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

The use of recycling aluminum from beverage containers and rice-hull ash (RHA) offers to be an attractive alternative for the economic production of Al/SiCp composites. However, corrosion phenomena in the composites represent technological barriers yet to be resolved before they can be exploited to their full potential. A simple methodology involving characterization by XRD, SEM, EDX, FTIR and ICP was designed in order to investigate the causes of the rapid degradation in a humid environment of Al/SiCp composites produced with RHA and aluminum cans. Results reveal that the use of RHA was beneficial to avoid degradation through the formation and subsequent hydration of the Al4C3 phase. However with condensed moisture acting as an electrolyte, localized corrosion took place with aggressive damage manifested by the disintegration of the composite into a powdery mixture. The relevant corrosion mechanism was mainly attributed to microgalvanic coupling between the Mg2Si intermetallic compound and the matrix (although other phases such as SiC, Si, MgAl2O4 could also work as microcathodes).
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PMID:Degradation of Al/SiCp composites produced with rice-hull ash and aluminum cans. 1732 Mar 70

A method of fluorination assisted electrothermal vaporization (FETV)-ICP-MS with polytetrafluoroethylene as fluorinating reagent was developed for the direct determination of trace rare earth elements (REEs) in coal fly ash and atmospheric particulates. Under the optimal conditions, the detection limits for REEs were 0.1 pg m(-3)(Eu) to 6.7 pg m(-3)(Nd) with the precisions of 4.1%(Yb) to 10%(La) (c=1 microg L(-1), n=9). The proposed method was applied to determine trace REEs in coal fly ash, airborne particulates and NIES SRM No. 8 Vehicle Exhaust Particulates. It was found that the determined values for Y, La, Pr and Nd obtained by slurry sampling FETV-ICP-MS with external calibration coincided with that obtained by pneumatic nebulization (PN)-ICP-MS and slurry sampling FETV-ICP-MS with standard addition. However, the determined values for Ce and Sm obtained by slurry sampling FETV-ICP-MS with external calibration were lower than that obtained by PN-ICP-MS and slurry sampling FETV-ICP-MS with standard addition.
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PMID:Determination of trace rare earth elements in coal fly ash and atmospheric particulates by electrothermal vaporization inductively coupled plasma mass spectrometry with slurry sampling. 1746 23

A sequential extraction method has been applied for the determination of binding forms of trace elements in the municipal solid waste incineration (MSWI) fly ash and evaluating their leaching behavior in view of their potential environmental impact. The elemental determinations in the different leachates are performed by ICP-AES and ICP-MS, respectively. The morphology and mineralogical phases after extraction step were performed by scanning electron microscopy (SEM). Total of 20 elements in the samples are investigated. A reference material of city waste incineration fly ash (BCR No. 176) is also tested to examine the applicability as well as accuracy of the proposed method. The sum of most elements present in the individual fractions shows a good agreement with the total elemental concentrations. The extraction efficiencies are generally higher than 80% except for that of Cr and V. The extractable data of most elements give information about the binding forms of various elements in both incineration fly ashes. It was found that the elements such as Ca, K, Na, Pb, Zn, Cd, Cu and Sr have exhibited a remarkable mobility in fly ash. More than half of them would be dissolved or exchanged under a mild leaching condition. The toxic elements such as Pb, Cd, Zn and Cu have a great potential to be released into the environment under normal conditions.
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PMID:Sequential extraction for evaluating the leaching behavior of selected elements in municipal solid waste incineration fly ash. 1747 37

The present study assesses the single extraction of Sb from two coal fly ashes with aqueous solutions at a range of pHs (1-12) and with citrate 1 mol L(-1) at pH 5, in order to obtain preliminary information about Sb leaching from this matrix. Speciation analysis of the coal fly ash extracts by HPLC-ICP-MS and HPLC-HG-AFS was carried out in order to identify the presence of individual Sb species. Sb(V) was the main Sb species in the leachates, although minor amounts of Sb(III) were also detected in some extracts. Citrate at pH 5 gave the best extraction efficiency for both samples whereas Sb species were also fairly soluble in aqueous solutions at acidic pHs. Analysis by HPLC-ICP-MS provided the most accurate results in some extracts (aqueous solution at pH 1 and citrate at pH 5) when both coupled techniques used were compared. The presence in these leachates of higher content of interfering metal ions (Ca, Fe and Pb) than those obtained for the Sb species reduced stibine generation in the HPLC-HG-AFS analysis. The proposed methodology can be considered reliable and useful for antimony speciation in environmental studies.
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PMID:Leachability and analytical speciation of antimony in coal fly ash. 1772 33

The E.U. Directive on incineration of waste regulates the harmful emissions of particles and twelve toxic elements, including copper, chromium, and arsenic. More information is critically needed on the speciation and behavior of these trace elements during combustion, including the effects of different process variables, as well as of different fuels and fuel mixtures. Using a 15 kW pellets-fueled grate burner, experiments were performed to determine the fate of copper, chromium, and arsenic during combustion of chromate copper arsenate (CCA) preservative wood. The effects of co-combustion of CCA-wood with peat were also studied since peat fuels previously have proved to generally reduce ash related problems. The fate and speciation of copper, chromium, and arsenic were determined from analysis of the flue gas particles and the bottom ash using SEM-EDS, XRD, XPS, and ICP-AES. In addition, chemical equilibrium model calculations were performed to interpret the experimental findings. The results revealed that about 5% copper, 15% chromium, and 60% arsenic were volatilized during combustion of pure CCA-wood, which is lower than predicted volatilization from the individual arsenic, chromium, and copper oxides. This is explained by the formation of more stable refractory complex oxide phases for which the stability trends and patterns are presented. When co-combusted with peat, an additional stabilization of these phases was obtained and thus a small but noteworthy decrease in volatilization of all three elements was observed. The major identified phases for all fuels were CuCrO2(s), (Fe, Mg, Cu)(Cr, Fe, Al)04(s), Cr2O3(s), and Ca3(AsO4)2(s). Arsenic was also identified in the fine particles as KH2AsO4(s) and As2O3(s). A strong indication of hexavalent chromium in the form of K2CrO4 or as a solid solution between K3Na(CrO4)2 and K3Na(SO4)2 was found in the fine particles. Good qualitative agreement was observed between experimental data and chemical equilibrium model calculations.
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PMID:Fate of Cu, Cr, and As during combustion of impregnated wood with and without peat additive. 1794 5

Continuous flow (CF) chemical hydride generation (CHG) and electrochemical hydride generation (ECHG) directly coupled to a novel 40W, atmospheric pressure, 2.45GHz microwave microstrip Ar plasma exiting a microstrip wafer has been developed for the emission spectrometric determination of As and Sb using a miniaturized optical fiber spectrometer and a CCD-array detector. The experimental conditions for both procedures were optimized with respect to the relative net intensities of the As I 228.8 nm and Sb I 252.8 nm lines and their signal-to-background intensity ratios. Additionally, the susceptibility to interferences from Cd, Co, Cr, Cu, Fe, Ni, Pb and Zn and other hydride-forming elements in the determination of As and Sb using the CHG and ECHG techniques was investigated in detail. Under the optimized conditions, it was found that ECHG is more prone to interferences compared to CHG. The detection limits (3sigma) of As (6 ngmL(-1)) and Sb (7 ngmL(-1)) obtained for the ECHG-MSP-OES method are about three times lower than in the case of the CHG-MSP-OES method due to a two-fold lower amount of H2 introduced into the MSP in case of the ECHG, resulting in a better plasma stability and reduced background level. The linearity ranges for both calibration curves to a concentration of up to 5 microgmL(-1) and a precision between 2% and 7% (2 microgmL(-1) and 0.050 microgmL(-1) of As and Sb, respectively) were found for both methods. The developed ECHG-MSP-OES method was validated for As through the analysis of a certified coal fly ash standard reference material (NIST SRM 1633a) after sample dissolution. The derived concentration (140+/-8 microgg(-1)) was found to agree well with the certified data (145+/-15 microgg(-1)). The method was also successfully applied to the analysis of both a galvanic bath sample, which contained Sb and was spiked with As, and a tap water sample spiked with both analytes. Recovery rates of 99-101% and a Sb concentration of 6.6 microgmL(-1) in the galvanic bath sample were revealed. The latter value showed a good agreement with the data obtained from ICP-OES analysis, which was also used for validation purpose.
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PMID:Optimization and comparison of chemical and electrochemical hydride generation for optical emission spectrometric determination of arsenic and antimony using a novel miniaturized microwave induced argon plasma exiting the microstrip wafer. 1806 65

The production and use of polymeric materials worldwide has reached levels of 150 million tonnes per year, and the majority of plastic materials are discarded in waste landfills where are burned generating toxic emissions. In the present study we conducted laboratory experiments for batch combustion/burning of commercial polymeric materials, simulating conditions of open fire combustion, with the purpose to analyze their emissions for chemical characteristics of toxicological importance. We used common types of plastic materials: poly(vinyl chloride) (PVC), low and high density poly(ethylene) (LDPE, HDPE), poly(styrene) (PS), poly(propylene) (PP) and poly(ethylene terephthalate) (PET). Samples of particulate smoke (soot) collected on filters and residue solid ash produced by controlled burning conditions at 600-750 degrees C are used for analysis. Emissions of particulate matter, persistent free radicals embedded in the carbonaceous polymeric matrix, heavy metals, other elements and PAHs were determined in both types of samples. Results showed that all plastics burned easily generating charred residue solid ash and black airborne particulate smoke. Persistent carbon- and oxygen-centered radicals, known for their toxic effects in inhalable airborne particles, were detected in both particulate smoke emissions and residue solid ash. Concentrations of heavy metals and other elements (determined by Inductively Coupled Plasma Emission Spectrometry, ICP, method) were measured in the airborne soot and residue ash. Toxic heavy metals, such as Pb, Zn, Cr, Ni, and Cd were relatively at were found at low concentrations. High concentrations were found for some lithophilic elements, such as Na, Ca, Mg, Si and Al in particulate soot and residue solid ash. Measurements of PAHs showed that low molecular weight PAHs were at higher concentrations in the airborne particulate soot than in the residue solid ash for all types of plastic. Higher-ringed PAHs were detected at higher concentrations in the residue solid ash of PVC as compared to those from the other types of plastic. The open-air burning of plastic material and their toxic emissions is of growing concern in areas of municipal solid waste where open-fires occur intentionally or accidentally. Another problem is building fires in which victims may suffer severe smoke inhalation from burning plastic materials in homes and in working places.
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PMID:Persistent free radicals, heavy metals and PAHs generated in particulate soot emissions and residue ash from controlled combustion of common types of plastic. 1824 66

Immobilization of Cr3+ with fly ash geopolymers was investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopic (XPS) techniques. The chromium sludge, as Cr(OH)3, was prepared with chemical precipitation method. The amounts of aluminum and silicon leached before and after the chromium sludge addition were measured using ICP-AES. The results suggested that the amounts of silicon and aluminum leached were reduced for the fly ash geopolymers after chromium sludge was incorporated. The decrease of silicon leaching was more pronounced than aluminum. FTIR results showed that the intensity of the main peak shifted into lower and the wave number of Si--O--Si and Al--O--Si became higher. The XPS results indicated that the O(1s) bind energy decreased, Si(2p) and Cr(2p) bind energy increased, while Al(2p) bind energy remained unchanged due to Cr3+ addition. It was also confirmed that the chromium is easily incorporated into the fly ash geopolymers paste, and polymerized with silicate units. The immobilization of Cr3+ using fly ash geopolymers is attributed not only to physical encapsulation, but also to chemical reaction.
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PMID:[An FTIR and XPS study of immobilization of chromium with fly ash based geopolymers]. 1842 21

This study describes the partitioning of 18 trace elements (As, Ba, Cd, Co, Cr, Cu, Li, Mn, Mo, Ni, P, Pb, Sb, Se, Sn, Tl, V, Zn) and 9 major and minor elements (Al, Ca, Fe, K, Mg, Na, S, Si, Ti) during co-firing of olive residue, hazelnut shell and cotton residue with high sulfur and ash content lignite in 0.3 MW(t) Middle East Technical University (METU) Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) test rig with limestone addition. Concentrations of trace elements in coal, biomass, limestone, bottom ash, cyclone ash and filter ash were determined by inductively coupled plasma optical emission and mass spectroscopy (ICP-OES and ICP-MS). Partitioning of major and minor elements are influenced by the ash split between the bottom ash and fly ash and that the major proportion of most of the trace elements (As, Ba, Co, Cr, Cu, Li, Mn, Mo, Ni, Pb, Tl, V and Zn) are recovered in fly ash when firing lignite only. Co-firing lignite with biomass enhances partitioning of these elements to fly ash. Co-firing also shifts the partitioning of Cd, P, Sb and Sn from bottom to fly ash.
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PMID:Trace elements partitioning during co-firing biomass with lignite in a pilot-scale fluidized bed combustor. 1862 79

The effects of chlorides (including inorganic chloride NaCl and organic chloride PVC) on Cd emission in MSW (municipal solid waste) incineration was investigated using a simulated tubular furnace and the simulated MSW spiked with heavy metals. The concentrations of heavy metals were measured by ICP-AES after the digesting of samples including bottom ash, fly ash and flue gas according to related USEPA Methods. Heavy metal species in bottom ash and fly ash were identified by X-ray diffraction technique and the spectra of elements distributed and micrographs of bottom ash and fly ash were detected by energy dispersive X-ray system and scanning electron microscope, respectively. The results indicated that the emission of Cd tended to be enhanced with the increasing of chloride content, and 97% Cd partitioned in fly ash after spiked chlorides. However, the content effect of inorganic chloride NaCl and inorganic chloride PVC on Cd emission had no significant difference. The effect of PVC on Cd partitioning was affected by temperature, 80.51% Cd partitioned in fly ash at 550 degrees C and 97.91% Cd partitioned in fly ash at 850 degrees C, when temperature went above the melting point of CdCl2 (568 degrees C), the effect of temperature became less important. The effect of NaCl on Cd partitioning was not affected by temperature, 95.02% Cd partitioned in fly ash at 550 degrees C and 96.58% Cd partitioned at 1 000 degrees C when spiked NaCl. Residence time had no significant effect on Cd partitioning with spiked chlorides. The two different mechanisms of chlorides effects on Cd emission were identified by bottom ash and fly ash analysis using SEM/EDS and XRD technique.
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PMID:[Effects of chlorides on Cd partitioning and speciation in a simulated MSW incinerator]. 1862 22


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