An excellent example of the actual recovery of precursor-type precious metals utilizing cluster nucleation is our currently operating, small-scale pilot system which is using cenospheres from coal-fired fly ash as the precursor ore. The initial seed consisted of 5 grams of rhodium and 2-liters of cenosphere slurry. During the following 6-months of production testing, this initial 2-liters was expanded to approximately 380-liters (approx. 100 gallons) of nucleation slurry which now contains percentage amounts of nucleated and recoverable rhodium-to-metal relative to the cenosphere ore. Approximately 800 lbs of cenospheres have been processed through this small pilot system during this 6-months of production testing. Conventional fire assaying and spectrographic analysis of the cenosphere precursor ore prior to cluster nucleation showed no rhodium present.
Using activated charcoal, nucleated rhodium clusters may be selectively removed from the nucleation system and, as such, yield a “rhodium on charcoal” product. The photomicrograph below shows, at 100X, an activated charcoal powder onto which rhodium cluster complexes have been adsorbed. This test was done in a batch rather than column mode.
Fine-grained charcoal with adsorbed Rh (100X)
Below is (Left) the SEM/EDS spectrum and (Middle) EDS elemental analyses of the above rhodium-bearing activated charcoal powder. It has been determined that a large portion of the adsorbed rhodium clusters are very small and below the resolution limits of the EDS system that was used for this analysis. The photomicrograph below (Right) identifies a rhodium particle in the charcoal matrix that is above this resolution limit.
In summary, the above data show that there is an abundance of recoverable, precursor-type precious metals that are contained in coal combustion products (and other geologic materials) that are not characterized or recovered using so-called conventional methods. It should be noted that similar results have been obtained with gold and platinum. It is expected that precursor-type silver, palladium, osmium, ruthenium and iridium can also be recovered using similar secondary nucleation and recovery techniques. A.C.J. (9/28/08)
