Immobilization of TiO2 Photocatalysts for Water Treatment in Geopolymer Based Coatings
Round 1
Reviewer 1 Report
The author prepared photocatalytic coatings on aluminum substrate using three different processes to degrade methylene blue dyes in the ultraviolet range. I think we need to address some issues before publishing.
1.In Chapter 2.2, 1-B, 2-R, 3-S appear. Please explain the meanings of 1, 2, and 3, as well as the 2-S appearing in the following text. In your description, there is no mention of 2-S, but it appears twice consecutively in the following text. Is there any special meaning.
2.Since it is mentioned that the 2-S scan is similar to the 2-R image, it is recommended to add a 2-S scan image for scientific rigor.
3. In section 2.4, it is mentioned that it has repeatability, and it is recommended to add a cyclic experimental diagram.
Minor editing of English language required
Author Response
Dear Reviewer,
please see our comments to your review in the document attached.
Best reagrds,
Lukas Dufner
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This manuscript describes a coating process for incorporating TiO2 onto the surface of a cementitious geopolymer. The work builds on a great deal of work involving TiO2 coatings on various surfaces, but seems to have focused its introduction on building materials, for which the new materials are not intended. I would suggest rewriting the introduction around this focus.
Among the missing items are the works by Singh, et al, and Nee, et al., among others who have done similar works for buoyant photocatalysts, as this is more common in the degradation of ORGANIC pollutants (which are not mentioned in the introduction).
Results are generally high quality and convincing, but some improvements can be made:
1. Table 1 has only one row, which is missing the point of a table, which is to compare results across dimensions. This might be better as part of the text.
2. Figure 3 refers to the samples with a number, a letter, and a location, which seems redundant and confusing. Instead, label the panels (a), (b), and (c) and refer to the data in the panels as Figure 3(a), for example.
3. Line 153 ends with the phrase "in the following chapter". Do they mean section? Or is this just a result of thesis first, publication second? That is totally ok to do. But referencing chapters doesn't really make sense.
4. Figure 2, the curve labelled Geosil 14517 + Stabilsil40 should not contain any TiO2, and yet the low angle dominant peak is labelled A + C1. Which is it?
5. How are the error bars shown in Figure 8 determined? Have multiple experiments been done to confirm the work, and assess variability? I am actually a bit surprised that the two curves for the coated samples are so very similar, even though their error bars are still quite large. This needs to be addressed.
6. The authors choose not to do direct comparisons to other literature, which is unfortunate. I know well that the comparisons from material to material are not always honest as a comparison. Could an experiment be performed with TiO2 suspension directly in the target solution? Maybe the amount dispersed could be determined based on an estimate of the exposed mass of TiO2 in the materials?
7. Figure 7: the caption says this is sample 2-R, but the text says this is 3-S. Which is it?
8. Figure 10 is a very standard arrangement -- it can be moved to supplemental information if desired.
9. Durability is definitely an important question for any new photocatalytic material. There needs to be some assessment of the durability, and I do not believe that that should be relegated to future work.
Overall, I find that this work will become publishable, as long as these concerns can be addressed, but some new experiments may help to provide important context.
Overall, this mansuscript is very well written. There a few minor errors that are quick to adjust (noted in the general comments), but overall this is quality writing.
Author Response
Dear Reviewer,
please see our comments to your review in the document attached.
Best reagrds,
Lukas Dufner
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have addressed all of the writing and presentation-based concerns, for which I am appreciative. However, they have elected not to perform further experiments. I leave this as a decision for the editors. In future, it will be vital for this group of researchers to be able to perform the necessary control experiments prior to submission, or risk rejection.
Author Response
Dear Reviewer 2,
thank you for your comments on our article. We have clarified and improved all points which could be tackled.
Concerning the control experiments - after an intense internal discussion - we would like to stay with our argumentation of the previous round. MDPI journals are fast track. If a sufficient amount of time would be available we would have repeated some experiments to confirm our results, this is impossible within the typical review period.
