Soil sorption of two nitramines derived from amine-based CO2 capture

Abstract

Nitramines are potentially carcinogens that form from the amines used in post-combustion CO₂ capture (PCCC). The soil sorption characteristics of monoethanol (MEA)- and dimethyl (DMA)-nitramines have been assessed using a batch experimental setup, and defined indirectly by measuring loss of nitramine (LC-MS/MS) from the aqueous phase (0.01 M CaCl₂ and 0.1% NaN₃) after equilibrium had been established with the soil (24 h). Nitramine soil sorption was found to be strongly dependent on the content of organic matter in the soil (r² = 0.72 and 0.95, p < 0.05). Soil sorption of MEA-nitramine was further influenced by the quality of the organic matter (Abs_{254 nm}, r² = 0.93, p < 0.05). This is hypothesized to be due to the hydroxyl group on the MEA-nitramine, capable of forming hydrogen bonds with acidic functional groups on the soil organic matter. Estimated organic carbon normalized soil–water distribution coefficients (K_OC) are relatively low, and within the same range as for simple amines. Nevertheless, considering the high content of organic matter commonly found in the top layer of a forest soil, this is where most of the nitramines will be retained. Presented data can be used to estimate final concentrations of nitramines in the environment following emissions from amine-based PCCC plants.