title: Heterogeneous uptake of amines by citric acid and humic acid.
abstract: Heterogeneous uptake of methylamine (MA), dimethylamine (DMA), and trimethylamine (TMA) onto citric acid and humic acid was investigated using a Knudsen cell reactor coupled to a quadrupole mass spectrometer at 298 K. Acid-base reactions between amines and carboxylic acids were confirmed. The observed uptake coefficients of MA, DMA, and TMA on citric acid at 298 K were measured to be 7.31 ± 1.13 × 10(-3), 6.65 ± 0.49 × 10(-3), and 5.82 ± 0.68 × 10(-3), respectively, and showed independence of sample mass. The observed uptake coefficients of MA, DMA, and TMA on humic acid at 298 K increased linearly with sample mass, and the true uptake coefficients of MA, DMA, and TMA were measured to be 1.26 ± 0.07 × 10(-5), 7.33 ± 0.40 × 10(-6), and 4.75 ± 0.15 × 10(-6), respectively. Citric acid, having stronger acidity, showed a higher reactivity than humic acid for a given amine; while the steric effect of amines was found to govern the reactivity between amines and citric acid or humic acid.
authors.affiliation: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Yongchun
authors.initials: Y
authors.lastname: Liu
authors.forename: Qingxin
authors.initials: Q
authors.lastname: Ma
authors.forename: Hong
authors.initials: H
authors.lastname: He
mesh_terms: D000042:Absorption; D000393:Air Pollutants / Q000737:chemistry; D000588:Amines / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D004123:Dimethylamines / Q000737:chemistry; D006812:Humic Substances; D008744:Methylamines / Q000737:chemistry; D008956:Models, Chemical; D012989:Soil Pollutants / Q000737:chemistry*
chemical_list: D000393:Air Pollutants; D000588:Amines; D004123:Dimethylamines; D006812:Humic Substances; D008744:Methylamines; D012989:Soil Pollutants; D019343:Citric Acid; C034516:dimethylamine; C023336:trimethylamine