Search Results
Summary
Room temperature Mössbauer spectrum of fly ash-recycled glass (FARG), prepared with more than 86 mass% of fly ash and less than 14 mass% of Fe2O3, comprises two types of doublets due to Fe(II) and Fe(III) of magnetite nanoparticles. Isothermal annealing of fly ash-recycled glass at 1100 °C for 60 minutes results in a precipitation of ferrimagnetic magnetite phase having an internal magnetic field of 46.4-48.2 T. When the Fe2O3 content is equal to or more than 14%, room temperature Mössbauer spectrum of FARG shows a magnetic hyperfine structure due to a magnetite phase, in addition to two doublets due to Fe(II) and Fe(III). An increase in the electric conductivity is observed from the order of 10-8 to 10-6 S . cm-1 after heat treatment at around the crystallization temperature. This can be ascribed to an improved step-by-step electron hopping from Fe(II) to Fe(III) of distorted FeO4 tetrahedra in the three-dimensional glass network.
Abstract
The adsorption of lanthanum and cerium on modified fly ash bed has been studied. The effect of pH on the adsorption of both lanthanum and cerium by the bed material has been discussed. The exchange capacities of lanthanum and cerium have been determined. The method has been applied to monazite sand solution. The elution of both lanthanum(III) and cerium(IV) was studied using buffer and suitable eluting agent. The process is simple and may be considered as a low cost-methodology for separation of lanthanum and cerium.
Abstract
Municipal solid waste incineration (MSWI) significantly reduces volume and mass by as much as 80%, prolonging the life span of landfills. The concentration of heavy metals in the ash and their ability to leach into ground water is a serious concern when siting and designing MSWI ash landfills. Improved technology captures most heavy metals in the ash. The distribution of elements among the different ash particle sizes was determined by NAA. The bottom ash residue was separated into fractions ranging from 
9.5 mm to 
0.3 mm. The fly ash was separated into fractions from 250 
m to 20 m. Landfills usually bury a mixture of both. The combined ash was separated into fractions over the entire range from >9.5 mm to <20 m. Thermal and epithermal neutron irradiations of size fractionated MSW bottom, fly and combined ash were performed to determine the distribution of various metals within the ash. Compared to normal soil, the ashes contained elevated amounts of numerous elements. Concentrations of the more enriched elements (Ag, Cd, Cr, Cu, Hg, Sb, Se, Sr and Zn) in fly ash were of particular interest as source markers.
Abstract
Samples of coal, slag, emissions retained on the separating devices, fly ash, aerosols and hair taken in the area of coal-fired power plant were analyzed by means of instrumental neutron activation analysis. 13 to 23 elements were determined in the samples. The data obtained for emissions and aerosols were further evaluated by calculation of enrichment factors, correlation coefficients and by the ratio matching method. The concentrations of elements determined in the hair of exposed group were compared with the data of control and out control groups as well as with the recent data found for hair in other countries. It can be seen from the results that arsenic is the most serious pollutant in the area.
Abstract
Four paste mixtures with varying replacement level of the cement content by fly ash have been studied. Due to fly ash, the acceleration period decreased and a third hydration peak was noticed with isothermal calorimetry. The total heat after 7 days increased with increasing fly ash content. From 1 to 7 days, thermogravimetry showed a higher chemically bound water and Ca(OH)2-content for the pastes with fly ash. Between 7 and 14 days the calcium hydroxide started to be depleted due to the pozzolanic reaction. A unique relation was found between calcium hydroxide and total heat development.
A lime-pozzolan cement was used to make pastes containing different quantities of MSW fly ash. After setting, the pastes were cured in water at room temperature from 1 h to 260 days. The hydration characteristics and the nature of the hydration products of the various pastes were studied by simultaneous TG/DSC thermal analysis and X-ray diffractometry. The MSW fly ash was found to induce a slowing of the hydration process in lime-pozzolan pastes, and after some days an evident acceleration of hydration reactions occurred. Sulphate and chloride in the MSW fly ash yield hydration products forming a cementitious matrix.
Radioanalytical procedures for the characterization of fly-ASH leaching by water
I. The use of a radioactivated sample
Abstract
The use of neutron activated fly ash to measure its leaching by water is discussed. Results can be expressed by a simple mathematical equation which permits the characterization of the process in terms of four parameters.
Abstract
A systematic comparison of thermal and epithermal irradiations in the instrumental activation analysis of coal and fly ash was made. From a total of 44 elements, the epithermal irradiation technique appeared advantageous in 20 cases, namely Ni, Ga, As, Se, Br, Rb, Sr, Zr, Mo, In, Sb, Cs, Ba, Sm, Ho, Hf, Ta, W, Th and U. Data are presented for the National Bureau of Standards’ coal (SRM 1632) and fly ash (SRM 1633).
Effects of fly ash amendments in soil (0%, 25% and 50% vol/vol), Ralstonia solanacearum, Meloidogyne incognita and Phomopsis vexans were observed on the growth, chlorophyll and carotenoid contents of eggplant. Addition of 25% fly ash in soil caused a significant increase in plant growth, chlorophyll and carotenoid contents over plants grown without fly ash. However, amendments of 50% fly ash in soil had an adverse effect on the growth, chlorophyll and carotenoid contents of eggplant. Inoculation of the pathogens caused a significant reduction in growth, chlorophyll and carotenoid contents. Inoculation of R. solanacearum caused the greatest reduction followed by P. vexans and M. incognita. Root galling and nematode multiplication was reduced with the increase in fly ash. Wilting and blight indices were 3 in plants grown in 0% and 25% fly ash amended soil while 4 in 50% fly ash amended soil.
Abstract
DTA/TG thermoanalytical investigations and X-ray diffractometry were carried out which demonstrate the effect of MSW fly ash on the hydration reactions of pozzolanic cement. The MSW fly ash has high content of calcium sulphate, alkali chlorides and heavy metals. During the first curing period the calcium aluminate reacts with the sulphate to form ettringite. In that period also the presence of syngenite is noted in the pastes. With the growth of the fly ash content of the mixture there is a lengthening of the period in which the hydration reactions of the calcium silicates are inhibited. Subsequently with the progress of hydration in the pastes the CSH phase develops and the formation of calcium chloroaluminate phase is observed.
