The authors presented a study for the photocatalytic degradation of Methylene blue as a model dye using TiO2 catalyst in a UV-based photoreactor setup. The manuscript is well written and data is well presented. I have some major and minor comments on this manuscript as follows.

My major concerns are

1- I find the methodology used can prevent the correct interpretation of the results. The authors didn't leave the dye and the catalyst in the dark conditions before running the experiments. This will lead to the confusion between adsorption and photocatalytic degradation. In other words, the removal of the dye may be due to the adsorption phenomenon rather than due to actual photocatalytic degradation. I suggest that the authors repeat the experiments and the optimum conditions reported and compare the results after waiting for at least for 24 h in the dark before turning the lamp on.

2- The authors didn't define the knowledge gap in the introduction section. Moreover, most of the cited previous studies were published more than 7 years ago (e.g. ref. 3, 4, 7, 10, 12, 13, 16, 17, 19 and 21). I suggest that the authors rewrite the introduction relying on recent articles and introducing the knowledge gap while highlighting the impact of their research question for the field of study.

3- The pH was studied in the range from 3-7. The authors found that the removal efficiency increases with pH value. Why not studying the removal at higher pH values. Moreover, according to my experience MB is optimally removed at pH=9 not 7 as the study reported. I suggest that the authors study pH values of 9 and 12 and report their results.

The minor comments are

1- The details of XRD analysis should be removed from the discussion section and added to the materials and methods section.

2- Figure 2 is hizzy and needs to be replaced with a higher resolution version.

3- There is no discussion for the blue curve in figure 3. What does this curve represents?

4- The caption of figure 8 is not clear. What does the authors mean by "removal under different experimental conditions."?

5- The caption of figure 11 is not correct. The authors wrote "Percentage color removal- time profile for different catalyst loadings." It should be corrected to Percentage color removal- time profile for different air velocities."

6- The authors concluded that " Air contributed efficiently to enhancing the degradation reaction," I think the study concluded that air lowered the TiO2 agglomeration and improved the mass transfer coefficient but not the degradation reaction itself. I suggest that this part should be modified in the conclusion section.

7- The authors didn't present any comparison with other published studies in the field. I have read several published articles presenting results close to those presented by the authors. I suggest that the authors add a new table summarizing recent findings and the operating conditions used by previous authors. To that table the authors can add the results presented by their study to allow for data comparison.

Finally I wish to thank the authors for their work.