PHREEQC Modelling of Leaching of Major Elements and Heavy Metals From Cementitious Waste Forms

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Abstract

In this study, Ca, Mg, Al, and Pb concentrations leached from uncarbonated and carbonated ordinary Portland cement – dried waste incinerator bottom ash samples during single extraction tests (EN12457 test) at a pH from 1 to 12, were modelled using the geochemical code PHREEQC. A good agreement was found between modelling results and experiments in terms of leached concentrations for Ca, Mg, and Al by defining a single set of pure mineralogical phases for both the uncarbonated and carbonated (three levels) samples. The model also predicted well the observed decrease in Ca leaching with increasing carbonation. Modelling results further revealed that leaching of Pb is not controlled by dissolution/precipitation of pure Pb containing minerals only (carbonates and (hydr)oxides). The addition of solid solutions (calcite-cerrusite and gibbsite-ferrihydrite-litharge solid solutions) and adsorption reactions on amorphous Fe- and Al-oxides improved the model representation of the experimentally observed amphoteric leaching profile of Pb from the cementitious material.

Details

Original languageEnglish
Title of host publicationScientific Basis for Nuclear Waste Management XXXI
Place of PublicationWarrendale, United States
Pages475-482
Publication statusPublished - Sep 2008
EventMRS 2007 - Materials Research Society - UK - Materials Research Society, Sheffield, United Kingdom
Duration: 17 Sep 200723 Sep 2007

Publication series

NameMRS Proceedings
Number1107

Conference

ConferenceMRS 2007 - Materials Research Society - UK
CountryUnited Kingdom
CitySheffield
Period2007-09-172007-09-23

Keywords

  • cementitious waste forms, PHREEQC modelling, lead leaching, chemical toxicity, source term models, solid-solutions, surface complexation

ID: 134695