Polyaniline/Bi12TiO20 Hybrid System for Cefixime Removal by Combining Adsorption and Photocatalytic Degradation
, Noureddine Nasrallah 1, Hamza Kenfoud 1, Khaled Wassim Bourkeb 2 and Ahmad K. Badawi 3
Round 1
Reviewer 1 Report
This manuscript reported the PANI/BTO combination/hybrid system for the removal of CFX in a good structure. Materials were characterized fine and the mechanism of CFX removal was explained well. I suggest a publication after the questions below have been addressed.
1. Abbreviation of CFX (Cefixime) should be explained where it shows first in the manuscript, it should be added into the abstract section in a similar way to PANI/BTO.
2. Definition of k1 (actually K?)was explained in line 211, however, it’s not shown in Eq (4).
3. In Figure 8(a), the absorption efficiency reached the peak near 60 min and it decreased after that as shown up to 80 min. The authors claim that the ‘the adsorbent has achieved equilibrium between the adsorption and desorption’. Actually, the data at 60 min can also be described as an outlier according to the tendency of the curve. Either the error bar for each data point or more data (e.g., 0 – 100 min) is suggested to consolidate the statement.
4. The unit of k in Eq (5) was determined as sec-1, it’s better to transfer into min-1 to be constant with Eq (4) and Figure 8(b).
5. What’s the point of using 0.5 g/L of PANI and 1.5 g/L of BTO hybrid system to achieve 94.95% removal efficiency when 1.0 g/L of PANI can already achieve 89.65% removal efficiency in a much shorter time of treatment (110 min vs 60 min) with the advantage of process simplicity (without making and mixing with BTO). Let alone that the gap in removal efficiency might be narrowed down at higher absorbent concentration (e.g., 1.5 g/L of PANI). From this perspective, the authors may add statements illustrating the importance of decomposing CFX with the help of BTO to consolidate the introduction of BTO into the hybrid system.
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Reviewer 2 Report
[ChemEngineering]: Manuscript ID-ChemEngineering-1899751-Reviewer Report
Fortunately, this paper is suitable for publishing in ChemEngineering after minor revision to the following:
1. line-138: 1.5 mg/L (optimal) change into 1.5 g/L.
2. line-183: Could you add and explain the XRD diffractogram of the hybrid PANI-BTO composite in Figure 6?
3.line-286: Please change into the lowest unoccupied molecular orbital (LUMO).
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Reviewer 3 Report
The authors presents a manuscript dealing with Polyaniline/Bi12TiO20 hybrid material for Cefixime removal by combining adsorption and photocatalytic degradation.
This paper seems to be an upgrade of a recent paper of the same authors “High efficient Cefixime removal from water by the sillenite Bi12TiO20: Photocatalytic mechanism and degradation pathway” published on Journal of Cleaner Production, 330 (2022) 129934.
However, the approach used for the removal of antibiotics by a combination of both adsorption and photodegradation processes is not innovative, not convincing, as described by the authors, and poorly treated.
Below, I report some suggestions to help the authors to enhance the quality of their work to resubmit the manuscript. However, in my opinion in this form the manuscript cannot be accepted for publication on ChemEngineering.
1) The coupling of different techniques for pollutants abatement in wastewater has been investigated by several authors by different approaches.
In this regard, the introduction has to be properly expanded, introducing recent papers that applied methods similar to those reported from the authors (adsorption by PANI powder followed by photocatalytic degradation), for example “C. Cionti et al., Combining pH-triggered adsorption and photocatalysis for the remediation of complex water matrices, Journal of Environmental Chemical Engineering 10 (2022) 108468. https://0-doi-org.brum.beds.ac.uk/10.1016/j.jece.2022.108468”
2) It is not clear what is the real advantage related to the coupling of both adsorption and photocatalytic degradation of pollutants. In fact, the methods based on adsorption phenomena consist in the mass transfer of the pollutants from the solution to proper sorbents (here PANI) that gradually reach saturation levels, after which they must be regenerated. During the regeneration processes the pollutants are desorbed from the materials and sent to proper plants for the final treatment, whereas the sorbents undergo proper treatments (thermal and/or chemical processes, etc.), when possible. All these steps increase the costs of the global process.
On the contrary, AOPs (including photocatalysis) represent valid alterative, reaching high levels of mineralization. The authors should explain in more detail the real advantages related to the use of coupled system.
3) In the paragraph 2.4. the authors describe the PANI/Bi12TiO20 system as a hybrid system. This is not correct. In fact, a hybrid material is not a simple physical mixture of different components but innovative structures that show new and advanced properties if compared to those of the bare constituents. As a consequence, also the title has to be properly modified.
Moreover, the choice of the 75/25 ratio for the PANI/Bi12TiO20 is not clear. The optimization investigation is not reported.
4) In the section results the characterization data are poor and those of the PANI/Bi12TiO20 mix are completely missing. In particular, for PANI and PANI/Bi12TiO20 FT-IR and Raman studies must be carried out, along with SEM and TEM investigations. These investigations will permit to identify possible interaction between the inorganic component and the polymer.
5) On page 6 lines 197-199 the authors report “This value was selected as an ideal adsorbent dose because it has a good adsorption efficiency and did not remove all Cefixime concentration and that is why it was selected”. On the basis of the results, this dose is able to remove almost the 80% of pollutant. Why is this percentage the most convenient for the adsorption process?
On page 6 lines 199-202 the authors affirm “Another critical point about the adsorbent dose is to select as low as possible to not increase the opacity of the solution, which decreases the light penetration due to a scattering effect for an expansion of the dose, this effect can decrease the catalyst's efficiency after in photocatalysis process”. However, before the addition of the photocatalyst the adsorbent is remove from the solution. Therefore, how does the selected dose can affect the opacity of the solution during the subsequent step?
6) Concerning the results obtained by the use of the mechanical mix PANI/Bi12TiO20, the authors hypothesize a possible synergistic effect between the two components. It is more realistic to take into consideration that in the presence of the mix the two processes (adsorption and photocatalysis) concur from the beginning for the pollutant abatement.
Moreover, on pages 9 and 10 the system PANI/Bi12TiO20 and its photocatalytic properties are discussed as for heterojunctions without any experimental data regarding the band gap value, DRS spectra, etc. It is important to remember that PANI/Bi12TiO20 is not a heterojunction system but a mix of two materials not thermally treated.
The higher efficiency of the mix PANI/Bi12TiO20 is justified as follows: “Another aspect that can be a reason for this increase is the ultra-fine nature of the mixture, where the polyaniline is always agglomerate when it is alone; however, by mixing it with the catalyst BTO, it gets an ultra-fine nature. This has a major role in increasing the adsorption effect by increasing the specific surface area of the adsorbent”. These claims must be proved on the basis of experimental data.
7) Recycling tests are fundamental to affirm the validity of the hybrid system.
Author Response
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Reviewer 4 Report
The comments are in the attached file.
Comments for author File: Comments.pdf
Author Response
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Round 2
Reviewer 3 Report
The authors have improved the work, but there are still major issues to be solved.
1) A proper characterization of the materials is fundamental to discuss their properties and activity. This aspect can't be faced in a future paper.
SEM, TEM and FT-IR investigations are needed to justify the obtained results.
2) The authors report that the band gap investigations have been in a previous article and that are not discussed here to avoid overlap. However, since band gap values are crucial for photocatalytic materials, this aspect must be citated in the present work.
In my opinion without this modifications the present work cannot be accepted for publication.
Author Response
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Reviewer 4 Report
Thank you for the explanation. I believe the work may be published in Chemical Engineering.
Author Response
Dear Reviewer 4: We deeply appreciated your valuable comments and constructive suggestions which are much beneficial to improving the scientific quality of this manuscript. We also thank the reviewer for appreciating our work. Thank you very much.
Round 3
Reviewer 3 Report
Accepted for publication
