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Stabilization of Heavy Metals in MSWI Bottom Ash by Enhanced Carbonation
Bottom ashes (BA) constitute the dominant solid residue of municipal solid waste incineration (German BA production: 4.5 million mt/year). Disposal to landfill or geotechnical re-use are the main management options for this waste stream. Costs and revenues of either option are related to the mobility of heavy metals as assessed in standardized leaching protocols. The ageing of BA in contact with carbon dioxide causes a carbonation of the Portlandite buffer system and reduces the mobility of amphoteric metals. In this study we focused on enhanced carbonation to stabilize heavy metals in the BA matrix. Composite BA samples were collected at the slag discharge of an incinerator. After homogenization the samples were subjected to carbonation tests as follows. First, a screening for the optimum moisture conditions for carbonation was undertaken, and the mobility of metals was studied in comparative batch leaching tests. Second, a semi-technical scale carbonation test was conducted at natural BA moisture to obtain sufficient material for the column leaching experiment prescribed by the German Ordinance on Secondary Construction Materials. Optimum carbonation was obtained when the BA was treated at inherent water contents. The maximum uptake of CO2 amounted to about 3.6% wt., and the pH dropped from 12.1 to 10.5. For amphoteric metals, stabilization efficiencies were up to 99.9%. Overall, it was demonstrated that enhanced carbonation makes the material suitable for disposal on a more economic landfill class or for geotechnical re-use.
Stabilization of Heavy Metals in MSWI Bottom Ash by Enhanced Carbonation
Bottom ashes (BA) constitute the dominant solid residue of municipal solid waste incineration (German BA production: 4.5 million mt/year). Disposal to landfill or geotechnical re-use are the main management options for this waste stream. Costs and revenues of either option are related to the mobility of heavy metals as assessed in standardized leaching protocols. The ageing of BA in contact with carbon dioxide causes a carbonation of the Portlandite buffer system and reduces the mobility of amphoteric metals. In this study we focused on enhanced carbonation to stabilize heavy metals in the BA matrix. Composite BA samples were collected at the slag discharge of an incinerator. After homogenization the samples were subjected to carbonation tests as follows. First, a screening for the optimum moisture conditions for carbonation was undertaken, and the mobility of metals was studied in comparative batch leaching tests. Second, a semi-technical scale carbonation test was conducted at natural BA moisture to obtain sufficient material for the column leaching experiment prescribed by the German Ordinance on Secondary Construction Materials. Optimum carbonation was obtained when the BA was treated at inherent water contents. The maximum uptake of CO2 amounted to about 3.6% wt., and the pH dropped from 12.1 to 10.5. For amphoteric metals, stabilization efficiencies were up to 99.9%. Overall, it was demonstrated that enhanced carbonation makes the material suitable for disposal on a more economic landfill class or for geotechnical re-use.
Stabilization of Heavy Metals in MSWI Bottom Ash by Enhanced Carbonation
Wieser, T. (author) / Weigand, H. (author)
Geo-Congress 2014 ; 2014 ; Atlanta, Georgia
Geo-Congress 2014 Technical Papers ; 2226-2234
2014-02-24
Conference paper
Electronic Resource
English
Stabilization of Heavy Metals in MSWI Bottom Ash by Enhanced Carbonation
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