Coprecipitation of europium with barium sulphate

Abstract

Abstract The distribution behaviour of the trivalent europium ion at a micro-component scale, between barium sulphate and aqueous solution, was studied at ambient temperature. Experiments were carried out using radioactive tracers. Results indicate an enrichment of the micro component in the solid phase relative to the solution. The effects of the concentrations of the micro and macro-elements on the coprecipitation have been examined. Europium distribution coefficient D Eu increases from 1.1 ± 0.2 to 3.2 ± 0.4 when initial europium concentration decreases from more than 17 × 10−5 to 1.4 × 10−5 M, in sulphuric media with SO4 2− in excess or C Ba2+ /C SO4 2− < 1. The excess of barium in opposite, results in a decreasing D Eu. The coprecipitation of europium with barium sulphate as a heterovalent solid-solution is described by heterogeneous model obeying the Doerner and Hoskins logarithmic partition law. The weaker partition coefficients lower than unity (λ = 0.25 when C Eu(III) ≈ 1.4 × 10−5 M and λ = 0.13 when C Ba2+ /CSO4 2− < 1 and 17.8 × 10−5 ≤ C Eu(III) ≤ 153.5 × 10−5 M) lead to crystals increasingly enriched in the trace element.