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Peer-Review Record

Modifications and Improvements to the Collector Metal Method Using an mhd Pump for Recovering Platinum from Used Car Catalysts

Catalysts 2020, 10(8), 880; https://doi.org/10.3390/catal10080880
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Catalysts 2020, 10(8), 880; https://doi.org/10.3390/catal10080880
Received: 11 July 2020 / Revised: 28 July 2020 / Accepted: 29 July 2020 / Published: 4 August 2020
(This article belongs to the Special Issue Recent Advances Utilized in the Recycling of Catalysts)

Round 1

Reviewer 1 Report

The paper addresses one of the important aspects of the catalyst using in the real world -- catalyst recycle. The paper itself is not hard to follow and we would suggest the paper to be published in the current form. 

Author Response

Dear Reviewer,

We are grateful for taking your time to read our paper and for comments.

 

The paper addresses one of the important aspects of the catalyst using in the real world -- catalyst recycle. The paper itself is not hard to follow and we would suggest the paper to be published in the current form. 

 

Reviewer 2 Report

The authors reported improvements to the metal collector method to recover platinum from used car catalysts. This work is an extension to their previous studies. They carried out some experiments to find the optimal parameters for recovering platinum. The introduction is well written. This work shows significant results. However, some points need to be clarified before the manuscript could be considered for publication. Suggestions of revision include:

Page 8 Figure 6. Figure 6(b) and 6(c) look very the same. The current density is 20 A at 50 Hz for Figure 6(b) and 40 A at 50 Hz for Figure 6(c). However, in Figure 4(b), the velocity of metal flow seems to be different between 20 A and 40 A at 50 Hz. The authors shall explain it in the text.

Page 9 line 295. "The tests were carried out for three values of secondary voltage on transformer covers, equal to 19, 40 and 60 V, respectively." Why do the authors choose the secondary voltage as 19 V rather than 20 V? The values of secondary voltages for tests do not look evenly spaced.

Page 9 Figure 7. From this chart, the optimal time for washing platinum is 600 s. Any time longer than 600 s does not seem to have a better result. Can a shorter time less than 600 s get a better result?

Page 10 Figure 8. Can the frequency of 12.5 Hz get a better result than 25 Hz? An inductor supply frequency of 12.5 Hz is shown in Figure 4(a), but is not applied in Figure 8.

Page 11 line 366-369. The authors stated "Figure 10 shows...platinum coated surface was 3.261 mm2, 3.466 mm2, 3.422 mm2, 2.356 mm2, respectively,..." How is the platinum coated surface determined? Figure 10(c) and 10(d) look similar, but the coated surfaces are quite different.

Author Response

Dear Reviewer,

We are grateful for taking your time to read our paper and for your constructive comments. We have carefully reviewed the comments and have revised the manuscript accordingly. Our responses are below given in a point-by-point manner. Changes to the text are shown in red in the revised manuscript. We hope the revised version is now suitable for publication.

 

The authors reported improvements to the metal collector method to recover platinum from used car catalysts. This work is an extension to their previous studies. They carried out some experiments to find the optimal parameters for recovering platinum. The introduction is well written. This work shows significant results. However, some points need to be clarified before the manuscript could be considered for publication. Suggestions of revision include:

Page 8 Figure 6. Figure 6(b) and 6(c) look very the same. The current density is 20 A at 50 Hz for Figure 6(b) and 40 A at 50 Hz for Figure 6(c). However, in Figure 4(b), the velocity of metal flow seems to be different between 20 A and 40 A at 50 Hz. The authors shall explain it in the text.

The following sentence was added to the text:

The change in current does not cause a significant change in the velocity and structure of the liquid metal, which can be seen in Figs. 6b and 6c. Changing the frequency does not affect the structure, but the speed of the metal decreases as the frequency decreases.

Page 9 line 295. "The tests were carried out for three values of secondary voltage on transformer covers, equal to 19, 40 and 60 V, respectively." Why do the authors choose the secondary voltage as 19 V rather than 20 V? The values of secondary voltages for tests do not look evenly spaced.

The secondary voltage for a typical transformer that was used in the research is 19 V. Therefore, this value was adopted. Successive secondary voltage values were adopted as doubled and tripled values of 19 V, i.e. 40 and 60 V, rounded for computational comfort.

Page 9 Figure 7. From this chart, the optimal time for washing platinum is 600 s. Any time longer than 600 s does not seem to have a better result. Can a shorter time less than 600 s get a better result?

Shorter time was not taken into account for technological reasons. Initial tests have shown that a time of less than 600 s is insufficient for lead to infiltrate the catalyst channels. Additionally, conducting the tests in less than 600 seconds is logistically difficult (loading the catalysts, obtaining full lead flow, changing the direction of lead flow, replacing the catalysts). Therefore, in the relevant studies, 600 s were used as a reference point.

In the text the following sentence was added:

Initial tests have shown that less than 600 s is not sufficient for lead to penetrate the catalyst channels. In addition, carrying out the tests in less than 600 seconds is logistically difficult (loading catalysts, obtaining full lead flow, changing the direction of lead flow, catalyst replacement). Therefore, this time was used as a reference point in the research.

Page 10 Figure 8. Can the frequency of 12.5 Hz get a better result than 25 Hz? An inductor supply frequency of 12.5 Hz is shown in Figure 4(a), but is not applied in Figure 8.

The most uniform velocity distribution in the channel is obtained for a frequency of 25 Hz. Changing the frequency practically does not affect the flow structure of the liquid metal in the channel. This is also confirmed by the distribution (Fig. 4) of the velocity of the liquid metal in the channel over the entire width of the catalyst (l = 0-0.06 m). However, an increase in frequency causes an increase in the maximum values of the forces acting on liquid lead at the unit walls for both types of field, i.e. transverse and longitudinal. Fig 4 is the result of numerical research, which allowed to select experimental research. Therefore, in laboratory tests, the frequency of 12.5 Hz was rejected and not included in the tests.

In the article the following text was added:

Changing the frequency practically does not affect the flow structure of the liquid metal in the channel. This is also confirmed by the distribution (Fig. 4) of the velocity of the liquid metal in the channel over the entire width of the catalyst (l = 0-0.06 m). However, an increase in frequency causes an increase in the maximum values of the forces acting on liquid lead at the device walls for both types of field, i.e. transverse and longitudinal. Fig 4. is the result of numerical research, which allowed to select experimental research. Therefore, in laboratory tests, the frequency of 12.5 Hz was rejected and not included in the tests. In the same time, the frequency value of the device (50-100 Hz) generates too high liquid metal velocity in the channel. It is disadvantageous due to the difficulty of wetting the catalyst capillaries and problems with liquid lead splashing.

Page 11 line 366-369. The authors stated "Figure 10 shows...platinum coated surface was 3.261 mm2, 3.466 mm2, 3.422 mm2, 2.356 mm2, respectively,..." How is the platinum coated surface determined? Figure 10(c) and 10(d) look similar, but the coated surfaces are quite different.

Size of PbLi alloy drop surface area was calculated as the arithmetic mean of three attempts to determine the surface area. The obtained test samples were photographed along with the scale, and then placed in the Fusion 360 graphic program. The software allows to determine the surface of the drop by tracing its contour. The drops were also processed on a stereoscopic optical microscope to determine their dimensions. Both results, both the droplet dimensions and the plotted area with the calculated surface area are presented in Fig. 10.

Below is an example for Pb with Li (16%).

Example:

 

Fig. 16% lead-lithium alloy sample and the calculated drop surface area with the drawn area in the Fusion 360 graphics program

 

In the text added the following sentence and changed the Fig. 10

 Size of PbLi alloy drop surface area was calculated as the arithmetic mean of three attempts to determine the surface area. The obtained test samples were photographed along with the scale, and then placed in the Fusion 360 graphic program. The software allows to determine the surface of the drop by tracing its contour. The drops were also processed on a stereoscopic optical microscope to determine their dimensions. Both results, both the droplet dimensions and the plotted area with the calculated surface area are presented in Figure 10.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper titled “Modifications and improvements to the metal collector method using an mhd pump for recovering platinum from used car catalysts” is aimed to intensify the extraction process of platinum and palladium from the spent automobile catalysts. The topics considered in the paper are more suitable for another journal, like Processes. Anyway, the paper requires significant revision. The comments are listed below. 

 

  1. The type of manuscript is noted as Article (not chosen in the paper). At the same time, it seems to be a mini-review. 
  2. The abstract looks inappropriate. It mostly describes the problem than the achievements of the work. I guess it should be rewritten.
  3. Dimensions of the metal flow velocity (m/s m) are unclear – see Fig. 4.
  4. All the results are taken from previously reported sources. It is not clear if this is a research article, what was done within the current study.
  5. Slight polishing of English is required.

Author Response

Dear Reviewer,

the answers to the remarks are enclosed in the file.

Yours sincerely,

Authors

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have answered my questions. The manuscript can be published as is.

Author Response

Dear Reviewer,

We are grateful for taking your time to read our paper and for all comments.

Yours sincerely,

Authors

Reviewer 3 Report

The authors have revised the manuscript thoroughly. Most of the questions are dropped. Since the paper belongs to a special issue ‘Recent Advances Utilized in the Recycling of Catalysts’, it can be accepted for publication. Just a slight remark – change ‘Fig. 4’ (line 342) and ‘Fig. 9’ (line 374) to ‘Figure 4’ and ‘Figure 9’, correspondingly.

Author Response

Dear Reviewer,

We are grateful for taking your time to read our paper and for all comments improving our article.

We corrected the pointed Figures.

Yours sincerely,

Authors

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