Heavy metals extraction from municipal solid waste incineration fly ash using adapted metal tolerant Aspergillus niger

This study focused on the adaptation of Aspergillus niger tolerating high concentration of heavy metals for bioleaching of fly ash. The Plackett–Burman design indicated that Al and Fe inhibited the growth of A. niger (AS 3.879 and AS 3.40) significantly. The single metal (Al and Fe) and multi-metals adapted AS 3.879 strain tolerated up to 3500 mg/L Al, 700 mg/L Fe, and 3208.1 mg/L multi-metals, respectively. The order of metal extraction yield in two-step bioleaching of 60 and 70 g/L fly ash using Al adapted, multi-metals adapted and un-adapted AS 3.879 strains was as follows: multi-metals adapted > Al adapted > un-adapted. The multi-metals adapted strain grew with up to 70 g/L fly ash and secreted 256 mmol/L organic acids after 288 h, where 87.4% Cd, 64.8% Mn, 49.4% Zn and 45.9% Pb were dissolved. The extracted metals in TCLP test of the bioleached fly ash by multi-metals adapted strain were under the regulated levels in China.