A novel technology for biosorption and recovery hexavalent chromium in wastewater by bio-functional magnetic beads

The goal of this study was to develop an applied technique for the removal and recovery of heavy metal in wastewater. It is novel that the Cr(VI) could be adsorbed and recovered by bio-functional magnetic beads. Furthermore, the magnetic separation technology would make their separation more convenient. The beads were constituted by the powder of Rhizopus cohnii and Fe3O4 particles coated with alginate and polyvinyl alcohol (PVA). The parameters effecting Cr(VI) removal were obtained: the optimum pH 1.0 and optimum temperature 28 °C. The biosorption took place mainly in form of Cr(VI) and R. cohnii   biomass played a key role in Cr(VI) adsorption. The model of Langmuir isotherm and Lagergren could be better used to fit the sorption process and kinetics, respectively. The beads still maintained predominant characteristics of adsorption, recovery and magnetism after five cycles for adsorption–desorption. The mechanism of adsorption was gained by Fourier transform infrared spectroscopy (FTIR), raman spectroscopy (RS) and scanning electron microscopy (SEM). The groups of –NH3+, –NH2+–, and NH– played an important role in the Cr(VI) adsorption. Consequently, the beads exhibited the superior performances in Cr(VI) cleanup, separation and recovery and the perspective potential in application.