Biosorption of Inorganic Mercury onto Dead Biomass of Marine Aspergillus niger : Kinetic,Equilibrium,and Thermodynamic Studies

Abstract

Large numbers of reports are available on metal binding capacity of different groups of microorganisms. However, reports on the equilibrium and thermodynamic studies on biosorption process are few. The present study was carried out in a batch system using dead biomass of marine Aspergillus niger for the sorption of Hg(II). Preliminary experiments revealed that removal rate of Hg(II) was maximum at pH 3. A. niger exhibited the highest Hg(II) uptake of 40.53 mg/g of biomass at pH 3 and 40°C. Kinetic studies reveal that pseudo-second order model showed best fit to experimental data. Two linear portions in the plot q_t (mg/g) vs t^1/2 (min^1/2) indicate the existence of an intraparticular diffusion resistance in the sorption process. Experimental sorption data were analyzed using four and three, two-parameter models (Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin) and three-parameter equilibrium models (Khan, Sips, and Toth), respectively. It was observed that Langmuir among two parameters models and, Sips among three parameter models, exhibited the best fit to the experimental data. Thermodynamic parameters on the biosorption (ΔG°, ΔH°, Δ S°) were also determined.