Microbially enhanced chemisorption of nickel into biologically synthesized hydrogen uranyl phosphate: A novel system for the removal and recovery of metals from aqueous solutions

Ni2+ was removed quantitatively from aqueous flows by columns loaded with polycrystalline hydrogen uranyl phosphate (HUP) bound to immobilized cells of Citrobacter sp. The columns functioned effectively in Ni uptake/regeneration cycles; five cycles were completed without significant decrease in the Ni-removing capacity of the column. The influence of pH, temperature, and flow rate on the Ni-removing capacity of the columns was examined. The composition of the Ni/HUP cell-bound deposits was confirmed by X-ray diffraction analysis (XRD) and proton-induced X-ray emission (PIXE) spectroscopy following several consecutive metal challenges and is discussed in relation to the mechanism of Ni2+ removal from solution via ion-exchange intercalation into the interlayer space of HUP. Ni was selectively recovered from the columns using citrate or tartrate. The regenerated columns functioned effectively in Ni removal throughout repeated Ni challenge and desorption cycles. (C) 1997 John Wiley & Sons, Inc.