Transport Models of Ammonium Nitrogen in Wastewater from Rare Earth Smelteries by Reverse Osmosis Membranes
Round 1
Reviewer 1 Report
This manuscript investigates the removal of ammonium nitrogen from rare earth smeltery wastewater via the reverse osmosis (RO) process. Experiments were performed under varying operating conditions with convincing evidences provided to support experimental observations. The proposed use of the RO process is novel and without doubt of interest to readers, but some work on membrane autopsy should be performed. In addition, experimental data acquired during the initial stages of the RO process were as expected and hence do not exactly qualify as novel findings. Long-term operation of the RO system in the treatment of simulated rare earth smeltery wastewaters to observe any potential fouling phenomenon would add more value to this study. The authors ought to address these issues and the following suggestions/comments:
Line 27, rare ‘earth’ industry
Line 32, in ‘the’ demand for…
Line 33, remove comma after (REEs)
Line 37, ammonium hydroxide ‘is’ added…
Line 48, ‘perspectives’
Line 62, ‘fall’ in the range…
Line 85, abbreviate ‘reverse osmosis’
Line 86, ‘systematic’ study…
Line 98, ‘is’ commonly expected…
Line 100, ‘has been’ observed…
Lines 100–101, which ‘could be’ explained…
Line 103, ‘had also been’ reported
Line 104, ‘become’ inconvenient
Line 106, ‘to interpret experimental observations’ remove ‘the’
Lines 106–107, a clear guideline ‘on improving’ membrane performance
Line 110, by ‘modifying’ classical mass transfer models
Line 115, the analysis of the outcomes ‘offers’ a new approach…
Line 116, abbreviate ‘reverse osmosis’
Line 251, a very ‘low’ permeate flux… would be more appropriate
Lines 281–282, how does a permeate concentration of 1.68 g/L meet emission standards? That’s more than 30 times higher than the standard for indirect discharge.
Lines 228, 286, ‘…removal performance of RO membrane’ would be more appropriate
Lines 309–310, please perform membrane autopsy (SEM/FESEM/AFM) instead of speculating
Line 311, using ‘low’ to describe flux would be more appropriate
Lines 321–322, … was lower than NaCl. Remove the word ‘to’.
Lines 388–389, why is CP more severe in NaCl solutions at high operating pressures?
Line 397, the following equation ‘is’ derived
In Paragraph 4 of the Introduction Section, a short description of the working principles of the RO process will be beneficial to readers who are not familiar with the process.
Please explain why SG membranes were chosen. What desirable properties do these membranes have?
Please be consistent in presenting units. For example, g/L vs L m-2 h-1 (Section 2). Either use g L-1 and L m-2h-1 or g/L and L/m2h.
In Section 4.2, please include information on the types of pores that typically exist within the polyamide matrix (i.e., size) and how they affect salt rejection. This will better justify your observations. This information should be readily available in the literature.
How certain are the authors that 4h is sufficient to achieve steady-state operation of the RO system? In my opinion, 4h is too short of an operating duration to determine the feasibility of the RO process as a standalone treatment option for rare earth smeltery wastewater. There should be at least one long-term experiment (could be ~1 week) conducted to observe fouling. Studying the anatomy of the layer of foulants would add more value to this study.
Author Response
Dear reviewer,
Thank you very much for your positive response. We are truly grateful to you for the constructive comments and thoughtful suggestions. According to these comments and suggestions, we have made careful modifications on the original manuscript. All changes have been marked with red color.
Below you will find our point-by-point responses to your comments. We hope that the revisions are acceptable and our responses adequately address the comments.Please see the attachment.
Yours sincerely,
Shuanglin Gui
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The present paper deal with the uqse of RO to separate NH4-N compounds from rare earth smelteries.
A model of mass transfer was developped as a temptative to predict mass transfer in RO for NH4Cl and NaCl.
A general remark is that the authors have to improve their paper; errors are reported and it is under-referenced.
- Abstract : keywords : add the king of model mass-transfer used please
- A question in the introduction : is NH4Cl well representative of NH4-N compounds ?
- An error in the introduction : page 2 line 58-61 : brackish water is less than 10,000 ppm and seawater around and more 35,000 ppm please check it
- In the theory : the units of Js and B are not usual : Js is in mol.h-1.m-2 and B as a consequence in L-1.h-1.m-2 not Bar-1 unit presence in B please !
- I can suggest a more simple approach to linearize your mass transfer as reported E Ould Mohamedou et al in DESALINATION 2010 : New lives for old reverse osmosis (RO) membranes E Ould Mohamedou, DBP Suarez, F Vince, P Jaouen, M Pontie Desalination 253 (1-3), 62-70 and in 2017 : Recycling and energy recovery solutions of end-of-life reverse osmosis (RO) membrane materials: A sustainable approach M Pontié, S Awad, M Tazerout, O Chaouachi, B Chaouachi Desalination 423, 30-40 You follow Cp=f(1/Jv) ==> from the slope you can calculate B. and you claim that you work Under low concentration polarization.
- For take into account the polarization effect I can ALSO suggest to use this eQUATION /
- ln [(1- TRobs)/TRobs]= ln [(1- TRreal)/TRreal]+ Jv/K AND OBTAINED Rreal USABLE TO ESTIMATE THE PRESENCE OF A POLARIZATION or not.
- What could you say about the fouling attempted on the SG membrane ?
- The conclusion has to be rewritten with more détails on the model and the more original results to be highlighted
Author Response
Dear reviewer,
Thank you very much for your positive response. We are truly grateful to you for the constructive comments and thoughtful suggestions. According to these comments and suggestions, we have made careful modifications on the original manuscript. All changes have been marked with red color.
Below you will find our point-by-point responses to your comments. We hope that the revisions are acceptable and our responses adequately address the comments.Please see the attachment.
Yours sincerely,
Shuanglin Gui
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I'm satisfied with the authors' response.
Author Response
Thank you very much for your kindly review and the positive feedback.
Reviewer 2 Report
The authors have improving their previous paper. But some fundamental aspects are not taken into consideration as a response to our review and some errors are also to correct for a better version of the paper submitted :
- first one : page 2 line 60 replace up to 10,000 mg/L by under 10,000 mg/L (brackish waters : see the book reference to add in the present article : Angelo Basile, Catherine Charcosset Editors, bRITICH LIBRARY WILEY, 2016, ISBN9781118739082, see chapter 7 M. PONTIE AND C. CHARCOSSET, p 165 to 192) p. 169 see table 7.2 for the definition of salted waters. Please add the reference of the book in your list of references
- The model in RO is not concentration polarization, it is Hydration-diffusion please check
- Concerning this model behind it you have to considered that the RO membranes are not controled by sieving exclusion but by their propensity to be hydrated by the polyamide active layer that is the more correct explanation of the mass transfer occuring in RO; aS A CONSEQUENCE YOU HAVE NOT TO COMPARE ONLY THE RADIUS OF THE IONS (Na+ vs NH4+) but their hydration enegies values and considered that a lower hydration energy for Na+ explain its higher rejection vs NH4+ : the size of a cation and also its energy of dehydration must be considered and must be cosidered to explain the selectivity between cations
- Concerning your response about SKK model, I'm not right with your response; could you please to reconsider it because in the SKK you have the solution-diffusion modle. In the SKK you add a convective part of the membrane that play i.e. in NF but it contains the RO mass transfer of course !
Author Response
Dear reviewer,
Thank you very much for your kindly review and insightful suggestions. We appreciate for your constructive comments below and have made revisions accordingly again. Also, we have enriched the background in paragraph 5 of the introduction chapter (lines in 89-107).
Below you will find our point-by-point responses to your comments. We hope that the revisions are acceptable and our responses adequately address the comments. Please see the attachment.
We would like to express our great appreciation to you for comments on our paper once again.
Yours sincerely,
Shuanglin Gui
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
The present paper study the possibilities to treat NH4-X compounds by RO. As a MODEL NH4Cl is study vs NaCl and the selectivity between NH4+ and Na+ discussed.
I consider that again Fundamentals knowledges are not enough master i.e. hydration effect on selectivity between Na+ and NH4+ apparent rejections observed. If the enthalpy of deshydration (REMARK : negative value due to the fact this is an energy that need to be given to the ion to help it to be dehydrated) of Na+ is higher than NH4+ ( in absolute value) with 420 kJ/mol for Na+ and 307 kJ/mol for NH4+ (différents data from those furnished in the paper ! ?), the order of rejection follow the order of deshydration enthalpy so RNa+ > RNH4+ as well observed on the Figures 2 and 3.
As a consequence on page 9 LINE please replace the values LINES 308 AND 309 by -420 and -307 for Na+ and NH4+ respectively
So I suggest to support those kowledge by the following papers :
Pontié et coll. Desalination 151 (2002) 267-274
SOMRANI et coll. Desalination 317 (2013) 184–192
Finally you can consider that the selectivity between Na+ and NH4+ is not based on size condideration but by hydration exclusion (like a new solvent, water in the membrane is not as water in the bulk !).
Author Response
Dear reviewer,
Thank you very much for your kindly review and insightful suggestions. We really appreciate for your constructive comments below and have made revisions accordingly once again.
Below you will find our point-by-point responses to your comments. We hope that the revisions are acceptable and our responses adequately address the comments.
We would like to express our great appreciation to you for comments on our paper once again.
Yours sincerely,
Shuanglin Gui
Author Response File: Author Response.pdf
