4th Swiss Geoscience Meeting, Bern 2006 Chemical reactions of bottom ash with CO2-saturated water (TVA-Test)

• Main Authors: Eggimann Manuel, Eggenberger Urs
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Carbonic acid
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.517.1598; http://geoscience-meeting.scnatweb.ch/sgm2006/sgm06_abstracts/01_geological_disposal/eggimann_manuel_talk.pdf

The TVA test was created by the Federal Office for the Environment for the classification of waste materials according to the legislation “TVA ” (BAFU 1999), which supplies threshold values for several toxic organic and inorganic constituents. The batch eluate test is performed in two parts. Anionic constituents are extracted in pure water, whereas cations, especially heavy metals, are extracted using CO2-saturated water. The water is continuously flushed with gaseous carbon dioxide, so that the system is continuously at equilibrium with CO2. The added carbonic acid lowers the pH-value of pure water to 4 and to about 6.5 for municipal solid waste incineration (MSWI) bottom ash samples (the solid to liquid ratio is 1:10). The pH of MSWI bottom ash extracted with distilled water yields typical values of 11. In this study, the role of carbonic acid was investigated by means of experimental work and by geochemical modelling using PHREEQC (Parkhurst and Appelo 1999). Two titration experiments with bottom ash samples were performed, using different acids with the same pH-value of 4: CO2-saturated water (carbonic acid) and 10-4 M nitric acid (HNO3).