Ligand-Enhanced Reduction of Perchlorate in Water with Heterogeneous Re-Pd/C Catalysts

摘要

Ongoing concerns over the ingestion of perchlorate from water and food, especially for infants, have prompted the EPA to issue a health advisory target of 15 ppb for drinking water sources; two states, California and Massachusetts, have mandated even lower limits. Removal of perchlorate from a water supply can be accomplished by selective ion exchange or reverse osmosis, but complete destruction of the contaminant requires pyrolysis or reduction by biological or chemical means. Perchlorate reduction by dihydrogen with heterogeneous metal catalysts is extremely clean, producing only chloride and water, but the systems currently available have various limitations in terms of activity, longevity, and operating conditions. Here we describe how one of these systems, derived from the combination of a Pd/C hydrogenation catalyst with the perrhenate ion, can be improved dramatically in activity and stability by the presence of simple pyridine compounds as ligands. Furthermore, the observed ligand effects provide key mechanistic insight into the operation of the system and also open an avenue for further development toward sustainable operation.