Development of Novel Polymer Supported Nanocomposite GO/TiO2 Films, Based on poly(L-lactic acid) for Photocatalytic Applications
Round 1
Reviewer 1 Report
This work deals with the study of the photocatalytic effect of graphene oxide/TiO2 incorporated in PLLA films for the removal of a mixture of nine different antibiotics, as well as the characterization of prepared nanocomposites.
The investigation is properly addressed but there are some points that need to be improven:
- It must be specified that GO refers to graphene oxide in the abstract. GO is not defined until line 59.
- Line 19: “at environmental samples” is too general, it must have cited wastewater.
Authors claim that there is not data available regarding the photocatalytic effect on PLLA (Line 83-84). However, there are plenty of investigations on which the photocatalytic effect of different nanoparticles have been investigated, and specifically, there are different papers on the photocatalytic effect of TiO2/PLLA composites (Review of Recent Advances in Polylactic Acid/TiO2 Composites. Mosab Kaseem, Kotiba Hamad and Zeeshan Ur Rehman. Materials 2019, 12, 3659; doi:10.3390/ma12223659; ACS Sustainable Chem. Eng. 2018, 6, 2, 2445-2452; Polymer Degradation and Stability, Volume 97, Issue 6, June 2012, Pages 856-862). Thus, this previous literature should be considered in the introduction section.
DTG curves do not required an specific figure, they could be incorporated in Figure 1A.
Results show that NPS incorporation enhances PLLA thermal decomposition, as in the literature. The origin of this fact must be mentioned. The same for the reduction in the melting point (line244).
3.2.1. Section must be deleted. Certainly “the preliminary studies” are part of the 3.2.2 section, they must not be differentiated. Lines 266-272 must be rewritten accordingly to the order in which the results are discussed ( in the absence of PLLA, figure 5, and in the presence of PLLA..).
Line 266: “ In order to examine the extent of the absorbance on the newly synthesized catalyst”...This sentence seems to not match with the study, or it is not clearly described: In order to examine the extent of the effect of the newly synthesized catalyst on the concentration of the antibiotics on solutions........could be more clarifier. Nevertheless, what absorbance is measured?.
Absorbance bands of the antibiotics must be shown to illustrate the photocatalytic application and support discussion (Line 279).
Photocatalytic elimination must be calculated with respect to the initial concentration of each antibiotic, as it is done for measurements in the absence of PLLA. However, in the presence of PLLA, an initial decrease takes place due to the adsorption on the polymer, thus the elimination of antibiotic in solution must be calculated as C0-Cads. However, in this study in the presence of PLLA measurements have been calculated regarding the adsorbed concentration. This is not correct to evaluate elimination in solution. Nevertheless, how do you calculate the adsorbed concentration in mg/L? It should be the mg present in the film, thus mg/g or mg/cm2.
The units of k and t1/2 are defined after data are presented.
The title for 3.2.4. section is not appropriate, it is too specific.
Line 343: Which is the strong attachment of TiO2 NPs on the polymer?. The interaction NPs-polymer is not possible to be observed by SEM, as authors claim, perhaps the homogeneity of the sample.
Surface PLLA degradation is hard to observe by SEM, AFM images are required and roughness values could clarify this point.
The need of repeating the experiments on wastewater in comparison to pure water is not clear. If authors want to analyze a more realistic situation, they must analyze separately the effect of bicarbonates, chlorides or sulphates in order to give sense to the investigation. Experiments with Wastewater do not provided further information.
The title must be changed. The adjective “floating” has not be considered, nor studied in the paper, and it does not add further information.
Author Response
We also thank the Reviewers for carefully reading of our manuscript and offering their constructive comments to improve this manuscript. We have taken them into consideration in preparing the revised form of manuscript. In the attachemnt file is our point-by-point response to their comments. The appropriate corrections to the revised manuscript are presented with different highlighted font each time. We hope that our appropriate corrections based on their comments increased the quality of our work.
Please see the attachent.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this manuscript, the authors fabricate a polymer supported nanocomposite GO/TiO2 films, which can be used as photocatalytically degrade antibiotics. Overall, the experiment is well-designed and the results are clearly presented. The manuscript can be accepted after the following minor improvement.
- The results indicate that higher TiO2 concentration in the composite leads to higher photocatalytic activity. If the authors further increase the loading amount of TiO2 above 50%, will the degradation performance be further improved?
- The author should provide some characterizations of the P25 particles, e.g. size and size distribution. The author should also provide high-magnification SEM image that shows how the P25 particles reside within the polymer matrix.
Author Response
We also thank the Reviewers for carefully reading of our manuscript and offering their constructive comments to improve this manuscript. We have taken them into consideration in preparing the revised form of manuscript. Please find in the attachment our point-by-point response to their comments. The appropriate corrections to the revised manuscript are presented with different highlighted font each time. We hope that our appropriate corrections based on their comments increased the quality of our work.
Please see the attachment.
Author Response File: Author Response.pdf
