Extraction from fly ashes

Dreesen, D. R., Gladney, E. S., Owens, J. W., Perkins, B. L., Wienke, C. L. Wangen, L. E. 1977. Comparison of levels of trace elements extracted from fly ash and levels found in effluent waters from a coal fired power plant. Environmental Science and Technology, 10, 1017-1019. 

Surface water photolytic t/2 = 3.5 h in the extract from fly-ash in tetradecane solution, for native congener and t,/2 = 3.1 h for 13C labelled congener (Tysklind Rappe 1991)... 

Our experiences show that the composition of the tar is dependent on several parameters such as gasification temperature, fuel properties and ER-value. The tars from tests at low ER-value and low temperature in the LU-gasifier (ER= 0.25, temp"800 C) a total number of 65 different compounds could be recognised. The number of tar species was lower for the experiments performed at high ER and high temperature. The tars extracted from fly ash contained the lowest number of tar species. Typical chromatograms of different tars are shown in Figure I. 

There is a very clear difference between the compositions of the tars in the gas and the tars extracted from fly ash. Whilst naphthalene is the main constituent of the tars in the gas, heavy PAHs such as phenanthrene, flouranthene and pyrene are more abundant in the tars from the fly ash. However the proportion of the tars condensed on the fly ash particles is very small and only equal to a few parts per thousands of the total tar in the system. 

Fig. 8-15. Separation of arsenate in an aqueous extract from fly ash. - Chromatographic conditions see Fig. 8-13 injection 50 pL sample (undiluted).

Dresser, D.R., Gladney, E.S., Owens, J.W. Perkins, B.L., Winke, C.L. and Wangen, L.E., Comparasion of trace elements extracted from fly ash levels found in efflunt waters from coal fired powerplant. Envion. Sci. Technol., 1977, 11, 1017. 

Calsinter A process for extracting aluminum from fly ash and from flue-gas desulfurization sludge. The ash is sintered with calcium carbonate and calcium sulfate at 1,000 to 1,200°C and then leached with sulfuric acid. Developed at Oak Ridge National Laboratory, United States in 1976, but not known to have been piloted. 

Organic contaminants. The concentration of polynuclear aromatic hydrocarbons (PAH) in the particulate phase of flue gases of oil-shale-combusting thermal power plants has been estimated to range from 0.04 to 3.16 mg/m3 (Aunela et al. 1995). The solvent-extractable fraction (<1.5 wt%) from fly ash particles collected from Narva power plant smog chambers included several PAHs (phenanthrene,... 

A method for determining CDDs in municipal incinerator fly ash has been reported (Alexandrou and Pawliszyn 1990). The method uses supercritical fluid extraction (SFE) to recover CDDs from fly ash samples prior to GC. Supercritical fluid extraction is faster and less expensive than the typically used Soxhlet extraction and gives quantitative removal of CDDs and CDFs from fly ash. Extracts obtained using SFE will still require additional clean-up steps prior to analysis. Supercritical C02 has also been used to assist solvent-based extraction of CDDs from soils (Friedrich and Kleibohmer 1997). In this case, the supercritical fluid was combined with accelerated solvent extraction (liquid extractions conducted under elevated temperature and pressure) to provide good recoveries relative to Soxhlet extractions. 

Van den Berg M, Olie K, Hutzinger 0. 1983. Uptake and selection in rats of orally administered chlorinated dioxins and dibenzofurans from fly-ash and fly-ash extract. Chemosphere 12 537-544. 

Eiceman et al. [16] reported the ultrasonic extraction of polychlorinated dibenzo-p-dioxins (PCDDs) and other organic compounds from fly ash from municipal waste incinerators. Ten to 20 grams of sample was extracted with 200 mL of benzene for 1 hour. Results from five replicate analyses yielded averages and RSDs (ng/g) for the tetra- to octachlorinated dibenzo-p-dioxins of 8.6 + 2.2, 15.0 + 4.0, 13.0 + 3.4, 3.2 + 1.0, and 0.4+ 0.1, respectively. 

Kooke RMM Lustenhouwer JWA, Olie K, Hutzinger O (1981), Anal. Chem. S3 461-463. Extraction efficiencies of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofu-rans from fly ash ... 

Onuska FI, Terry KA (1991), HRC CC 14 829-834.. .Supercritical fluid extraction of polychlorinated dibenzo-p-dioxins from municipal incinerator fly ash" van Bavel B, Hartonen K, Riekkola ML, Rappe C (1992), Organohalogen Compounds 8 15-18.. .Optimization of supercritical fluid extraction of PCDD/PCDFs and PCBs from fly ash", Eds. Finnish Institute of Occupational Health, Helsinki, Finnland ISBN 951-801-932-0... 

For soil/sediment samples the results of these analyses are reported based on the wet weight of the sample. However, use of the SDS apparatus allows the water content of a sample to be determined from the same aliquot of sample that is also extracted for analysis. The amount of water evolved from the sample during extraction is used to approximate the percent solids content of the sample. The percent solids data may be employed by the data user to approximate the dry weight concentrations. The percent solids determination does not apply to the extraction of particulates from the filtration of water samples or to the extraction of fly ash samples which are treated with an HC1 solution prior to extraction. 

As with sediment, Soxhlet extraction has been preferred for extraction of PCDEs from fly ash. Before extraction of fly ash, acid treatment with HC1 increases the recoveries of PCDDs and PCDFs, and was applied by Kurz and Ballschmiter [43], Koistinen et al. [57] did not use pretreatment with HCl when they extracted a fly ash for analysis of PCDEs. 

The DPHSE technique has also been used for the determination of organic pollutants and metals in fly ash and coal, respectively. The extraction of dioxins [48,179] and PAHs [180] from fly ash was accomplished with toluene [48,180] or a toluene-methanol mixture [179], with results as good as or even better than those provided by Soxhiet extraction for 24 h. On the other hand, the extraction of major ash-forming elements (Fe, AI, Ca, Mg, Na and K) [148] and minor inorganic pollutants (As, Se and Hg) [46] from coal was done with acidified water. In the latter case, a combination of static and dynamic extraction was found to provide quantitative recoveries within a shorter time and with less dilution of the extracts than dynamic extraction alone. Acidified water is more corrosive than pure water, so the high temperatures required for extraction (150-200°C) call for the use of an extractor made of a material more corrosion-resistant than steel hastel-loid. However, in proportions above 4%, nitric acid — the acidulant most frequently added to the water — has been found to result in clogging of the system and the restrictor, so the recommended acid concentration is much lower than that. 

One way of improving SFE efficiency is by using a more suitable SF to extract the target analyte. Unfortunately, the choice of fluids other than CO, is restricted by the desire to have reasonable critical parameter values and costs, chemical inertness, low toxicity and little environmental impact. The use of supercritical N2O has proved to increase the extraction efficiency for high-molecular weight PAHs and chlorinated dibenzo-p-dioxins from fly ash and sediment [52]. This extractant, however, does not always improve the extraction efficiency [53] also, it can be explosive in the presence of reactive organics. Other polar fluids such as CHCIF, (Freon-22) have exhibited increased efficiency in the extraction of nitrated and non-nitrated PAHs from particulate matter in diesel exhaust [54]. Freon-22 has also been found to allow significantly fast and effective extraction of... 

Fig. 7.20. Extraction efficiency achieved in the SFE of PAHs from fly ash. (A) By adding various binary modifiers to CO, [bars represent the following combinations from left to right trifluoroacetic acid (TFA) in toluene, triethylamine (TEA) in toluene, isopropylamine in toluene, pure toluene, tetra-butylammonium hydroxide in methanolt-toluene, citric acid in a methanol-toluene mixture and the absence of modifier]. (B) By successive application of a liquid modifier (four times) compared to Soxhiet extraction (shaded, left bars) and conventional SFE with CO,/pure toluene (right bars) CO,/TEA in toluene (-0-) and CO,/TFA in toluene (-A-). Fluo fluorene, phen phenanthrene, Anth anthracene, F fluoranthene, Py pyrene, B(a)A benz(a)anthracene, Chry chrysene, B(b)F benzo(b)flu-oranthene, B(k)F benzo(k)fluoranthene, B(a)P benzo(a)pyrene, D(ah)A dibenz(a,h)anthracene, B(ghi)P benzo(g,h,i)-perylene, I(cd)P indeno(l,2,3-c,d)pyrene. (Reproduced with permission of Springer-Verlag.)...

Sulfur gases arising during synthetic crude production from the bitumen and from the high-pressure hydrogenation process for synthetic crude stabilization are captured in amine scrubbers, and subsequently converted to sulfur via the Claus process (Chap. 9). Approximately 1500 tonnes of sulfur are produced daily from these sources by the two older hot water extraction plants. Occasionally these control measures have been inadequate to maintain low ambient air sulfur dioxide concentrations, particularly during an inversion episode. The potential of vanadium and nickel recovery from fly ash, which is possible on the scale of 1,600 and 3,900 tonnes/year, respectively, has also been considered. 

---