Rapid reduction of N-nitrosamine disinfection byproducts in water with hydrogen and porous nickel catalysts

There is a need for new technologies to rapidly and economically treat water contaminated with N-nitrosodimethylamine (NDMA) and related compounds because of their high toxicity and recent detection in drinking water sources as a consequence of industrial releases and chlorine disinfection of wastewater effluent Treatment of N-nitrosamines with H-2 in conjunction with a high surface area porous nickel material, a model nonprecious metal catalyse has been evaluated. Experiments show that NDMA is reduced rapidly and catalytically to dimethylamine and N-2 (e.g., t(1/2) = 1.5 min for 500 mg/L catalyst and P-H2 = 1 atm), and kinetic trends are consistent with a surface-mediated mechanism involving scission of the N-nitrosamine N-N bond and subsequent reactions with adsorbed atomic hydrogen. The metal-loading-normalized pseudo-first-order rate constant (77.9 +/- 13.1 Lg(Ni)(-1) h(-1)) exceeds values reported for Pd-based catalysts. Several related N-nitrosamines react at rates similar to those of NDMA, indicating a weak dependence on structure. The reaction rates for NDMA reduction are not significantly affected by changing pH, and the presence of high concentrations of many common water constituents (Na+, Ca2+, Mg2+, Cl-, SO42-, HCO3-, and NOM) exerts only a small effect on reaction rates. Nitrate is also reduced by the Ni catalyst and high nitrate concentrations competitively inhibit the reduction of NDMA. (Bi)sulfide poisons the catalyst by strong chemisorption to the Ni surface. Cost-normalized rate constants for the Ni catalyst are highly favorable compared to Pd-based catalysts, indicating that with further development Ni-based catalysts may become attractive alternatives to precious metal catalysts.