Hydrodehalogenation of Trichlorofluoromethane over Biogenic Palladium Nanoparticles in Ambient Conditions.

Among a number of persistent chlorofluorocarbons (CFCs, or freons), the emissions of trichlorofluoromethane (CFCl 3 , CFC-11) have been increasing since 2002. Zero-valent-Pd (Pd 0 ) catalysts are known to hydrodehalogenate CFCs; however, most studies rely on cost-inefficient and eco-unfriendly chemical synthesis of Pd 0 NPs and harsh reaction conditions. In this study, we synthesized Pd 0 nanoparticles (Pd 0 NPs) using D. vulgaris biomass as the support and evaluated hydrodehalogenation of CFC-11 catalyzed by the biogenic Pd 0 NPs. The presence of D. vulgaris biomass stabilized and dispersed 3-6 nm Pd 0 NPs that were highly active. We documented, for the first time, Pd 0 -catalyzed simultaneous hydrodechlorination and hydrodefluorination of CFC-11 at ambient conditions (room temperature and 1 atm). More than 70% CFC-11 removal was achieved within 15 h with a catalytic activity of 1.5 L/g-Pd/h, dechlorination was 50%, defluorination was 41%, and selectivity to fully dehalogenated methane was >30%. The reaction pathway had a mixture of parallel and sequential hydrodehalogenation. In particular, hydrodefluorination was favored by higher H 2 availability and Pd 0 :CFC-11 ratio. This study offers a promising strategy for efficient and sustainable treatment of freon-contaminated water.