Enhanced Separation of Incinerator Bottom Ash: Composition and Environmental Behaviour of Separated Mineral and Weakly Magnetic Fractions

The paper reports an investigation on the compositional characteristics and environmental behaviour of eight fractions deriving from an advanced separation process applied to waste incineration bottom ash to recover ferrous and non-ferrous metals. Specifically, five mineral fractions and three weakly magnetic mixed metal/mineral fractions were analyzed for their physical properties, chemical composition and leaching behaviour in order to assess their recycling potential and estimate the expected environmental impacts. While the mineral fractions were found to contain only small amounts of undesired waste glass fragments, the weakly magnetic materials turned out to be commingled with a consistent portion of mineral components, resulting in a heterogeneous mixture with limited utilization potential. Their bulk and chemical composition as well as leaching properties were strongly affected by the presence of mineral particles associated with molten magnetic metals. The most critical elements with a view to leaching turned out to be, for both the mineral and the weakly magnetic fractions, Sb and Cr, which exceeded the quality standards for inert waste disposal in landfills.