226Ra dynamic lixiviation from phosphogypsum samples by an automatic flow-through system with integrated renewable solid-phase extraction

Publication date: 15 May 2017
Source:Talanta, Volume 167
Author(s): Melisa Rodas Ceballos, Antoni Borràs, Rafael García-Tenorio, Rogelio Rodríguez, José Manuel Estela, Víctor Cerdà, Laura Ferrer
The release of ²²⁶Ra from phosphogypsum (PG) was evaluated by developing a novel tool for fully automated ²²⁶Ra lixiviation from PG integrating extraction/pre-concentration using a renewable sorbent format. Eight leached fractions (30mL each one) and a residual fraction were analyzed allowing the evaluation of dynamic lixiviation of ²²⁶Ra. An automatic system allows this approach coupling a homemade cell with a ²²⁶Ra extraction/pre-concentration method, which is carried out combining two procedures: Ra adsorption on MnO2 and its posterior co-precipitation with BaSO4. Detection was carried out with a low-background proportional counter, obtaining a minimum detectable activity of 7Bqkg⁻¹. Method was validated by analysis of a PG reference material (MatControl CSN-CIEMAT 2008), comparing the content found in fractions (sum of leached fractions + residual fraction) to the reference value. PG samples from Huelva (Spain) were studied. ²²⁶Ra average activity concentration of the sum of leached fractions with artificial rainwater at pH 5.4±0.2 was 105±3Bqkg⁻¹d.w. representing a ²²⁶Ra lixiviation of 37%; while at pH 2.0±0.2, it was 168±3Bqkg⁻¹ d.w., which represents a 50%. Also, static lixiviation, maintaining the same experimental conditions, was carried out indicating that, for both considered pH, the ²²⁶Ra release from PG is up to 50% higher in a dynamic leaching that in a static one, may have both environmental and reutilization implications.

Graphical abstract

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