Simple and Rapid Synthesis of Organically Modified Natural Acid Clay for the Adsorption of Anionic and Cationic Dyes

Round 1

Reviewer 1 Report

The manuscript presents the studies of organically modified natural acid clay applied for the adsorption of anionic and cationic dyes. The results presented in the manuscript are interesting. However, I have some questions/remarks that in my opinion should improve the quality of the manuscript.

1)      More information about clay used, including the types of mineral components, CEC potential, chemical composition, should be presented and discussed in the revised version of the manuscript?

2)      Were the adsorption experiments conducted with the selected grain fraction of the clay? Is this parameter important in these studies?

3)      Have authors used any detection system for analysis of gas products formed in TG analysis? In which way evolutions of water (evaporation of physically adsorbed water and water produced by clay dehydroxylation) and products of alkylamine decomposition were determined?

4)      Have author verified reproducibility of clays synthesis as well as reproducibility of adsorption studies?

Author Response

Please find the separate sheet.

Author Response File: Author Response.pdf

Reviewer 2 Report

The work needs correction:

1. FTIR spectra of the sorption products should be presented and discussed

2. Thermal decomposition spectra of the sorption products should be presented and discussed

3. mechanism sorption of the dyes should be discussed

Author Response

Please find the separate sheet.

Author Response File: Author Response.pdf

Reviewer 3 Report

The study reports on a successful modification of a local origin natural clay with organic spacer molecules in order to enhance its sorption properties towards organic pollutants.

The experimental study is done accurately, and the analysis of the sorption capacities in the function of the modification parameters, and the correlation with the modified clay structure is rather instructive for future researches. I can recommend the paper for publication in Minerals, after a revision.

1. The visual correlations of the fitted linarized Langmuir and Freundlich isotherms look similarly good, in spite of the somewhat lower determination coefficients for the latter model. However, very few points have been used in the studied concentration range, which may be too narrow for revealing the prevalent behavior of the sorption mechanism. Therefore, it would be instructive to see the quality of the fits in their original, not scale-transformed representations. The superiority of the Langmuir fit should be shown convincingly, either by such representation, or by repeating the sorption measurements in an extended concentration range, especially if further characteristics, i.e. the separation factor, is derived from the fitted data.

2. Comparison of the properties of the studied clay with those of some recently reported mesoporous silica sorbents may be added, as such materials are closer in their composition to the clays, than many of the sorbents reported in Table 6. E.g., these studies:

https://doi.org/10.1016/j.chemosphere.2020.127737

https://doi.org/10.1007/s10934-019-00821-y

https://doi.org/10.1016/j.matpr.2018.02.066

Author Response

Please find the separate sheet.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

In by opinion the manuscript could be published in the present form.

Author Response

Thank you very much for your constructive comments to improve the quality of the manuscript.

Reviewer 2 Report

The paper can be published .

Author Response

Thank you very much for your constructive comments to improve the quality of the manuscript.

Reviewer 3 Report

Author has improved the study according to suggestions, and the paper is suitable for publication. Minor editions can be recommended.

ref. 48 – The presently used form is a commonly occurring mistake in citing this paper.

The original paper was written by H. Freundlich, and the journal is the german Zeitschrift für Physikalische Chemie.

https://doi.org/10.1515/zpch-1907-5723

see also:

https://en.wikipedia.org/wiki/Freundlich_equation#cite_note-3

The proper citation should be used.

Author Response

Thank you very much for your valuable comments. According to your advice, Ref. 48 has been revised as follows:
(Line 472) 48. Freundlich, H. Über die Adsorption in Lösungen. Z. Phys. Chem. 1907, 57, 385–470. https://doi.org/10.1515/zpch-1907-5723.
Thanks again for your time.