The release of Ra from phosphogypsum (PG) was evaluated by developing a novel tool for fully automated Ra 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 Ra. An automatic system allows this approach coupling a homemade cell with a Ra extraction/pre-concentration method, which is carried out combining two procedures: Ra adsorption on MnO and its posterior co-precipitation with BaSO. Detection was carried out with a low-background proportional counter, obtaining a minimum detectable activity of 7Bqkg. 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. Ra average activity concentration of the sum of leached fractions with artificial rainwater at pH 5.4±0.2 was 105±3Bqkgd.w. representing a Ra lixiviation of 37%; while at pH 2.0±0.2, it was 168±3Bqkg d.w., which represents a 50%. Also, static lixiviation, maintaining the same experimental conditions, was carried out indicating that, for both considered pH, the 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.
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http://dx.doi.org/10.1016/j.talanta.2017.02.036 | DOI Listing |
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