Study of the Applicability of Fly Ash for Immobilization of Heavy Metals

Abstract

Fly ashes from energy industry are a valuable raw material that can be used to remove pollutants from the leachates generated in landfills. The degree of using fly ashes received from coal combustion as a raw material to form active barriers depends mainly on the their sorption properties and ion exchange. Active barriers, as opposed to passive barriers, have capabilities to bind pollutants, which mean immobilizing them by sorption, exchange, or other chemical reactions.

The presented results concern the possibility of using fly ash from coal combustion as efficient raw material for creating active barriers able to immobilize metals contained in leachates from landfill sites. Conducted analyses of selected sorption and physicochemical properties of fly ash included, among others, Scanning Electron Microscopy (SEM-BSE), X-ray Powder Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). In addition, a thermal analysis of analyzed samples with DTA - Differential Thermal Analysis and TGA -Thermogravimetric Analysis and porosimetric analysis was conducted. Kinetics of adsorption was described based on the pseudo-first and pseudo-second order kinetic equations and intramolecular diffusion model. The release susceptibility of adsorbed Cu(II), Mn(II), Pb(II) and Zn(II) ions was set out, which determines the possibility of application of the fly ash as an permeable, active barrier in remediation of contaminated soils. The release susceptibility was determined with BCR sequential fractionation method (European Community Bureau of References – now Standards, Measurements and Testing Programme).