Metal leaching of fly ash from incineration wastes by Thiobacillus ferrooxidans

摘要

Fly ash from a local solid waste incinerator was characterized, and chemical and bioleaching experiments were performed at various pulp densities (1 to 7% w/v) using sulphuric acid and Thiobacillus ferrooxidans. The very fine amorphous ash particle showed a non-porous struture with a low specific surface area. Although chemical leaching generally resulted in higher metal extraction than bioleaching, the results also showed that bioleaching give rise to higher metal extractions than the fresh medium and the cell-free spent medium (i.e. controls). T. ferrooxidans effected high metal extraction (in particular aluminium and zinc) from fly ash, although the extraction efficiency generally decreased with increased pulp density. pH decreased with time in bioleaching, but remained relatively constant in both the fresh medium and the cell-free spent medium, thus indicating that the microorganisms play a role in effecting metal extraction from the fly ash.