Trace elements volatile

During the combustion process, the low volatile trace elements tend to stay in the bottom ash or to be distributed between the bottom and fly ash. The more volatile trace elements (volatile and especially highly volatile trace elements) are vaporized in the furnace and they may be incorporated... 

All trace elements (volatile, non-volatile and intermediate) show the inverse concentration— particle size dependence, more pronounced in the material from runs with recirculation. One notable exception among the trace elements is Mn which shows a direct concentration—particle size dependence in the material from runs with recirculation and no dependence in the run without recirculation. 

The emission of volatile trace elements from roasting, smelting, and converting processes is undesirable from both an air pollution and an economic standpoint. Gravity collectors, cyclones, and ESPs are used to attain collection efficiencies of up to 99.7% for dust and fumes. 

The atmosphere may be an important transport medium for many other trace elements. Lead and other metals associated with industrial activity are found in remote ice caps and sediments. The transport of iron in wind-blown soil may provide this nutrient to remote marine areas. There may be phosphorus in the form of phosphine, PH3, although the detection of volatile phosphorus has not been convincingly or extensively reported to date. 

Mining and industrial activities produce large quantities of volatiles and dust particles and increase concentrations of trace elements and heavy metals in soils, waters, and vegetation. When mineral deposits containing concentrated trace elements and heavy metals are exposed at the earth s... 

Frankenberger W.T. Jr. Effects of trace elements on arsenic volatilization. Soil Bio Biochem 1997 30 269-274. 

The determination of an inorganic element in an organic matrix usually requires a preliminary treatment to remove the organic matter completely, either by dry-ashing or by oxidation with acids such as nitric, sulfuric or perchloric. Then, the problem reverts to the determination of an inorganic analyte in an inorganic matrix, as above. You should be aware that losses of trace elements can occur during such oxidation processes, either by volatilization or by adsorption onto the surface of the equipment used. 

In the following discussion, three types of air pollutant analytical data will be examined using principal component analysis and the K-Nearest Neighbor (KNN) procedure. A set of Interlaboratory comparison data from X-ray emission trace element analysis, data from a comparison of two methods for determining lead In gasoline, and results from gas chromatography/mass spectrometry analysis for volatile organic compounds In ambient air will be used as Illustrations. 

A more recent analytical tabulation covering individual trace elements, amino acids, and volatile fatty acids, together with proximate analyses, ADF, MADF, NDF, cellulose, lignin, starch, water soluble carbohydrates, etc., has the title UK Tables of Nutritive Value and Chemical Composition of Feedingstuffs (MAFF, 1990). 

Fine particles from coal combustion are a threat to human health and air quality. Numerous studies have reported higher concentrations of volatile trace elements in small particles... 

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. 

In Eggborough power plant it was found that Zn, Pb, Mo, Cu and As are concentrated in the fly ash compared with the bottom ash, whereas for the other trace elements studied (Ba, Cr, Nb, Rb, Sr, V, Y, Zr) there was very little fractionation (Martinez-Tarazona Spears 1996, tables 3 and 4). Mass balance calculations show that for the elements studied only S and As are depleted in the combustion ashes and all the other elements analysed appear to have been retained. Not included within the analyses were Hg, Cl, and F, and loss of these elements would be anticipated based on their volatility (Sloss Davidson 2001). 

Many trace elements are present in coal ashes at concentration levels far in excess of average crustal values. Although new uses are being found for fly ashes, there remains an excess production that ends in lagoons, ash mounds and landfill sites. In the ashes produced in coal-fired power plants trace elements are present in minerals such as quartz, mullite and magnetite, but their overall contribution to the bulk is minimal. The trace elements present in the glass are quantitatively more important, but for the more volatile elements it is surface association that is particularly important, because this is the major location in the ash for some elements and they are potentially leachable. 

Studies of fresh ash produced by coal combustion have shown that many trace elements (As, B, Bi, Cd, Cr, Cu, Ge, Hg, Mo, Pb, Ni, Se, Sr, Tl, V, W, Zn) are enriched in the fly ash compared to the bottom ash (Hansen Fisher 1980 Eary et al. 1990 Mukhopadhyay et al. 1996 Karayigit et al. 2001). For example, Mukhopadhyay et al. (1996) reported 10-20 times enrichment of most trace elements in the fly ash compared to the feed coal and association of As with crystalline Fe-0 and Fe-S phases in the bottom ash from a power plant in Nova Scotia fed by eastern Canadian coal. Elements enriched in fly ash are typically those more easily volatilized. Because fly ash particles also have smaller sizes and therefore greater reactivity than bottom ash, the probability of metal leaching is correspondingly greater. Ainsworth Rai (1987) and Rai et al. (1988) found that most of the Cu, Mo, Se, Sr, and V in fly ash was readily soluble. 

As implied by their names, chondritic IDPs have roughly cosmic bulk compositions. Element ratios for hundreds of analyzed particles are roughly chondritic (data for CP IDPs are shown in Fig. 12.7) (Schramm et al., 1989). An exception, though, is carbon, which is significantly more abundant in IDPs. The mean carbon content of I DPs is 10 wt.%, relative to 3.2 wt.% for Cl chondrites (Bradley, 2004). The abundances of trace elements in bulk IDPs scatter from 0.3 to 3 times Cl, and volatile elements especially tend to be enriched (Flynn and Sutton, 1992). Higher abundances of carbon and of volatile elements, relative to the most solar-like carbonaceous chondrites, support the contention that IDPs are among the most primitive materials known. 

Trace element measurements in lunar basalts also indicate that the Moon is depleted in highly volatile elements (Taylor et al., 2006a). Estimates of some of the Moon s volatile element concentrations are compared with the Earth in Figure 13.11 a. The absence of water in lunar basalts suggests that the mantle is dry. The Moon may also be enriched in refractory elements (Fig. 13.11b). Volatile element depletion and refractory element enrichment are expected consequences of the giant impact origin and subsequent high-temperature accretion of the Moon. 

In addition, the residue of the digestion should be quantitatively dissolved in a small volume of high purity acid. The decomposition and accuracy of analytical data should be checked with the aid of certified reference materials. Possible contamination and losses of trace elements by absorption or volatilization should be avoided. 

Similar to the analytical procedure for trace analysis in high purity GaAs wafers after matrix separation, discussed previously,52 the volatilization of Ga and As has been performed via their chlorides in a stream of aqua regia vapours (at 210 °C) using nitrogen as the carrier gas for trace/matrix separation.58 The recoveries of Cr, Mn, Fe, Ni, Co, Cu, Zn, Ag, Cd, Ba and Pb determined after a nearly quantitative volatilization of matrix elements (99.8 %) were found to be between 94 and 101 % (except for Ag and Cr with 80 %). The concentrations of impurities measured by ICP-DRC-MS (Elan 6100 DRC, PerkinElmer Sciex) after matrix separation were compared with ICP-SFMS (Element 2, Thermo Fisher Scientific) and total reflection X-ray fluorescence analysis (TXRF Phillips). The limits of detection obtained for trace elements in GaAs were in the low ngg-1 range and below.58... 

Until recently, chemical analyses of coals were done on ash produced from the coal at relatively high temperatures. This was the standard approach for many years, and analyses of trace elements in coals do have a long history. An early article on an element as rare as cadmium in coal was published 125 yrs ago (28). One limitation of high-temperature ash sample is that volatile elements may be lost during combustion and will not be detected. Another problem which applies especially to analyses for trace and minor elements is that there have not been any coal standards available until very recently. 

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