Interaction of Fe3+, Ca2+, and SO4 2- at the jarosite/alkaline coal fly ash interface

Radio tracer diffusion experiments have been carried out to study self-sealing/healing isolation and immobilization of two chemically contrasting wastes: acidic jarosite and alkaline coal fly ash. Precipitation of iron oxyhydroxide FeO(OH) and gypsum CaSO₄2H₂O occurs at the interface between jarosite and fly ash due to diffusion and interaction among the principal reacting solutes Fe+ , SO₄ ^2- , Ca+ . and OH^- . A layer with low permeability is formed at this interface because of pore filling by such precipitates causing a change in the transport properties of the bulk system. Precipitation at the interface between jarosite and fly ash affects also the mobility of chemical constituents including contaminants from the wastes. Co-disposal of chemically contrasting wastes may therefore lead to a self-forming barrier layer between them, which. next to isolating the wastes, also immobilizes contaminants from their leachates. Such systems will have a wide application in waste management.