Challenges Related to the Processing of Fines in the Recovery of Platinum Group Minerals (PGMs)

Round 1

Reviewer 1 Report

This paper is a comprehensive review of the mineral processing of platinum group metals. The mineralogy of the PGM's is very complex and highly irregular and varies through time in a given production plant. Extremely fine grind sizes are necessary and the authors comprehensively review the competing factors in this complex environment.

This is a scholarly work and engages each of the relevant topics starting with broad principles and then rehearsing the key research findings down to the detail of the latest developments for each topic. Given the numerous conflicting claims in the literature, it is most worthwhile to have this review with its even handed approach at explaining and resolving the differing claims found in the literature. It is especially useful in that it explains well the relatively recent improvements in recovery experienced in the industry, the first for many years.

There is a minor inconsistency, or need to cross reference the parts of the paper (lines 336-339) on power and bubble size with the statement on line 287.

The paper rightly elaborates on the success of ultra-fine grinding using stirred mills when the mineralogy dictates their use. It would benefit from reference to why this was also so successful in the base metal industries some years earlier than its application for PGM's.

Author Response

Thank you for your valuable input into our paper, we appreciate your time. 

There is a minor inconsistency, or need to cross reference the parts of the paper (lines 336-339) on power and bubble size with the statement on line 287: “However as will be noted below it is necessary to maintain a careful balance between power input and bubble size” has been added following the statement on line 287

It would benefit from reference to why this was also so successful in the base metal industries some years earlier than its application for PGM's: "Isamills had been operating at Mt ISA in Australia for several years and after IP issues had been resolved AngloPlatinum decided to integrate this technology into their PGM circuits as they offered significant energy savings over ball milling." has been added to line 199

Reviewer 2 Report

This is a well written and useful review of issues related to PGM flotation with focus in the necessity for, and difficulties of, fine particle sizes. The reference list is comprehensive and extensive. Minor edits are suggested but overall the the writing is coherent and easily readable (I note that higher and larger (or greater) do not mean the same thing and nor do lower and smaller). Also, a number of links in the text to Figures have dropped out.

Comments for author File: Comments.pdf

Author Response

Thank you for your valuable input into our paper, we appreciate your time.

Higher and larger (or greater) do not mean the same thing and nor do lower and smaller: Owing to the nature of a review paper, we have maintained the terminology used within the original literature reference.

A number of links in the text to Figures have dropped out: All cross-referencing errors for Figures and Tables have been corrected

Line 101: PGE has been inserted

Line 142: “Despite” has been replaced with “Considering”

Line 143: “these both require” has been removed

Line 144: “are required” has been inserted

Line 297: Comma has been removed

Line 314: “in fact” has been removed

Line 393: “However” has been removed

Line 399: “However” has been removed

Line 403: “by the column flotation cells” has been removed

Line 511: “so as” has been removed

Line 535: “so as” has been removed