Removal of CrO 4 2- , a Nonradioactive Surrogate of 99 TcO 4 - , Using LDH-Mo 3 S 13 Nanosheets.

Removal of chromate (CrO 4 2- ) and pertechnetate (TcO 4 - ) 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 [Mo IV 3 S 13 ] 2- intercalated layer double hydroxides (LDH-Mo 3 S 13 ) for the removal of CrO 4 2- as a surrogate for TcO 4 - , from ppm to ppb levels from water and a simulated LAW off-gas condensate of Hanford's WTP. LDH-Mo 3 S 13 removes CrO 4 2- from the LAW condensate stream, having a pH of 7.5, from ppm (∼9.086 × 10 4 ppb of Cr 6+ ) to below 1 ppb levels with distribution constant ( K d ) values of up to ∼10 7 mL/g. Analysis of postadsorbed solids indicates that CrO 4 2- removal mainly proceeds by reduction of Cr 6+ to Cr 3+ . This study sets the first example of a metal sulfide intercalated LDH for the removal of CrO 4 2- , as relevant to TcO 4 - , from the simulated off-gas condensate streams of Hanford's LAW melter which contains highly concentrated competitive anions, namely F - , Cl - , CO 3 2- , NO 3 - , BO 3 3- , NO 2 - , SO 4 2- , and B 4 O 7 2- . LDH-Mo 3 S 13 's remarkable removal efficiency makes it a promising sorbent to remediate CrO 4 2- /TcO 4 - from surface water and an off-gas condensate of nuclear waste.