Valorization of Mining Waste by Application of Innovative Thiosulphate Leaching for Gold Recovery
Round 1
Reviewer 1 Report
The importance of the findings in this paper to the treatment of mining tails indicate good gold recoveries can be achieved with the targeted materials though the quality of the English expression detracts substantially from this paper. There is a lack of discussion on the thiosulfate leaching results while it is notable that the kinetic data for the 3 M ammonia concentration do not seem to fit with the other data (nor that previously published, e.g. Ref. 11).
It is worth making the point here that the thiosulfate process as studied in the laboratory is not innovative though its commercial application certainly is, and would also be for the treatment of Romanian mine tailings. I agree, however, that the use of the word “innovative” in the title can be substantiated given the other words present in the title. However, subsequent usage of this word does need to be carefully managed as this should refer to your (potential) application of thiosulfate technology not to the technology itself (especially as stated above, when used in a laboratory).
A range of other comments and suggestions for improvement to the English expression have been included in the attachment. As there are a substantial number of these, a major revision of the manuscript is recommended.
Comments for author File: 
Comments.pdf
Author Response
Dear reviewer, we kindly thank you for reviewing the manuscript and for the recommended changes. The manuscript has been modified based on the recommendations and suggested implementations. I attach the document with detailed answers to your comments.
With my best regards
Stefano Ubaldini
Author Response File: Author Response.pdf
Reviewer 2 Report
The manuscript investigates thiosulfate leaching of gold from mining waste materials. Although using thiosulfate resulted in some interesting results, the paper lacks a meaningful discussion on the gold recovery mechanism.
The reviewer suggests that before recommending this paper in present form for publication, it needs some revision.
1. The details on the mineralogical characterization and chemical composition of waste materials studied are missing. XRD patterns and the results of chemical analysis of the studied samples should be included to the ms.
2. The ”recovery” parameter used for the quantification of the gold content needs to be separately defined for all stages (i.e., chemical leaching, adsorption and electrowinning process) of the proposed method.
3. The role of ammonia in the mechanism of the gold leaching process should be explained.
4. To make the derived conclusions more general and useful to the potential readers the authors should also provide:
- the detailed mathematical dependence of the leaching reaction rate on the concentrations of reactants and other species present;
- the details on the type of adsorption isotherm for the selected adsorption system and its adsorption capacity.
Author Response
Dear reviewer, we kindly thank you for reviewing the manuscript and for the recommended changes. I inform you that the review is underway, according to your recommendations and suggestions, and that will be finalised as soon possible.
With my best regards
Stefano Ubaldini
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The premise for undertaking the study was to recover gold from mine tailings though the introduction rightly makes a strong case for this based upon environmental considerations and not just economic ones. The scientific content seems sound and authors now offer explanations for the unusual trends noted. It is now accepted that their approach to what is a significant problem in Eastern Europe is a novel and necessary one. While further work is proposed to examine the enhancement of gold recovery via pre-treatment of the pyrite, further words could be added to indicate how the issues of Acid Mine Drainage and potentially copper recovery might also be addressed given the significance of the environmental issue even though these topics are not the major thrust of the study.
As it was difficult to read the upgraded version of the manuscript it is suggested that the authors double check to ensure that it reads well and does not contain any additional words that need not be there.
Overall, a nice piece of work from a group with recognized expertise in the gold processing space.
Comments for author File: Comments.pdf
Author Response
Dear reviewer, I kindly thank you for the revision of the manuscript. The text has been improved according to your recommendations and suggested implementations. I attach the document with detailed answers to your comments.
With my best regards
Stefano Ubaldini
Author Response File: Author Response.pdf
