Ruthenium Catalysts for the Reduction of <i>N</i>‑Nitrosamine Water Contaminants

<i>N</i>-Nitrosamines have raised extensive concern due to their high toxicity and detection in treated wastewater and drinking water. Catalytic reduction is a promising alternative technology to treat <i>N</i>-nitrosamines, but to advance this technology pathway, there is a need to develop more-efficient and cost-effective catalysts. We have previously discovered that commercial catalysts containing ruthenium (Ru) are unexpectedly active in reducing nitrate. This study evaluated supported Ru activity for catalyzing reduction of <i>N</i>-nitrosamines. Experiments with <i>N</i>-nitrosodimethylamine (NDMA) show that contaminant is rapidly reduced on both commercial and in-house prepared Ru/Al₂O₃ catalysts, with the commercial material yielding an initial metal weight-normalized pseudo-first-order rate constant (<i>k</i>₀) of 1103 ± 133 L·g_Ru^–1·h^–1 and an initial turnover frequency (TOF₀) of 58.0 ± 7.0 h^–1. NDMA is reduced to dimethylamine (DMA) and ammonia end-products, and a small amount of 1,1-dimethylhydrazine (UDMH) was detected as a transient intermediate. Experiment with a mixture of five <i>N</i>-nitrosamines spiked into tap water (1 μg L^–1 each) demonstrates that Ru catalysts are very effective in reducing a range of <i>N</i>-nitrosamine structures at environmentally relevant concentrations. Cost competitiveness and high catalytic activities with a range of contaminants provide a strong argument for developing Ru catalysts as part of the water purification and remediation toolbox