Alkaline Activation as a Procedure for the Transformation of Fly Ash into New Materials. Part II - An Assessment of Mercury Immobilisation

摘要

This paper presents total and soluble Mercury contents for three coal fly ashes and alkali-activated fly ash (AAFA) cements consisting of 100% fly ash as starting material. To evaluate the potential of the AAFA cement matrix to immobilise Hg from an external source, another batch of cements, doped with 5000mg/kg Hg as HgCl2, was prepared. The ashes alone complied with Mercury leaching criteria according to the TCLP and EN 12457 tests. Control AAFA cement samples complied with TCLP criteria but exceeded acceptable limits for wastes according to the EN 12457 test by varying degrees. Fly ash activated cements doped with 5000mg/kg Hg and aged for 2 days immobilised 98.8-99.6% and 97.3-98.8% of Hg according to TCLP and EN 12457 tests respectively. The results for Hg-doped cements contribute to the body of evidence showing that alkali-activation of fly ash can be considered as a useful process for immobilizing elevated concentrations of toxic and hazardous elements.