Use of combined solvent extraction-electrodeposition techniques to uranium and thorium isotopes analysis in industrial phosphoric acid, phosphate and phosphogypsum by alpha-particle spectrometry

Abstract

Uranium / Thorium / Phosphate / Phosphogypsum / Phosphoric acid / Electrodeposition / Solvent extraction / α-particle spectrometry Summary. A method combining liquid-liquid extraction and electrodeposition procedures is carried out to determine isotopic composition of uranium and thorium in technical wet phosphoric acid, phosphate rock and phosphogypsum leachates, by α-particle spectrometry. Extraction experiments are performed with diethylether from 5.57 M calcium nitrate solution with nitric acid concentration of 2 M. Uranium is extracted in the pH range 0.6-0.8 and thorium is extracted after acidification with 2 M HNO 3 . Alpha-sources are obtained by a selective electrodeposition of U(VI) or Th(IV) directly from the extracting solution without applying back-extraction or purification steps.The dependence of the electrodeposition and the overall recovery of U and/or Th are examined as a function of the amount of phosphate ions (C PO 4 3− ) in the electrolyte and of the aqueous phase, respectively. In all cases a decrease of the deposition yield with C PO 4 3− is observed. An improvement in the uranium overall recovery is achieved from 7.57 to 9.57 M nitrate solution and PO 4 3− concentration lower than 0.8 M. The method proposed is applied to technical wet phosphoric acid, phosphate rock and phosphogypsum leachates. Recoveries of 74%-93% are obtained for uranium and 54%-69% for thorium. Good resolutions (37-52 keV) are also achieved under optimum conditions. These resolutions allow to make accurate determination of U and Th isotopes in the above mentioned samples.

Preparation of U(VI) and Th(IV) alpha-sources from sea and fresh water samples by combining coprecipitation, solvent extraction and electrodeposition procedures

“…To obtain an alpha source with high purity, a second decontamination of a specific nuclide was achieved by a selective electrodeposition using suitable electrolyte. For this purpose, electrodeposition of uranium was performed in 70% ethanol, 0.51 M hydrochloric acid, 0.09 M acetic acid and 108 µg of Fe 2 O 3 added as carrier, while electrodeposition of thorium was carried out in a similar solution but HCl and HNO 3 concentrations were about 0.45 M and 0.06 M, respectively [15,22,28].…”

Investigation of key factors in preparation of alpha sources by electrodeposition

“…The radiochemical separation methods used prior to the source preparation should be highly selective and sensitive to produce solutions of analytes as free as possible from any spectral or chemical interferences, and the source preparation itself should be quantitative and reproducible, giving homogenous, stable sources suitable for measurements at all source-detector distances. Many different source preparation techniques for alpha-particle spectrometry have been developed over the years to meet these necessary requirements (Aggarwal, 2016;Crespo, 2012;Lally and Glover, 1984;Sibbens and Altzitzoglou, 2007), but electrodeposition is certainly the most studied and still one of the most frequently used methods for determination of alpha-emitters in a variety of samples: environmental (Carvalho and Oliveira, 2009;Jia et al, 2002), geological (dos Santos et al, 2004), biological (Gaburo et al, 2006;Rzemek et al, 2015), industrial (Carvalho and Oliveira, 2009;Zarki et al, 2003), etc. Optimization of the electrodeposition method usually focuses on the usage of different aqueous and/or organic electrolyte solutions (Hallstadius, 1984;Ingelbrecht et al, 1997;Jobbágy et al, 2013;Kressin, 1977;Lee and Lee, 2000;Puphal and Olsen, 1972;Talvitie, 1972;Torrico et al, 2015) or on the improvements made on the system itself (e.g.…”