Biosorption of cadmium, lead, mercury, and arsenic ions by the fungus Penicillium purpurogenum

Abstract

The potential use of the fungus Penicillium purpurogenum to remove cadmium, lead, mercury, and arsenic ions from aqueous solutions was evaluated. Biosorption of heavy metal ions reached equilibrium in 4 h. Heavy metal ions binding by Penicillium purpurogenum was clearly pH dependent. Heavy metal loading capacity increased with increasing pH under acidic conditions, presumably as a function of heavy metal speciation and due to the H+ competition at the same binding sites. The adsorption of heavy metal ions reached a plateau value at around pH 5.0. The maximum adsorption capacities of heavy metal ions onto the fungal biomass under noncompetitive conditions were 35.6 mg/g for As(III), 70.4 mg/g for Hg(II), 110.4 mg/g for Cd(II) and 252.8 mg/g for Pb(II). Their adsorption behavior can be described at least approximately with the Langmuir equation. The competitive adsorption capacities of the heavy metal ions were 3.4 mg/g for As(III), 15.8 mg/g for Hg(II), 13.1 mg/g for Cd(II), and 41.8 mg/g for Pb(II) at 50 mmol/L initial concentration of metal ions. The same affinity order on a molar basis was observed under noncompetitive and competitive adsorption conditions, which was as follows: Pb(II)>Cd(II)>Hg(II)>As(III). The equilibrium loading capacity of Pb(II) was greater than that of other metal ions. This fungal biomass showed a preference for binding Pb(II) over Cd(II), Hg(II), and As(III). Elution of heavy metal ions was performed using 0.5 M HCl. The fungus Penicillium purpurogenum could be used for ten cycles for biosorption.