Unexpected enhancement of sulfuric acid-driven new particle formation by alcoholic amines: The role of ion-induced nucleation

Abstract

New particle formation (NPF) contributes more than half of the global aerosol. Diethanolamine (DEA) and methyldiethanolamine (MDEA) are the most common amines used to remove CO₂ and H₂S, which are lost to the atmosphere from CO₂ chemical absorbers, livestock and consumer products and are involved in sulfuric acid (SA)-driven NPF. Ion-induced nucleation (IIN) is an important nucleation pathway for NPF. We investigated the role of IIN on DEA and MDEA enhancing SA-driven NPF using density functional method (DFT), molecular dynamics (MD) simulation and atmospheric cluster dynamics code (ACDC). The effects of SO₄²⁻, H₃O⁺, NH₄⁺, HSO₄⁻, NO₃⁻, ammonia, methylamine, dimethylamine, trimethylamine and water (W) on the nucleation of SA-DEA were further investigated. The enhancement ability of DEA is greater than that of dimethylamine (DMA) and MDEA. Participation in SA-based NPF is a removal pathway for DEA and MDEA. DEA-SA clusters are generated that not only aggregate DEA and SA molecules, but also increase further growth of atmospheric ions. The very low Gibbs formation free energy highlights the importance of ion-induced nucleation for SA-based NPF. The order of the ability of common atmospheric ions to increase the (SA)(DEA) cluster nucleation is SO₄²⁻ > H₃O⁺ > NH₄⁺ > HSO₄⁻ > NO₃⁻. The addition of 20 water molecules increases the (SA)(DEA)₉ cluster from 1.882 nm to 2.053 nm, promoting SA-based NPF. The atmospheric ions accelerate the aggregation rate of the (SA)₅(DEA)₅ cluster within 15 ns?