Sorption of zinc onto elemental selenium nanoparticles immobilized in Phanerochaete chrysosporium pellets

The use of a novel hybrid biosorbent, elemental selenium nanoparticles (nSe⁰) immobilized in pellets of Phanerochaete chrysosporium, to remove Zn from aqueous solutions was investigated. Fungal pellets containing nSe⁰ (nSe⁰-pellets) showed to be better biosorbents as they removed more Zn (88.1 ± 5.3 %) compared to Se-free fungal pellets (56.2 ± 2.8 %) at pH 4.5 and an initial Zn concentration of 10 mg L⁻¹. The enhanced sorption capacity of nSe⁰-pellets was attributed to a higher concentration of sorption sites resulting in a more negative surface charge density, as determined by analysis of the potentiometric titration data. Fourier transform infrared spectroscopy (FT-IR) analysis of fungal pellets prior to and after being loaded with Zn showed the functional groups, including hydroxyl and carboxyl groups, involved in the sorption process. The experimental data indicated that the sorption rate of the nSe⁰-pellets fitted well to the pseudo-second order kinetic model (R² = 0.99), and the sorption isotherm was best represented by the Sips model (Langmuir-Freundlich) with heterogeneous factor n = 1 (R² = 0.99), which is equivalent to the Langmuir model. Operational advantages of fungal pelleted reactors and the Zn removal efficiencies achieved by nSe⁰-pellets under mild acidic conditions make nSe⁰-pellet based bioreactors an efficient biosorption process.