Different routes of bismuth mineral transformation during pertechnetate and perrhenate uptake for subsurface remediation

We investigated basic bismuth subnitrate for removal of radioactive technetium-99 as pertechnetate ( 99 TcO 4 − ) from contaminated groundwater. This material removed 93% of the initial concentration of 99 TcO 4 − within a week via formation of pH-dependent mineral phases that were identified here, but not reported previously. Perrhenate (ReO 4 − ) removal was also studied because it is a widely used non-radiological analogue for 99 TcO 4 − , considering their similar physicochemical properties. We found that removal of ReO 4 − was not identical to removal of 99 TcO 4 − and led to formation of an additional transitional phase. This demonstrates that perrhenate and pertechnetate have different kinetics of contaminant removal as a result of variations in mineral transformation.