The Chemistry of Protactinium

Abstract

AND INSTITUT FUR RADIOCHEMIE, GESELLSCHAFT FUR KERNFORSCHUNG MBH., KERNFORSCHUNGSZENTRUM KARLSRUHE (GERMANY) Dedicated to Professor W. Klemm in honor of his 70th birthday Protactinium exhibits an ambivalent chemical behavior. In non-aqueous solutions and in the solidstate, both quadrivalent and quinquevalent protactinium has properties which characterize it as a typical actinide element. On the other hand, investigations in aqueous solution show quinquevalent protactinium to be a homologue of niobium and tantalum. It exhibitsexcept in hydrofluoric acid solutionsa marked tendency to undergo irreversible hydrolysis and condensation reactions, which leads to the situation that tracer amounts (ca. 10-12 molell) and macroscopic amounts (10-3-10-6 molell) of protactinium often behave differently. Reduction with strong reducing agents gives aqueous solutions of Pa(IV), the properties of which again correspond in general to those of Th(IV) and show no relation to Nb(IV). Our knowledge of the chemical behavior of this rare radioelement has been advanced, in particular, by the production in 1958-1960 of 100 g of pure protactiniumthe largest amount so far -from residues of the British production of uranium. ringt1] later found this intermediate (ux2 = 234mPa) [ l ] K . Fnjans and 0. GdrrinR, Naturwissenschaften I , 339 (1913). Element 91, protactinium, comes between thorium and uranium in the periodic table. On the basis of the radioactive displacement laws, FajanS, Russell, and SOddY 91. Fajans and Aiigcrv. Chrni. iiitcriiot. Edit. V d . 5 (1966) No. I

Revealing Disparate Chemistries of Protactinium and Uranium. Synthesis of the Molecular Uranium Tetroxide Anion, UO4–

“…In contrast to uranyl, protactinyl is not a stable species in solution but rather undergoes hydrolysis. 28,29 Accordingly, PaO 2 (C 2 O 4 ) − did not appear in the ESI mass spectrum. Instead, the gas-phase protactinyl complex was produced by CID of the Pa Both actinyls are distorted from linear, with that for protactinyl substantially more so.…”

Double photoexcitation involving2pand4felectrons inL3-edge x-ray absor

“…On the other hand, aqueous protactinium shows a complicated solution chemistry because it undergoes easy hydrolysis and polymerization reactions followed by precipitation. 33 This occurs also in HClO 4 and HNO 3 solutions; therefore, the Pa͑V͒ sample could not be prepared in the same way as the actinides used for the first study of multielectron excitations. 12 The formation of Pa͑V͒ polymers can be suppressed in HF and concentrated H 2 SO 4 solutions.…”

Protactinium

“…The extraction with salicylate can be used for the separation of protactinium from rare earth and other di-and tervalent elements. The quantitative extraction of protactinium oxychinolate with chloroform from solutions with pH 3-9 was described (Keller, 1966a).…”

“…Ternary oxides and oxide phases of different compositions and structures have been prepared by reaction of PaO 2 and Pa 2 O 5 with the oxides of other elements (Table 4.8) (Keller, 1964a(Keller, ,b, 1965a(Keller, -c, 1966a(Keller, ,b, 1971Iyer and Smith, 1966). 1240-1400 Roberts and Walter (1966) The pale yellow product, which precipitates upon addition of H 2 O 2 to a solution of Pa(V) in 0.25 M H 2 SO 4 , has been assigned the formula Pa 2 O 9 · 3H 2 O (Stchouzkoy et al, 1966b).…”

“…understanding of Pa chemistry, as summarized in numerous critical review articles (Gmelin, 1942(Gmelin, , 1977Elson, 1954;Katz and Seaborg, 1957;Haïssinsky and Bouissières, 1958;Kirby, 1959;Salutsky, 1962;Brown and Maddock, 1963;Sedlet, 1964;Guillaumont and deMiranda, 1966;Keller, 1966a;Brown and Maddock, 1967;Guillaumont et al, 1968;Muxart et al, 1969;Muxart and Guillaumont, 1974;Morgan and Beetham, 1990), books (Cotton et al, 1999) and presentations (Weigel 1978;Jung et al, 1993;Greenwood and Earnshaw 1997;Sime, 1997).…”