Title
The leaching of trace elements from municipal solid waste incinerator bottom ash at different stages of weathering
Author
Meima, J.A.
Comans, R.N.J.
Nederlands Instituut voor Toegepaste Geowetenschappen TNO
Publication year
1999
Abstract
For a proper assessment of the environmental impact of the utilisation and disposal of Municipal Solid Waste Incinerator (MSWI) bottom ash it is necessary to understand weathering processes and their effects on (trace) element leaching. The authors have investigated the processes that control the leaching of Cd, Pb, Zn, Cu, and Mo from 3 categories of bottom ash: (A) unweathered bottom ash (grate siftings and unquenched samples), (B) quenched/non-carbonated bottom ash (freshly quenched and 6-week-old samples), and (C) weathered bottom ash (1.5- and 12-year-old samples). Leaching experiments were performed in a pH-stat at a large range of pH values. The speciation code MINTEQA2 was used for subsequent modelling of precipitation/dissolution processes. The speciation of trace elements in weathered bottom ash was also investigated by microanalytical techniques. In A- and B-type bottom ash the general controlling processes are thought to be precipitation/dissolution of relatively soluble minerals or, in the case of Cu in particular, extensive complexation with dissolved organic C. At the 'natural' pH of the samples, the leaching of Cd, Pb, Cu, Zn and Mo is generally significantly lower from C-type bottom ash than from less weathered types of bottom ash. This reduction in leaching is due to the neutralisation of bottom ash pH and the formation of less soluble species of these elements as weathering continues. In the more weathered (C-type) bottom ash trace element leaching does not seem to be solubility-controlled; although slow precipitation reactions cannot be totally excluded, it is hypothesised that the controlling mechanism in those samples is sorption to neoformed minerals.
Subject
Geosciences
Chemical reactions
Complexation
Computer simulation
Dissolution
Mathematical models
Municipal engineering
pH effects
Precipitation (chemical)
Refuse incinerators
Solid wastes
Trace elements
Weathering
Microanalytical techniques
Municipal solid waste incinerator
Leaching
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DOI
https://doi.org/10.1016/s0883-2927(98)00047-x
TNO identifier
234964
Publisher
Elsevier Science Ltd, Exeter, United Kingdom
ISSN
0883-2927
Source
Applied Geochemistry, 14 (2), 159-171
Document type
article