Recyclable Adsorbents for Potash Brine Desalination Based on Silicate Powder: Application, Regeneration and Utilization
, Aruzhan K. Kenessova 1,2, Bagashar B. Zhaksybai 1,2, Diana N. Dauzhanova 1,2, Yitzhak Mastai 3 and Gulziya A. Seilkhanova 1,2,*
Round 1
Reviewer 1 Report
The subject of the presented investigation is actual, with a high applied significance. The objects and investigation methods are adequately chosen to solve the problem of the research. However, the first comment is about the formulating the aim of the research (paper).
The authors did not specify the clear and specific aim of the carried out investigation, the results of which they intend to present for the audience of the journal Colloids and Interfaces. Instead, the authors presented an extensive dual purpose of the practical application of the obtained results, lines 64-66 «The aim is twofold – to simplify the process of obtaining sorbents while reducing the cost of separating minerals as well as to leverage disposal by reusing the soil saturated with trace elements as fertilizer». In your further detailing of the purpose of the research (lines 66-67) «Two issues are thus addressed – brine desalination by abundant SMP and its regeneration and utilization for fertilization» it is expected that you specify what exactly has been studied in the presented research to solve the problem of brine desalination. Obviously, you mean the creation of the sorbent by acid activation of silicate powder, its characterization and assessment of its efficiency in desalination, etc. This specific goal of the research should be posted as an aim.
Other comments from the review of the manuscript:
1. It is not clear from figures 1 and 2, and table 2 – which concentration of the acid was used for silicate treatment? Why the other data for samples treated by other concentrations of HNO3 did not represented? What was the effect of acid concentration on composition and properties of the samples?
2. Only starting from line 292 in Results and discussion section the authors considered the effect of acid concentration on sorption properties of materials. At this, in the phrase «It can be assumed that all possible changes in the structure appear at this amount of acid as greater concentrations do not improve sorption properties» (lines 301-302) the authors make an assumption about the effect of acid concentration on the structure of aluminosilicates, although this effect is well known for various natural aluminosilicates in a wide range of concentrations and conditions for acid modification. The explanations and the references to the literature are needed here, as well as the relation of these results to the XRD spectra presented in Fig. 1.
3. In the present view the structure of the article seems not fully logical. The authors begin to consider the Results&Discussion with the data on the transformation of structure, composition and other physical chemical properties of silicate sorbents, without substantiating the effect of acid concentration during processing. It would be more logical, first, to consider the choice of optimal conditions for the acid treatment of an aluminosilicate sorbent, and then, for the optimal sample, to present in detail the transformations of its composition, structure, and features of adsorption (kinetics, equilibrium, thermodynamics).
4. Line 175 - Check the units of R - universal gas constant, Kelvin is missing…;
5. The chemical equations should be numbered. The equation at line 193 should be balanced.
6. The conditions of sample outgassing during the BET-measurements were not specified (duration and temperature).
7. The accuracy and reproducibility of the BET-technique make it possible to determine specific surface values only up to integer values. Therefore, the values of S given should be rounded to integers, not to hundredths.
8. The authors say nothing on the change of carbon content in chemical composition of the samples (Table 3).
9. The authors attribute the sorption of ions by feldspars to physical adsorption, but its mechanism is mainly ion-exchange due to the structure and composition of the minerals (in phase composition of samples) capable of ion exchange and the composition of external solution. The conclusion of the authors contradicts the definition of physical adsorption.
10. It is not clear, how formula (1) was obtained? The value of CEC is missed, the units of equivalent mass and mass of sorbent are not shown. What is the final dimension? What is a factor of 10?
11. What is interesting to discuss and explain, is why namely K+ ions are sorbed to a greater extent than Na+?
12. The quality of Figures 4a-4f is very low, row markers for Na, K, Cl are not distinguishable, the type of markers should be changed and the quality of the figures should be improved. The legend in fig. 4b is hard to read.
13. Fig.4(a-f) is overloaded with data and subfigures. It is better two separate them into logical sections and discuss in more detail.
14. Lines 349-350 - the ARE equation source is missing and a misprint is present in this phrase.
15. Table S2 - It makes no sense to use the value of ARE, if its values ​​exceed 100% and amount to hundreds and even thousands of %.
16. The sorption isotherms for natural and acid treated silicates need to be compared, as well as the kinetic curves of sorption. Why did not you present these data for natural samples?
17. Why did you used different contact time for experiments at Fig.4a (the contact time is 3 hours)? From the kinetic curves in fig. 4e you deduced 2 hours.
18. Lines 369-370 has a wrong reference to TableS2 which represents parameters of isotherms modelling, but not the kinetic parameters.
19. The resolution of figures 5 is very poor. Digitals, markers, lines, designations should be increased and better resolved.
20. Fig.5a – it is not clear if all adsorbed amount of K+/Na+ desorbed or not? What was the extent of desorption as compared to sorbed value?
21.Lines 443-444 – a mistake “sodium ions” in sentence “Thus, AS can be used to selectively adsorb sodium ions from brine to produce K-form silicates that can be further assessed as a potassium nutrient source in 444 other applications”. References list does not follow the recommended rules from the journal. See Reference Formatting Guide at https://www.mdpi.com/authors/references DOI did not provided for the references.
22.The efficiency of brine desalination using samples S and AS did not exceed 20-38 % (Table 4). Are they effective for brine desalination? It is necessary to complete and explain this situation and how it be increased in case of using these materials.
The quality of english language use should be sligtly improved.
Past simple should be used insted of present simple along the text narration.
Author Response
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Reviewer 2 Report
The manuscript reports the recyclable adsorbents for potash brine desalination based on silicate powder: application, regeneration and utilization, which is interesting with great value. The manuscript is well organized and is recommend to be accepted after minor revision. Following are some comments.
1. About the application, the limit contents of Na and Cl in Potash fertilizers are suggested to be given.
2. Line 106-113, the related possible reactions during the cation-exchange capacity test are suggested to be discussed more.
3. There is a question about line 118“The pH was maintained by addition of HNO3 or NaOH.“. As the authors also care about the adsorption of Na, is it appropriate to use NaOH to adjust the pH?
4. Line 203, “according to the reaction” a number should be given for each equation.
5. Line 238-239 “). Notably, after treatment with 1 M HNO3 the content of Na, Ca and Mg decreases. “ According to the Table 3, the contents of Na, Mg increase. Please check.
6. For “Table 6. Kinetic parameters of Na + , K+ and Cl - ions adsorption onto AC.” The parameters such as k, q, R2 should also be given.
7. Figure 5. Effect of external factors on K+ /Na + desorption of from A: desorption rate is suggested to be given.
8. Some REFa. Are suggested to be cited to improve the manuscript.
A） https://doi.org/10.1016/j.seppur.2022.122499
B） https://doi.org/10.1016/j.jclepro.2023.136479
Author Response
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Round 2
Reviewer 1 Report
The authors fulfilled the review comments and significantly improved the quality of the papers.
The last comments left require minor revision:
1. The titles of figures 5, 6, 7 should be corrected as they represent the corresponding effects on the adsorption of ions (Na+, K+, Cl-) by AS and S sorbents, but not the adsorption of AS and S.
2. Fig.10 – the authors obviously mean “adsorption” instead of “absorption”?
3. The comment from the first review was not corrected, but it requires to be improved: “The accuracy and reproducibility of the BET-technique make it possible to determine specific surface values only up to integer values. Therefore, the values of S given should be rounded to integers, not to hundredths.”Please, correct specific surface values in line 271 and in Table 4.
4. The English stile and the tenses should be improved. The narration of the manuscript should be in the past tense but not in the present.
The english stile and the use of tenses should be improved. Do use past tense instead of present.
Author Response
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