Adsorption Ability of Soft Magnetic FeCo Alloys for Microplastics
, Pinhua Xia 1, Zhenming Zhang 3, Xianfei Huang 1,* and Xuetao Guo 4,*
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors described a study of ”Adsorption performance of soft magnetic FeCo alloys on microplastics". The studies addressed in this manuscript are to explore the removal potential of metal nano-adsorbents for microplastics (MPs) in water, but many questions in this manuscript have to be solved. The specific comments are as follows:
- In the abstract, the author mentions that the surface area is 132.31 m²/g, is it the external surface area that they are mentioning on page 9? How to find the micropore and the external surface area by t-plot could not be found in this manuscript.
- Refer to Point 1, is the surface area of soft magnetic FeCo alloys (FeCo) after they are loaded onto carboxy methyl cellulose?
- How does the mechanism of FeCo surface interact with microplastics via hydrophobic interactions and hydrogen bonding? Please support it by figure.
- The overall structure in the introduction lacks coherence. It would be more effective to start with the background (FeCo role in adsorption), followed by the problem urgency, proposed solution, and finally, the research gap.
- How important is CMC in the production of soft magnetic FeCo alloys as an adsorbent?
- What was the number of replicates of this experiment and analyses? Then the statistical reporting could be improved by including error bars and standard deviations.
- Please provide detail of the SEM analysis used in this research.
- The characterization (SEM, EDX, XRD, FTIR) is robust, but somehow the discussion does not adequately link properties like surface area and crystallinity that influenced on the adsorption process.
- How about the pHzpc of the adsorbent? Why does the removal/adsorption capacity on the influence of pH seem not stable? Please explain it. Supported it with the references.
- Please add the fixed operational condition in Fig. 6 to Fig. 10.
- How is the stability of the material (FeCo) in the solution during its functions for microplatics removal? Did the authors use regeneration of the materials after using them?
- How about the performance of FeCo for microplastics removal as a potential material compared to the others for the same adsorption processes? Result must be compared with those obtained by other so as to show the advantages of the proposed materials
Author Response
Dear reviewers,
Thank you for your feedback concerning our revised manuscript. Below, we have responded to the reviewers’ individual comments. For clarity, the reviewer comments are shown in blue font, and our responses are presented in black font.
Reviewer #1
Comments and Suggestions for Authors:
The authors described a study of “Adsorption performance of soft magnetic FeCo alloys on microplastics". The studies addressed in this manuscript are to explore the removal potential of metal nano-adsorbents for microplastics (MPs) in water, but many questions in this manuscript have to be solved. The specific comments are as follows:
Comment 1: In the abstract, the author mentions that the surface area is 132.31 m²/g, is it the external surface area that they are mentioning on page 9? How to find the micropore and the external surface area by t-plot could not be found in this manuscript.
Response 1: We appreciate this targeted feedback. The surface area mentioned in the abstract is 132.31 m²/g, which refers to the external surface area provided on page 9. To better describe the total surface area per unit mass of a material, the specific surface area, which has a standardized measurement method, should be used. Therefore, we have replaced the relevant parts of the abstract with specific surface areas. The t-plot analysis of the micropores and external surface areas of porous materials is based on establishing a relationship between the thickness (t) of a standard adsorption isotherm and the amount of sample adsorption (V). The external surface area and micropore volume are calculated from the slope and intercept of the curve, respectively, which in turn allows for the derivation of the micropore surface area. In the actual measurement cases, the values are obtained directly through instruments.
Comment 2: Refer to Point 1, is the surface area of soft magnetic FeCo alloys (FeCo) after they are loaded onto carboxy methyl cellulose?
Response 2: Thank you for your comments. The surface area shown in the abstract is the surface area of a soft magnetic FeCo alloy (FeCo) loaded onto carboxymethyl cellulose.
Comment 3: How does the mechanism of FeCo surface interact with microplastics via hydrophobic interactions and hydrogen bonding? Please support it by figure.
Response 3: Thank you for your comments. We explain how the FeCo surface interacts with microplastics through hydrophobic interactions and hydrogen bonding using both diagrams and text. Regarding FeCo particles, studies have shown that their surfaces can be modified with various functional groups (Wang et al., 2014; Zhou et al., 2020; Wang et al., 2023). Second, microplastic particles can adsorb various pollutants in aquatic environments, and their surface properties are crucial for determining their adsorption behaviors. The surfaces of microplastics usually contain multiple oxygen-containing functional groups, such as carboxyl (-COOH) and hydroxyl (-OH) groups, which may form during the aging process of microplastics in the environment (Narwal et al., 2024). Hydrogen bonding is an important type of noncovalent interaction between different substances. Hydrogen bonds can form between the hydroxyl groups on the surfaces of FeCo particles and the carboxyl groups on the surfaces of microplastics; they typically occur between atoms with high electronegativity (such as oxygen, nitrogen, or fluorine) and hydrogen atoms that are covalently bonded to another electronegative atom (Balamurali et al., 2024; Kim et al., 2024). Hydrophobic interactions represent the tendency of two or more nonpolar substances to aggregate in aqueous solutions to reduce their contact area with water molecules (Ferreira et al., 2023), thereby lowering the free energy of the system. Microplastics generally have hydrophobic surfaces, which facilitate interactions with other hydrophobic substances (such as heavy metal complexes) in aquatic environments (Xiao et al., 2022).
The above figure illustrates the molecular mechanism of hydrogen bonding between hydroxyl groups and other functional groups in composite materials, where the red dashed lines represent hydrogen bonds. This further confirms that it is reasonable for hydrogen bonds to form between the hydroxyl and carboxyl groups of FeCo and microplastics (Guo et al., 2024).
The above figure clearly shows various intermolecular interactions, including hydrogen bonds, electrostatic interactions, π–π interactions, and hydrophobic interactions. Among them, hydrogen bonds are represented by green dashed lines, and hydrophobic interactions are also clearly marked (Rath et al., 2023).
References:
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Zhou, C., Ding, D., Zhu, W., Chang, X., Zhang, T., Wu, H., Yang, H., & Sun, L. 2020. Mechanism of formaldehyde advanced interaction and degradation on Fe3O4 (1 1 1) catalyst: Density functional theory study. Applied Surface Science, 520: 146324.
Wang, Y., Wang, T., Rong, Z., Wang, Y., & Qu, J. 2023. Role of hydroxyl on metal surface in hydrogenation reactions. Journal of Catalysis, 418: 216–224.
Narwal, N., Kakakhel, M. A., Katyal, D., Yadav, S., Rose, P. K., Rene, E. R., Rakib, Md. R. J., Khoo, K. S., & Kataria, N. 2024. Interactions Between Microplastic and Heavy Metals in the Aquatic Environment: Implications for Toxicity and Mitigation Strategies. Water, Air, & Soil Pollution, 235(9): 567.
Balamurali, M., & Rajan, M. 2024. Coconut shells based MrGO@CMC adsorbent for the chromium (VI) ion removal from contaminated water through batch adsorption method. Results in Surfaces and Interfaces, 17: 100346.
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Ferreira, J., & Castro, F. 2023. Advances in protein solubility and thermodynamics: quantification, instrumentation, and perspectives. CrystEngComm, 25(46): 6388–6404.
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Rath, R., Mohanty, S., Kumar, P., Nayak, S. K., & Unnikrishnan, L. 2023. Synergistic effect of silica-covered graphene oxide (in-situ) hybrid nanocomposites for use as a polymer electrolyte membrane for fuel cell applications. Surfaces and Interfaces, 38: 102761.
Comment 4: The overall structure in the introduction lacks coherence. It would be more effective to start with the background (FeCo role in adsorption), followed by the problem urgency, proposed solution, and finally, the research gap.
Response 4: We appreciate this constructive feedback. The Introduction section has been comprehensively restructured to enhance its logical coherence.
Comment 5: How important is CMC in the production of soft magnetic FeCo alloys as an adsorbent?
Response 5: CMC can act as a dispersant, helping FeCo alloy particles disperse evenly during the preparation process and preventing particle agglomeration (Barbosa et al., 2020). For example, when preparing FeCo alloy adsorbents via the coprecipitation method, the addition of CMC can cause Fe²⁺, Co²⁺ and other ions in the metal salt solution to form finer and more uniform particles during the precipitation process, thereby increasing the specific surface area and adsorption performance of the adsorbent (Liu et al., 2023). Moreover, CMC can also serve as a binder, enhancing the bonding between particles during the adsorbent formation process, making the prepared adsorbent mechanically stronger, less prone to breakage, and easier to use and handle.
CMC molecules contain many functional groups, such as carboxyl (-COOH) and hydroxyl (-OH) groups, which can form chemical bonds with atoms on the surface of the FeCo alloy or interact through hydrogen bonding, thereby altering the chemical properties of the FeCo alloy surface and enhancing its adsorption capacity (Hashem et al., 2025). In addition, CMC itself also has certain adsorption properties and can adsorb some ions or molecules in a solution through ion exchanges, complexation, and other mechanisms (Arumughan et al., 2021). When CMC is combined with a FeCo alloy to form an adsorbent, the two can work synergistically to improve the adsorption efficiency achieved for the target pollutants (Lin et al., 2025).
CMC can form a protective film on the surface of a FeCo alloy, preventing the alloy from undergoing chemical reactions with certain substances in the external environment, thereby improving the chemical stability of the adsorbent (Yuan et al., 2025). Moreover, owing to the presence of CMC, the adsorbent is less likely to agglomerate and precipitate in aqueous solutions, maintaining a good dispersed state, which is beneficial for the continuous progress of the adsorption reaction (Pellenz et al., 2023). For example, in acidic or alkaline solutions, CMC can buffer changes in the pH of the solution, reduce the corrosion suffered by the FeCo alloy, and extend the service life of the adsorbent (Legrand et al., 2024).
References:
Barbosa, F.F., Paulista, A.P.F., Torres, M.A.M., Braga, T.P., 2020. Synthesis of the Fe–Co alloy from hybrid spheres using carboxymethylcellulose as template and its application in catalysis. Materials Chemistry and Physics, 242: 122550.
Liu, Z., Wang, B., Wei, S., Huang, W., et al., 2023. Novel preparation of FeCo alloy/graphene foam composites for efficient microwave absorption. Carbon, 215: 118452.
Hashem, A., Farag,S., Badawy, S.M., 2025. Carboxymethyl cellulose: Past innovations, present applications, and future horizons. Results in Chemistry, 17: 102534.
Arumughan, V., Nypelö, T., Hasani, M., Brelid, H., et al., 2021. Specific ion effects in the adsorption of carboxymethyl cellulose on cellulose: The influence of industrially relevant divalent cations. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 626: 127006.
Lin, K., Chen, M., Zhou, Z., Zhang, Z., et al., 2025. Optimized electronic structure of N-doped carbon@FeCo alloys: Remarkable bifunctional oxygen catalyst for rechargeable zinc-air batteries. Journal of Power Sources, 641: 236882.
Yuan, J., Cui, X., Dai, B., Fu, X., et al., 2025. Corrosion resistance, binding and biodegradability of CMC/CaP coating on magnesium alloy. Journal of Alloys and Compounds, 1010: 177113.
Pellenz, L., Oliveira, C. R. S. d, Júnior, A H. d. S., et al., 2023. A comprehensive guide for characterization of adsorbent materials. Separation and Purification Technology, 305: 122435.
Legrand, G., Baeza, G.P., Peyla,M., Porcar,L., et al., 2024. Acid-Induced Gelation of Carboxymethylcellulose Solutions. ACS Macro Letters, 13(2): 234–239.
Comment 6: What was the number of replicates of this experiment and analyses? Then the statistical reporting could be improved by including error bars and standard deviations.
Response 6: The experiment was repeated three times, with two parallel sets employed for each data group, and the data analysis was performed three times. Error bars and standard deviations have also been added to the original text to improve the statistical report. The reason why error bars were not added to the adsorption fitting data is that, among multiple fitting sets, the set with the best fitting results was selected for analysis purposes.
Comment 7: Please provide detail of the SEM analysis used in this research.
Response 7: Thank you for your comments. The following is the detailed information regarding the SEM analysis used in this study: the sample was in powder form and directly adhered to a conductive adhesive to prepare the sample, which contained strong magnetism. The morphology and surface scanning (mapping) properties were tested in the secondary electron mode: the ruler was between 10 W and 150 W, and the position was Mag=80K–100KX; the magnification was 80K–100KX; the element colors were C (red), Fe (green), Co (blue), and O (yellow); and semiquantitative testing was conducted on the elements.
Comment 8: The characterization (SEM, EDX, XRD, FTIR) is robust, but somehow the discussion does not adequately link properties like surface area and crystallinity that influenced on the adsorption process.
Response 8: Thank you for your comments. The discussion section has been supplemented to explain the effects of crystallinity and the surface area on the adsorption process. In fact, the specific surface area provides the basis for the number of “adsorption sites”, whereas the crystallinity determines the stability of the material.
Comment 9: How about the pHzpc of the adsorbent? Why does the removal/adsorption capacity on the influence of pH seem not stable? Please explain it. Supported it with the references.
Response 9: Thank you for your comment. When iron-based alloy composite materials adsorb microplastics, their adsorption capacities become unstable with changes in the pH, mainly because of the presence of complex multifactor interactions between the surface chemical properties of the composite materials, the surface characteristics of the microplastics, and the chemical environment of the solution (Zhang et al., 2023; Zhao et al., 2025; Tang et al., 2025). The equilibrium adsorption capacity of the material sharply decreased from approximately 9 mg/g to approximately 7 mg/g when the pH increased from 1.0 to 4.0, sharply increased from 7.0 to 9.0, and gradually decreased from 10–12 (Figure 10). Combined with the removal efficiency, these results indicate that the material is more conducive to the adsorption of microplastics in neutral and weakly alkaline environments. This is because the surface charges of iron-based composite materials vary with respect to the pH, and a change in the surface charge directly affects the electrostatic interactions between the material and the microplastics. (Xiong et al., 2016; Joshi et al., 2024). The other chemical components in the solution, including the form of the metal ions, the dissolved organic matter (DOM), and the presence of competitive ions, are all regulated by pH and indirectly affect the instability of adsorption (Tian et al., 2024). In a low-acidity environment with a pH ≤ 2, surface protonation of iron-based materials occurs, and microplastics are adsorbed in the form of smaller particulate NPs through hydrogen bonding (Longo et al., 2019); at pH values of 3–6, surface hydroxyl groups form inner-layer complexes with MPS (Tamura et al., 2001); at pHs of 7–10, the MPs are negatively charged and generate electrostatic repulsion with negatively charged iron-based surfaces (Rong et al., 2021); at pH values of 9–12, their surface forms a complex with adsorbates through surface hydroxyl groups, and the functional groups in the iron-rich matrix precipitate through the dissolution of Fe(III); this reaction is inhibited by the pH (Xie et al., 2025; Deng et al., 2017).
References:
Zhang, J., Zhan, S., Zhong, L.-B., Wang, X., Qiu, Z., & Zheng, Y.-M. 2023. Adsorption of typical natural organic matter on microplastics in aqueous solution: Kinetics, isotherm, influence factors and mechanism. Journal of Hazardous Materials, 443: 130130.
Zhao, F., Zhang, Y., Tang, Y., Liu, X., Xu, T., Feng, Y., & Li, H. 2025. Dual regulatory mechanism of microplastics surface electric field in arsenic adsorption: Experimental and computational insights. Chemical Engineering Journal, 525: 170174.
Tang, Z., Wei, F., Song, J., Gao, Y., Duan, Y., Xiang, C., Gong, Z., Zhu, F., Su, Y., Wang, J., & Zhou, S. 2025. Unraveling the influence of pH on uranium adsorption by polystyrene microplastics: An integrated experimental-density functional theory analysis. Chemical Engineering Journal, 506: 160233.
Xiong, W., Qiu, X., Zhong, R., & Yang, D. 2016. Characterization of the adsorption properties of a phosphorylated kraft lignin-based polymer at the solid/liquid interface by the QCM-D approach. Holzforschung, 70(10): 937–945.
Joshi, V. C., Gupta, A. R., Karthik, M., & Sharma, S. 2024. Emerging iron based porous metallopolymeric material with cross-linked networks for the separation of ultra-trace arsenic from aqueous environment and simulation with artificial neural network. Journal of Hazardous Materials Advances, 14: 100417.
Tian, H., Cui, K., Sun, S., Li, H., Chen, X., 2024. Construction of acidic microenvironments to overcome the pH dependence of iron-based catalysts and application to the degradation of micropollutants by AOPs, Chemical Engineering Journal, 488: 150934.
Longo, G.S., Pérez-Chávez, N.A., Szleifer, I., 2019. How protonation modulates the interaction between proteins and pH-responsive hydrogel films. Current Opinion in Colloid & Interface Science, 41: 27-39.
Tamura, H., Mita, K., Tanaka, A., Ito, M., 2001. Mechanism of Hydroxylation of Metal Oxide Surfaces, Journal of Colloid and Interface Science, 243(1): 202-207.
Rong, H., He, L., Li, M., et al., 2021. Different electrically charged proteins result in diverse transport behaviors of plastic particles with different surface charge in quartz sand. Science of The Total Environment, 756: 143837.
Xie, K., Xie, J., Zhao, Z., Meng, X., & Chen, B. 2025. Synthesis of iron-modified montmorillonite/Al2O3 composite adsorbents and their phosphorus adsorption performance study. Scientific Reports, 15(1): 1-12.
Deng, S., Li, D., Yang, X., Xing, W., Li, J., & Zhang, Q. 2017. Iron [Fe(0)]-rich substrate based on iron–carbon micro–electrolysis for phosphorus adsorption in aqueous solutions. Chemosphere, 168, 1486–1493.
Comment 10: Please add the fixed operational condition in Fig. 6 to Fig. 10.
Response 10: Thank you for your comment. The experiments conducted in the same scenario are shown in Figures 6 and 10, with only their different influencing factors being investigated.
Comment 11: How is the stability of the material (FeCo) in the solution during its functions for microplatics removal? Did the authors use regeneration of the materials after using them?
Response 11: Thank you for your comment. The material is stable before and after adsorption, and the SEM characterization performed before and after adsorption reveals that the material only undergoes slight deformation and breakage. After the material is used, it is recycled, and its regenerability will be further studied in subsequent research.
Comment 12: How about the performance of FeCo for microplastics removal as a potential material compared to the others for the same adsorption processes? Result must be compared with those obtained by other so as to show the advantages of the proposed materials
Response 12: Thank you for your comment. Several iron-based alloy materials with better performance under the same adsorption process are listed (3.4. Study on the adsorption behaviors observed under different driving factors).
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors“Adsorption performance of soft magnetic FeCo alloys on micro-plastics” by Zhang et al. poses the attention on microplastics adsorption on FeCo alloys presenting a new adsorbent for the removal of this toxic contaminant. The work is well organized, with a strong and exhaustive introduction. Experiments are properly designed and characterization of synthesized material before and after adsorption is well conducted, using different techniques to investigate and confirm microplastics capture on FeCo-CMC adsorbent. For this reason, this work deserves publication in Water. Three minor revisions are only required:
- Where is Figure S1??
- Figure 6. The authors refer that adsorption isotherms are best described through Freundlich model. Anyway, considering model fitting of Figure 6, it seems that isotherm behavior is best described from the curve obtained from Langmuir model. How is it possible? Please explain.
- Paragraph 3.2. “A positive value of ΔG corresponds to the feasibility and spontaneity of the system, indicating that the reaction in the system is non-spontaneous [….]”. How could be possible that a positive ΔG corresponds to the spontaneity of the system?? What are the authors implying? Please rephrase in a more comprehensive form.
Author Response
Reviewer #2
Comments and Suggestions for Authors
“Adsorption performance of soft magnetic FeCo alloys on micro-plastics” by Zhang et al. poses the attention on microplastics adsorption on FeCo alloys presenting a new adsorbent for the removal of this toxic contaminant. The work is well organized, with a strong and exhaustive introduction. Experiments are properly designed and characterization of synthesized material before and after adsorption is well conducted, using different techniques to investigate and confirm microplastics capture on FeCo-CMC adsorbent. For this reason, this work deserves publication in Water. Three minor revisions are only required:
Comment 1: Where is Figure S1?
Response 1: Thank you for your comments. S1 is not included in the text and has been corrected to the correspondingly named Figure 2 in the text.
Comment 2: Figure 6. The authors refer that adsorption isotherms are best described through Freundlich model. Anyway, considering model fitting of Figure 6, it seems that isotherm behavior is best described from the curve obtained from Langmuir model. How is it possible? Please explain.
Response 2: We appreciate this constructive feedback. This article contains parts that are expressed imprecisely, and the specific explanations are as follows. Porous adsorbent materials (such as modified iron-based composites) theoretically exhibit site heterogeneity, but the functional modification groups introduced in experiments (such as PDA and hydroxyl groups) may be distributed uniformly on the surface, making the originally heterogeneous sites appear "pseudohomogeneous." SEM revealed that the adsorbate is stacked on the material surface, whereas XPS revealed that adsorption occurs on various functional groups. Therefore, this finding physically supports the notion that it conforms more closely to the Freundlich model. The reason the reviewer believes that the Langmuir model fits better is likely due to the fitting in the initial part of the curve. Indeed, the Langmuir model fits better at low concentrations, but when the concentration is increased (raising the microplastic concentration to 1.5–2 times the saturated adsorption capacity), the observed upward trend further supports the fit of the Freundlich model.
References:
Lorenc-Grabowska, E., Stasiak, O., & Kordek-Khalil, K., 2024. Polymer-based porous carbon doped with iron nanoparticles for enhanced organic compounds removal. Adsorption, 30: 279–291.
Meng, X., Crestini, C., Ben, H., Hao, N., et al., 2019. Determination of hydroxyl groups in biorefinery resources via quantitative 31P NMR spectroscopy. Nat Protoc, 14: 2627–2647.
Comment 3: Paragraph 3.2. “A positive value of ΔG corresponds to the feasibility and spontaneity of the system, indicating that the reaction in the system is non-spontaneous [….]”. How could be possible that a positive ΔG corresponds to the spontaneity of the system?? What are the authors implying? Please rephrase in a more comprehensive form.
Response 3: We appreciate this constructive feedback. The relevant section has been revised to enhance its logical coherence and accuracy. A positive value of ΔG corresponds to the feasibility and nonspontaneity of the system, and the decrease in the ΔG value with increasing temperature confirms that increasing the temperature benefits the progress of the reaction, which is consistent with the results of the adsorption isotherm and adsorption kinetic studies.
References:
Ji, C., Wu, D., Lu, J., Shan, C., Ren, Y., Li, T., et al., 2021. Temperature regulated adsorption and desorption of heavy metals to A-MIL-121: Mechanisms and the role of exchangeable protons. Water Res, 189: 116599.
Xu, X., Liu, H., Wang, J., Chen, T., Ding, X., Chen, H., 2021. Insight into surface hydroxyl groups for environmental purification: characterizations, applications and advances. Surf Interfaces, 25: 101272.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsI write my opinion about the present manuscript, entitled “Adsorption performance of soft magnetic FeCo alloys on micro-plastics”. In this research work, the authors demonstrated an interesting method (adsorption) to remove the microplastics (MPs). Working on such topics is very important, as we are currently facing water scarcity and contamination. In this research work, the authors successfully achieved a removal rate of 89.33% which is comparable with literature. The results obtained, along with the manner in which they are presented, are of high quality. Moreover, the manuscript is well written in terms of grammar, with only a few editorial typos and minor errors that can be addressed during the revision process. In summary, the manuscript can be accepted after a minor revision.
Comments
- The absence of line numbers makes it difficult to follow the reviewers' comments. However, to help the authors follow the comments more easily, I have included the reviewed section in parentheses after each comment.
- It is recommended to avoid using a lot of abbreviations in the abstract section. Using a number of abbreviations in the abstract can reduced the interest of readers to continue reading and citing the manuscript. (abstract)
- SEM, XRD, BET, XPS, and FTIR should be initially introduced. Then the abbreviated form can be used. (abstract)
- I have a question regarding the following sentence “Furthermore, XPS and FTIR analyses elucidated that hydroxyl groups on the FeCo surface interact with microplastics via hydrophobic interactions and hydrogen bonding, with the resulting redox vacancies providing ample active sites for microplastic adsorption.”. Do hydroxyl groups interact with microplastics via hydrophobic interactions, or should it be hydrophilic interactions? (abstract)
- In the following sentence “This study provides innovative insights into the adsorption of novel persistent pollutants in the environment by novel modified adsorbent materials.”, the novelty of the research work is written in in the bold format. If this is not required by the journal's formatting guidelines, it should be revised. (environmental implication)
- In the following sentence “Current research on the removal of microplastics from aquatic systems includes traditional methods such as coagulation, microbial degradation, and photodegradation.”, membrane technology should be included. Indeed, membrane technology is the one of the most promising methods (removal rate: 99.99%) to remove MPs from the water. Such information should be included (1. introduction).
- “Nedylakova et al” should be replaced with “Nedylakova et al.”. Always include the period after "al." because it is an abbreviation of the Latin word alii. This remark should be addressed in the whole manuscript. (1. introduction section)
- “can not” should be replace with “cannot” in the following sentence “These defects can not only change the surrounding … .” (1. introduction).
- LDH should be introduced, then it can be used in the abbreviated format. The same remark for CMC. This issue should be check for the all abbreviations. (1. introduction)
- It is suggested to revise the section of “chemicals and materials” in a standard way. Exp: X was bought from Z company (some specifications of X, company name, city, country). (2.1. chemicals and materials)
- “Ct, qt, and c0” should be replaced with “Ct, qt, and c0”. Furthermore, each formula or equation must be accompanied by a citation to its original source. (2.4. adsorption of FeCo on PE-MPs)
- To enhance the readability of the manuscript, it is recommended to present the best results (adsorption and removal rate) of the current research alongside those from published articles in a comparative table. (3.4. study on adsorption behavior under different driving factors)
- As the authors mentioned in the manuscript, there are some effective methods for the removal of the MPs from water, such as coagulation, microbial degradation, photodegradation, adsorption, and membrane technology. It is recommended that the authors identify (based on their opinion) the most practical and efficient method for the removal of MPs from water and wastewater.
Author Response
Reviewer #3
Comments and Suggestions for Authors
I write my opinion about the present manuscript, entitled “Adsorption performance of soft magnetic FeCo alloys on micro-plastics”. In this research work, the authors demonstrated an interesting method (adsorption) to remove the microplastics (MPs). Working on such topics is very important, as we are currently facing water scarcity and contamination. In this research work, the authors successfully achieved a removal rate of 89.33% which is comparable with literature. The results obtained, along with the manner in which they are presented, are of high quality. Moreover, the manuscript is well written in terms of grammar, with only a few editorial typos and minor errors that can be addressed during the revision process. In summary, the manuscript can be accepted after a minor revision.
Comment 1: The absence of line numbers makes it difficult to follow the reviewers' comments. However, to help the authors follow the comments more easily, I have included the reviewed section in parentheses after each comment.
Response 1: Thank you for your comments. Line numbers have been added to the manuscript.
Comment 2: It is recommended to avoid using a lot of abbreviations in the abstract section. Using a number of abbreviations in the abstract can reduced the interest of readers to continue reading and citing the manuscript. (abstract)
Response 2: Thank you for your comments. Some unnecessary abbreviations have been removed, but owing to the word count requirement for the abstract and the testing methods, some necessary abbreviations are unavoidable.
Comment 3: SEM, XRD, BET, XPS, and FTIR should be initially introduced. Then the abbreviated form can be used. (abstract)
Response 3: Thank you for your comments. The full forms of the relevant abbreviations have been added to the original text.
Comment 4: I have a question regarding the following sentence “Furthermore, XPS and FTIR analyses elucidated that hydroxyl groups on the FeCo surface interact with microplastics via hydrophobic interactions and hydrogen bonding, with the resulting redox vacancies providing ample active sites for microplastic adsorption.”. Do hydroxyl groups interact with microplastics via hydrophobic interactions, or should it be hydrophilic interactions? (abstract)
Response 4: We appreciate this constructive feedback. The relevant section has been revised to enhance its logical coherence and accuracy: Furthermore, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy (XPS and FTIR) analyses indicate that the surface of FeCo is modified to be hydrophilic because of catalytic oxidation reactions, resulting in the exposure of polar groups (such as carboxyl and hydroxyl groups) on the microplastic surface, which form hydrogen bonds with oxygen or water molecules on the FeCo surface. The resulting redox vacancies provide ample active sites for the adsorption of microplastics.
Comment 5: In the following sentence “This study provides innovative insights into the adsorption of novel persistent pollutants in the environment by novel modified adsorbent materials.”, the novelty of the research work is written in in the bold format. If this is not required by the journal's formatting guidelines, it should be revised. (environmental implication)
Response 5: Thank you for your comments. The sections where the environmental impact was inaccurately described in bold have been removed.
Comment 6: In the following sentence “Current research on the removal of microplastics from aquatic systems includes traditional methods such as coagulation, microbial degradation, and photodegradation.”, membrane technology should be included. Indeed, membrane technology is the one of the most promising methods (removal rate: 99.99%) to remove MPs from the water. Such information should be included (1. introduction).
Response 6: Thank you for your comments. The introduction section has been updated to include information related to membrane treatment processes.
Comment 7: “Nedylakova et al” should be replaced with “Nedylakova et al.”. Always include the period after "al." because it is an abbreviation of the Latin word alii. This remark should be addressed in the whole manuscript. (1. introduction section)
Response 7: Thank you for your comments. In the introduction section, the Latin abbreviation 'al.' is already followed by a period.
Comment 8: “can not” should be replace with “cannot” in the following sentence “These defects can not only change the surrounding … .” (1. introduction).
Thank you for your careful review and useful feedback. In the introductory sentence “These defects can not only change the surrounding...”, 'can not' has replaced with 'cannot'.
Comment 9: LDH should be introduced, then it can be used in the abbreviated format. The same remark for CMC. This issue should be check for the all abbreviations. (1. introduction)
Response 9: Thank you for your careful review and useful feedback. The relevant abbreviations have been introduced with their full forms.
Comment 10: It is suggested to revise the section of “chemicals and materials” in a standard way. Exp: X was bought from Z company (some specifications of X, company name, city, country). (2.1. chemicals and materials)
Response 10: Thank you for your comments. The 'Chemicals and Materials' section has been revised according to the standard format.
Comment 11: “Ct, qt, and c0” should be replaced with “Ct, qt, and c0”. Furthermore, each formula or equation must be accompanied by a citation to its original source. (2.4. adsorption of FeCo on PE-MPs)
Response 11: Thank you for your comments. “Ct, qt, and c0” have been replaced with “Ct, qt and c0”. Moreover, each formula or equation has been referenced to its original source.
Comment 12: To enhance the readability of the manuscript, it is recommended to present the best results (adsorption and removal rate) of the current research alongside those from published articles in a comparative table. (3.4. study on adsorption behavior under different driving factors)
Response 12: Thank you for your comments. Since there is currently no clear research indicating which iron-based alloy material has the best adsorption capacity and microplastic removal rate, this paper lists several iron-based alloy materials that achieve superior performance.
References:
Li, X., Zhang, Z., Wang, J., 2023. Deformation twinning in body-centered cubic metals and alloys. Progress in Materials Science, 139: 101160.
Wang, J., Yuan, Y., Chen, T., Wu, L., et al., 2022. Multi-solute solid solution behavior and its effect on the properties of magnesium alloys. Journal of Magnesium and Alloys, 10(7): 1786-1820.
Li, Y., Chen, H., Li, S., Feng, L., et al., 2024. Corals-inspired magnetic absorbents for fast and efficient removal of microplastics in various water sources. RSC Advances, 14(17): 11908-11913.
Cao, Y., Sathish, C.I., Li, Z., Ahmed, M.I., 2024. Plastics adsorption and removal by 2D ultrathin iron oxide nanodiscs: From micro to nano. Chemical Engineering Journal, 497: 154610.
Xia, H., Duan, N., Song, B., Li, Y., et al., 2025. Efficient Removal of Micro-Sized Degradable PHBV Microplastics from Wastewater by a Functionalized Magnetic Nano Iron Oxides-Biochar Composite: Performance, Mechanisms, and Material Regeneration. Nanomaterials-Basel, 15(12): 915.
White, J.J., Hinsch, J.J., Bennett , W.W., Wang, Y., 2022. Theoretical understanding of water adsorption on stepped iron surfaces. Appl Surf Sci, 605(15): 154650.
Comment 13: As the authors mentioned in the manuscript, there are some effective methods for the removal of the MPs from water, such as coagulation, microbial degradation, photodegradation, adsorption, and membrane technology. It is recommended that the authors identify (based on their opinion) the most practical and efficient method for the removal of MPs from water and wastewater.
Response 13: Thank you for your comments. Currently, there is no “most practical and most effective” single method. Owing to their broad applicability and stable efficiency, adsorption and membrane technologies are the two types of technologies that perform best overall in terms of removing microplastics (MPs) from water and wastewater. Specific choices should be made on the basis of a comprehensive assessment of the water quality level, cost, and treatment objectives. Adsorption is suitable for small-scale treatment scenarios and for addressing different types of MPs, whereas membrane technology is more suitable for treating high concentrations of nanoscale MPs and for advanced treatments involving large wastewater treatment plants.
References:
Momina, Ahmad, K., 2023. Feasibility of the adsorption as a process for its large scale adoption across industries for the treatment of wastewater: Research gaps and economic assessment. Journal of Cleaner Production, 388: 136014.
Satyam, S., Patra, S., 2024. Innovations and challenges in adsorption-based wastewater remediation: A comprehensive review, Heliyon, 10(9): e29573.
Zhang, H., Duan, Y., Elimelech, M., Wang, Y., 2025. Scalable catalytic nanofiltration membranes for advanced water treatment. Nature Water, 3: 1038–1047.
Julian, H., Nurgirisia, N., Qiu, G., Ting, Y-P., Wenten, I.G., 2022. Membrane distillation for wastewater treatment: Current trends, challenges and prospects of dense membrane distillation. Journal of Water Process Engineering, 46: 102615.
Mulindwa, P., Kasule, J. S., Nantaba, F., Wasswa, J., & Expósito, A. J. 2024. Bioadsorbents for removal of microplastics from water ecosystems: a review. International Journal of Sustainable Engineering, 17(1): 582–599.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have responded to the comments of our review previously, so the revised manuscript is more clearly right now.
