Reductive destruction of multiple nitrated energetics over palladium nanoparticles in the H-based membrane catalyst-film reactor (MCfR).

Nitrated energetics are widespread contaminants due to their improper disposal from ammunition facilities. Different classes of nitrated energetics commonly co-exist in ammunition wastewater, but co-removal of the classes has hardly been documented. In this study, we evaluated the catalytic destruction of three types of energetics using palladium (Pd) nano-catalysts deposited on H-transfer membranes in membrane catalyst-film reactors (MCfRs). This work documented nitro-reduction of 2,4,6-trinitrotoluene (TNT), as well as, for the first time, denitration of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and pentaerythritol tetranitrate (PETN) over Pd at ambient temperature. The catalyst-specific activity was 20- to 90-fold higher than reported for other catalyst systems. Nitrite (NO) released from RDX and PETN also was catalytically reduced to dinitrogen gas (N). Continuous treatment of a synthetic wastewater containing TNT, RDX, and PETN (5 mg/L each) for more than 20 hydraulic retention times yielded removals higher than 96% for all three energetics. Furthermore, the concentrations of NO and NH were below the detection limit due to subsequent NO reduction with > 99% selectivity to N. Thus, the MCfR provides a promising strategy for sustainable catalytic removal of co-existing energetics in ammunition wastewater.