H2-Based Membrane Catalyst-Film Reactor (H2-MCfR) Loaded with Palladium for Removing Oxidized Contaminants in Water

Scalable applications of precious-metal catalysts for water treatment face obstacles in H-2-transfer efficiency and catalyst stability during continuous operation. Here, we introduce a H-2-based membrane catalyst-film reactor (H-2-MCfR), which enables in situ reduction and immobilization of a film of heterogeneous Pd-0 catalysts that are stably anchored on the exterior of a nonporous H-2-transfer membrane under ambient conditions. In situ immobilization had >95% yield of Pd-0 in controllable forms, from isolated single atoms to moderately agglomerated nanoparticles (averaging 3-4 nm). A series of batch tests documented rapid Pd-catalyzed reduction of a wide spectrum of oxyanions (nonmetal and metal) and organics (e.g., industrial raw materials, solvents, refrigerants, and explosives) at room temperature, owing to accurately controlled H-2 supply on demand. Reduction kinetics and selectivity were readily controlled through the Pd-0 loading on the membranes, H-2 pressure, and pH. A 45-day continuous treatment of trichloroethene (TCE)-contaminated water documented removal fluxes up to 120 mg-TCE/m(2)/d with over 90% selectivity to ethane and minimal (<1.5%) catalyst leaching or deactivation. The results support that the H-2-MCfR is a potentially sustainable and reliable catalytic platform for reducing oxidized water contaminants: simple synthesis of an active and versatile catalyst that has long-term stability during continuous operation.

Automated summary

The H-2-MCfR introduces a method for in situ reduction and immobilization of Pd-0 catalysts, with high yield and controllable forms. This reactor allows rapid catalytic reduction of various oxyanions and organics at room temperature, with controlled reduction kinetics and selectivity through adjustments in Pd-0 loading, H-2 pressure, and pH.