A Comparative Study of Microwave and Resistance Heating for the Efficient Thermal Desorption of Mineral Oil from Contaminated Soils

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work focus on the comparison of mineral oil removal performance in polluted soil between conventional resistance heating and microwave heating method. The work is not well organized and the analysis methods are very questionable due to lack of citation and clear description.  Here are issues to be addressed:

1) In Line 31, please change the cited paper number into [1]. It is more friendly for readers. Also, the period or full stop should be placed behind the [1]. Please revise it in the rest of the work.

2) Please combine your 2.1 experimental materials and 2.3 experimental device together as 2.1 Experimental materials & device. Normally it is more reasonable to introduce our materials and device first, and then the analysis method.

3) For the properties in Table 1, petroleum hydrocarbon contaminants, what standard method (e.g., US EPA 8015C TPH) is used? This should be specified. This is very important!

4) In 2.2.1, Obviously, this organic matter content analysis method is not developed by you. Please cite the original paper to give the credit to the researchers and also allow readers to assess whether the method is reasonable or not in your case.

5) For the 2.2.2. The description here is not clear. It is a mixture of two tests: 1) CEC analysis 2) the organic matter analysis from the heat treated soil. But the title only covers the CEC, first part. Plus, for CEC analysis and organic matter analysis, we have to put the citation to support this method's feasibility. Otherwise, all the analysis results in this work are questionable.

6) In Figure 1, why the resistance heating device is shown within the microwave heat unit? It is so confusing. Is it better to draw these two heating method system separately? The team want to compare the different performance between microwave heat and resistance heat right?

7) In Figure 2 Since you want to compare the performance of mineral oil removal between these two methods, why not put the oil removal data of two different treatment together to provide more direct look for readers? Water content drop is not as important as the oil removal rate. Please put water removal rate together.  Plus, the inner label of the curve "water removal rate" means different thing to the Y axis Cwater (%), water content (%). Based on your dropping curve, it is water content not water removal rate!

In the whole paper, the authors talk about mineral oil. Why here in the Figure 2 legend, it suddenly change the concept to toluene removal? I don't understand it at all! There is no explanation why the author want to shift it to toluene. So confusing.

8) Please check the soil type name in Table 3,  important information is missing.

9) For Figure 4, isn't it better to draw the first order kinetics via the ln(Ct/C0)=-kt? As the whole process is making the mineral oil level drop not increase in the soil.

10)For Figure 5, in order to provide a more direct comparison between the two heating method, it is better to set the Y axis the same scale like 0-25. In this way, the difference or the advantage of using microwave heating will be obvious.

11) serious wrong statement: Based on Figure 6, microwave heating's Ea is higher than resistance heating, why you say the opposite in Line 347-351 and Line 367-370? It is so wrong! 

Comments on the Quality of English Language

English is fine. No serious errors were detected.

Author Response

请参阅附件。

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

This article highlights a rather acute problem in finding effective methods for soil remediation of organic contaminants. The article presents quite promising data in this area of research. For a better understanding of the results obtained, there are a number of comments: 

1. The first thing that catches the eye is the incorrect format of references. I recommend to read the guide for authors and format the article according to the requirements of the journal.

2.           I think it is necessary to add to the list of references some articles from the library of the journal Sustainability, which are close to the topic of the peer-reviewed paper.

3. I recommend to replace the color identification with numerical identification for the convenience of information perception from the unit setup scheme. Make changes in the text and include numbered elements in the caption of the figure 1.

4. What is a temperature sensor? How does it work under microwave conditions? If it is a thermocouple, what type? Can there be measurement errors due to electromagnetic interraction with the device?

5. What wave-absorbing material was used to modify the reaction vessel (red line)? Does this material heat up during MWI absorption and if so, to what temperatures? Does it contribute to the heating of the sample?

6. The mechanism of interaction of the studied objects with electromagnetic radiation is not completely clear. MWI interacts with polar substances (e.g. H2O, which boils up to 100 °C). In the composition of transformer oil, the main part is non-polar organic compounds of various classes, which should not absorb MWI. What is the reason for reaching the temperature of 300 °C?

7. What products are obtained during the experiment? Can you give the composition of the gas and liquid fractions?

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Please see the comments

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed most of the comments, however, there are still some serious issues to address:

1) for the new statement added above Figure 6 on activation energy derived from Arrhenius equation. Based on your thermal desorption data, figure 5 and table 4, the Ea of microwave heating should be lower than conventional heating (I think that's the reason why your team made a different statement saying Microwave heating has a lower Ea in your previous submitted manuscript). Ea or the activation energy in this case, it means the minimum energy needed to desorb the mineral oil from the soil via heating. Based on Figure 5 and Table 4, when temperature increase 50 C for both conventional heating and microwave heating,  the desorption rate K (see your table 4) and the desorption efficiency  of microwave method is always higher than the conventional one, indicating same temperature increase will trigger more mineral oil release, which suggests the Ea of microwave method should be lower, not higher than conventional method! Your new explanation makes no sense at all. Please take time to figure out what Arrhenius equation really means before applying it. If this issue cannot be well solved, the chance to be accepted will be small. Once suggestion is to redo your test at 3 different  temperatures to get a new Ea.

2) inconsistent format, please unify the format of the whole manuscript. For example, 3.0, the whole paragraph format is totally different from the rest. Another example, for all the cited reference [1], [2] ..., please check the format of the Arabic number and make them consistent with the whole manuscript. 

 

Comments on the Quality of English Language

No issue with English

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I recommend to replace the color identification with numerical identification for the convenience of information perception from the unit setup scheme. Make changes in the text and include numbered elements in the caption of the figure 1.

 

Author Response

Comments : I recommend to replace the color identification with numerical identification for the convenience of information perception from the unit setup scheme. Make changes in the text and include numbered elements in the caption of the figure 1.

Response :Thank you very much for your thoughtful suggestion. I agree that replacing the color identification with numerical identification in the unit setup scheme of Figure 1 will improve the clarity and ease of information perception. We have now made the necessary changes in the text and included numbered elements in the caption of Figure 1 to provide a clearer reference for readers.

 

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have addressed my comments properly. No other issues.