ELSEVIER zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Internu&ionnlBiodeterioration & Bioakgmdation (1995) 93-121 Copyright @ 1995 Elsevier Science Limited Printed in Great Britain. All rights reserved ~~-8305~95/$9.SO+.~ 0964-8305(95)00052-6 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM Enzymically-enhanced Extraction of Uranium from Biologically Leached Solutions M. G. Roig,“* T. Manzano,a M. Diaz,” M. J. Pascual,a M. Patersonb & J. F. Kennedyb aDepartamento de Quimica Fisica, Facultad de Farmacia, Universidad de Salamanca, Salamanca, Spain ‘Birmingham Carbohydrate and Protein technology Group, School of Chemistry, The University of Bi~n~am, Bi~ingham B15 2TT, UK zyxwvutsrqponmlkjihgfedcbaZ ABSTRACT zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONM Many wastes contain heavy metals which are toxic and refractory: further problems arise in the production and discharge of waste radionuclides which have ~dd~t~o~l r~d~otoxic effects on the biosphere. Currently the problem may be tackled in four ways: (i) direct chemical method; (ii) electrochemical treatments; (iii) ion exchange and biosorption meth- ods; (iv) intracellular sequestration by growing microbial cells. A hybrid approach exploits the advantages of processes (iii) and (iv) with the disadvantages of neither. In this context, a biotechnological process for removing and recovering heavy metals from aqueous solutions has been evaluated at low PH. Metal uptake relies upon the in situ cumulutive deposition of insoluble metal phosphffte tightly bound to the cell surfff~e of Citrobaeter N14. Localized high loading of phosphate is contributed via a phosphatase-catalysed hydrolysis of an organic phosphate ‘donor’ molecule added to the metal solution with precipitation of metals (M) as cell-bound MHPO+ The present work reports on the potential of this immobilized microbial biomass for uranium recovery from the dilute uranium acid drai- nage of ENWSA mine in the Ciudad Rodrigo district of Spain. A range of supports (organic and inorgunic~ and immobilization method for Citro- batter cells have been screened. Finally, bio~lm and entrapped cells on polyurethane foam and cells coxdently immobilized on silanized and glutaraldehyde coated A1203 Raschig rings were chosen, characterized and *To whom correspondence should he addressed. 93