Removal of chromate (CrO42-) and pertechnetate (TcO4-) from the Hanford Low Activity Waste (LAW) is beneficial as it impacts the cost, life cycle, operational complexity of the Waste Treatment and Immobilization Plant (WTP), and integrity of vitrified glass for nuclear waste disposal. Here, we report the application of [MoIV3S13]2- intercalated layer double hydroxides for the removal of CrO42- as a surrogate for TcO4-, from ppm to ppb levels from water and a simulated LAW off-gas condensate of Hanford’s WTP. This material removes CrO42- from the LAW condensate stream, having a pH of 7.5, from ppm (~ 9.086 ×104 ppb of Cr6+) to below 1 ppb levels with distribution constant (Kd) values of up to ~107 mL/g. Analysis of post-adsorbed solids indicates that CrO42- removal mainly proceeds by reduction of Cr6+ to Cr3+. This study sets the first example of a metal-sulfide intercalated LDH for the removal of CrO42-, as relevant to TcO4-, from the simulated off-gas condensate streams of Hanford’s LAW Melter which contains highly concentrated competitive anions, namely F-, Cl-, CO32-, NO3-, BO33-, NO2-, B4O72-, and sulfate. Overall, [MoIV3S13]2- intercalated layer double hydroxide's remarkable removal efficiency and selectivity make it promising sorbent to remediate CrO42-/TcO4- from surface water and off-gas condensate of nuclear waste.

Sequestration of chromate: A nonradioactive surrogate of pertechnetate, using metal sulfide interclated LDH nanosheets

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