Author(s)

T. Van Gerven, K. Imbrechts, E. Van Keer, M. Jaspers, G. Wauters & C. Vandecasteele

Abstract

MSWI-bottom ash often may not be recycled as construction material in Flanders, because leaching of Cu exceeds the limit value of 0.5 mg/kg. Leaching of other components such as Mo and Sb is critical as well, but limit values for these elements are to date only informal. Three treatment techniques were investigated to lower Cu leaching: thermal treatment destroying organic matter still present in the incinerator residue and ligands that may form complexes with Cu and enhance leaching, washing with solutions of organic complexants to extract Cu and accelerated carbonation. Carbonation decreases pH and causes metal hydroxides to react to carbonates. Heating the bottom ash to 400°C decreases Cu leaching to 0.1 mg/kg. Washing was performed with six solutions, of which washing with citric acid and ammoniumcitrate decreases Cu leaching to below the limit value. Carbonation decreased Cu leaching from 3.3 mg/kg to 1.0 mg/kg, but further improvement should be possible. Although heating and washing gave better results in the laboratory, accelerated carbonation seems to be the most promising technique. Keywords: MSWI-bottom ash, leaching, heavy metals, recycling, carbonation, washing, heating.

Keywords

MSWI-bottom ash, leaching, heavy metals, recycling, carbonation, washing, heating.