TheremovalofthepertechnetateionandactinidesfromradioactivewastestreamsatHanford,Washington,USAandSellafield,Cumbria,UK:theroleofiron-sulfide-containingadsorbentmaterialsOriginalResearchArticle

Inpreviousworktheadsorptionofanumberofradioactiveionsfromsolutionbyastrongly-magneticironsulfidematerialhasbeenstudied.Thematerialwasproducedbysulfate-reducingbacteriainanovelbioreactor.Theuptakeisrapidandtheloadingontheadsorbentishighduetothehighsurfaceareaoftheadsorbentandbecausemanyoftheionsarechemisorbed.Thestructuralpropertieshavebeenexaminedusinghigh-resolutionimagingandelectrondiffraction,bytransmissionelectronmicroscopy(TEM).Themagnetisationversusfieldandtemperature,extendedX-rayabsorptionfine-structure(EXAFS)spectroscopy,X-rayabsorptionnearedgestructure(XANES)spectroscopyandneutrondiffractionhavebeenreportedpreviously.Thesurfaceareaisoftheorderof400–500m2g−1,asdeterminedbytheadsorptionofheavymetals,themagneticproperties,neutronscatteringandtransmissionelectronmicroscopy.Followingthesuccessofthebiologically-generatedmaterial,LidzeyatBioSeparationLtd.wasabletoproduceanironsulfidematerialwiththetochilinitestructurewhichhassimilaradsorptionpropertiesforcations,butnotanions,asthebiologically-generatedmaterialbuttheLidzeymaterialisconsiderablycheapertoproduce.OneoftheradionuclidesofparticularinterestisthepertechnetateionTcO4−.99Tcisaradionuclidedeterminingthelong-termenvironmentalimpactofthenuclearfuelcyclebecauseofitslonghalf-lifeandbecauseitoccursnormallyintheformofthehighlysolublepertechnetateionwhichcanenterthefoodchain.Thispaperexaminesmethodsbywhichadsorbentmaterialscontainingironsulfidecanplayapartintheextractionandthesafelong-termstorageofmanyradionuclidesandinparticularthepertechnetateionoccuringattheHanfordPlant,Washington,USAandtheSellafieldPlant,Cumbria,UK.