Dynamics of Strontium and geochemically correlated elements in soil during washing remediation with eco-complaint chelators.

In the study, the dynamics of Sr and geochemically correlated elements (Ca, Ba, and Y) in soil with chelators in the mix (soil to chelator ratio, 1:10; matrix, HO) were assessed to understand chemical-induced washing remediation of radiogenic waste solids. Specifically, EDTA (2,2',2″,2‴-(ethane-1,2-diyldinitrilo)tetraacetic acid), EDDS (2-[2-(1,2-dicarboxyethylamino)ethylamino]butanedioic acid), GLDA (2-[bis(carboxymethyl)amino]pentanedioic acid), and HIDS (2-(1,2-dicarboxyethylamino)-3-hydroxy-butanedioic acid) are chelators that are used as extractants. The effect of solution pH on chelator-induced extractions of the target elements (t-Es: Sr, Ca, Ba, or Y) from soil and stability constants of the t-Es complexes with chelators were used to explain the trends and magnitudes in interactions. Pre- and post-extractive solid-phase speciation was used to define the extent of the competence of each chelator in persuading dissolution of t-Es in the soil. The effects of ultrasonic energy, admixtures of biodegradable chelators, and excess chelators in solution (1:20) were also analyzed on the extractive removal of t-Es from soil. The results indicate that the Sr removal with biodegradable chelators significantly exceeded (approximately 70%) when compared to that of environmentally-persistent EDTA at lower solution pHs and a higher soil to chelator ratio (GLDA > HIDS > EDDS ≈ EDTA). However, the extraction of the geochemically related element was significantly lower.