Selective recovery of Zn2+ from waste slag from a metal-processing plant by the microscopic fungus Verticillium marquandii

The successful use of hay extract medium for growth of Verticillium marquan dii in the presence of toxic black slag, resulted in selective and efficien t Zn2+ recovery. An alkaline black waste slag originating from short rotary furnace, contained Zn2+ and Pb2+ (20% and 3.5%, respectively) in a form of compounds only slightly soluble in water. After 90 h of the culturing in b ioreactor on hay extract medium with starch (50 g l(-1)) and black waste (5 g l(-1)) supplements, 80% of zinc and 0.5% of lead were bound by the mycel ium. The pH value of the culture medium played a crucial role for limitatio n of the waste inhibitory effect on mycelium growth and for heavy metal rec overy by the fungus.