Coprecipitation of Thorium with Barium Sulfate

Abstract

The amount of thorium coprecipitated with barium sulfate at various thorium concentrations is investigated as function of sulfuric acid and potassium sulfate concentrations. There is a correlation between the mol ratio of thorium and potassium in the coprecipitate and the mol ratio of these ions in the solution. Within the limits Κ : Th = 30 and 500 in solution the mol ratio Κ : Th in BaSO" is « 2. Dissolution in steps shows that this mol ratio is approximately constant throughout the whole crystal. Anomalous mixed crystals containing Κ : Th : Ba in mol ratios « 2 : 1 : 6 are formed. The decrease in lattice parameters is in agreement with the concept that 3 Ba J + are substituted by 1 Th 4+ and 2 K + . General procedure of coprecipitationIt is known that chemical exchange between Th carrier and added tracer may be so slow that serious errors can be caused. 234 Th tracer and thorium nitrate solution were therefore boiled with a small amount of nitric acid, perchloric acid and sulfuric acid until fuming of sulfuric acid began. The solution was diluted with water to 30 ml and potassium sulfate was added. Then 2.0 ml of 0.485% barium nitrate were added drop by drop into a boiling solution [4], After cooling the solution the precipitate was filtered and washed with 20 ml of 0.5 % sulfuric acid

Coprecipitation of Th with SrSO4 and Uptake of Th by SrSO4

“…Separation of Th, U and transuranium elements by coprecipitation with BaS0 4 has been reported by Sill et al [1 -4], Coprecipitation of Th with BaS0 4 has been investigated in detail by Ambe and Lieser [5] and it has been found that anomalous mixed crystals (anomalous solid solutions) are formed in which 3 Ba 2+ ions in the lattice of BaS0 4 are substituted by 2 K + and 1 Th 4+ . This is surprising, because the ionic radius of Th 4+ is by about 24% smaller than that of Ba 2+ , whereas the generally accepted prerequisite for formation of mixed crystals is that the ionic radii should not differ by more than 15% [6].…”

Radionuclides in the Geosphere: Sources, Mobility, Reactions in Natural Waters and Interactions with Solids

“…Coprecipitation of trace elements with Fe(III) hydroxide or Fe(III) phosphate, respectively, is often used as an effective procedure in the preparation of drinking water [174], Actinides(IV) and actinides(III) are very effectively coprecipitated with BaS0 4 [175][176][177], although they do not form compounds that are isomorphous with BaS0 4 . Detailed investigation showed that by coprecipitation of Th and U(IV) with BaS0 4 anomalous solid solutions are formed in which in the lattice of BaS0 4 3Ba 2+ ions are substituted by 2K + and lTh 4+ or 1U 4+ , respectively [178,179]. Coprecipitation of actinides(IV) with SrS0 4 is taking place in a similar way by formation of anomalous solid solutions [180], The results show that even if the microcomponent and the macrocomponent have different stoichiometry and do not form isomorphous crystals, if considered separately, the microcomponent may be coprecipitated very effectively by lattice substitution.…”

Isolation of uranium mill tailings and their component radionuclides from the biosphere; some earth science perspectives

“…Thorium, like radium, forms acid-soluble chloride salts (Rogers and Adams, 1969), and hence its removal from the tailings by an HCl leaching process would also appear possible. Concentration of thorium in solution by coprecipitation with barium sulfate may be possible (Ambe and Lieser, 1978). For this reason, the radium concentrate proposed above may also contain much of the thorium.…”