Controllable synthesis of pomelo peel-based aerogel and its application in adsorption of oil/organic pollutants

Oil/water separation is a field of high significance as it might efficiently resolve the contamination of industrial oily wastewater and other oil/water pollution. In this paper, an environmentally-friendly hydrophobic aerogel with high porosity and low density was successfully synthesized with renewable pomelo peels (PPs) as precursors. Typically, a series of sponge aerogels (HPSA-0, HPSA-1 and HPSA-2) were facilely prepared via high-speed dispersion, freeze-drying and silanization with methyltrimethoxysilane. Indeed, the physical properties of aerogel such as density and pore diameter could be tailored by different additives (filter paper fibre and polyvinyl alcohol). Hence, their physico-chemical properties including internal morphology and chemical structure were characterized in detail by Fourier transform infrared, Brunauer–Emmett–Teller, X-ray diffraction, scanning electron microscope, Thermal gravimetric analyzer (TG) etc. Moreover, the adsorption capacity was further determined and the results revealed that the PP-based aerogels presented excellent adsorption performance for a wide range of oil products and/or organic solvents (crude oil 49.8 g g−1, soya bean oil 62.3 g g−1, chloroform 71.3 g g−1 etc.). The corresponding cyclic tests showed the absorption capacity decreased slightly from 94.66% to 93.82% after 10 consecutive cycles, indicating a high recyclability.

more characterization results are needed to show this. 5. The properties of pores are obtained through N2 adsorption-desorption method and only micropores and mesopores can be analyzed. While I think that maybe macropores are very important for oil adsorption. So I suggest more characterization on the macropores should be provide. 6. For the description in Line 8~9, P. 5, "Clearly, the sample was completely absorbed by the dyed kerosene, otherwise the water in the beaker was not absorbed by the sample", please describe how can you determine that there is no water adsorbed. 7. Can you please give results about the strength of the material? And can you please give images for the aerogels after reusing for many times? 8. Anhydrous ethanol was used in the oil separation. Maybe you can used other solvents consider its future application.

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Comments to the Author(s)
The manuscript reported a pomelo peel-based aerogel for oil/organic pollutants adsorption. The authors used the natural pomelo peel as the starting material, however, the employment of fibercontained nature materials as the precursors is not a new topic in this field. Apart from that, I didn't see any attractive innovations on both the synthesis and performance. The most disappointing thing is that the authors did not give any data analysis and academic discussion on their results. The whole manuscript is more like a experiment report. In order to improve the current manuscript, I suggest the author place their focus on the following aspects: First, improve the architecture of the paper, including the logic and the organization. First come up a problem, then look back the current researches in this field, finally put forward your work….. Then, as for the detail, try to explain the formation of the aerogel and understand the function of each units in your material. Try to understand the mechanism of the hydrophobic property after coupling with MTMS. Discuss and compare the advantages and disadvantages of the your aerogels prepared in this paper with other reported works on the synthesis, properties and oil/organic solvent adsorption capacity. Before doing this, I highly recommend the author to read more related literatures to make a clear understanding of the current research status. Finally, please try your best to improve the english writing. I found many sentences that I even could not understand: "….Different from adding filter paper aerogel, the addition of PVA aerogels can see a large number of filamentous fiber structure, mainly due to the fiber in the filter paper is formed by PP fiber [27], the scattered distribution in a suspended solution……The synthesized sponge aerogels in this work did not reach the superhydrophobic state of the samples after hydrophobic modification (WCA≫150︒) [33]asillustrated in the literature, which was regarded as the main reason for the amount of hydrophobic modification agents. It was anticipated to use a small amount of MTMS in order to modify the sample to achieve similar hydrophobic effect…" Review form: Reviewer 4 (Yuchang Zhang)

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
In this manuscript the authors investigated oil adsorbent using renewable pomelo peel and filter paper (or polyvinyl alcohol) via facile method. This biomass-based aerogel shows low density, high porosity, hydrophobicity, high absorption capacity and excellent recyclability. Based on these results, this paper is valuable. I recommend accepting this paper after minor revised. Following is a list of a few to address: 1. In page 1 line 45: author wrote "in situburning", it should be "in-situ burning". similarly, in page 2 line 3, "nonocoating" should be "nanocoating". 2. In page 3, discuss of aerogel microstructure (SEM) should be improved. 3. The title of figure 5 need to correct. 4. The English level of manuscript should be updated by a native English editor.

23-Nov-2018
Dear Professor Tan: Title: Controllable synthesis of pomelo peel-based aerogel and its application in adsorption of oil/organic pollutants Manuscript ID: RSOS-181823 Thank you for your submission to Royal Society Open Science. The chemistry content of Royal Society Open Science is published in collaboration with the Royal Society of Chemistry.
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RSC Subject Editor:
Comments to the Author: (There are no comments.) ********************************************** Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) "Controllable synthesis of pomelo peel-based aerogel and its application in adsorption of oil/organic pollutants", reports preparation of oil-absorbing aerogel from a mixture of pomelo peel and polyvinyl alcohol (or filter papers) with methylsilane treatment. Selective oil absorption was obtained from an aerogel made of cheap raw materials, and the materials was easily prepared and cost effective. The structure of the article was reasonable and the experimental results were discussed in detail and in good agreement with the physicochemical features of the as-prepared materials. Based on the results, I recommend the publication of this manuscript after a minor modification. Following is a list of a few to address. 1. First of all, this manuscript is required to have consult in terms of English. 2. Why are the pomelo peel and polyvinyl alcohol (or filter paper) mixed together? 3. The introduction of this manuscript need improve.

Reviewer: 2
Comments to the Author(s) The paper has shown some interesting results. But there are still some problems I suggest to solve.
1. The English language should be improved because some sentences cannot be understood clearly and there are some mistakes in the expression. 2. I suggest the authors characterize the raw material, pomelo peel, so as to make clear the composition of it. 3. For the Eq. 1.2, please tell us how you obtained the aerogel skeleton density. 4. Are chemical bonds formed during the formation of the aerogels of PSAs and HPSAs? I think more characterization results are needed to show this. 5. The properties of pores are obtained through N2 adsorption-desorption method and only micropores and mesopores can be analyzed. While I think that maybe macropores are very important for oil adsorption. So I suggest more characterization on the macropores should be provide. 6. For the description in Line 8~9, P. 5, "Clearly, the sample was completely absorbed by the dyed kerosene, otherwise the water in the beaker was not absorbed by the sample", please describe how can you determine that there is no water adsorbed. 7. Can you please give results about the strength of the material? And can you please give images for the aerogels after reusing for many times? 8. Anhydrous ethanol was used in the oil separation. Maybe you can used other solvents consider its future application.

Reviewer: 3
Comments to the Author(s) The manuscript reported a pomelo peel-based aerogel for oil/organic pollutants adsorption. The authors used the natural pomelo peel as the starting material, however, the employment of fibercontained nature materials as the precursors is not a new topic in this field. Apart from that, I didn't see any attractive innovations on both the synthesis and performance. The most disappointing thing is that the authors did not give any data analysis and academic discussion on their results. The whole manuscript is more like a experiment report. In order to improve the current manuscript, I suggest the author place their focus on the following aspects: First, improve the architecture of the paper, including the logic and the organization. First come up a problem, then look back the current researches in this field, finally put forward your work….. Then, as for the detail, try to explain the formation of the aerogel and understand the function of each units in your material. Try to understand the mechanism of the hydrophobic property after coupling with MTMS. Discuss and compare the advantages and disadvantages of the your aerogels prepared in this paper with other reported works on the synthesis, properties and oil/organic solvent adsorption capacity. Before doing this, I highly recommend the author to read more related literatures to make a clear understanding of the current research status. Finally, please try your best to improve the english writing. I found many sentences that I even could not understand: "….Different from adding filter paper aerogel, the addition of PVA aerogels can see a large number of filamentous fiber structure, mainly due to the fiber in the filter paper is formed by PP fiber [27], the scattered distribution in a suspended solution……The synthesized sponge aerogels in this work did not reach the superhydrophobic state of the samples after hydrophobic modification (WCA≫150︒) [33]asillustrated in the literature, which was regarded as the main reason for the amount of hydrophobic modification agents. It was anticipated to use a small amount of MTMS in order to modify the sample to achieve similar hydrophobic effect…" Reviewer: 4 Comments to the Author(s) In this manuscript the authors investigated oil adsorbent using renewable pomelo peel and filter paper (or polyvinyl alcohol) via facile method. This biomass-based aerogel shows low density, high porosity, hydrophobicity, high absorption capacity and excellent recyclability. Based on these results, this paper is valuable. I recommend accepting this paper after minor revised. Following is a list of a few to address: 1. In page 1 line 45: author wrote "in situburning", it should be "in-situ burning". similarly, in page 2 line 3, "nonocoating" should be "nanocoating". 2. In page 3, discuss of aerogel microstructure (SEM) should be improved.