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

Abstract The release of 226 Ra from phosphogypsum (PG) was evaluated by developing a novel tool for fully automated 226 Ra lixiviation from PG integrating extraction/pre-concentration using a renewable sorbent format. Eight leached fractions (30 mL each one) and a residual fraction were analyzed allowing the evaluation of dynamic lixiviation of 226 Ra. An automatic system allows this approach coupling a homemade cell with a 226 Ra extraction/pre-concentration method, which is carried out combining two procedures: Ra adsorption on MnO 2 and its posterior co-precipitation with BaSO 4 . Detection was carried out with a low-background proportional counter, obtaining a minimum detectable activity of 7 Bq kg −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. 226 Ra average activity concentration of the sum of leached fractions with artificial rainwater at pH 5.4±0.2 was 105±3 Bq kg −1 d.w. representing a 226 Ra lixiviation of 37%; while at pH 2.0±0.2, it was 168±3 Bq kg −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 226 Ra release from PG is up to 50% higher in a dynamic leaching that in a static one, may have both environmental and reutilization implications.