Mechanism of Hg(II), Cd(II) and Pb(II) Ions Sorption from Aqueous Solutions by Aspergillus Niger Spores

Recent work has focused on the removal of Pb2+, Hg2+, and Cd2+ by using an organ of Aspergillus niger - spores, which were spherical particles with small diameter (2 mu m) characterized by negative charge. Results shown that the biosorption of Pb2+, Hg2+, and Cd2+ from aqueous solutions using spores was analyzed at varying biosorbent dosages, pH levels, contact times and initial heavy metal concentrations. The maximum biosorption capacities of Pb2+, Hg2+, and Cd2+ were 23.9, 27.2, and 21.5 mg/g at a natural pH with the initial concentration were 30 mg/L, respectively. The sequence of biosorption capacity for cationic heavy metals was Pb2+>Cd2+>Hg2+. Spores exhibited a short biosorption equilibrium time of 60 min at a pH range of 4.0-6.0, and the main biosorption mechanism was electronic attraction, ion exchanges and complexation(involved in C = C, C-H, C-O, N-H), the data fit well in the pseudo-second-order kinetic equation and the Freundlich isotherm. In addition, Spores can grow on many kinds of moist agriculture waste without any added nutrition. The results showed that spores could be considered as a potential biosorbent for the removal of cationic heavy metals from aqueous solutions.