Enhancement of bioleaching of a spent Ni/Mo hydroprocessing catalyst by Penicillium simplicissimum

► Experimental designs were used to screen effective factors and optimize the process. ► The maximum predicted recoveries by models were 97.6% Mo, 45.7% Ni, and 14.29% Al. ► The growth kinetics of the fungus in the presence of the spent catalyst was modeled. ► The relationship between the specific growth rate and pulp density was found.