Studies On Micro-structure,Chemical Composition Of Fly Ash And Its Application

Based on a lot of documents and condition of the laboratory, the situation of fly ash collected from Shajiao Power Station of Guangdong is tested by SEM/EDS,FIB and etc.. When the fly ash react with acid to form some salt Al and salt Fe at some degree, the changes are tested by SEM/EDS, and a proper acid is selected, which is useful for preparing the poly-aluminum chloride made by the acided fly ash in this paper. The project is supported by Guangdong Research Foundation Grant(2003A3060302).This paper has three chapters.Micro-structure and chemical composition of fly ash are measured with FE-SEM,SEM/EDS,FIB and OM in the first chapter, which is good material for dealing with waste water.The fly ash are spherical translucent particles with diameter ranged from 100nm to 5um and gather together to be larger body by 6~8 particles. Oxides of Si,Al,Fe,Ca,Mg,Cu,Zn,Ti,Ba are mixed together to randomly form the particles, and the main elements are Al,Si,O(the element percent is 15%,21% and 57% respectively). But some special micro-structure is found and some special element distribution is discovered—there are single particles composed with SiO2 or Fe2O3, and a little Fe2O3 distribute on the surface of particle tested by backscatter of SEM/EDS. In the second chapter, reaction process of fly ash with acid at solid state is studied, in order to choose optimum acid to form salt Al and salt Fe in the surface of fly ash at some degree, which are good flocculation and will be good ingredient in the poly-aluminum chloride. After comparing the changes of micro-structure,elements on the surface of reacted particles and the crystal substance washed from it by the SEM,FTIR and etc., H2SO4 is determined. By the images of SEM, the reaction process is captured. With acids fly ash is pasted and some crystal substance is formed on the surface. After washed by the two-de-ionized, defects,pore on the surface of fly ash and the SiO2 in nanometer on the sample plate are imaged by S-5200 SEM, which shows the reactions recur on the surface, and the reaction depth is less than 1um.△G and △H of reactions between the oxides and H2SO4 demonstrate the reactions are easy, even the most stabile substance (3Al2O3·SiO2) in the fly ash can react quickly. The FTIR spectrum shows the reaction heat between H2SO4 and fly ash damages the crystal SiO2, whose character peaks are disappeared. But the other acid has no such effect. Poly-aluminum chloride is a new concept which gets a good result in processing waster water,having the advantage of lowed up-front investment,no separate process and etc. On the last chapter we prepare poly-aluminum chloride with acided fly ash. It's a gray lacunaris substance and the poly-aluminum chloride is distributed among them, which gradually send out to flocculate waste. And the fly ash can also adsorb the organic substance,heavy metal ion and etc.. So, we expert a good result.