Ruthenium Catalysts for the Reduction of N-Nitrosamine Water Contaminants

摘要

N -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 N -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 N -nitrosamines. Experiments with N -nitrosodimethylamine (NDMA) show that contaminant is rapidly reduced on both commercial and in-house prepared Ru/Al_(2)O_(3) catalysts, with the commercial material yielding an initial metal weight-normalized pseudo-first-order rate constant (k _(0)) of 1103 ± 133 L·g_(Ru)~(–1)·h~(–1) and an initial turnover frequency (TOF_(0)) 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 N -nitrosamines spiked into tap water (1 μg L~(–1) each) demonstrates that Ru catalysts are very effective in reducing a range of N -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.