Natural Flocculant from a Combination of Moringa oleifera Seeds and Cactus Cladodes (Opuntia ficus-indica) to Optimize Flocculation Properties
Round 1
Reviewer 1 Report
The manuscript reports the result on the effect of natural flocculants from Moring and cactus in terms of turbidity removal. What they did is understandable, and some information would be practically useful. My comments are below.
I know some papers were published around 2000 for Moringa seeds as flocculant. After that, many papers are published for this topic as well. But these works are missing. Proper reviews should be added, and then please emphasize the novelty of this work.
These days, numerical values of floc strength are reported, and floc strength is around a few nN. This information should be added.
Figure captions should be more informative.
The outer frames of figures should be removed.
Error bar should be added for each data point.
The manuscript should be checked by English natives.
Author Response
Good day,
Thank you for taking the time to provide a thorough review of our manuscript. I have incorporated your suggestions as far as possible.
I have expanded the references used to include recent ones dealing with flocculation by Moringa seeds to also take into account recent research findings.
Unfortunately, no other parameters were included in the experiments conducted and it is not possible to calculate floc strength in nN. However, I will make sure to include these in future experiments.
I have changed the labeling of some figures, I hope these are now more descriptive.
The frames of the figures have also been removed.
An english check will be done at the end of the review process by the offered mdpi service.
Reviewer 2 Report
Natural flocculant from a combination of moringa oleifera seeds and cactus cladodes is an interesting work. I recommend this paper be published after minor revision such as text editing. For exanple:
Page 5，Line 162: According to the context, "Figure 1" should be "Figure 2."
Author Response
Good day,
Thank you for taking the time to provide a review of our manuscript. I am glad that you find our work interesting. Thank you for pointing out the incorrect reference of our figures.
Reviewer 3 Report
In this study, Moringa seeds (Moringa oleifera) and cactus cladodes (Opuntia ficus-indica) were investigated as innovative and environmentally friendly flocculants for water treatment. The parameters investigated included absolute turbidity reduction and flocculation activity, as well as shear strength of the resulting flocs. The flocculation experiments were conducted as simultaneous tests in beakers. Experiments were conducted using both a laboratory-prepared model suspension with an initial turbidity of approximately 139 NTU and natural surface water with an initial turbidity of approximately 136 NTU. This study is quite interesting with some useful information about the flocculation using natural flocculants. However, there are some concerns which needs to be addressed:
1) Line 22: The flocculant dosages used ranged from 100 to 300 mg/l. In some cases, it was higher than 300 and lower than 100 mg/l.
2) Did the authors try to measure the floc size, particularly as a function of shearing speed (Figure 3)?
3) Why there is no flocculation in case of cactus with 100 or 300 mg/l by using model suspension while the flocculation is observed in case of natural water?
4) Lines 172-173: Results in Figure 3 (left) show a trend of increasing Figure 100. % Moringa. Is it a typo?
5) Lines 187-188: The flocs sank fastest when flocculant from 100 % cactus was used (which means bigger flocs). At what concentration? Which kind of water, model suspension or natural water? Because with model suspension, pure cactus did not show any flocculation at lower and higher concentration.
6) In this study, the authors mainly describe their results without any discussions of the results with the help of literature knowledge. Therefore, the discussion of the results using literature information is needed.
7) First two paragraphs of the conclusion section should be included in the results section.
8) The authors should use following references for discussing their results:
· Shakeel, A., Safar, Z., Ibanez, M., van Paassen, L., & Chassagne, C. (2020). Flocculation of clay suspensions by anionic and cationic polyelectrolytes: A systematic analysis. Minerals, 10(11), 999.
· Mietta, F., Chassagne, C., Manning, A. J., & Winterwerp, J. C. (2009). Influence of shear rate, organic matter content, pH and salinity on mud flocculation. Ocean Dynamics, 59(5), 751-763.
· Deng, Z., He, Q., Safar, Z., & Chassagne, C. (2019). The role of algae in fine sediment flocculation: In-situ and laboratory measurements. Marine Geology, 413, 71-84.
Author Response
Good day,
Thank you for taking the time to provide a thorough review of our manuscript. I have incorporated your suggestions as far as possible.
1) The dosages above and below the indicated range have been removed from the charts.
2) Measuring the resulting flocs was attempted, however, reliable results could not be obtained due to excessive measurement inaccuracies, therefore the data was not included.
3) I have included the question in the added discussion section of the manuscript and attempted to answer it satisfactorily.
4) The typo has been corrected.
5) The missing information to understand the experimental results has been added.
6) A new Discussion section was added to the manuscript. With the help of various sources, the results are now also put into context and discussed.
7) The two paragraphs have been moved to the results section as suggested.
8) Thank you for the extremely useful literature suggestions! The suggested references were very helpful and were used to discuss the results.
Round 2
Reviewer 3 Report
The authors satisfactorily included all of my comments, except there are a few remaining things to highlight:
1) The heading 3.3 experimental conclusion should be written as 3.4 Experimental conclusion
2) There are two dots at the beginning of the Discussion section, which should be removed.
3) Why is there no flocculation in the case of cactus with 100 or 300 mg/l using model suspension while the flocculation is observed in the case of natural water? The authors tried to answer this comment in the discussion section. However, I am still unable to understand why there is no flocculation at the highest concentration of cactus (300 mg/l). Is it an experimental artifact? The authors should highlight this fact and explain it with possible reasons.
Author Response
Good day,
again I would like to thank you for your time and your comments. I have taken them on board and revised the relevant parts of the manuscript.
1) The heading has been numbered correctly.
2) The two items have been removed from the section.
3) An explanation of described observation has been added to the appropriate section of the discussion. (Restabilization of particles due to high flocculant doses).
