Biosorption of Tungsten by Escherichia coli for an Environmentally Friendly Recycling System

In this study, tungsten (W) recovery via biosorption using Escherichia coli was assessed to establish an environmentally friendly recycling system for W. The recovery fraction of soluble W-VI was highly dependent on the solution pH, and E. coli cells exhibited the highest W-VI uptake capacity for an initial pH of 1.08-2.56. Fourier transform infrared analysis revealed that carboxyl and phosphate functional groups on the surface of the bacteria play a crucial role in adsorption of W-VI. Equilibrium and kinetic modeling of W-VI biosorption showed that the equilibrium adsorption data fit the Langmuir isotherm model better than the Freundlich model. Kinetic studies revealed that W-VI adsorption followed a pseudo-second-order rate model. W-VI was recovered by desorption and heating, and adjustment of the pH enabled 95.8% W-VI desorption from the E. coli cells. Heating at 1000 degrees C for 2 h under atmospheric conditions produced concentrates with relatively high concentrations of W-VI (97.1% WO3).