Selective separation of Eu{sup 3+} using polymer-enhanced ultrafiltration

Abstract

The U.S. Department of Energyis activelypursuingnewand improvedseparationtechniquesto " concentratehigh-levelliquidradioactivewaste,particularlyat the HanfordSite, inorderto minimizethe waste volumerequiringvitrification. A processto selectivelyremove24tAmfromliquidradioactivewaste was investigatedas an actinideseparation methodthatcouldbe applicableto Hanfordandother waste sites. The experimentalproceduresinvolvedremovalof Eu, a nonradioactivesurrogatefor:41Am,from aqueoussolutionsat pH 5 using organicpolymersin conjunction with ultrafiltration.Commercially availablepolyacrylicacid (60,000 MW)and PacificNorthwestLaboratory's ! (PNL) synthesizedE3 copolymer(-10,000 MW)were tested. Test solutionscontaining10_tg/mLof Eu were dosed with each polymerat various concentrationsin orderto bindEu (i.e., by complexationand/orcation exchange)for subsequentrejectionby an ultrafiltration coupon. Test solutionswere filteredwith and withoutpolymerto determineif enhancedEu separationcouldbe achieved_om polymertrealanent.Both polymers significantly increasedEu removal. The optimumconcentrationswere20 gtg/mLof polyacrylicacid and 100 _tg/mLof E3 for 100%Eu rejectionby the AmiconPM10membraneat 55 psi. In additionto enhancementof removal,the polymersselectivelybound Eu overNa, suggesting that selective separation of Eu was possible. _. The results of this studysuggest that polymer-enhancedultrafiltration is a potential process for separationof 241Am fromHartfordtank waste. Thus, furtherinvestigationof binding agents and membraneseffective under conditions similarto the tank waste (e.g., very alkaline and high ionic strength) is warranted. This process also has potentialapplications for selectiveseparationof metals from industrial 1Operated for the U.S. Departmentof Energyby Battelle MemorialInstitute underContract DE-AC06-76RLO 1830. 111 process streamsandthe use of the polymersevaluatedinthis studyandotherhigh molecularweight bindingagentsthatexhibitan affinityforregulatedtoxic metalsshouldbe furtherexamined.