Rapid removal of Pb²⁺ from aqueous solution by phosphate-modified baker's yeast

Phosphate-modified baker's yeast (PMBY) was prepared, and used as a novel bio-sorbent for the adsorption of Pb²⁺ from aqueous solution. The influencing factors, absorption isotherms, kinetics, and mechanism were investigated. The scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) characterization and elemental analysis of PMBY showed that phosphate groups were successfully grafted onto the surface of yeast. The kinetic studies suggested that the adsorption process followed a pseudo-second-order chemisorption. The adsorption process of Pb²⁺ using PMBY was spontaneous and endothermic. Furthermore, the adsorption of Pb²⁺ on PMBY can rapidly achieve adsorption equilibrium (in just 3 min), and the maximum adsorption capacity of Pb²⁺ on PMBY was found to be 92 mg g^-1 at 30 °C, which was about 3 times that of the pristine baker's yeast. The suggested mechanism for Pb²⁺ adsorption on PMBY was based upon ion-exchange, electrostatic interaction and chelation between the phosphate groups and Pb²⁺. However, compared with the pristine baker's yeast, the higher capacity and rapid adsorption of PMBY for Pb²⁺ was mainly due to the chelation and electrostatic interactions between the phosphate groups and Pb²⁺. In addition, the regeneration experiments indicated that the PMBY was easily recovered through desorption in 0.01 M HCl, and that PMBY still exhibited 90.77% of the original adsorption capacity for Pb²⁺ after five regeneration cycles. These results showed the excellent regeneration capability of PMBY for Pb²⁺ adsorption. PMBY has shown significant potential for the removal of heavy metals from aqueous solution due to its rapid adsorption, high-capacity and facile preparation.