Hirofumi Sakanakura* and Nobutoshi Tanaka*

* Division of Environmental and Resource Eng., Graduate School of Eng., Hokkaido Univ.

+ Correspondence should be addressed to Nobutoshi Tanaka :
Faculty of Eng., Hokkaido Univ.
(Kita 13 Nishi 8, Kita-ku, Sapporo 060-0813 Japan)

Abstract

It is necessary to examine the influence of molten slag of waste (e.g., Municipal Solid Waste, and MSW Incinerator Ash) to the environment when utilized as recycled resources. In this paper, various leaching experiments for 8 kinds of waste molten slag, include 6 materials obtained from municipal facilities, were undertaken under batch type conditions without leachant exchange.Results indicated: (1) there are two leaching mechanisms, hydrogen ion acts directly on the slag surface (acid leaching zone), and each component leaches accoding to each hydrolysation characteristic (alkaline leaching zone) . The two zones can be divided clearly according to the quantity of hydrogen ion supplied from the leachant. (2) It is considered that under SiO2 saturated conditions in the alkaline leaching zone, slag components stop leaching due to a SiO2 film at the slag surface. (3) Under batch conditions, some elements (e.g., Fe, Mn and Mg) form carbonate salts/hydroxides when they reach solubility, and other trace elements, e.g., Pb, Zn and Cu may coprecipitate when Fe (OH) 2 precipitation forms.

Key words: waste molten slag, batch type experiment, leaching mechanism, hydrogen ion, solubility