Mineralogical and Chemical Characteristics of Slags from the Pyrometallurgical Extraction of Zinc and Lead

Round 1

Reviewer 1 Report

Review on the paper

“Mineralogical and chemical characteristics of slags from the pyrometallurgical extraction of zinc and lead”

by K. Nowinska

The paper provides analysis of phase and elemental composition of the waste slag from Pb/Zn smelting in a plant from Poland. The results may be of interest for future recycling of the slag in order to extract remaining valuable components, as well as to estimate the environmental hazards due to presence of phases with various chemical activity and solubility.

The study can be published after minor revision.

1. Line 31: PSI abbreviation – is it ISP?
2. Line 36: CdO – CaO?
3. Line 38 and further: For all mineral names occurring in the text, chemical formula description should be given at least once, e.g. zincite ZnO, wustite FeO, hematite Fe₂O₃…
4. Line 40: Fayalite, kirschsteinite and forsterite are all olivine varieties, should be put in brackets.
5. Line 43 and further: “cerusite” should be cerussite.
6. Line 43: No need to list the same “pure metals” after mentioning them as “metal alloys”. Really pure metals are not possible to occur in such a complex material.
7. Line 67: Energy-dispersive spectrometers are known to have low resolution of certain lines, e.g. Pb Ma, Mo La and S Ka, Pb La and As Ka, As La and Mg Ka, Sb La and Ca Ka. How did the author deal with this fact, and how accurate the analysis is to be expected considering this?
8. Line 75: Mixed PbO-ZnO oxide phases are unknown (the possible mutual solubility is negligible) – may be measurement artefact.
9. Line 141: Please explain the term “diadochal” or provide a reference.
10. Line 210: Why the oxidation states FeO (not Fe₂O₃), CuO (not Cu₂O), SO₃ (not S or S^2-) are considered?
11. Line 210: “The total content of these constituents is over 74% wt. FeO content is only slightly diversified…” – seems grammatically incorrect.
12. Line 216: What means “quantitatively significant”?
13. Line 230: Too many digits for As concentration. What are the estimated uncertainties of the given numbers? Please provide them, and limit all digits to approximately the uncertainty of the given value in Tables 3 and 4. Note that “standard deviation” in Table 3 corresponds to the difference between the 4 slags, but gives no information on the internal uncertainty of each slag.
14. Line 238: lower than limit of detection.
15. Line 314: Fe is usually not considered as a valuable component of nonferrous slags, but Cu is.

Comments for author File: Comments.pdf

Author Response

Please find below the changes introduced according to Reviewer’s comments.

Line 31: “PSI” has been changed to “ISP”.

Line 36: “CdO” has been changed to “CaO”.

Line 38 and further: For all mineral names chemical formula description have been given .

Line 40: Fayalite, kirschsteinite and forsterite are all olivine varieties, have been put in brackets.

Line 43 and further: “cerusite” has been changed to “cerussite”.

Line 43: “pure metals Zn, Pb, Cu, Fe”  have been removed from the text.

Line 67: Measurements on the X-ray microanalyser were carried out using the wave-length dispersive spectrometer (WDS). In this part of the manuscript is incorrectly placed “... an Oxford Instruments ISIS 300 energy-dispersive spectrometer” and it has been corrected as follows: ” ...an Oxford Instruments ISIS 300 wave-length dispersive spectrometer”.

The following sentences have been added to the text: The “WDS method is characterized by high energy resolution, it means that the amount of overlap between peaks of similar energies is low.

The studies were mainly conducted on such grains that the beam did not extend beyond the grain outline, each wave spectrum measurement was preceded by the determination of the grain diameter. In the case of multiphase grains, the boundary between the intergrowth and the dominant phase was determined based on microscopic observations in reflected light. The  series of ten microanalyses were carried out for each of the grains to determine the main chemical components and trace elements”.

Line 75: Mixed PbO-ZnO oxide phases is measurement artifact, so “PbO-ZnO” has been removed from the text.

Line 141: Description of “diadochal” and reference have been added to the text. This part of the manuscript has been corrected as follows: “due to their crystallographic similarity (similar ionic radius),which is quite common in silicates [17]”.  

Line 210: The oxidation states FeO (not Fe₂O₃), CuO (not Cu₂O), SO₃ (not S or S^2-)  are the result of the conditions of the lead refining process and they predominate in the chemical composition of slags, for this reason they were considered.

Line 210: The sentence “FeO content is only slightly diversified…” has been changed to “The content of FeO is slightly diversified...”

Line 216: The sentence “A quantitatively significant chemical constituent is ZnO.” has been changed to “Another significant constituent in terms of quantity is ZnO”.

Line 230: This part of manuscript has been changed and the contents of As and other trace elements are given as %wt.  The estimated uncertainties have been provided to Tables 3 and 4.

Line 238: “lower limit of detection” has been changed to “lower than limit of detection”.

Line 314: “Fe” has been removed from the text.

Reviewer 2 Report

I have a few specific comments about the paper.

1. It would be extremely helpful for the reader if nominal formula or stoichiometry for the all of the phases reported were provided.
2. In the experimental, line 67, is "Joel" meant to be "JEOL"?
3. It is unclear whether WDS or EDS was used to determine which elements. This limits confidence in the compositions determined for each phase. Is the beam diameter given for the beam at the surface of the sample or is it for the full interaction volume? You have used quite a high voltage, is this voltage necessary for analysis of the heavy elements is possible, or could it be carried out at 15 kV, with a smaller interaction volume? It is later claimed that the phases were finely dispersed, does this beam diameter mean that the area (volume) analysed actually includes more than one phase?
4. A structural comment, you have provided the XRD and SEM-EDS results first, followed by the bulk compositional analysis by XRF. I think that it would flow better if the XRF results were provided first, followed by the XRD and SEM.
5. Why were the quantitative XRD results provided in the discussion and not in the results?
6. How was the glass content of the samples determined?
7. The contrast on the micrographs appears to be limited, and actually appear to be of generally poor quality.
8. In Table 1, there are many elements analysed at a low level, many elements are in the order of ~0.2% and others at ~0.02%. If these results came from EDS, then it would be optimistic to use these as quantitative data. However, if the analyses came from WDS analysis, then the confidence in the data would be much higher.
9. In Table 1, how many points for each phase were analysed in order to get the statistics?
10. Page 5, line 118. It is stated that Cu and Zn content increases with increasing Fe. I believe that the authors meant to write that Cu and Zn "decrease".
11. In Table 3, how many analyses were performed on each sample in order to get the statistical data?
12. Table 4, I believe that the analyses are given in ppm, and not wt%.
13. In Table 5, why are the statistics given across the 4 types of the samples. From the discussion leading to this point, the four layers would not be expected to be the same, so this analysis seems redundant.
14. Based on your analysis of the different phases (or types of phases) within the samples, does the author have any comment to make about what layers may be the most useful or easiest to utilise?

Author Response

Please find below the changes introduced according to Reviewer’s comments.

1.  For all mineral names chemical formula description have been given. 

2. In the experimental, line 67, ” Joel” has been changed to “Jeol”.

3. Measurements on the X-ray microanalyser were carried out using the wave-length dispersive spectrometer (WDS). In this part of the manuscript is incorrectly placed “... an Oxford Instruments ISIS 300 energy-dispersive spectrometer” and it has been corrected as follows: ” ...an Oxford Instruments ISIS 300 wave-length dispersive spectrometer (WDS)”.

According to the Reviewer’ comment the following sentences have been added to the text: “The WDS method is characterized by high energy resolution, it means that the amount of overlap between peaks of similar energies is low.

The studies were mainly conducted on such grains that the beam did not extend beyond the grain outline, each wave spectrum measurement was preceded by the determination of the grain diameter. In the case of multiphase grains, the boundary between the intergrowth and the dominant phase was determined based on microscopic observations in reflected light. The  series of ten microanalyses were carried out for each of the grains to determine the main chemical components and trace elements”.

4. The structure of the paper has been changed, the XRF results have been provided first, followed by the XRD and SEM.

5.  Quantitative XRD results are provided in the discussion, not in the results, because these are the results of calculating the relative percentage content of individual phases in the slag samples based on the results of conducted studies.

6. The glass content is calculated from results of analyses, it is relative percentage content resulting from the participation of all other mineral phases.

7. The contrast on the micrographs has been increased.

8. The analyses came from WDS analysis.

9. In Table 1, 30 points for each phase were analyzed.

10. Page 5, line 118. “the content of copper and zinc also increases” has been changed to “the content of copper and zinc decrease”.

11.  In Table 3, 10 analyses were performed on each sample.

12. Table 4, The analyses were given in ppm, not wt%. According to the Reviewer’s comment they have been changed and given in wt% (the same in Table 3).

13. In Table 5, The statistics are given across the 4 samples from the top layer (WI, WII, WIII, WIV), which represented the slag from current lead refining. The slags from one layer would be expected to be the same, so this analysis is reasonable.

14.   After analyses of the slags from all 4 layers author will be able to specify what layers may be the most useful or easiest to utilize.