Microbially-enhanced chemisorption of Ni~(2+) ions into biologically-synthesised hdyroen uranyl phosphate (HUP) and selective recovery of concentrated Ni~(2+) using citrate or chloride ion

摘要

Hydrogen uranyl phosphate (HUP) deposited enzymatically on Citrobacter N14 immobilized in polyacrylamide gel removed nickel ions from solution via intercalatice ion-exchange into-exchange into the HUP lattice.Usig flow-through columns containing 100 mg dry weight of biomass and approx 200-250 mg loaded uranium column saturation and breakthrough of Ni~(2+) occurred after ca.600 ml,with a total of approx 30 mg Ni~(2+) loaded per column,corresponding to a molar ratio of U:Ni of approx2:1 ,in accordance with the identity of the material as Ni(UO_2PO_4)_2,identified previously.Ni~(2+) was selectively desorbed using 100 mM sodium citrate-citric acid buffer over 140 ml or a short pulse (5 ml) of 500 mM citrate buffer followed by a water wash,giving a total recovery volume of 80 ml,with a total citrate concentration of approx 30 mM in the wash solution of the latterAs an alternative eluant which gives no residual BOD NaCl(0.6M) or seawater gave comparable recovery of Ni~(2+) to the 0.5 M citrate pulse,but with a Ni~(2+) recovery volume of 40-50 ml.The concentration ratio of Ni~(2+)-deposition:desorption (vol:vol) was 3-4 fold better with chloride ion than with 100 mM citrate.