Control of Endogenous Phosphorus Release at the Sediment–Water Interface by Lanthanum-Modified Fly Ash

Round 1

Reviewer 1 Report

I have gone through manuscript entitled „Control of Endogenous Phosphorus Release at the Sediment-Water Interface by Lanthanum-modified Fly Ash”. The first part of Introduction is properly written, describing  backgroung of the work. However, I found no clear description of the goal of the work. Why do you study fly ash? What has it in common with wastewater treatment? It should be completely clear for a reader, also in the abstract.

Figure 1 – the presentation of the composition of fly ash is not good, colors are not possible to be distinguished

Pragraphs 2.1 and 2.2.1 – repetition of the information about fly ash preparation

Methods – too much paragraphs about fly ash preparation – I recommending one paragraph with fly ash preparation/modification procedures

All acronyms must be explained. Here, it has not been done (e.g. SMT, ORP, DO etc. – not explained). In this situation it is often not possible to understand what authors investigated (e.g. paragraph 3.3).

I can see no description of statistics for all the experiments. Were they single experiments?

Figure 4 – what is on x axis? Poor description of the results.

Line 220 – the sentence not bring any information, not in scientific style

Figure 5  - I do not see the information authors describe in the text, I do not agree with the description of the figure, the differences between pictures are too small to conclude

Figure 6  - not good description, poor quality of the figure

Figure 7 – I do not find explanation of this situation here ; What is this scale on y axis?

Paragraph 3.2  - where are theses results you describe?

The description of the results in Results and Discussion is poor. The article needs very deep corrections and re-writing almost from the beginning.

Author Response

Dear Editor:

Thank you for your valuable suggestions. We have carefully read through the comments and made proper revisions. In addition, the language of this article has also been improved by professional company. Our responses to the reviewer's questions are listed below. We greatly appreciate your time and efforts to improve our manuscript for publication.

Sincerely,

Pan Ying

Author Response File: Author Response.docx

Reviewer 2 Report

GENERAL COMMENTS AND SUGGESTIONS

In principle, this paper is potentially of interest for readers; however, it is not publishable in this version.

A lot of data and measurements are presented here, it is not clear which is the Authors’ intent, considering that results are reported in a very quickly and in a very draft way and hasty way, and comments are, in my opinion, more Authors’ convictions than discussion. May be, such convinctions, could be potentially correct, but readers are obliged to take their word for. To support my statements some examples are reported in the following; however, I want believe this paper is more the result of inexperience rather than little respect for the readers.

I’m 63 years old, and I’ve been working in reasearch since 1984; thus, I consider paper publication may be the old way, where to publish just to publish, i.e. to have an extra paper, it is never a good idea. On the contrary, is a way to communicate and disseminate our work that could be profitably used by other researchers or by the society.

Please, take into account my suggestion: much does not necessarily mean better. This is the reason way I suggest the Author to divide the paper in 2 parts, one devoted to materialscharacterization, and the other to materials testing. Then, please, completely re-wright the text putting much more attention and care. I’m not English native speaker, thus I do not feel entitled to comment English style; however, in this case language MUST be completely, because some parts of the text are fully ununderstandable.

 

SPECIFIC COMMENTS (SOME EXAMPLES)

In the following few specific remarks are reported, only few because they are so many that it becomes difficult to list them all.

1. To give details on which technique and experimental conditions have been used to perform characterization is mandatory. Characterization description in the experimental, it is not a mere list of the techniques...”..... Scanning electron microscopy (SEM), X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), and a specific surface area test were used to analyze the modified fly ash. Transmission electron microscopy (TEM; FEI Tecnai G2 F20, USA), X- 195 ray fluorescence spectrometry, XRD, and other techniques were used to characterize the blank fly ash pellets and fly ash pellets from the experimental water body, and study their adsorption principle. The different phosphorus forms in sediment were determined by the SMT method......” For instance, how did you measure surface area? In Table 2 four significant figures are reported, to my knowledge, there is no instrument capable of measuring surface area with such a precision. Moreover, difference between 2 m2/g and 6 m2/g, are whitin the experimental error, but this also depend on the technique you used to measur it, not reported (Hg intrusion? N2 adsorption? Other?)

Figure 1, hardly to be red, better a Table

Supernatant separation: how is it made? (e.g. line 130)

Line 138 Pretreated fly ash: which?

In Table 2 Which is the difference between Pore nm and Average pore size?

Moreover, If I got well magnification is the ratio between La-modified and original fly ash. Therefore, 6/2 = 3, but 89.63/ nothing is 7?

Figure 4 x axis? what are the units of measurement?

Figure 4 and other figures, y axis, the word “rate” can suggest somenthig related to kinetic, may be better degree? Figure 4 which alkaly od acid treated samples are reported?

Figure 5 Which is the real meaning of this analysis? Pictures appear to be ALL the same, moreover surface area cannot be determined by SEM

Lines 235-239 which is the meaning of these sentences?

Which is the meaning of this 4.70%? Which was the initial value?

Comments to Fig 5. In research, how can data be defined obvious? If obvious there is no reason to measure it

Figure 6 presentation unaccetable

Line 274-275 “....From the variance ratio, the magnitude of extreme differences in fly ash/montmorillonite ratio, roasting temperature, roasting time, and particle size were 0.381, 0.050, 0.037, and 0.198, respectively...” 0.381, 0.050, 0.037, and 0.198 what?

Line 276-287 NO NUMBERS are reported to support statement, readers have to trust Auth

Author Response

Dear Editor:

Thank you for your valuable suggestions. We have carefully read through the comments and made proper revisions. In addition, the language of this article has also been improved by professional company. Our responses to the reviewer's questions are listed below. We greatly appreciate your time and efforts to improve our manuscript for publication.

Sincerely,

Pan Ying

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

 

This study deals with the problem of endogenous phosphorus release at the sediment-water interface of water bodies and optimization of the modification and granulation through laboratory simulations of fly ash to make it more stable at the sediment-water interface.

There are some points that need to be addressed. Firstly, English language needs to be slightly improved. My specific comments are listed as follows:

1. In order for the other researchers to be able to repeat and solely conduct the experiments, in Sections 2.2.2., 2.2.3., 2.2.4. and 2.2.5. (lines 127-154) the producer of the chemicals (i.e. acid, alkali, phosphate and lanthanum) needs to be stated.
2. Section 2.3.1. (Lines164-165) The figure needs to be explained. Not only the figure to be present in the whole Section.
3. Line 200 – Table 2 – This table shows results of the measurements, it should be moved to Results and discussion Section and explained in more detail.
4. Lines 227-228 It should be stated that rougher surface can be observed from SEM images
5. EDS or XPS measurements should be conducted and shown in order to confirm the statement from Line 237.
6. Lines 298-301 – Reference needed
7. Line 322 It should be stated PO₄^-3 (with sub- and superscripts)
8. Line 419 It needs to be rewritten. What is a), what is b)? Also Figure 15 needs to be labeled A and B (Line 418).

Author Response

Dear Editor:

Thank you for your valuable suggestions. We have carefully read through the comments and made proper revisions. In addition, the language of this article has also been improved by professional company. Our responses to the reviewer's questions are listed below. We greatly appreciate your time and efforts to improve our manuscript for publication.

Sincerely,

Pan Ying

Author Response File: Author Response.docx

Reviewer 4 Report

In my opinion, it is a practical article but it needs to be considered the following comments before publishing.

The result in abstract part must be extended.

The introduction must be improved based on recent literature. The manuscript does not illustrate great attention and activity in the field. The purpose of the study is not well expressed. At the end of the introduction, the necessity and novelty of the work must be expressed well.

Please use the references for your methods.

Figure 1 changed into table form

Methods: Why and how the said parameters were selected for this work. More specific details are needed to be added with use of latest reference. Use of some pictorial; diagram will be more elaborative for readers.

QA/QC information has to be included in manuscript.

The innovation of the study is not well expressed.

Please check your tables and figures numbering throughout the manuscript

Figure 4: provide magnification of the micrographs, Figure 5 (A) show important peaks inside the spectra, Figure 5 (B) arrange like figure 14, all the characterization should be in the form of before and after process for the better presentation

Adsorption mechanism parts, better to show reaction mechanism too

Conclusion: state main findings only

Future scope of this study can be added as well as social impact can also be discussed in this paper.

References are not unified and systematic.

Author Response

Dear Editor:

Thank you for your valuable suggestions. We have carefully read through the comments and made proper revisions. In addition, the language of this article has also been improved by professional company. Our responses to the reviewer's questions are listed below. We greatly appreciate your time and efforts to improve our manuscript for publication.

Sincerely,

Pan Ying

Reviewer:  #4

Thank you very much for your comments on the manuscript. According to your suggestion, we revised the relevant part of the original manuscript. Here are some answers to your questions.

1. The result in abstract part must be extended.

Response: Thank you for your reminder. We have rewritten it and mark the text in red.

Before the change: To address the problem of endogenous phosphorus release at the sediment-water interface of water bodies, this study optimizes the modification and granulation of fly ash to make it more stable at the sediment-water interface. Through laboratory simulations, the modified fly ash pellets were optimally granulated to cover the sediment-water interface, and its control effect and mechanism were evaluated. The results showed that the phosphorus adsorption effect of lan-thanum-modified fly ash was 34% and 40% higher compared with those of acid-modified and alkali-modified fly ash, respectively, with the phosphorus adsorption effect reaching 85%. Adsorption was affected by pH and was more effective under weak alkalinity, close to the Langmuir adsorption model, which was con-sistent with the unimolecular layer adsorption characteristics and the presence of chemisorption and physical adsorption. The optimized granulation conditions for lanthanum-modified fly ash pellets were a fly ash/montmorillonite ratio of 7:3, a roasting temperature of 900 C, a roasting time of 4 h, and a particle size of 3 mm. After covering for 60 days, the modified fly ash pellets better controlled the release of endogenous phosphorus at the sediment-water interface. After 60 days, active phosphorus in the surface layer of the sediment was gradually transformed into a stable phosphorus form, with calcium phosphorus accounting for 70% of the total inorganic phosphorus. The ability of the sediment to release phosphorus to the overlying water body was also significantly weakened. Meanwhile, the total phosphorus removal rate in the overlying water at the sediment-water interface reached more than 40%, and orthophosphate removal reached more than 60%, indicating an obvious phosphorus control effect. Transmission electron microscopy analysis showed that lanthanum was present at locations enriched with elemental phosphorus, and was adsorbed onto the material surface. Therefore, lanthanum-modified fly ash pellets are a promising in situ phosphorus control agent with good endogenous phosphorus pollution control abilities in eutrophic water bodies.

After the changes: To address the problem of endogenous phosphorus release at the sediment-water interface of water bodies, tThis study optimizes the modification and granulation of fly ash to make it more stable at the sediment-water interface. Through laboratory simulations, the modified fly ash pellets were optimally granulated to cover the sediment-water interface, and its control effect and mechanism were evaluated. The results showed that the phosphorus adsorption effect of lanthanum-modified fly ash was 34% and 40% higher compared with those of acid-modified and alkali-modified fly ash, respectively, with the phosphorus adsorption effect reaching 85%. The best dosing ratio was about 0.3g/L. Adsorption was affected by pH and was more effective under weak alkalinity, close to the Langmuir adsorption model, which was consistent with the unimolecular layer adsorption characteristics and the presence of chemisorption and physical adsorption. The saturation adsorption amount of phosphate by lanthanum-modified fly ash was 8.89 mg/g. The optimized granulation conditions for lanthanum-modified fly ash pellets were a fly ash/montmorillonite ratio of 7:3, a roasting temperature of 900 °C, a roasting time of 4 h, and a particle size of 3 mm. After 20 days, the ortho-phosphate removal rate was more than 60% higher than that of the control group, with a total phosphorus removal rate of 43%.  After covering for 60 days, the modified fly ash pellets better controlled the release of endogenous phosphorus at the sediment-water interface. After 60 days, active phosphorus in the surface layer of the sediment was gradually transformed into a stable phosphorus form, with calcium phosphorus accounting for 70% of the total inorganic phosphorus. The ability of the sediment to release phosphorus to the overlying water body was also significantly weakened. Meanwhile, the total phosphorus removal rate in the overlying water at the sediment-water interface reached more than 40%, and orthophosphate removal reached more than 60%, indicating an obvious phosphorus control effect. Transmission electron microscopy analysis showed that lanthanum was present at locations enriched with elemental phosphorus, and was adsorbed onto the material surface. Therefore, lanthanum-modified fly ash pellets are a promising in situ phosphorus control agent with good endogenous phosphorus pollution control abilities in eutrophic water bodies.

 

 

2. The introduction must be improved based on recent literature. The manuscript does not illustrate great attention and activity in the field. The purpose of the study is not well expressed. At the end of the introduction, the necessity and novelty of the work must be expressed well.

Response: Thank you for pointing this out and marked in red. (lines 64-72;83-88;)

Phosphorus sources in water are mainly divided into endogenous phosphorus, exogenous phosphorus, and a small amount of atmospheric deposition phosphorus. After exogenous phosphorus input, a series of physical, chemical, and biochemical effects occurs in the water column, and part of the phosphorus is deposited on the bottom. However this is not stable and will be released into the overlying water with changes in environmental factors, such as dissolved oxygen, temperature and season, such that and eutrophication will still occur in the water column. Therefore, controlling endogenous phosphorus in the substrate becomes key to preventing and controlling eutrophication in the water column. The adsorption method has advantages of high efficiency, simple operation, no secondary pollution, and recyclability, among others, and has been widely favored by domestic and foreign researchers in recent years. The identification of cost-effective adsorbents is key to phosphorus removal by adsorption, with some industrial waste materials, such as fly ash, applied as phosphorus removal materials. However, incomplete binding of lanthanum with phosphate alone greatly reduces its effective utilization, making phosphorus removal difficult and causing harm to aquatic organisms. To overcome this challenge, researchers have prepared different lanthanum-doped materials by combining lanthanum with other materials. Lanthanum-modified adsorbents have promising applications as new adsorbent materials. This work is expected to provide a theoretical basis and scientific basis for the practical application of lanthanum-modified fly ash adsorption of endogenous phosphorus release in water.

3. Please use the references for your methods.

Response: Thank you for pointing this out. We have added and marked red in the text. (lines 157;159;194;199;219;228)

4. Figure 1 changed into table form

Response: Thank you for pointing this out. We have changed into table form.

Table original fly ash fraction

Compound	SiO2	Al2O3	Cr2O3	Fe2O3	MnO	CaO	TiO2	K2O	FeS	SO3	Na2O
Original fly ash	36.3%	13.0%	7.0%	3.6%	2.3%	2.0%	4.9%	5.0%	3.5%	15.4%	3.9%

5. Methods: Why and how the said parameters were selected for this work. More specific details are needed to be added with use of latest reference. Use of some pictorial; diagram will be more elaborative for readers.

Response: Thank you for pointing out this detail problem and we have cited some references.

Before the change: Emission scanning electron microscopy (FESEM, SU 8020, Hitachi, Japan), X-ray diffractometry (XRD) pattern of samples was determined by D/max-2500 X-ray diffractometer (X’Pert PRO, PANalytical, Netherlands) in the 2θ range of 10–80 ◦, Fourier-transform infrared spectroscopy (FTIR)( The IR spectra were recorded at room temperature with a Nicolet Magna 550 FTIR spectrometer (resolution 4 cm-1) after quenching the samples.), and a specific surface(the total pore volume, and the porosity of the adsorbents before and after adsorption were determined using an ASAP2020M porosimeter analyzer (Micromeritics, USA). The samples were degassed at 80 ◦C for 24 h before BET analysis.) area test were used to analyze the modified fly ash. Transmission electron microscopy (TEM; FEI Tecnai G2 F20, USA), X-ray fluorescence spectrometry, XRD, and other techniques were used to characterize the blank fly ash pellets and fly ash pellets from the experimental water body, and study their adsorption principle. The different phosphorus forms in sediment were determined by the SMT (The SMT method was used to determine the content of different forms of phosphorus in the sediment, including TP (total phosphorus), IP (inorganic phosphorus), OP (organic phosphorus), NAIP (non-apatite inorganic phosphorus), and AP (calcium phosphorus) mainly.) method.

After the changes: Emission scanning electron microscopy (FESEM, （SU 8020, Hitachi, Japan) was used to obtain the apparent morphology, pore structure and cross-sectional element distribution of materials, X-ray diffractometry (XRD)( was used to analyze the surface crystal-phase changes of materials before and after loading HLO)pattern of samples was determined by D/max-2500 X-ray diffractometer (X’Pert PRO, PANalytical, Neth-erlands) in the 2θ range of 10–80 ◦, Fourier-transform infrared spectroscopy Information about the functional groups and specific chemical bonds on the surface of materials was obtained with FTIR(Nicolet 8700, Thermo Fisher Scientific, USA) [57]  (The IR spectra were recorded at room temperature with a Nicolet Magna 550 FTIR spectrometer (resolution 4 cm-1) after quenching the samples.), and a specific surface (the total pore volume, and the porosity of the adsorbents before and after adsorption were determined using an ASAP2020M porosimeter analyzer (Micromeritics, USA). The samples were degassed at 80 ◦C for 24 h before BET analysis.) area test were used to analyze the modified fly ash. Transmission electron microscopy (TEM; FEI Tecnai G2 F20, USA), X-ray fluorescence spectrometry, XRD, and other techniques were used to characterize the blank fly ash pellets and fly ash pellets from the experimental water body, and study their adsorption principle. The different phosphorus forms in sediment were determined by the SMT [58] (The SMT method was used to determine the content of different forms of phosphorus in the sediment, including TP (total phosphorus), IP (inorganic phosphorus), OP (or-ganic phosphorus), NAIP (non-apatite inorganic phosphorus), and AP (calcium phos-phorus) mainly.) method.

 

The selection of parameters is to first consult the relevant literature, and then carry out the scope of experimental exploration according to this work, and also set up parallel experiments to ensure the validity of the experimental data.

The Brunauer–Emmett–Teller method (Tristar II 3020, Micromeritics) was used to determine the pore size, pore volume, and specific surface area of adsorbents, and the corresponding nitrogen adsorption and desorption curve was obtained. SEM coupled with an energy-dispersive X-ray spectroscopy (SEM-EDS) system (NOVA 450, FEI, USA) was used to obtain the apparent morphology, pore structure and cross-sectional element distribution of materials. XRD (ARL XTRA, Thermo Scientific, USA) was used to analyze the surface crystal-phase changes of materials before and after loading HLO (36 kV, 20 mA, Cu Kα radiation source, 10◦–80◦). Information about the functional groups and specific chemical bonds on the surface of materials was obtained

with an FT-IR system (Nicolet 8700, Thermo Fisher Scientific, USA). XPS (PHI 5000 VersaProbe, Japan) was used to detect the types of chemical elements and the chemical states of LMR before and after reaction. All binding energies were corrected based on the C1s peak at 284.8 eV, and then the spectra of specific elements were fitted with XPSPEAK41 software. The Shirley method was used to subtract the background.

<Insight into simultaneous selective removal of nitrogen and phosphorus

species by lanthanum-modified porous polymer: Performance, mechanism

and application>

6. QA/QC information has to be included in manuscript.

Response: Thank you for pointing out this detail problem and we have cited some references.

Each experiment was set up to repeat the experiment, and three parallel experiments were carried out. (lines 232-233)

 

7. The innovation of the study is not well expressed.

Response: Thank you for pointing out this detail problem.

The innovation of the study is to supply a novel method to control endogenous phosphorus release by using optimized granulated lanthanum-modified fly ash pellets, Thus the fly ash which was waste originally, can be used as endogenous phosphorus controller combined with lanthanum, and the phosphate adsorbed which was harmful to water environment, can be revised and reused again.

The revision has been marked in the part of introduction of the manuscript.

In this study, fly ash was subjected to different modifications and the adsorption performance was compared after modification. Lanthanum modification achieved a better adsorption effect and was preferentially selected. To make the modified fly ash more stable at the sediment-water interface and less likely to be disturbed and float, further optimized granulation experiments were conducted to determine optimal process parameters. The optimized granulated lanthanum-modified fly ash pellets were placed at a simulated sediment-water interface in the laboratory to study the effect on in situ endogenous phosphorus pollution at the sediment-water interface of eutrophic water bodies. Thus the fly ash which was waste originally, can be used as endogenous phosphorus controller combined with lanthanum, and the phosphate adsorbed which was harmful to water environment, can be revised and reused again. The pollution control mechanism was also explored to provide a theoretical and scientific basis for the practical application of lanthanum-modified fly ash adsorption to the release of endogenous phosphorus in water.

 

8. Please check your tables and figures numbering throughout the manuscript

Response: Thank you for pointing out this detail problem. We have made the corresponding changes.

9. Figure 4: provide magnification of the micrographs, Figure 5 (A) show important peaks inside the spectra, Figure 5 (B) arrange like figure 14, all the characterization should be in the form of before and after process for the better presentation

Response: Thank you for pointing out this detail problem. We will pay attention to this issue next time.

Electron microscope magnified 400 times; Figure 5 is the XRF curve of lanthanum content under three kinds of fly ash loading, mainly to compare the loading of lanthanum after acid modification, alkali modification and lanthanum modification.

10. Adsorption mechanism parts, better to show reaction mechanism too

Response: Thank you for your reminder. We have cited other literature for mechanistic diagrams

 

A schematic diagram for the P binding mechanisms of different La species.

 

 

Schematic diagram of the structures of different types of La-based adsorbents: (A) single La compounds; (B) La-metal composites; (C) "La-carrier" absorbents.

Li, J.; Li, B.; Yu, W. Lanthanum-based adsorbents for phosphate reutilization: Interference factors, adsorbent regeneration, and research gaps. Sus Hori, 2022, 1: 100011.

11. Conclusion: state main findings only

Response: Thank you for pointing out this detail problem and we have made some changes.

The conclusion part summarizes the comparison of the four modification methods, and concludes that the modification effect of lanthanum is the best and the best conditions, and then optimize the granulation, and finally cover it on the mud-water interface to evaluate the effect and mechanism of phosphorus control. Each conclusion is a summary of an experiment.

 

Before the change: (ii) In the granulation study of modified fly ash particles, the optimum synthesis conditions were a fly ash/montmorillonite ratio of 7:3, a roasting temperature of 900 C, a roasting time of 4 h, and a particle size of 3 mm. (iii) The dissolved oxygen concentrations in the test and control groups remained basically the same. The pH of the water column also remained basically the same. Furthermore, changes in the ORP were not obvious because the dissolved oxygen con-tent did not fluctuate much. These observations indicated that the addition of modified fly ash pellets did not change the ecological environment of the eutrophic water column. (iv) In the laboratory simulation of application to eutrophic water bodies, water quality analysis showed a relatively stable phosphorus content. After experimental monitoring for 20 days, orthophosphate in the injection group basically reached ad-sorption equilibrium, and the orthophosphate removal rate more than 60% higher than that of the control group, with a total phosphorus removal rate of 43%. (v) The experimental water was generally alkaline, and HCL–P in the sediments was relatively stable. Phosphorus release from the sediment to the overlying water was mainly affected by the iron, aluminum, and phosphorus contents in the sediment. The difference between HCl–P and NaOH–P in the original sediment sample was large, while the HCl–P content in the more stable state at this time was small, accounting for about 26% of inorganic phosphorus. The HCl-P content accounted for about 40% of in-organic phosphorus after 20 days of the experiment, and about 70% of total inorganic phosphorus after 60 days. At this time, the active phosphorus content in the sediment was greatly reduced, and the ability of the substrate to release phosphorus into the overlying water body was weakened.

After the changes: (ii) In the granulation study of modified fly ash particles, the optimum synthesis conditions were a fly ash/montmorillonite ratio of 7:3, a roasting temperature of 900 C, a roasting time of 4 h, and a particle size of 3 mm. (iii) The dissolved oxygen concentrations in the test and control groups remained basically the same. The pH of the water column also remained basically the same. Furthermore, changes in the ORP were not obvious because the dissolved oxygen con-tent did not fluctuate much. These observations indicated that the addition of modified fly ash pellets did not change the ecological environment of the eutrophic water column. (iv iii) In the laboratory simulation of application to eutrophic water bodies, water quality analysis showed a relatively stable phosphorus content. After experimental monitoring for 20 days, orthophosphate in the injection group basically reached ad-sorption equilibrium, and the orthophosphate removal rate more than 60% higher than that of the control group, with a total phosphorus removal rate of 43%. (v iv) The experimental water was generally alkaline, and HCL–P in the sediments was relatively stable. Phosphorus release from the sediment to the overlying water was mainly affected by the iron, aluminum, and phosphorus contents in the sediment. The difference between HCl–P and NaOH–P in the original sediment sample was large, while the HCl–P content in the more stable state at this time was small, accounting for about 26% of inorganic phosphorus. The HCl-P content accounted for about 40% of in-organic phosphorus after 20 days of the experiment, and about 70% of total inorganic phosphorus after 60 days. At this time, the active phosphorus content in the sediment was greatly reduced, and the ability of the substrate to release phosphorus into the overlying water body was weakened.

 

12. Future scope of this study can be added as well as social impact can also be discussed in this paper.

Response: Thank you for pointing out this detail problem. We have added and marked red in the preface. (lines 109-113)

Currently, most studies focus on the desorption and resorption efficiencies of lanthanum-based adsorbents. Only a few studies focus on the influencing factors in the adsorbent regeneration process, and future research can focus more on this aspect, which is beneficial to reduce energy and water consumption and improve adsorption efficiency.

13. References are not unified and systematic.

Response: We are so sorry that references are not unified and systematic and we have made the corresponding changes.

 

 

      

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors responded to all my comments and I can see they really care about the improvement of the text.

Author Response

Thank you for your appreciation of our work. The comments are very important for improving our manuscript.

Reviewer 2 Report

-

Author Response

Thank you very much for your comments on the manuscript. According to your suggestion and question, we have checked and revised the relevant part of the original manuscript carefully again. The revision section have been marked in red.