Condensation trace elements

As was previously mentioned, trace elements that sublime at temperatures below those attained during coal combustion (e.g., As, Se, Hg, Zn), and are associated with thermally unstable solid phases (in particular organic matter and sulphide minerals), are subject to vaporization into furnace gases. Once these gases, and fly ash particles entrained in the gases, are vented from the combustion furnace they quickly cool, leading to the condensation of volatilized elements onto the... 

Retorting of oil shales to produce shale oil results in wastes (condensate water and solid semi-coke residue) that are heavily contaminated with organic compounds, especially phenolic compounds. Semi-coke leachate is typically alkaline (Kundel Liblik 2000) and can contain several hundred mg/L phenol in Estonia, in addition to potentially toxic heavy metals and trace elements, for example, As, B, F, Mo, and Se, which might be mobilized during leaching by water. Volatilization of phenols from leachate lagoons can also impact atmospheric quality. 

Unburnt carbon is another minor component of fly ash. Ideally its content should be less than 1 wt%, but concentrations of 3-4 wt% or higher may be recorded if the combustion efficiency falls. Any trace elements contained within the unburnt carbon are likely to have condensed from the gas stream rather than inherited from the original organic matter. Loss of Hg from the gas stream due to unbumt... 

Nadkarni RA, Ehmann WD, Burdick D. 1970. Investigations on the relative transference of trace elements from tobacco into smoke condensate. Tobacco 170 25-27. 

C60 has not yet been detected in primitive meteorites, a finding that could demonstrate its existence in the early solar nebular or as a component of presolar dust. However, other allotropes of carbon, diamond and graphite, have been isolated from numerous chondritic samples. Studies of the isotopic composition and trace element content and these forms of carbon suggest that they condensed in circumstellar environments. Diamond may also have been produced in the early solar nebula and meteorite parent bodies by both low-temperature-low-pressure processes and shock events. Evidence for the occurrence of another carbon allotrope, with sp hybridized bonding, commonly known as carbyne, is presented. 

Partition (Distribution) Coefficients In describing the partitioning of a trace element among coexisting phases, we frequently use a partition (distribution) coefficient for a given element, defined as a concentration ratio C2/Cj. Here C is concentration, and the subscripts identify the phases often the normalizing phase is some convenient reservoir, such as a silicate melt, with which several other phases may equilibrate. For noble gases, it is often most convenient to normalize to a gas phase. If the concentrations are expressed in the same units, the distribution coefficient is dimensionless. It is conventional to cite noble gas concentrations in condensed phases in cm3 STP/g, however, and to describe the gas phase by partial... 

The trace elements do not condense strictly according to their condensation temperatures of the pure elements or their components. For example, in spite of their considerably lower condensation temperatures the REE elements... 

Figure 24 Concentration profiles of siderophile elements in a radially zoned Fe,Ni grain in the CBb chondrite, QUE 94411 (a) electron microprobe data (b) and (c) trace element data from laser ablation ICPMS (Campbell et ai, 2001). The nickel, cobalt, and chromium profiles can be matched by nonequilibrium nebular condensation assuming an enhanced dust-gas ratio of —36 X solar, partial condensation of chromium into silicates, and isolation of 4% of condensates per degree of cooling (Petaev etal, 2001). Concentrations of the refractory siderophile elements, osmium, iridium, platinum, ruthenium, and rhodium, are enriched at the center of the grain by factors of 2.5-3 relative to edge concentrations, which are near Cl levels after normalization to iron (reproduced by permission of University of Arizona on behalf of The Meteoritical Society from Meteorit. Planet. ScL, 2002, 37, pp. 1451-1490).

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