Release of metals from MSW I fly ash and availability in alkali condition

The release and availability of Pb, Cd, Cu, Zn from municipal solid waste (MSW) fly ash were studied with an emphasis on its behavior under alkaline conditions. Serial batch tests using acidic and alkaline solutions as leachant and a pH stat test were carried out. From the results of serial batch test: (1) Even if the ash comes into contact with strong acid for a long period, pH of the leachates from some fly ashes are high, and the concentration of Pb in the leachate is high. (2) When the ash comes into contact with the alkaline leachant, even if the Ay ash has little alkalinity, the pH of the leachate soon increases and the concentration of the Pb and Zn in it are high. (3) The fact that leaching of heavy metals from fly ash depends on the pH of the leachate was certificated. From the pH stat test: (1) The larger the liquid per solid ratio (L/S), the more metals are released. (2) Leaching behavior of Pb is different from other metals and leached in high concentration in alkali condition. (3) Concentration of metals in leachate is controlled not only by solubility but other factors and were certificated. Moreover, considering the properties of the ashes, the optional procedure of the availability test for Pb was proposed. (C) 1997 Elsevier Science Ltd.