Post-combustion CO2 capture using amine solvents is the most feasible method of reducing anthropogenic CO2 emissions, which are the largest contributor to global warming. The formation of carcinogenic N-nitrosamines (i.e. by-products) can hinder the industrial application of this technology. In this study, the effects of direct UV photolysis (N-nitrosamine concentration and amines) and advanced oxidation processes (UV/H2O2 and UV/O3) on the three specific N-nitrosamines that are commonplace in amine-based CO2 capture (i.e. N-nitrosodiethylamine (NDEA), N-nitrosodiethanolamine (NDELA), and N-nitrosomorpholine (NMOR)) were examined. A significant decrease in the photodegradation rate constants was observed for NDEA (1.02 × 100 to 2.94 × 10-1 min-1), NDELA (1.52 × 100 to 3.32 × 10-1 min-1), and NMOR (1.93 × 100 to 2.20 × 10-1 min-1) as their concentrations increased within 1-50 mg/L. This is the first report of a significant increase in the degradation rate constants of N-nitrosamine with an increase in amine concentrations (i.e. monoethanolamine, diethanolamine, and morpholine) within 10-200 mM. The photodegradation rate constants increased as the molar ratio of H2O2 to N-nitrosamine increased to 20, but then decreased at molar ratios beyond this. O3 had a negligible effect on the photodegradation of N-nitrosamines.
Keywords: CO2 capture; N-nitrosamine; hydrogen peroxide; ozone; photodegradation.