Removal of Phosphate from Wastewater with a Recyclable La-Based Particulate Adsorbent in a Small-Scale Reactor
Round 1
Reviewer 1 Report
Zhang et al. reported the “Removal of phosphate from wastewater with a recyclable La-based particulate adsorbent in a small-scale reactor”. Both batch experiments and continuous experiments were carried out in a laboratory environment and mimicked in a practical environment. The design of a replaceable filler-type integrated reflux aeration reactor sounds interesting.
Overall, the experiment was carried out in a systematic order and the findings are acceptable. The article could be published after the major revision.
1. The EDS mapping graph is not clear (no colour is observed in the dark background), you need to increase your scanning duration, or else better to remove it. EDS spectra are fine.
2. Represent the fitting parameters of kinetics and isotherm in tabular form with error calculation.
3. It could be better to provide the porosimetry data in relation to adsorption behaviour. How the surface area of the composite (La-CZ) affects the phosphate adsorption capacity
4. Have you examined the effect of the amount of zeolite/AC/La on phosphate adsorption capacity?
5. Provide details of all the figures. None of the figures has a legend. 6. Explain the material section in detail. Which zeolite and activated carbon?7. Kindly provide formulas for equilibrium adsorption capacity and removal rate.
8. If possible provide the XRD pattern of the initial material (zeolite, AC and La) and then the composite to have a better understanding.
9. Line 219 and 220, page 5 (And it could be assured that the even La loading on the materials: revised statement).
10. De* is defined as the dosage of material per liter wastewater that degrades 20 mg L-1 phosphorus to the sewage discharge standard (0.5 mg L-1): more clarity is required how is it evaluated?
11. Figures 4, and 9 are not visible. Try to have one font size in all of the figures which should be the same as the font size of your text and need to be visible.
12. Is Freundlich's isotherm correctly written? If yes, provide the citation.
13. Few more characterizations such as zeta potential and FTIR could also be carried out to explain the surface functionality of the composite and electrostatic attraction with phosphate (optional).
14. A desorption study and cyclic adsorption study of phosphate would be better, please provide.
15. Page 2, Line 73-75, provide more citations regarding adsorption in diversified applications
https://doi.org/10.3390/app12115334
https://doi.org/10.1016/j.jcou.2020.101223, https://doi.org/10.1016/j.enmm.2022.100649, https://doi.org/10.1021/acs.iecr.8b03958 https://link.springer.com/article/10.1007/s13204-020-01397-9
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer:
Thank you for your careful review and valuable comments. We have revised the manuscript accordingly. The modifications were marked with red color in this new version and detailed corrections are attached in the Attachment point by point.
Hangjun Zhang
Author Response File: 
Author Response.docx
Reviewer 2 Report
Title: Removal of phosphate from wastewater with a recyclable La-based particulate adsorbent in a small-scale reactor
Reviews:
· The area of study is relevant, but the design of experiments is not scientifically sound.
· Also, presentation of results in tabular and graphical forms is not of good quality. For example, many figures do not have accurate captions to describe the contents of the figure considering most of the figures do not contain enough information for a reader to easily comprehend the data being presented.
· The work has a very significant flaw: the design of experiments is not correct. Here are some questions to keep in mind when designing experiments for a work like this:
1) How can you show that Lanthanum is contributing to the performance of the adsorbent? Specifically, if you compare the performance of activated carbon only to the performance of the La-CZ, is La-CZ doing better than the control adsorbent activated carbon? Activated carbon (even just by itself) is already among the best and industrially applied for a long time now. So, how does your La-CZ compare to this benchmark?
2) How can you be sure that the trends you are seeing are the correct trends? I do not see signs of replication of the experiments and analysis of difference (no error bars, no statistical testing of significance, etc.). This concern on replication is very crucial in the fitting/regression of the isotherm models since noise in the experimental data arising from replicated runs can significantly lower the fitting performance of models.
3) Also, the major parameters of performance shown in the paper are not clearly defined. For example, how exactly is the removal of PO4 by % being calculated? If that is based on the change in the concentration of PO4 in the solution, then how can you be sure the removal of PO4 is due to adsorption by the solvent and not by other effects such as microbiological growth? Or maybe PO4 in solution is converted into another chemical as the pH is being changed (such as the drop of PO4 at pH 10 in Figure 5)? Please clearly discuss or even show formula on how these parameters of performance measure are calculated/derived from raw data measurements.
Author Response
Dear Reviewer:
Thank you for your careful review and valuable comments. We have revised the manuscript accordingly. The modifications were marked with red color in this new version and detailed corrections are attached in the Attachment point by point.
Hangjun Zhang
Author Response File: Author Response.docx
Reviewer 3 Report
Manuscript Number: water -1805318
Removal of phosphate from wastewater with a recyclable La-based particulate adsorbent in a small-scale reactor.
GENERAL COMMENTS
The present work analyzes the degree of phosphate adsorption using a Lanthanum compound, activated carbon and zeolites. They analyze both the morphology of the compound and its adsorbent properties under different conditions, even carrying out pilot-scale experiments with a proposed configuration for the process.
I think the work is interesting and it should be accepted after minor revision.
I only have some recommendation and questions for the authors:
Authors refer to other researchers as Scholars, I think that the appropriate term should be authors.
The figures should be accompanied by a footnote that in a summarized way allows knowing all the details of the same without having to go to the text.
In the sixth line of section 2.3. and in the sixth line of section 3.3.2 there is an error in the nomenclature of the nitrate ion NO3-.
In figure 1 c and d, the scale bar is imperceptible, the authors should improve this.
In Figure 4a, the concentrations in the legend do not coincide with the concentrations indicated in the text.
In all those figures in which it has been decided to use a bar graph as the type of graph, the bars of the standard deviations of the data should be able to be adequately distinguished, and it is not occur.
In figure 6, what is CK?
Is the text at the end of section 3.5 correctly placed?
Of the conditions tested whose results are shown in figure 9a, which one has been used to vary the conditions and obtain the results of figures 9b and c?
In the adsorbed phosphorus fractionation assay, has it been thought to carry out the experiment at other concentrations to test whether the fractions that are mostly adsorbed remain?
Longer tests have been carried out to determine the useful life of the pellets formed from La-CZ? Have tests been carried out to determine the saturation point of the formed pellets?
For what type of water is its use considered? The sand filter prior to the adsorption process is due to the fact that it has been designed to treat an effluent from a secondary treatment of wastewater?
Author Response
Dear Reviewer:
Thank you for your careful review and valuable comments. We have revised the manuscript accordingly. The modifications were marked with red color in this new version and detailed corrections are attached in the Attachment point by point.
Hangjun Zhang
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Thank you for revising the article. The revision is satisfactory.
