The Devastation of Waste Plastic on the Environment and Remediation Processes: A Critical Review

Round 1

Reviewer 1 Report

Manuscript ID: sustainability-2237771

Authors tried to write a critical review entitled “The devastation of Waste plastic on the environment and remediation processes: A Critical Review”. However, based on my reading, I cannot find it is critical but routine. In addition, from a technical point of view, it looks weak. Hence, I suggest the below correction and revision.

Depending on the polymer structure (thermoplastic and thermosetting), the recycling strategy might be different. About this issue, I suggest authors may address in details.

Figure 1: Number is not sequential. In addition, I do not agree the categories such as “Recyclable”, “Maybe recyclable” and Unrecyclable”. What is a scientific background about it?

Line 208-210: “Microplastics”: Authors defined its size is less than 5 mm. Then, how authors can say that “Due to their large specific surface area, microplastics are more likely to adsorb other pollutants and cause toxic effects when combined.”?  5 mm is a macro-scale. If authors want to say “large specific surface area”, authors should describe nano-materials, e.g., nanoplastics. Hence, I suggest that authors may define carefully & systematically, all the related terminologies concerning primary/secondary microplastics, and nanoplastics in an appropriate place in the manuscript.  

Table 1. (1) Color is not needed in this table. (2) “Not classified” should not be included in Table but placed in the caption area. (3) Although monomer is toxic, polymer does not have to be toxic, indicating that if we well recycle the polymers mentioned in Table 1, it could be fine. Hence, Authors may give some comments about it. (4) Some polymer (e.g., PF) is repeated in the table. Also sometimes, there is unnecessary “.” at that end of polymer names. (5) “S and some numbers” are displayed but not defined.

Figure 2. “WWTPs” Its full name should be introduced in the table’s caption.

Line 196: “Nanoplastic (< 100 nm)” => “it should be <100 nm or <1000 nm”, depending on authors.

Line 208-209: this is a repetition. Check Line 65.

Line 55: White pollution: Please define it carefully for reader-friendly.

Abstract and Conclusion: it is not much critical. Improve it.

Line 36: “Plastics are chemically manufactured polymers” (Is there any better definition for plastic?)

Line 45: Broken English

Line 53-57: Improve English. (It should be parallel when compare something.)

Line 71: I recommend that thermosetting and thermoplastic should be addressed in details from the recyclability point of view.

Figure 1. From the polymer science point of view, I do not agree this category. (I suggest Authors may receive some consulting from the professionals who major in Polymer Science and Engineering.) In my view, the paper is not much technical.  

Line 107-110: As I mentioned before, please address some comments the relationship between monomer and polymer from the view point of (1) hazard categorization and (2) recyclability. Table 1. Class I => I do not see there is any meaning for "green-color category". In addition, too much color makes the paper non-scientific (Please check the original paper).  Furthermore, the polymers mentioned in “non-classified” have a similar repeat unit with the classified ones. Hence, authors may give some comments about it although the original papers did the same things.

Figure 4. Of course, everyone wants “Circular economy”. However, there is some technical restriction. Authors may think about re-processable polymers from polymer's structure point of view. In addition, if authors would add some “Life Cycle Assessment” about polymer materials, it would be better.

Table 2: Authors can add some more critical view about it because Table 2's contents looks nice and informative. 

Currently, my feeling is that the manuscript is not much critical. Hence, a major revision is needed with enhancing the quality of this manuscript. 

1

Author Response

Authors tried to write a critical review entitled “The devastation of Waste plastic on the environment and remediation processes: A Critical Review”. However, based on my reading, I cannot find it is critical but routine. In addition, from a technical point of view, it looks weak. Hence, I suggest the below correction and revision.

Depending on the polymer structure (thermoplastic and thermosetting), the recycling strategy might be different. About this issue, I suggest authors may address in details.

Response:

This explanation was done in lines 39-46;

Figure 1: Number is not sequential. In addition, I do not agree the categories such as “Recyclable”, “Maybe recyclable” and Unrecyclable”. What is a scientific background about it?

Response:

Based on the evidence/information provided in the available literature, the categories are correct as referenced. The plastics are categorized according to their recyclability and not numerically, Which was confirmed in A. A. Adeniran and W. Shakantu, “The Health and Environmental Impact of Plastic Waste Disposal in South African Townships: A Review,” Int J Environ Res Public Health, vol. 19, pp. 1–11, Jan. 2022, doi: 10.3390/ijerph19020779

Line 208-210: “Microplastics”: Authors defined its size is less than 5 mm. Then, how authors can say that “Due to their large specific surface area, microplastics are more likely to adsorb other pollutants and cause toxic effects when combined.”?  5 mm is a macro-scale. If authors want to say “large specific surface area”, authors should describe nano-materials, e.g., nanoplastics. Hence, I suggest that authors may define carefully & systematically, all the related terminologies concerning primary/secondary microplastics, and nanoplastics in an appropriate place in the manuscript.  

Response:

The statement where nanoparticle was mentioned is now removed.

Table 1. (1) Color is not needed in this table. (2) “Not classified” should not be included in Table but placed in the caption area. (3) Although monomer is toxic, polymer does not have to be toxic, indicating that if we well recycle the polymers mentioned in Table 1, it could be fine. Hence, Authors may give some comments about it. (4) Some polymer (e.g., PF) is repeated in the table. Also sometimes, there is unnecessary “.” at that end of polymer names. (5) “S and some numbers” are displayed but not defined.

Response:

Thanks for your comment. (1,2) color and “not classified” are now removed (3) the reuses or recycle of plastic waste will help to completely remove the microplastic and suggestion were provider in page 14 to this effect. (4) repeated word now removed and (5) S and other is now defined.

Figure 2. “WWTPs” Its full name should be introduced in the table’s caption.

Response:

Thanks for your comment. The name was given in full.

Line 196: “Nanoplastic (< 100 nm)” => “it should be <100 nm or <1000 nm”, depending on authors.

Response:

The microplastic are in microns and that is the word used in the manuscript

Line 208-209: this is a repetition. Check Line 65.

Response:

It was not a repetition, the statement in these lines are different idea talking to different subjects

Line 55: White pollution: Please define it carefully for reader-friendly.

Response:

Thanks for your comment. White pollution was well defined in the manuscript, please check lines 66-69

Abstract and Conclusion: it is not much critical. Improve it.

Line 36: “Plastics are chemically manufactured polymers” (Is there any better definition for plastic?)

Response:

Plastic are now defined and classified in to thermoplastic and thermosetting, please check lines 39-46.

Line 45: Broken English

Response:

Statement in this line has be rewritten.

Line 53-57: Improve English. (It should be parallel when compare something.)

Response:

The manuscript was checked for grammar holistically.

Line 71: I recommend that thermosetting and thermoplastic should be addressed in details from the recyclability point of view.

Response:

This explanation was done in lines 39-46; thermoplastic and thermosetting polymers were also defined.

 

Figure 1. From the polymer science point of view, I do not agree this category. (I suggest Authors may receive some consulting from the professionals who major in Polymer Science and Engineering.) In my view, the paper is not much technical.  

Response:

 

Based on the evidence/information provided in the available literature, the categories are correct as referenced. The plastics are categorized according to their recyclability and not numerically, Which was confirmed in A. A. Adeniran and W. Shakantu, “The Health and Environmental Impact of Plastic Waste Disposal in South African Townships: A Review,” Int J Environ Res Public Health, vol. 19, pp. 1–11, Jan. 2022, doi: 10.3390/ijerph19020779

 

Line 107-110: As I mentioned before, please address some comments the relationship between monomer and polymer from the view point of (1) hazard categorization and (2) recyclability. Table 1. Class I => I do not see there is any meaning for "green-color category". In addition, too much color makes the paper non-scientific (Please check the original paper).  Furthermore, the polymers mentioned in “non-classified” have a similar repeat unit with the classified ones. Hence, authors may give some comments about it although the original papers did the same things.

Response:

Based on the evidences/information provided in available literature, the categories are correct as referenced. The plastics are categorized according to their recyclability and not numerically, which was confirmed in A. A. Adeniran and W. Shakantu, “The Health and Environmental Impact of Plastic Waste Disposal in South African Townships: A Review,” Int J Environ Res Public Health, vol. 19, pp. 1–11, Jan. 2022, doi: 10.3390/ijerph19020779.  “not classified” and repeated word are now removed

 

Figure 4. Of course, everyone wants “Circular economy”. However, there is some technical restriction. Authors may think about re-processable polymers from polymer's structure point of view. In addition, if authors would add some “Life Cycle Assessment” about polymer materials, it would be better.

Response:

Life cycle assessment polymer materials is another broad area and it shall look into it in the future studies.

 

Table 2: Authors can add some more critical view about it because Table 2's contents looks nice and informative. 

 

Reviewer 2 Report

This manuscript reviews the devastation of Waste plastic on the environment and re- 2

mediation processes. This scoping review reveal a life style of application of plastics from waste reduction to recycling. The topic is interesting, but the paper requires certain modifications and discussion.

1. The abstract should show more briefly-clearly what problem you want to reviews and what contribution of the manuscript you want provide.

2.The originality of this work should be more clearly stated after fully reviewing the related previous works.

3.The regulations and popular knowledge occupies a lot of the manuscript. The review is suggested to more description on devastating effect and recycling of plastic.

4. The forecast should be provided in conclusion.

5. Please check the language, grammar issues, format and logicality throughout the manuscript.

Author Response

This manuscript reviews the devastation of Waste plastic on the environment and re- 2

mediation processes. This scoping review reveal a life style of application of plastics from waste reduction to recycling. The topic is interesting, but the paper requires certain modifications and discussion.

1. The abstract should show more briefly-clearly what problem you want to reviews and what contribution of the manuscript you want provide.

Response:

The abstract has been corrected accordingly.

 

2.The originality of this work should be more clearly stated after fully reviewing the related previous works.

3.The regulations and popular knowledge occupies a lot of the manuscript. The review is suggested to more description on devastating effect and recycling of plastic.

Response:

Discussion on the devastating effect of plastic material is now included in the manuscript.

4. The forecast should be provided in conclusion.
5. Please check the language, grammar issues, format and logicality throughout the manuscript.

Response:

The manuscript was checked for grammar holistically.

Reviewer 3 Report

This study defined the sources of plastic and their applications to provide the evidence on plastic waste reduction. Moreover, this study summarized that the plastic waste can be converted into value-added fuels via different methods. The suggestions may guide the recycling of plastic waste to achieve the goal of circular economy. Overall, the manuscript can be accepted after minor revision.

 

Specific comments

1.     Page 1 Line 24: The keyword "Human health" may be revised into "Creature damage" or words similar.

2.     Page 14 Table 2: "For an inert atmosphere, use a vacuum or nitrogen."

It is true that pyrolysis is conducted under an inert atmosphere. But it may use other types of inert gas such as helium not only nitrogen. For example, GC/MS uses helium as the purge gas. Please refer to DOI: 10.1016/j.enconman.2021.114114. The authors could consider to revise this.

Author Response

3This study defined the sources of plastic and their applications to provide the evidence on plastic waste reduction. Moreover, this study summarized that the plastic waste can be converted into value-added fuels via different methods. The suggestions may guide the recycling of plastic waste to achieve the goal of circular economy. Overall, the manuscript can be accepted after minor revision.

 

Specific comments

1. Page 1 Line 24: The keyword "Human health" may be revised into "Creature damage" or words similar.

Response:

The manuscript was amended as advised.

2. Page 14 Table 2: "For an inert atmosphere, use a vacuum or nitrogen."

It is true that pyrolysis is conducted under an inert atmosphere. But it may use other types of inert gas such as helium not only nitrogen. For example, GC/MS uses helium as the purge gas. Please refer to DOI: 10.1016/j.enconman.2021.114114. The authors could consider to revise this.

 

Response:

The manuscript was amended as advised.

Round 2

Reviewer 1 Report

I find that the manuscript is improved compared to the original version. However, before publication, I suggest the below minor revision.

1) Figure 1. Authors claimed that based on the reference "Int J Environ Res Public Health 19 1-11 2022", the categories are correct.

However, from Reviewer's point of view, the categories "Recyclable", "May be recyclable" and "Unrecyclable" can not be justified scientifically.

For example, why PVC, PS and others (Acrylic, Nylon etc.) can not be recyclable? Based on what evidence?

Hence, I suggest that considering Authors' opinions, you may draw a thick arrow pointing left side ( <======= Degree of Recyclability), mentioning that the left side is more recyclable than the right.

This is because you do not know in future somebody may recycle PVC, PS and others. Also, based on my Polymer Science point of view, the categories can not be justified scientifically. 

2) Typo: Line 144

polystyrene (PE) => polystyrene (PS) 

 

Author Response

Response to comments:

1, A big arrow showing the recyclability of thermoplastic is included in the figure and referenced in the text.

 

2. It has been corrected. Thanks so much.

Reviewer 2 Report

Accept

Author Response

Thanks so much