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Article
Peer-Review Record

Adsorptive Removal of Iron and Manganese from Groundwater Samples in Ghana by Zeolite Y Synthesized from Bauxite and Kaolin

Water 2019, 11(9), 1912; https://doi.org/10.3390/w11091912
by Bright Kwakye-Awuah 1,*, Baah Sefa-Ntiri 2, Elizabeth Von-Kiti 3, Isaac Nkrumah 1 and Craig Williams 4
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Reviewer 4: Anonymous
Water 2019, 11(9), 1912; https://doi.org/10.3390/w11091912
Submission received: 13 May 2019 / Revised: 12 June 2019 / Accepted: 15 June 2019 / Published: 13 September 2019
(This article belongs to the Special Issue Technologies Developing in Heavy Metals' Removal from Water)

Round 1

Reviewer 1 Report

Dear Editor,

I think authors put genuine effort to address my previous concerns. Therefore, I think the quality of this manuscript has increased significantly to be accepted in this current form.


Thank You

Author Response

Dear Reviewer

Thank you for the comments to the editor recomending acceptance of the manuscript.

Reviewer 2 Report

This manuscript reported the removal of iron and manganese ions from groundwater using synthetic Zeolite Y. The authors have conducted a series of adsorption studies to analyze the adsorption behavior of synthetic zeolite, and the zeolite exhibited quite high removal efficiencies for both iron and manganese species from groundwater. Nonetheless, there seems much room to improve in presenting and explaining dataset. Also, the authors haven’t much included related references regarding the adsorption behavior of synthetic zeolites. The detailed comments are listed below without a specific order.

1.      Line 32: The speciation of iron and manganese in the groundwater should be addressed in the manuscript, which can be referred to the following literature: Environ. Sci. Technol., 1998, 32 (18), pp 2657–2664.

2.      Figure 1, table 1: According to the XRD and the elemental composition analysis, the synthetic zeolite seems to contain impurities which are able to affect the absorption behavior as described in line 62.

3.      Figure 1: What does the simplicated spectrum mean in the inset? What is the obtained experimental spectrum? The figure 1 looks very complicated.

4.      Table 1: The authors need to explain how the elemental compositions were calculated by EDX analysis.

5.      Figure 2 has the error, where the right figure should be relocated.

6.      Table 2 should be retitled, as it shows the water quality ‘after’ the treatment with the zeolite. What does ‘b.d.’ stand for?

7.      Line 378: The authors have used the groundwater throughout the adsorption studies, however, there could be partial oxidation of iron species in atmospheric condition to change the initial concentration of iron by time. The authors can clarify this point by showing the control experiment of iron concentration change in the groundwater under atmospheric condition.

8.      Line 424: The pH change by the hydrolysis of zeolite indicates the possible structural change of zeolite. How’s the XRD spectrum of recycled zeolite? Also, would such a pH change affect the speciation of tested metal ions?

 

With this stands, this manuscript needs a major revision for the publication in Water.


Author Response

Dear Sir,

Please, find the attached the responses to your comment.


Thank you.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments on manuscript entitled Adsorptive Removal Iron and of Manganese from groundwater samples in Ghana by Zeolite Y Synthesized from Bauxite and Kaolin

 

The authors reported on the adsorption of iron and manganese from groundwater using Zeolite Y. The topic follows the scope of this journal, and can be considered for publication on this journal with following suggestions addressed:

1.      Equation 1 should be revised, as it is not an equation

2.      All significant figures should keep in consistent

3.      Standard errors should be calculated to confirm the fitness of the model. Following references can be considered: Materials Research Bulletin 111, 238-244, 2019

4.      The quality of all figures in this manuscript should be improved

5.      A list of symbols should be added after the conclusion.


Author Response

Dear sir,

Please, find the attached the responses to your comments.


Thank you.

Author Response File: Author Response.docx

Reviewer 4 Report

Dear the authors:

Thanks for your submission.

The authors did not prepare this work carefully. Therefore, this work must be significantly improved and thoroughly revised before it is suggested to publish in the journal. My detail comments are listed as follows:

 

+ Abstract: “The samples were exposed to characterized  zeolite Y by x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, Fourier transformed spectroscopy and thermos gravimetric analysis.” …………. No data for thermos gravimetric analysis ?

+ “Several techniques and methods have been employed in the removal of manganese and iron from water, including aeration, settling, filtration and ion exchange [10, 11, 12]”…. The citation should be one by one, such as aeration [10], settling [11-12]……..

+ Table 1, this is the atomic percentage?

+ Please add some labels in Figure 4, i.e., —SiO for 947 cm-1.

+ Figure 5, please add the fitting line of the best fit model, similar for Figure 6.

+ Please add the adsorptive experiment conditions for Figure 5

+ In the 21th century, the non-linear method needs to be applied to correctly calculate the parameters of the models in adsorption kinetics and isotherms [1]. Please remove Figures 7–12 to avoid the repeated information, this will make the papers to become more concise.

+ Qe must be mg/g, not mg/L (see Table 5), the authors need to revise carefully the unit of parameters.

+ Did the authors conduct the adsorption experiments in triplicated or duplicated? Please add the SD bar in the data of adsorption study.

+ “The ? values at equilibrium are greater than 1, reflecting a favorable adsorption????????????? Please read the papers [1, 2]

+ To avoid some potential mistakes, the authors should read the papers [1, 3]

+ Discussion is relative weak is too general. Please revise this Section thoroughly.

+ Please give some updated references from 2017 to 2019.

+ Please give a table for comparison the Langmuir maximum adsorption capacity of adsorbent in this study and in the literature.

+ Please give some discussion on the potential adsorption mechanisms.

+ Any previously published data that were re-used in this study need to be cited. The authors should check again.

+ English should be improved.

+ Some mistakes that should be revised, such as 98% (not 98 %; no space); 100 °C (please use “Alt+0176” for °); Na+ , K+ , Ca2+, and Mg2 (a comma before “and”)…………

 

1.         Tran, H.N., et al., Mistakes and inconsistencies regarding adsorption of contaminants from aqueous solutions: A critical review. Water Research, 2017. 120: p. 88-116.

2.         Hai, T.N., Comments on “Effect of temperature on the adsorption of methylene blue dye onto sulfuric acid–treated orange peel”. Chemical Engineering Communications, 2017. 204(1): p. 134-139.

3.         Tran, H.N., P.V. Viet, and H.-P. Chao, Surfactant modified zeolite as amphiphilic and dual-electronic adsorbent for removal of cationic and oxyanionic metal ions and organic compounds. Ecotoxicology and Environmental Safety, 2018. 147: p. 55-63.

 


Author Response

Dear Reviewer,

Thank you for your comments. Attached is the response to the comments you raised.


Kind regards.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors have tried to reflect all the comments suggested by the reviewer. The manuscript can be accepted in the present form. 

Author Response

Dear reviewer,

Thank you for the comment.


Kind regards.

Reviewer 4 Report

Although the authors have replied that most of my comments, most replies and revisions are not satisfactory. In addition, the authors did not prepare a revision carefully. There are too many new mistakes. Therefore, to maintain the quality of published paper in the ISI journal, a major revision is required.

I suggested that the authors should thoroughly revise the manuscript as my previous suggestions before submitting the revised manuscript again to the journal.


Author Response

Dear Reviewer,

Thank you for the comments.


Kind regards.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.


Round 1

Reviewer 1 Report

In this manuscript, authors studied on adsorptive removal of iron and manganese from groundwater (Ghana) using their synthesized Y scheme Zeolite from Bauxite. Overall manuscript quality needs many improvements based on my following comments.

1.       Abstract: Line 15. Specify sample numbers. Lines 20-21 are not correct.

2.       Each abbreviation should state at first time.

3.       Section 2.2: Excessive chemicals have been used to convert Bauxite to Zeolite. The process looks like preparation of activated carbon. Then how realistic will be the process for practical application.

4.       Increasing in pH above 7.0 will automatically lead to deposition of most of the heavy metals. Explain in regards to design the whole procedure.

5.       Characterization part: Authors need to proof to claim their findings. Therefore, cite appropriate reference to support the claims.

6.       I have not find any standard deviation in all tables. How many times those experiments carried out is not clear from discussion.

7.       For heavy metals adsorption, using pH above 7.5 is not good as they will automatically deposit most of the heavy metals (Fig. 6).

8.       Fig. 5. I think the actual graph should not be like that as increase in concentration should either increase the q value or should remain same q value. Explain.

9.       Lots of figures and tables have been taken into main manuscript. I think authors can reduce those number by half of them.

Therefore, I recommend a major revision.

 


Comments for author File: Comments.docx

Author Response

Dear Sir

Thank you for reviewing our manuscript. Your comments have been considered and responded to accordingly.


Kind regards.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments.


-Elemental composition of zeolite.Are there heavy metals?.

-Is there any leaching of zeolite?.

-Is there any competitive advantage to synthesize a zeolite versus other natural geo/biomaterials?

-Include a comparative table  with other materials.

-Include errors in the parameters (slope/intercept) of fittings.

-Why heavy metals are not determined (nd) in table 3.?.

-Correct equations in the disscussion.For example,proton is not balanced in line 312.

Author Response

Thank you for reviewing our manuscript. Your comments have been considered and responded to accordingly.


Kind regards.


Author Response File: Author Response.docx

Reviewer 3 Report

Synthetic zeolites have been reported and applied for water treatment. However, the introduction does not review any of the previous studies.

Another important missing information in the introduction relates to alternative methods for the removal of iron and manganese. A new technology needs to be assessed in the context of current alternatives. 

A better description of the materials is needed, for examples, sodium hydroxide (pellets, solution,?). 

The methods for water characterization will be better presented in this section than in the results. 

Equation 1: show full equation, including  q, q= (...

The authors claim that since the adsorption mechanism will be the same for all samples, adsorption studies were only conducted with one sample. This is a major flaw of this work. The adsorption parameters will be affected by the water matrix, and therefore the values obtained for one particular groundwater will not necessarily be valid for the others. There are no control experiments or systematic variation of water parameters (pH, ionic strength, other ions concentrations) so generalization can be made. 

The detailed description of the models is not needed for the intended audience.

Table 1: compounds are listed under the element columns, and the atomic % shows (?) the percentage composition of those compounds. 

FTIR and XRD controls of Zeolite Y could help the discussion. 

Results:

It is not clear why the authors used the zeolite three times. Was it possible to use it a forth time? 

Can the capacity be estimated? Can the material be regenerated and reuse? 

Figure 5 shows an isotherm, but it is not clear from the caption. 

Figure 6 shows the pH variation with time during adsorption, and not the effect of pH on the adsorption as the caption reads.

Figure 7 and 10-12 can be omitted.

As I explained above, the experimental work presented in this article is not enough to support general conclusion presented here. This article may be resubmitted after significant revision and addition of experimental results.Given the extent of experimental work needed for this article to provide interesting information to readers, I recommend rejection in the present form. 

Author Response

Thank you for reviewing our manuscript. Your comments have been considered and responded to accordingly.


Kind regards.


Author Response File: Author Response.docx

Reviewer 4 Report

Overview and general recommendation:

The authors of the manuscript entitled “Adsorptive Removal Fe2+ and of Mn2+ from groundwater samples in Ghana by Zeolite Y Synthesized from Bauxite and Kaolin” aim to evaluate the adsorption efficiency of Zeolite Y for removing Fe2+ and Mn2+ ions from groundwater.  For this reason, they synthesized zeolite from bauxite and kaolin and they conducted adsorption experiments with contaminated groundwater.

 

The overall study scope is interesting as zeolites are promising materials for the removal of heavy metals from aqueous solutions. However, there are significant issues related to both text structure and scientific background that must be corrected in order the present manuscript to be published in the journal of Water.

 

Comments

-  You could add a small paragraph concerning the adverse effects of Fe and Mn on human health as afterwards you are referring to drinking water quality standards.

- In the Materials and Methods section, it is better to make two separate paragraphs for zeolite synthesis and adsorption experiments. In addition, you must include a paragraph about groundwater sampling and chemical analysis methods.

-  The columns of table 2 (parameter & method) can be attached to the supplementary material while the columns of drinking water standards and unit must be merged with table 3. In addition, you must include the detection limits for all the methods used for the determination of chemical parameters in table 3.

-Table 2 has missing values while you report some values with zero, this is not accurate. I suppose that zero values correspond to no detected values. What the columns before and after mean, be more specific.

- In the results, you must include a plot of removal versus contact time in order to show that equilibrium was achieved otherwise the kinetics that you performed are inaccurate.

-Discuss figure 5.

-  In the x axis of figure 6, why the maximum time is 8 minutes and not 120minutes?

- Why you used only the linearized forms of Langmuir and Freundlich equations? You must fit also the non-linear equations to consider the weight of the experimental points in order to fit better your experimental data. You could also add a small table to compare the calculated parameters from the linear and non-linear equations.

-Table 5 and Table 6 can be merged.

- Figure 11 lacks axis titles.

- Discussion section is short, you must discuss further your results with the literature.

- You must correct vocabulary mistakes.

 

 

 


Comments for author File: Comments.pdf

Author Response

Dear Sir

Thank you for reviewing our manuscript. Your comments have been considered and responded to accordingly.


Kind regards.


Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear Editor,

Authors have replied all of my concerns and did necessary corrections. I suggest to accept this manuscript.


Thanks for inviting me to review this manuscript.


Regards 

Mohammad Boshir Ahmed 


Reviewer 2 Report

Accept

Reviewer 4 Report

The authors performed the necessary revisions so I suggest that the present manuscript can be published in the journal of Water.

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