Activated Carbons Derived from Different Parts of Corn Plant and Their Ability to Remove Phenoxyacetic Herbicides from Polluted Water
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe title of the manuscript needs revision.
How did the authors obtain the correlation between adsorption efficiency and hydrophobicity?
It is recommended that the authors briefly mention the mechanism of activated carbon adsorption of pollutants in the abstract section. Factors affecting the adsorption related to this paper should also be mentioned.
The detailed data statistical analysis methods and software must be mentioned in 2. Materials and Methods.
I must express my concern that the manuscript is deficient in raw data. The authors' strategy centered on the application of multiple mathematical models to verify and gauge the efficiency of activated carbon adsorption, which regretfully restricted my capacity to undertake a detailed assessment of the research.
Of greater concern is the absence of experimental replication and the missing standard deviation for a significant number of data points in the provided charts. This omission inherently complicates the critical evaluation of the work.
Author Response
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Reviewer 2 Report
Comments and Suggestions for AuthorsHere re my comments:
1- Activated carbon from biomass wastes has been widely used to adsorb different organic compounds from wastewater. The novelty and signiface of this study should be clarify in the abstract.
2- Abstract does not included any data related to the adsorbent characteristics or adsorption capacity.
3- Reusibility of an adsorbent is very important factor for commercialization of that adsorbent. Refer to the following ref and confirm the recycling ability of your adsorbents. 10.1016/j.molliq.2018.12.050
4- Repeat your experiments and add error bar to all graphs.
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe study explores the use of activated carbon derived from corn biomass to adsorb phenoxyacetic acid and its chlorinated derivatives from water. The study is original and well-executed, offering valuable insights into the use of activated carbon from corn biomass for adsorbing phenoxyacetic acids and their derivatives. The rigorous analysis and clear correlation between adsorption performance and carbon structure highlight the study’s significant contributions to sustainable water treatment solutions.
The following can be improved:
1. The last paragraph of the introduction, you should summarize the main objectives of the study and its anticipated contributions. It is important to articulate the research gap being addressed and highlight the potential impact of the findings.
2. It is not necessary to provide the equations for the calibration curves in methodology.
3. Which models where used to estimate micropore and mesopore volume of the samples? It should be detailed in methodology.
4. In Fig. 2, it does not make sense to start the y-axis (qt) in the negative range.
5. The components of Figs. 2-6 could be more effectively presented in a single line rather than in a column format.
6. To improve the article, SEM images of the sample should be presented.
Author Response
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Reviewer 4 Report
Comments and Suggestions for AuthorsIn this study, the authors prepared activated carbon from corn biomass (different parts) and studied the ability of AC to remove different derivatives from the herbicide phenoxyacetic herbicides. Adsorption kinetics, adsorption isotherms, and the effect of solution pH were investigated.
The idea is novel and the manuscript could be improved from the following comments:
1. Introduction: In the objective part the authors should state their results. It is so general.
2. SEM analysis should be introduced to activated carbons (ACs) from corn kernels (AC-K), corn leaves (AC-L), and corn silk (AC-S) to show the pore size of AC.
3. As there is a big difference in the adsorption capacity at pH=2 than other pH values, Zeta potential measurements in differ pH should be carried out for AC to indicate the charge appears on the surface of AC that affect the adsorption through electrostatic attraction between herbicide and AC.
4. The values of R2 are high for AC-K, AC-L and AC-S when applying e PFO and PSO kinetic models. Why did you choose pseudo-second-order model as adsorption kinetics model the system follows?
5. In section 3.2.3. Effect of Solution pH, please explain the charge of the adsorbent and adsorbate at pH 2 and the expected mechanism for enhancing the adsorption process at this value.
6. It was stated that the AC charge at pH 2 is positive and the herbicide was undissociated/if the herbicide is dissociated it will have a negative charge and attract more to AC which can happen at pH 5 for example. How can you explain the decline at pH5?
7. Please explain Why the hydrophobicity of the adsorbate enhanced the adsorption capacity?
Comments for author File: Comments.pdf
Author Response
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Reviewer 5 Report
Comments and Suggestions for AuthorsThe authors have reported the fabrication of activated carbon from different parts of corn plants for use in water treatment to eliminate phenoxyacetic herbicides. The investigation has been conducted thoroughly. The manuscript itself is written clearly and understandably. The references cited in the paper are current and relevant to the presented results. The conclusions drawn from the results are sound, but there are some issues that need attention.
Section 2.3. Since the UV-VIS spectrophotometer has been used to determine the concentration, the Beer-Lambert law has been employed to obtain the calibration curves. Could the authors provide the physical meaning of the obtained intercepts in the calibration curve equations?
There should be an explanation of tables 2 and 3 headers in the table title and the text. Not all of the physical values used as row titles in the table have been mentioned in the manuscript.
In the section on adsorption kinetics investigation, the Boyd model was used to estimate the rate-limiting diffusion step in the adsorption process. The criterion used to determine the rate-limiting step was the proximity of the intercept value to zero. In nearly half of the cases, the intercept value has been less than 0.1. The authors concluded that the intercept is different from zero, indicating that film diffusion is the rate-limiting step. However, while these values are mathematically different from zero, they are very close to zero in physical terms. Upon visual inspection of the graphs in Figure 5, it can be observed that some of the plotted lines start from the origin. It rather seems that the rate-limiting step could vary depending on both the herbicide and the activated carbon used.
The R-squared values for the Boyd plot fit are not provided. However, upon visual inspection, it is evident that the dependence of the Boyd constant on time is not linear. This raises further questions about the conclusions drawn from this model. It would be safe to assume that both interparticle and film diffusion influence the adsorption process. However, depending on multiple factors, no single step is rate-limiting for all of the investigated systems.
Author Response
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Round 2
Reviewer 4 Report
Comments and Suggestions for AuthorsThe authors have addressed all the revision points.
Comments on the Quality of English Languagegood
Reviewer 5 Report
Comments and Suggestions for AuthorsThe authors have made an effort to improve the manuscript. The main issues from the initial submission have been addressed.
