Distribution of Lanthanides, Yttrium, and Scandium in the Pilot-Scale Beneficiation of Fly Ashes Derived from Eastern Kentucky Coals
, John G. Groppo 1,3, Prakash Joshi 4, Dorin V. Preda 4, David P. Gamliel 4, Daniel T. Mohler 1, John D. Wiseman 1, Shelley D. Hopps 1, Tonya D. Morgan 1, Todd Beers 5 and Michael Schrock 5
Round 1
Reviewer 1 Report
The study results and discussion may be interesting for engineers engaged in coal processing and industrial REE recovery, but not only them. It may also interest researchers, like me, who study geochemistry of natural processes. The paper is done almost perfectly. However, the data presentation is not always clear. In particular:
Some minor elements were analyzed by XRF in this study (Line 133, the Materials and Methods section). Which ones, all trace elements excluding REYSc?
Hf and Tl are mentioned in Line 139, the Materials and Methods section. However, they are not present in any table and not discussed in the text.
Lines 167-168: The phrase “Plant D recovery is greater than the Plant I recovery owing to the lesser amount of carbon and magnetics in the feed ash (Table 1)” is not absolutely correct. A significant portion of REE (about 8% and 11% for the D and I ashes, respectively) has gone with the grain size fractions >200 mesh. Are these coarser fractions partly resulted from the preceding beneficiation procedures? What are the coarser particles made of?
Table 1: Does REE show concentration on the basis including or excluding LOI? Please describe meaning of “w.b.” REE Recovery seems presenting REE distribution between the fly ash fractions rather than actual % of REE recovered from these fractions.
Table 2: Plant column is excessive. Please use uniformly either “200-mesh” or “200 mesh” in the “type” column.
Tables 2 and S1: LOI is missing there, but present in Table 1. How are the concentration values in these tables related to each other?
Some questions raised from the presented data have not been discussed. Why do REYSc have a distinct negative correlation with C in addition to CaO, SO3 and moisture in the Plant D runs (Table S1)? Why REYSc is highest in the ash of carbon froth there (Table 2)? As I can see, the used beneficiation procedures merely separate the more REYSc-refractory fractions of fly ash, but do not make them less refractory. May an open storage of fly ash or its washing/wetting for a while be a part of its beneficiation for REYSc, as it was done for the Plant D ash?
It is not obligatory to the authors to reply to all my questions above. These questions may result from my low knowledge of the coal processing and REYSc industrial extraction. However, many potential readers of the paper are so.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript reports an investigation on two samples of coal-derived fly ashes from two power plants in order to produce a final material with a relatively consistent concentration of REE.
To my mind, the manuscript can not be accepted for publication in Minerals in the present form. The data discussion needs to be deeply improved.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Detailed comments can be found in the file below
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
