Some improvements have been added on the:
Introduction
Spelling mistakes corrected
Gramma has been corrected
large spaces have been reduced
Font and size on graph labels and scale have been made uniform
