Recovery of Silver and Lead from Jarosite Residues by Roasting and Reducing Pyrometallurgical Processes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study focuses on the recovery of lead and silver from jarosite waste using a three-stage process, namely drying, roasting and reduction. Both lead and silver were almost completely recovered (>95%), while zinc and iron remained in the slag. Although this method is convenient, the manuscript presents several significant issues, outlined as follows:

1.       Page 2 Line 72: The authors believe the As will enter into the metal alloy during the reduction process. Table 1 also shows the jarosite residue contains 0.23% As. Why the authors did not mention the As? Where did the As go during reduction?

2.       Fig. 2 is too simple. Where do the metals go? What are the recoveries of metals? These information should be given. The characterizations can be labelled but not the part of the jarosite residue treatment process.

3.       In Page 6 Line 197~198: The proper mass ratio of CaO/SiO2 of fluxes is 0.92. When the authors added the fluxes, have they considered the part of Ca- and Si- containing compounds in the jarosite? Will they affect the calcium-silicon ratio during slag formation, thereby impacting the slag-making process?

4.       The jarosite contains 4.19% Zn and 11.05% Fe. If they remain in the slag, was it a big waste of resources?

5.       Table 3: The Fe content in the metallic phase for test 2 shows a significant difference compared to other test results. Have you conducted repeated experiments, or how can you prove the reproducibility of your experiments?

6.       In Section 3.5, according to the relationships described, if there is a peak for Fe in the XRD pattern, the characteristic peak for Ag should also be present. The reviewer believes that the results of SEM-EDS and XRD should be consistent to demonstrate the reliability of your experiment, rather than showing a complementary relationship.

7.       The workload of this study is insufficient, and the optimal roasting conditions have not been determined. It is suggested to increase the number of condition experiments.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you for this paper that brought souvenirs of my youth  when we have tried  to recover silver from  jarosite. Even if the process was working it was abandoned as far too expensive for the revenues generated by the silver. It is unfortunate that the authors did not comment on the economic feasibility of their process.  The numerous heating steps (drying, roasting and reduction)  as well as grinding must be very energy demanding, so the reduction of the jarosite volume will be at the price of a huge amount of greenhouse gas production? If the roasting is to remove S as SO₃ (as in Eq 2), would an acid plant be required to handle the gases? This should be discussed in an engineering journal.

The paper gives an excellent presentation of the experimental methodology.  The authors have done a very good work in terms of characterization (XRD, SEM, TGA). Is it unfortunately valid only for the studied jarosite? Any comments on the applicability of the process to other types of jarosite? Please indicate under which form are the Pb and Ag  in jarosite (sulphide or something else)?

Table 3 gives the Ag, Fe and Zn contents of the metallic phase. Under which form are these metals (elemental ,sulfides, silicates)?  If it is a metallic phase, I suppose it is elemental. The concentrations sum up to less than 2%. Please indicate what are the remaining constituents of the metallic phase? We assume that it is Pb, but it would reassure the readers if the authors could explicitly indicate it.

I am not sure that the authors have specified if the final plan is to produce Pb and Ag ingots  for selling or the objective is to remove these elements from the jarosite to respect environmental  regulation?  If the objective is to valorize the Pb and Ag, what is the plan to separate them in the bullion? Otherwise, how are they planning to dispose of the bullion -sell it to a Pb smelter-?

Did the authors give in a summary Table, the reduction of storage volume  that can be achieved by their process ? For example 1 ton of jarosite yields __ ton of slag and __ton of bullion? This would help the reader to assess the environmental and economic potential of the process.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Can be accepted now.