Process optimization and mechanistic studies of lead (II): <i>Aspergillus caespitosus</i> interaction for industrial effluent treatment

Abstract

The lead (II) accumulation potential of various biosorbent had been widely studied in the last few years, but an outstanding Pb(II) accumulating biomass still seems crucial for bringing the process to a successful application stage. This investigation describes the use of non-living biomass of Aspergillus caespitosus for removal of Pb from Pb(NO₃)₂ solution in a batch system under different experimental conditions. The highest Pb(II) sorption (351.7 ± 5.7 mg/g biomass) was observed at 600 µg/ml initial Pb concentration. Biosorption data were well defined by pseudo-second order, saturation mixed order and Langmuir isotherm models. The thermodynamic parameters: G (303 K), H and S were determined to be 4.64 kJ/mol, 75.4 kJ/mol and 26.2 J/mol-K respectively. The Pb uptake from binary solution was inhibited in the order of copper > nickel > zinc > manganese. Fourier transform infrared spectroscopy (FT-IR) characterization of Pb biosorption revealed the involvement of –SO3 and –CN groups along with other groups. The biosorbed Pb was stripped out (85.5%) using 0.01 M HCl and about 12% loss in Pb(II) sorption capacity was observed after five sorption-desorption cycles. High Pb (II) uptake (351.7 ± 5.7 mg/g biomass) by A. caespitosus proved it to be an outstanding biomaterial until now reported in literature for accumulating from solutions.

Key words: Aspergillus caespitosus, Pb, Langmuir isotherm, pseudo-second-order kinetic model, FTIR, SEM, EDAX.