Inorganic contaminants attenuation in acid mine drainage by fly ash and its derivatives: column experiments.

Treatment of AMD with fly ash (FA) is a promising technology but solid residues (SR) generated in the process pose a disposal challenge. This study evaluates the suitability of the SR and SR, FA/ordinary Portland cement (OPC) blends for backfill in mine voids and in-situ treatment of AMD flows. The mitigation of AMD in a mine void was simulated by addition of simulated acid mine drainage (SAMD) to FA, SR, SR + 25 % FA and SR + 6 % OPC packed columns. Acidity neutralisation in AMD was achieved over the study period. PHREEQC modelling indicated that precipitation of contaminants bearing mineral phases contributed to low levels of contaminants. Leaching of toxic trace elements and attenuation of contaminants strongly depended on the pH regime. Results revealed that backfill of coal mine voids with SR is a promising approach for large scale disposal of SR and treatment of AMD flows insitu. [ABSTRACT FROM AUTHOR]