| Under the experimental conditions, the mineralogy, morphology, magnetism and magnetic mineralogy of eight fly ash samples from 8 power plants in Zhejiang Province were studied, and the stability of fly ash's magnetic properties in response to different reduction conditions were also studied. The adsorption of phosphate by fly ash experiment, the acid rain batch experiment and leaching experiment were conducted. The main results were showed as follows:1.The mineralogy and morphology of eight fly ash samples from power plants in Zhejiang Province were studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The density, particle composition and water retention of fly ashes were also measured. The mineralogy of fly ashes was dominated mainly by mullite, quartz, hematite and magnetite. SEM observation showed that the fly ash had the porous structure and spherical shape of particle (cenosphere). The 63-72 % of the fly ashes was made up of coarse slit particles with diameter of 5-10 um. The density of the fly ashes ranged from 1.93 to 2.29 g/cm3. The field water holding capacity, wilting holding capacity and available water content of the fly ashes were 66-87%, 5-10% and 54-62%, respectively.2.Environmental magnetism parameters, including magnetic susceptibility (x) , frequency dcpendaent susceptibility (xfd) , anhysteretic remanent magnetization (ARM), saturation isothermal remanent magnetization(SlRM), had been measured on fly ashes. In comparison with the % values of soils, the fly ashes showed higher X values. The magnetic susceptibility of most fly ashes ranged from 409×10-8m3g-1 to 625 ×10-8m3kg-1 and xfd from 0.1% to5.2%. It indicated the magnetism of fly ashes not mainly come from the contribution of superparamagnetic(SP). X ray diffraction indicated that the predominant iron oxides of fly ashes is Fe3O4.3.Laboratory experiments aimed at understanding the changes in magnetic properties of fly ashes were carried out at different reduction conditions. For the fly ashes with low magnetic susceptibility, results showed that reduction would not cause a dramatic change in all the magnetic parameters. But for the fly ashes with highmagnetic susceptibility, it is a different matter that reduction cause a dramatic change. The ratio of L/S did not affect the magnetic properties of fly ashes.4.This study examined the effectiveness of fly ash in removing phosphate from water by adsorption. The results showed that fly ash rate, adsorption time, solution pH and particle size had significant effects on phosphate removal by fly ashes. The fly ash rate of 25 g/L was found to remove 95% phosphate from an initial concentration of 2.28-45.59 mg/L. The fly ashes removed 97% phosphate in 5 min, indicating that fly ash can absorb rapidly phosphate from low concentration solution. The high pH values of solution increased absorption capacity of phosphate by fly ashes. The absorption of phosphate by fly ashes increased with the decrease of fly ash panicle size. The fly ash particles with a diameter of 0.05-0.15 and <0.05 mm had a higher absorption capacity of phosphate than those with a diameter of >0.15.The fly ash's pH dynamic change and the release of element Cr, Cd, Pb, Cu, Mn were investigated in simulated acid rain with different acidity and different ratio of L/S. The results showed that the pH's decreasing degree and speed is in inverse proportion to CaO in fly ash, and in direct proportion to the ratio of L/S. The release of fly ash's element Cr, Cd, Pb, Cu, Mn is in direct proportion to the ratio of L/S in simulated acid rain. The concentration of element Cr get to equilibrium after one week with equilibrium concentration being 0.11-0.15mg/kg, and Cd , two weeks , 0.011-0.015mg/kg except that Cu, Mn get to equilibrium after one day with equilibrium concentration being 0.09-0.11 mg/kg, 0.04-0.06mg/kg. The concentration of Pb keeps decreasing all six weeks from 0.20-0.28mg/kg to 0.15-0.21 mg/kg. All above 5 elements' equilibrium concentration are not affected by the acid rain's acidity and the rat... |
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