Metal Foam Electrode as a Cathode for Copper Electrowinning

Round 1

Reviewer 1 Report

After carefully reading of the manuscript. Overall, this is an useful paper for the related research communities. However, there are several issues that need to be addressed before it can be considered for publication.

1. Line 96: ”1mm to 0.1 mm.” Use the same units (microm or mm).
2. Spaces should be inserted between numbers and units e.g. line 96: 1mm; line 102: 1x1cm2; line 122; 2mv/s; line 124: 0.6V, etc.
3. Line 122: replace mv/s with mV/s 
4. Line 122: ”voltammetry measurements”  It is worth mentioning the type of the used voltammetric technique, e.g. sweep, alternating current, potential step etc.
5. Experimental conditions for the chronopotentiometric experiments (mentioned in lines 305, 306) should be also described in section 2.2.
6. Instrumentation used or pH measurements of the solutions indicated din Table 1 should be indicated.
7. Figure 2b. The scale on the cathodic current axis should be checked because the distance between 1 and 10 is the same as between 10 and 100 and between 100 and 1000.
8. Line 164: ”chronoamperometric measurements have been done in 0.1 M CuSO4 and 0.4 M Na2SO4 solution”. The authors should explain why did they chose this solution for chronoamperometric measurements.
9. Line 165:”three fixed potentials -0.2, -0.4 and -0.6V vs Ag/AgCl ”. In Table 2 are listed 4 deposition potentials.
10. The authors should briefly explain why the deposition time listed in Table 2 for a given deposition potential is different for the two tested electrodes.
11. In the tables, the values ​​of each parameter must be written with the same number of decimals.
12. The date included in Table 3 are also presented in Fig 5 and 6, respectively. I recommend that the authors chose to present the data in one of the two forms (table or figures).
13. Lines 278-279. ”When looking at the effects caused by diffusion, at low concentrations the CPE(W) is almost equal on both surface geometries,” Please explain this statement in the context of the values given in table 4 indicating what exactly means low concentrations (e.g only 0,01 M.
14. Lines 281 - 283: ”The overall trend in mid-level and high concentrations is that with the increase of Cu2+ concentration, the CPE(W) value increases, and the R(Diff) decreases.” According to table 4 this statement is valid only for Cu foam electrode. Please explain the situation for the Cu plate electrode.

Author Response

Thank you very much for all the comments, corrections, and questions. Hopefully, all of them have been fully addressed in the manuscript and attached MS Word file. Thank you once again for all your hard work.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript entitled “Metal foam electrode as a cathode for copper electrowinning” studied the surface porosity differences to the electrochemical deposition process on a copper plate and copper foam. The experiments were well-organized and presented. However, there are a few minor things that need to be addressed:

• In Figure 3, the scale bar for the Cu foam at the potential of -0.6 V was larger than the other corresponding figure of Cu foam at the potential of -0.2 V. If situation allowed, please retake the SEM picture of this sample and have the same magnification under the scanning electron microscopy.
• On page 6, line 195, authors claimed that the surface morphology change would be minimal and can be ignored before and after EIS experiment measurements. Could you please provide some SEM pictures to compare the surface morphology differences to confirm this assumption?
• On page 9, line 251, please correct the “its clear that The 3D electrode displays…” to “it’s clear that the 3D electrode displays…”

 

The manuscript is suggested to accept after the revision.

Author Response

Thank you very much for all the comments, corrections, and questions. All the authors have carefully considered your questions and comments they have been fully addressed in the manuscript and attached MS Word file. Thank you once again for all your hard work.

Author Response File: Author Response.docx

Reviewer 3 Report

This paper presents metal foam electrode for Cu electrowinning. The introduction is very clear and presents the research motivation well and background for metal foam electrode. 

1) Can you explain the hump of cathodic current going down after up for 10 mM and 50 mM in Figure 2?

2) Line 210. How CPE (DL) was recalculated? need more explanation

 

3) The final  paragraph of introduction and conclusions are little too short considering the main text dealing with many things.

 

4) Minor..There are many formatting and grammatic error.

-Should define EIS firstly in abstract. 

-need space for unit...50 μm

-x axis in Figure 4, 1E+03 this expression is not good for scientific paper. recommend like this .10³

-see x axis in Figure 4a. need correction. 

Author Response

Thank you very much for all the comments, corrections, and questions. Hopefully, all of them have been fully addressed in the manuscript and attached MS Word file. 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I have carefully read the authors responses to my comments and I totally agree with them but I still have some recommendations:

1. To introduce also in the manuscript a brief explanation (a short version of the authors response) to the following two observations:

 

1000. My observation: Figure 2b. The scale on the cathodic current axis should be checked because the distance between 1 and 10 is the same as between 10 and 100 and between 100 and 1000.

The authors response: In this case, we used a logarithmic scale to represent cathodic current in Fig. 2 (a) and (b) graphs, because the differences between the currents during voltammetry experiments are quite big, and we decided to use a logarithmic scale which helps us better represent the differences in values.

1. My observation: ”The overall trend in mid-level and high concentrations is that with the increase of Cu2+ concentration, the CPE(W) value increases, and the R(Diff) decreases.” According to table 4 this statement is valid only for Cu foam electrode. Please explain the situation for the Cu plate electrode.

The authors response:  In this case, I imagine you are asking about differences between R(Diff) values obtained at 0.05 and 0.2 M concentrations. The difference there is around 14% and is quite small. However, the general trend still can be seen from other experiments we did on the Cu plate electrode, where we obtained R(Diff) values of 419, 523, and 583 for 0.05 M concentration and 384, 315 and 323 for 0.1 M concentration. The data shown in the manuscript was obtained during one day run, trying to reduce outside effects, and might not best represent the whole trend from the first look, however, we don’t feel confident trying to calculate statistical indexes from only 4 values.

2. Table 3. The values of R(CT) for Cu foam should be written with the same number of decimals.
3. Line 136: Insert a space between 0.6 and V.

Author Response

Thank you very much for your comments. All your suggestions have been considered and added to the manuscript. 

Author Response File: Author Response.docx