Qualitative and quantitative characterization of metallic aluminum in municipal solid waste incineration bottom ash

Abstract

The reaction of alkaline solution and metallic aluminum present in municipal solid waste (MSW) incineration bottom ash (IBA) generates hydrogen gas. Thus, it is crucial to characterize the metallic aluminum in IBA for its safe utilization and proper disposal. However, the inherent inhomogeneity of IBA, random distribution of metallic aluminum in IBA grains, presence of aluminum in compound forms, and lack of reliable quantitative characterization techniques pose significant challenges to the holistic understanding of metallic aluminum in IBA. This research aims to address these questions systematically and present a comprehensive understanding of metallic aluminum in IBA. A classification strategy based on mineralogical and particle size basis is adopted to minimize the inhomogeneity of IBA. Furthermore, the spatial distribution of metallic aluminum in IBA is studied through SEM/EDS of the IBA grains cross-sections of different particle sizes and mineralogical classes. Subsequently, a modified in-house designed collecting gas over liquid setup was developed for an easy and reliable quantitative characterization. The metallic aluminum content was the highest for 0.3–1.18 mm and lowest for < 0.3 mm range, and within a given mineralogical class, the metallic aluminum content decreases with decrease in particle sizes. The microanalysis of cross-sections of IBA grains showed that the aluminum is present as aluminum alloy formed during incineration or in oxide form, majorly in fine fractions (< 0.3 mm). The current study seeks to provide a complete picture of metallic aluminum distribution in IBA.