The Suitability of Methylene Blue Discoloration (MB Method) to Investigate the Fe0/MnO2 System
, Ghinwa Alyoussef 2, Nadège Gatcha-Bandjun 3, Willis Gwenzi 4 and Chicgoua Noubactep 2,5,6,*
Round 1
Reviewer 1 Report
The novelity is belong to Fe/Mno2/sand system only but not belong to MB method;
The authours not describe chemical, mineralogical, morhological and adsorbtional characteristics of used systems;
Images of curves on fig . 2 and 3 are detoriation level of article;
The composition and structures of sand are influence on its properties.
Author Response
Comments 1: The novelty is belong to Fe0/MnO2/sand system only but not belong to MB method.
Responses 1: We have used the MB method the clarify the operating mode of the Fe0/MnO2/sand system, thanks!
Comments 2: The authors not describe chemical, mineralogical, morphological and adsorbtional characteristics of used systems.
Responses 2: The MB method describes the dynamic of the systems and considers the intrinsic characteristics of each materials. There is no unified protocol to assess the reactivity of Fe0 or MnO2. There is no reference material as well. So the characterization is almost useless since obtained data cannot enable comparison to independent results. For the further development of the Fe0 remediation technology, at least a standardized method for the intrinsic reactivity is urgently needed.
To address the concern of the reviewer: MB adsorption onto sand is disturb by in-situ generated iron corrosion products (Fe0/sand system). When MnO2 is added the modification is compared to the operational reference: Fe0/MnO2/sand vs. Fe0/sand. Herein we have varied the Fe0 loading to have different amount of FeCPs in the system after 7 days.
Comments 3: Images of curves on Fig. 2 and 3 are deterioration level of article;
Responses 3: This concern is not clear to us, we have used the same program (Origin 8.0) for all three figures.
Comments 4: The composition and structures of sand are influence on its properties.
Responses 3: We fully agree, we have use the same sand for all experiments, and even the same loading. The dynamic of FeCPs generation is semi quantitatively monitored.
Many thanks for your evaluation!
Reviewer 2 Report
The aim of the article is to present a research study about using methylene blue discoloration (MB method) to characterize the Fe0/MnO2 system.
The topic of the paper is very important due to the fact that Fe0/MnO2 systems are important in aqueous solutions and polluted waters remediation.
The topic is suitable for the journal. It is of broad international interest.
The structure of the article fulfills the structure of a research article. The paper is properly organized.
The paper’s title is brief and reflects the theme of the paper. The abstract is informative and completely self-explanatory, briefly presents the topic, states the scope of the review, and points out major findings and conclusions.
The introductory part provides sufficient background information for readers in the immediate field to understand the problem that this study addresses. It clearly states the problem being investigated. The purpose and objectives of this study are clearly stated. The novelty of the study should be emphasized.
The authors present in the Materials and Methods part the reagents, the experimental device, the experimental method and the equipment used.
The authors accurately explain how the data were collected. The article identifies the procedures followed. They are ordered in a meaningful way. The methods and protocols are described in sufficient detail in order to allow another researcher to reproduce the results.
The following sections are suitable for the topic of the paper.
In the Results and Discussion part, the authors present and interpret the results of the experiments performed. The authors related their findings to other researches results.
The paper ends with a section regarding conclusions. In this section the authors mentioned the major and specific conclusions of their research study. The quality of data’s interpretation and conclusions is suitable.
The abbreviations and nomenclature are used according to the applicable international standards and rules. The indexes for chemical formula are written correctly.
The figures and tables are numbered sequentially, and they are clearly labeled and positioned close to the relevant text. Titles of figures and tables are brief and informative. All the figures and tables included are referred.
The references are accurate and relevant for the subject of the paper. The references are up to date.
The English language is appropriate and understandable. The text is presented in a manner that scientists in other disciplines will understand.
The used measurement units is according to the International System. The length of the paper is proper in keeping with its importance.
I have some minor suggestions for the authors to improve the level of the paper. The authors should check the entire paper to be written with the same font type. They also should check all the indexes of the chemical formula in reference part.
In my opinion, the work provides an advance towards the current knowledge.
Taking into account all that I already mentioned I suggest publishing the paper in Processes after minor changes.
Author Response
Many thanks for this evaluation!
I have some minor suggestions for the authors to improve the level of the paper. The authors should check the entire paper to be written with the same font type. They also should check all the indexes of the chemical formula in reference part.
In my opinion, the work provides an advance towards the current knowledge.
Taking into account all that I already mentioned I suggest publishing the paper in Processes after minor changes.
Thanks. We have checked and corrected the font as per journal template, and chemical formula in the reference list.
Reviewer 3 Report
In my opinion the method which was used in the experiments does not allow to drug reliable conclusions. The results of the tests should be measured more frequently to find real difference in reactions for each tested variant. I am afraid that if you measured Fe and MB concentrations using the spectrophotometer without filtration of the samples the results are disturbed by the particles which influence the measurements.
Author Response
Comments 1: In my opinion the method which was used in the experiments does not allow to drug reliable conclusions.
Responses 1:
We have considered the remark, but in our view the comment lacks details to enable us to provide a detailed response. For example, it is unclear which aspects of the method does not provide reliable results. The manuscript tests an established method (MB method) to investigate the Fe0/MnO2 system, which has been reported in several earlier studies, and concludes that Fe0 retards the availability of free corrosion products. This is in-tune with literature reports based on aqueous and solid phase analysis for several contaminants. So it is not clear to us what is wrong here.
Comments 2: The results of the tests should be measured more frequently to find real difference in reactions for each tested variant.
Responses 2:
This is not clear to us, all the experiments were performed for 7 days. For Fe0/H20 monitoring periods in the order of days provide more reliable results than short-term experiments conducted for a few hours. In fact, it has been shown that short-term studies running for a few hours give misleading results with respect to Fe0/H2O systems. This is what motivated the monitoring period. Note that the variable (X values) on the figure are material loadings (not time).
Comments 3: I am afraid that if you measured Fe (lmax = 510 nm) and MB (lmax = 665 nm) concentrations using the spectrophotometer without filtration of the samples the results are disturbed by the particles which influence the measurements.
Responses 3: There are no particles since shaking at 75 rpm cannot mediate any particle suspension. This experimental protocol was tested, validated and has been successfully used for 20 years already.
Many thanks for your evaluation!
