Biosorption of Tungsten by <i>Escherichia coli</i> for an Environmentally Friendly Recycling System

Abstract

In this study, tungsten (W) recovery via biosorption using <i>Escherichia coli</i> 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 <i>E. coli</i> 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 <i>E. coli</i> cells. Heating at 1000 °C for 2 h under atmospheric conditions produced concentrates with relatively high concentrations of W^VI (97.1% WO₃)