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Query: UMLS:C0205700 (ash)
 15,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A microwave digestion procedure for asphaltite ash was developed in an attempt to facilitate routine analysis and obtain reproducible conditions or comparable results. The conditions of the most effective procedure for 0.1 g asphaltite ash samples are 1 ml of HNO3 + 3 ml of HCl + 1 ml of HF + 1 ml of deionized water as acid mixture and 15 min for digestion time. The digestion was accomplished in five stages applying continuously 90% to 20% of the microwave power and 20 to 100 psi of the pressure for 10 min of total time. Concentrations of selected elements, Cr, Co, Fe, Mn, Ni and Zn were measured using inductively coupled plasma-atomic emission spectroscopy. The proposed method of digestion provided precise results with relative standard deviations generally less than 3% for investigated elements. Results for fly ash as standard reference material was in good agreement with certified values.
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PMID:Comparison of microwave digestion procedures for the determination of some elements in asphaltite ash using ICP-AES. 1255 36

The role of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/Fs) has been studied thoroughly in an entrained flow reactor during simulated waste combustion. The effects of gas-phase chlorine species such as chlorine (Cl2), hydrogen chloride (HCl), and chlorine radicals (Cl*), as well as ash-bound chlorine, on PCDD/F de novo formation were isolated for investigation. The ash-bound chlorine alone was observed to be a sufficient chlorine source for PCDD/F formation. The addition of HCl to the system did not influence the yields of the PCDDs/Fs nor the degree of chlorination due to its poor chlorinating ability. Addition of 200 ppm of Cl2 to the ash-feed system resulted in increased PCDD/F yields, especially for the octa- and hepta-chlorinated congeners. Altering the reaction temperature to enable the presence of only Cl2 to the system did not change the yields of PCDD/F compared to those when both Cl2/Cl* were present. However, comparison between ash-bound and gas-phase chlorine, the latter at a concentration typical of a realistic combustion process, revealed ash-bound chlorine to be the more important chlorine source for de novo formation of PCDD/F in a full-scale incinerator.
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PMID:Importance of chlorine speciation on de novo formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. 1268 Jun 62

CaO-Al(2)O(3)-SiO(2) system glass ceramics of incinerator fly ash have been prepared by vitrification and then heat-treated in different conditions. The thermal molten process (TMP) was applied to heat treat vitrified samples at high temperatures whereas in the powder sintering process water-quenched vitrified samples were ground into powder and then sintered at high temperatures. Gehlenite was found present as the major phase in all treated samples. Treated samples in general exhibited good leachability characteristics as well as chemical durability, except in the HCl solution. Microstructure and physical properties varied with the treatment condition. Fine and relatively high dense structures with desirable properties were obtained for samples treated by the TMP. For both processes, higher temperature treatments caused crystal growth and thus poor properties were attained. Good physical and mechanical properties achieved at 900-950 degrees C in this study imply the treated samples have attractive potential for engineering applications.
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PMID:On formation of CaO-Al(2)O(3)-SiO2 glass-ceramics by vitrification of incinerator fly ash. 1269 71

On the experimental table of fluidized bed which scale was phi 150 mm x 1000 mm and temperature interval was from 840 degrees C to 960 degrees C, the influence of desulfurizer variety, particle size and molar ratios Ca/S on nitrogen conversion to NO were studied. This paper elaborated on the mechanism of calcium-based desulfurizer lead to the increase of NO conversion rate. Experiment presented that given identical quantities, burnt calcium had maximum NO conversion rate, then limestone, calcite last. Nitrogen conversion to NO increased with increasing molar ratios Ca/S. When the particle size was between 1-2 mm, the NO conversion rate was the maximum, second was 2-3 mm, the last 0.2-1 mm. HCl, HF, SO2 decreased with calcium addition. At the same time H, OH, HO2 radicals increased. The CO oxidation was favored, the reaction of monoxide and NO catalyzed by char, sand, ash will weaken, therefore NO content will increase.
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PMID:[Influence and mechanism of calcium-based desulfurizer on NO conversion in fluidized bed of coal]. 1270 7

The use of heavy oil fly ash with high ash content (45 wt.%) as a precursor for the preparation of activated carbons has been investigated. The raw fly ash and the fly ash with lower ash content, obtained by a HCl/HF washing treatment, have been pyrolyzed at 900 degrees C and then activated with CO(2) in the temperature range of 800-900 degrees C for different times. The activated carbons have been characterised as regards the surface area and the pore volume. The evolution of the porosity has been related to the burn-off degree.
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PMID:Preparation of activated carbons from heavy-oil fly ashes. 1278 Dec 23

The use of ram horn hydrolysate (RHH) as a substrate for lactic acid production was investigated using Lactobacillus casei. For this purpose, first RHH was produced. Ram horns were hydrolyzed by treating with acids (6N-H2SO4 and 6N-HCl) and neutralizing the solutions. The amounts of protein, nitrogen, ash, some minerals, total sugars, total lipids and amino acids of the RHH were determined. The effect of different concentrations (1-10% v/v) of RHH on the production of biomass, lactic acid concentration and sugar consumption was investigated, and a concentration of 6% RHH was found to be optimal. The content of lactic acid in the culture broth containing 6% RHH (44 g x l(-1)) for 26 h was 22% higher than that of the control culture broth (36 g x l(-1)). From this result, RHH was demonstrated to be a suitable supplement for lactic acid production, a use that would resolve a local environmental problem.
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PMID:Utilization for lactic acid production with a new acid hydrolysis of ram horn waste. 1290 17

Due to the relatively high activity concentrations of (210)Po and (210)Pb that are found in tobacco and its products, cigarette smoking highly increases the internal intake of both radionuclides and their concentrations in the lung tissues. That might contribute significantly to an increase in the internal radiation dose and in the number of instances of lung cancer observed among smokers. Samples of most frequently smoked fine and popular brands of cigarettes were collected from those available on the Egyptian market. (210)Po activity concentrations were measured by alpha spectrometry, using surface barrier detectors, following the radiochemical separation of polonium. Samples of fresh tobacco, wrapping paper, fresh filters, ash and post-smoking filters were spiked with (208)Po for chemical recovery calculation. The samples were dissolved using mineral acids (HNO(3), HCl and HF). Polonium was spontaneously plated-out on stainless steel disks from diluted HCl solution. The (210)Po activity concentration in smoke was estimated on the basis of its activity in fresh tobacco and wrapping paper, fresh filter, ash and post-smoking filters. The percentages of (210)Po activity concentrations that were recovered from the cigarette tobacco to ash, post-smoking filters, and smokes were assessed. The results of this work indicate that the average (range) activity concentration of (210)Po in cigarette tobacco was 16.6 (9.7-22.5) mBq/cigarette. The average percentages of (210)Po content in fresh tobacco plus wrapping paper that were recovered by post-smoking filters, ash and smoke were 4.6, 20.7 and 74.7, respectively. Cigarette smokers, who are smoking one pack (20 cigarettes) per day, are inhaling on average 123 mBq/d of (210)Po and (210)Pb each. The annual effective doses were calculated on the basis of (210)Po and (210)Pb intake with the cigarette smoke. The mean values of the annual effective dose for smokers (one pack per day) were estimated to be 193 and 251 microSv from (210)Po and (210)Pb, respectively.
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PMID:Polonium-210 budget in cigarettes. 1455 35

The objectives of this work are to understand the details of the mechanism of dioxin formation in the part of a sintering bed termed the dry zone, and to obtain ideas on how to prevent their formation. Sinter mixtures of various composition types were heated in a packed bed reactor, and dioxins in the outlet gas and in the sinter mixture residue were measured. The dioxin formation potential of a simple sinter mixture composed of iron ore, coke and limestone was markedly lower than that of fly ash from a municipal solid waste incinerator (MSWI). In consideration of this result, a series of experiments were conducted using a sinter mixture impregnated with CuCl2. Experimental results showed that dioxin formation was temperature-dependent in the range of 300-550 degrees C, with the maximum observed at around 300 degrees C, which was quite similar to that of fly ash from the MSWI. The homologue distribution of PCDD/Fs in gas and solid reflected the possible difference in carbonaceous materials in coke and activated coke. Gaseous hydrogen chloride acted as a chlorinating reagent for dioxin formation.
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PMID:De novo formation characteristics of dioxins in the dry zone of an iron ore sintering bed. 1455 62

A simple, uniform procedure has been developed for microwave-based digestion of fly ash samples collected from the hoppers of an electrostatic precipitator (ESP), or collected from flue gases on a heat-resistant quartz fibre filter and for subsequent atomic absorption spectrometric analysis of trace metals (Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, V and Zn). HNO(3), HCl, HF and mixtures have been tested as digestion acids. The combination of HNO(3) and HF has been found to be efficient for the digestion of fly ash samples with and without quartz fibre filter material. In spite of the complicated matrix, results with satisfactory accuracy and precision (relative standard deviation below 10% for most of the elements) have been obtained. In the case of analysis of fly ash together with a quartz fibre filter, the calibration curve has to be determined by standard addition to a blank solution containing a dissolved blank quartz fibre filter.
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PMID:Trace metal analysis of coal fly ash collected plain and on a quartz fibre filter. 1504 29

The object of this study is to investigate the effect of different operation conditions on the catalytic oxidation of trace organic compounds [i.e., benzene, toluene, ethylbenzene, and xylene (BTEX); and polyaromatic hydrocarbons (PAHs)] in incineration flue gas. A commercial Pd-based honeycomb catalyst, which is applied to treat flue gas with low organic concentrations and high gas velocity, is employed in this study. The investigated parameters include (1) effect of different space velocities, (2) effect of heavy metals, (3) effect of acid gas, and (4) effect of water vapor and ash particles. In this work, an effective catalyst oxidation system is constructed and expected to purify the incineration flue gas. Catalyst oxidation is a potential purification system that will meet the stricter regulations on the emissions of incineration systems. Experimental results showed that the destruction efficiency of PAHs and BTEX in Pd catalyst was generally greater than 80%. Decreasing the space velocity increased the decomposition efficiency of organic compounds. When the feedstock contained the heavy metals Pb and Cr, the oxidation of organic compounds was not inhibited. But the presence of Cd significantly decreased the oxidation efficiency. The acid gases SO2 and HCl in the flue gas could have influenced the crystal structure of PdO and subsequently deactivated/poisoned the Pd catalyst. The effect of water vapor on the catalytic destruction of PAHs and BTEX was not obvious.
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PMID:Catalytic oxidation of organic compounds in incineration flue gas by a commercial palladium catalyst. 1514 95


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