Optimization of Silver Nanoparticle Separation Method from Drilling Waste Matrices
Round 1
Reviewer 1 Report
The paper “energies-1125633-Optimization of silver nanoparticles separation method from drilling waste matrices” investigated optimal method of silver nanoparticles (AgNPs) separation and pre-concentration from the drilling waste samples. The manuscript is well organized; to improve the quality, the following recommendations can be incorporated.
1.The authors should review the other investigation on their study way in the introduction part and finally note the novelty of the article. The introduction part needs to develop. Authors can use the following work in the introduction:
"Nanotechnology and it’s applications in environmental remediation: an overview." Vegetos 32, no. 3 (2019): 227-237.
"Application of Nano-Particles of Clay to Improve Drilling Fluid." International Journal of Nanoscience and Nanotechnology 13, no. 2 (2017): 177-186.
"Application of TiO 2 and fumed silica nanoparticles and improve the performance of drilling fluids." In AIP Conference Proceedings, vol. 1590, no. 1, pp. 266-270. American Institute of Physics, 2014.
- The methodology section is not well organized for the readers to understand the concept.
- It is written in line 361 that " It is possible that this is due to the composition of the matrix, which absorbs silver differently than other waste. "?! What is the reason? In addition, table and figures captions are very short.
- The language used in the introduction can be more specific to the scope and aim of the study.
- Section “results” is poorly written and limited. More details on quantities should be provided for each table and figure. In fact, the main body of your manuscript should be a result, not backgrounds and methodologies. The manuscript needs to be interpreted.
6 Structure of this paper is similar to the technical report, not an academic paper, so authors should again rewrite all of parts base on journal paper style.
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript reported a comparison between the two methods of centrifugation and cloud point extraction for the separation of silver nanoparticles from the drilling wastewater. The data provided in the manuscript supports the claim. However, in this reviewer’s opinion, the manuscript suffers from several drawbacks and should be edited before considering it for publication.
- The introduction is discussed too general topics but failed to specifically address the problem that the manuscript trying to deal with and the logic behind the technical approach that is chosen for this purpose. For example, only on page 4 of the introduction and the last two paragraphs, the authors mentioned the methods that they are aimed to compare:
“An important step in the nanoparticle determination method is the step of separating nanoparticles from the matrix. Currently, one of the most widely practiced sample preparation procedures for NPs determination from environmental samples is cloud point extraction (CPE). It has been shown to separate nanoparticles efficiently [28-30]. However, it has not been used for drilling wastes which are complex, heterogeneous, multi-component mixtures of chemicals, both inorganic and organic. They may contain: heavy metals (chromium, nickel, cadmium, arsenic, barium, mercury, vanadium, iron, etc.), as well as high levels of soluble salts, grease, petroleum hydrocarbons, which caused great environmental concerns [31].
Additionally, another NPs separation method, i.e. centrifugation has been tested. AgNPs size distribution, along with the state of aggregation was evaluated by single-particle inductively coupled plasma mass spectrometry”
- It reads as the CPE is a well-known method that is used to separate the nanoparticles efficiently, However, it has not been tested for drilling wastewater and wastewater is complex and multicomponent. Then, the authors should provide the logic that why the centrifuge method is selected as a possible alternative method for comparison with the CPE method. Brief literature on the centrifugation method is beneficial. Especially, as the time and RPM of the centrifuge are the main parameters that were altered later in the manuscript to find the supposed optimized method.
- Overall in the reviewer's opinion, the introduction should be restructured, the first two pages of the introduction are more suitable for a future review paper, but regardless, the introduction should deliver the issue and literature on why the authors presented a method to deal with the issue.
- Please double-check the centrifugation time on the flowchart on page 7 FIG 4, as it seems to not match with what is described in the body in lines 229 and 313.
- The conclusion should outline a summary of what concluded from the study. The first two paragraphs of the conclusion (Lines 371 to 388) do not provide any conclusion from the current study and better to be discussed only in the introduction.
- Paragraph 3 of the conclusion describe the most effective rpm and paragraph 4 describes the best centrifugation time, and paragraph 5 states that CPE is a more efficient method for separation of AgNPs, while paragraph 6 states there is no one-size-fits-all method for separating silver nanoparticles from the wastewater as the matrixes are so diverse. Then in terms of the objective of the study what significant conclusion is delivered? The abstract presented the objective of the study “to select the optimal method of separation and pre-concentration of AgNPs from drilling wastewater” Is there any optimal separation condition?
- The last paragraph again is not a conclusion of the current study and also is out of context. Please consider rewriting the conclusion.
Comments for author File: 
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Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The article can be accepted for publication.
Author Response
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Author Response File: Author Response.docx
Reviewer 2 Report
Dear Authors,
The introduction is improved. However, in this reviewer's opinion, the conclusion does not deliver any significant outcome from the current study other than this single sentence "The results of the studies indicated clearly that there is no one-size-fits-all method for separating silver nanoparticles from waste samples and drilling waste water extracts." Please elaborate on your results, and provide a summary of what "doing your experiments" resulted (in outcomes). Starting from the title "Optimization of silver nanoparticles separation method from drilling waste matrices" your conclusion delivered it is difficult to do so because the matrices are so diverse. At least a brief summary of what affected the sizes, distribution, and/or what parameters should be focused on in futures studies should be included. Again please avoid general sentences that are not directly concluded from the current study. There is no need for redundancy and justifying the reasons to perform the study again in the conclusion.
Author Response
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Author Response File: Author Response.docx
Round 3
Reviewer 2 Report
The conclusion is improved.
