CHEMICAL SPECIATION AND LEACHING PROPERTIES OF ELEMENTS IN MUNICIPAL INCINERATOR ASHES

Different chemical properties of bottom ash and fly ash from municipal solid waste incinerators were compared based on the results of the fi ve measuring techniques: (1) total contents and leaching amounts by re gulatory leaching test in Japan; (2) leaching properties by pH-depende nt leaching test; (3) modeling of pH-dependent leaching test using mod el compounds; (4) enriched chemical composition compared with bulk com position by an X-ray photoelectron spectrometer (XPS); (5) estimation of chemical states of elements by XPS analysis. The difference between bottom ash and EP ash was clearly found in element content, leaching behavior and release rate. The release rates of many elements in botto m ash were lower than in electrostatic precipitation (EP) ash even in an acidic condition of pH 3 as well as at the inherent pH of 12. Corre sponding to the relatively complicated components in bottom ash, leach ing patterns depending on pH were not simple. Comparison between the p H-dependent pattern of Ca in a sample and in model compounds resulted in the estimation of some Ca compounds in ash. The surface analysis by XPS showed results that Na, Cl, Zn, Pb and S were enriched in EP ash and Fe and Ti were rarely found in the surface of ash. Possible chemic al states of Na, Ca, K, Cl and S were estimated by a new method of com paring binding energies of standard compounds and their mixtures. (C) 1997 Elsevier Science Ltd.